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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Page 106
Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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Suggested Citation:"4. Animal Production Systems." Institute of Medicine. 2003. Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure. Washington, DC: The National Academies Press. doi: 10.17226/10763.
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4 Animal Production Systems DIRECT AND INDIRECT DLC PATHWAYS INTO FOOD PRODUCTS As discussed in Chapter 3, dioxin and dioxin-like compounds (referred to collectively as DLCs) may enter the animal feed to human food chain through both direct and indirect pathways. The direct environmental pathways include: air-to plant/soil, air-to plant/soil-to animal, and water/sediment-to fish (EPA, 2000~. Whether newly produced or from reservoirs, DLCs deposit on vegetation, soils, and in water sediments from the atmosphere or through agricultural pesti- cides, fertilizers, and irrigation, and are retained on plant surfaces and in the surrounding soil and sediment in waterways. It is estimated that 5 percent of aerial deposits of DLCs in terrestrial environments are retained on plants and the remaining 95 percent ultimately reaches the soil (Fries and Paustenbach, 1990~. The soil-borne DLCs then become a reservoir source that could reach plants used for animal feeds by volatilization and redeposition or as dust. Modeling studies by Trapp and Matthies (1997) indicated that volatilization of polychlorinated dibenzo-p-dioxins (PCDDs) from soil into vegetation is only significant in the case of highly contaminated soils. DLCs from contaminated plant products that are consumed by animals bioaccumulate in the animals' lipid tissues. DLCs can enter aquatic systems via direct discharge into water, by deposi- tion onto soil, and by runoff from watersheds. Aquatic animals accumulate these compounds through direct contact with the water, suspended particles, and bot- tom sediments, and through their consumption of other aquatic organisms. Lim- ited mass balance studies in dairy animals indicate that air and water are negli- gible sources of DLCs (McLachan et al., 1990~. Thus, both terrestrial and aquatic 71

72 DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY food animals may be exposed to DLCs primarily through soil-based ecological pathways. In addition to environmental pathways, animal agriculture practices in the United States may incorporate indirect pathways of DLC exposure that lead to contamination of plant and animal by-products used to formulate animal diets and manufacture animal feeds. These indirect pathways have the potential to produce elevated DLC levels in animals. Exposure to a contaminated commercial agricultural environment, such as through animal contact with pentachlorophe- nol-(PCP) treated wood used in animal housing (a practice now banned), through animal-feed contamination episodes (e.g., DLCs in poultry in the United States [EPA, 2000; FDA, 1997; FSIS, 1997, 20021), andthroughcontaminatedcitrus- pulp products in Belgium (Allsopp et al., 2000), have resulted in isolated groups of animals with high exposure levels (van Larebeke et al., 2001~. When point- source contamination episodes, such as those mentioned above, were identified, they were removed once causation was determined. Figure 4-1 shows the pathways through which DLCs enter into animal feed and human food systems. The figure shows sources and major routes (dark ar- rows) and minor routes (light arrows) by which DLCs can cycle between com- partments and ultimately reach humans. In Figure 4-1, the environmental reservoir represents the major production source and recyclable reservoir for DLCs. As stated in the EPA draft reassess- ment (see Chapter 2), there are a number of sources from which DLCs are derived (chemical processing, incineration processes, and other human activities), and most DLCs are stored in environmental reservoirs such as soils and sediments. DLCs are transported through atmospheric routes to animal forage, feed, and grasses used for feed; to vegetables, fruits and cereals consumed by humans; and to terrestrial and aquatic animals consumed by humans. The route of exposure through vegetables, fruits, and cereals consumed by humans is generally consid- ered a minor pathway, but, surface contamination by soils may increase expo- sure. Atmospheric contamination may also occur in plant products intended for animal rather than for human consumption, and may be eaten directly by a terres- trial food animal or used in animal feed, and thus may become a major source of DLC exposure to animals. The pathway to aquatic animals also is a major route by which DLCs can enter the human food supply. Aquatic organisms can accumulate elevated DLC levels from recent atmospheric deposition or historical reservoirs of DLCs in sediments or terrestrial drainage areas. These DLCs can enter the aquatic food web and concentrate in commercially important aquatic species, although levels of DLCs vary within this environment. Direct human exposure occurs through eating fish or shellfish that contain elevated levels of DLCs. This pathway repre- sents the exposure scenario that may predominate in subsistence fishers or spe- cific ethnic groups (see Chapter 5~.

ANIMAL PRODUCTION SYSTEMS / 1 Harvested Cereals, Forage, Grasses, Others ENVIRONMENT Generation Chemical Processing Combustion Worldwide Reservoir Sediments Waterways Soils -it` Vegetables, Fruits, Cereals 1K Terrestrial Animals \ 73 Animal Feed + Fishmeal, Fishoils, Animal Fats and Products HUMAN FOODS Meat, Fish, Dairy, Eggs, Fruits, Vegetables, Cereals Humans Aquatic Animals .~ FIGURE 4-1 Pathways leading to exposure to dioxin and dioxin-like compounds through the food supply. Boxes depict point sources in the pathways. Dark arrows refer to path- ways with a greater relative DLC contribution than the pathways with light arrows. Aquatic animal by-products may be used in animal feeds. The feeds may include cereals, forages, and terrestrial animal by-products. These feeds may then be fed to other terrestrial and aquatic animals, potentially contributing to their DLC load. This loop may provide an important intervention step in interrupting the DLC cycle. Terrestrial and aquatic animals represent the principal pathways

74 DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY for the production of meat, dairy products, eggs, and fish for human consumption and are therefore the primary route for introduction of DLCs to humans. The focus of this chapter is the identification of potential steps in agricultural production where interventions can be put in place to reduce DLC exposure to humans through the food supply. LIVESTOCK PRODUCTION SYSTEMS Livestock, for the purposes of this section, are defined as mammalian and avian species raised for human food production. Livestock production encom- passes a wide range of management systems, from predominantly extensive range and pasture systems for cow-calf and sheep production, to intensive production of poultry, pork, and dairy products. Extensive production will be used here to indicate systems in which animals have direct access to soils, including animals held in unpaved feedlot settings. Conversely, intensive production will be limited to animal production systems in which direct access to soil is eliminated. Livestock are recognized as DLC accumulators based on the amount of exposure they receive through their environment and diet. DLC exposure levels may be influenced by the production system employed and by other local envi- ronmental factors. The primary sources for DLC contamination of livestock can be categorized as environmental exposures, water sources, and feed rations. Cur- rent data suggest that animals raised on pasture grasses and roughage will be more likely to have higher DLC levels than concentrate-fed animals (Fries, 1995a). However, the relative weights of these factors may be influenced by the selected production system. Identification of Points of Exposure The DLC exposure risk to animal production systems can be predicted, to some extent, because environmental sources and chemical characteristics that allow these compounds to persist are known. However, quantitative, and some- times qualitative, data about DLC levels in specific production systems and local environments may be limited. Therefore, estimations of the relative risks for various production scenarios have been used where data are not available. Grain-Based Diets Grains that are traditionally fed to livestock (e.g., corn, wheat, oats, and barley) are not likely to acquire DLC contamination during production. Grains that are produced in pods, in inedible sheaths, or in shells are considered to have minimal opportunities for deposition or aerosol contamination pathways (Travis and Hattemer-Frey, 1991~. These characteristics are common in all the indig- enous grain foodstuffs used in North America. However, grain by-products, bran

ANIMAL PRODUCTION SYSTEMS 75 or middling, and recycled grains and vegetable by-products may contain residual DLC levels as a result of concentrated surface contamination contributed by local incinerators or by persistent soil contamination from past herbicide application (Roeder et al., 1998~. These products may comprise a substantial portion of the rations fed to individual groups of animals and thus increase exposure risk, whereas they represent minimal risks for larger animal populations. The significance of DLC contamination of grains and forage may be better understood by comparing relative risks. Travis and Hattemer-Frey (1991) pre- dicted a total concentration for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (wet weight) of 59 pa/kg in forages compared with 4.1 pa/kg in grains and protected produce. They also demonstrated the relatively higher exposure risk for forages compared with grains as a DLC source, although DLC contamination levels for concentrate-fed animals may vary in response to differing feed ingredients. Grasses and Forage Diets Intake of pasture grasses or roughage is considered to be the most important DLC exposure factor in extensive animal production systems. Grasses and forage represent a recognized pathway for organic contamination by air to leaf vapor transfer, deposition, and root uptake. Plant-root uptake of DLCs from soils has been shown to be minimal for most plants, except for members of the cucumber family (Fries, 1995a). Volatilization is not believed to be a major pathway for DLC contamination because of the relative vapor pressure for these highly chlo- rinated compounds (Shut et al., 1988, as reported in Roeder et al., 1998~. These relationships have been demonstrated by the observation that the levels of PCDD and polychlorinated dibenzofuran (PCDF) congeners in forage were not related to the concentration of DLCs in the soils in which they were grown (Hulster and Marschner, 1993~. Plant DLC concentrations are a reflection of the environmental contamina- tion levels in the areas where, and at times when, grown. Deposition of TCDD on the outer surface of plants is the primary route of contamination (Travis and Hattemer-Frey, 1991~. Aerial deposition efficacy depends on particle size, leaf area and roughness, and plant biomass and density (Fries, 1995a). Rain may move DLC particles to the soil or to the lower portions of the plants, where animals would be exposed to them during grazing, but they would be excluded from forage that was harvested. Commoner and colleagues (1998) observed that concentrations of DLCs in air and concurrently grown vegetation were linearly proportional. However, on eight farms located in two states they observed that for grazing dairy cows there was a greater than tenfold difference in DLC levels (0.027-0.346 pg toxicity equivalents [TEQ]/g) in the plant-based diets consumed by the cows, thus dem- onstrating diversity in the retention of DLC contaminants on the plants (Com- moner et al., 1998~. The density of grasses (spring pastures versus summer and

76 DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY fall) available for grazing or the provision of supplemental feeds may reduce DLC uptake by reducing soil ingestion (Fries, 1995b). Roughages that are har- vested and stored reflect the environmental contaminant levels during their grow- ing periods, although some forage processing techniques, such as hay drying, may reduce DLCs through volatilization (Archer and Crosby, 1969, as reported in Fries, 1995b). Some livestock production systems utilize nearly equivalent amounts of grain and roughage in animal diets, particularly for lactating dairy cattle. In these mixed diets, DLC levels would be intermediate between those of grain- and roughage-based diets. Soil Soil represents a significant reservoir for DLC contamination under grazing conditions and is a source of run-off and sediments that contaminate waterways. The bioavailability of DLCs in this reservoir varies from 20 to 40 percent, de- pending on the source from which they were generated (Fries, 1995a). Ninety- five percent of aerial contamination will eventually reach the soil (Fries and Paustenbach, 1990~; therefore, soil will reflect the environmental load from all sources for the area, both current and historic. It has been estimated that grazing dairy and beef animals may receive at least 20 and 29 percent, respectively, of DLCs per day through soil ingestion (Travis and Hattemer-Frey, 1991), and pasture conditions through the grazing season may significantly influence this uptake (Fries, 1995b). Animals in unpaved feed- lots also consume small amounts of soil that may lead to detectable residues (Fries et al., 1982, as reported in Fries, 1995a). In addition, soil erosion and sediment production will contaminate surface water sources, which may further enhance total daily DLC exposure levels under range conditions. Water The strongly lipophilic nature of DLCs reduces the potential for contamina- tion of water except through soil contamination. Filtration water systems (mu- nicipal or private) or wells with no surface contamination likely contain minimal DLC levels, whereas sediment particles in other water systems may contain adsorbed DLCs. This is important in the case of aquatic environmental contami- nation because surface water, used by grazing livestock, may represent another DLC exposure route as animals stir up sediments when they enter the waterways to drink. The contribution, however, of surface water to DLC accumulation in livestock is unknown.

ANIMAL PRODUCTION SYSTEMS Aerosols 77 Aerosol contamination contributes to environmental DLC sources through particle deposition onto plants and soils. Although limited data are available on the effects of inhalation of DLCs in livestock production, balance studies in lactating cows have shown inhalation exposure and water contamination to be negligible sources for DLCs (McLachlan et al., 1990~. Manure Manure contamination is a reflection of the DLC intake of the animal that may add to soil burdens if used in compost. Coprophagous activities, particularly in swine and poultry, may also contribute to DLC recycling. However, there is not enough available data to adequately characterize DLC exposure risks from manure, particularly as related to animal recycling effects. Point-Source Contaminants Animal housing and handling facilities may be a source for DLC contamina- tion because of the materials used in their construction. Prior to the 1980s, woods treated with pentachlorophenol (PCP) were used in feed bunks, fencing, and other structural components for livestock buildings, particularly for ruminants. Dioxin and furan contamination of the PCP-treated woods resulted in a point- source reservoir. Animals that licked the wood structure or came in contact with exposed feeds developed detectable DLC residue levels in their fat stores. Once identified, the use of these treated woods in animal contact areas stopped, and some remediation of existing facilities was completed. As older facilities have been remodeled, additional sources have been removed. Other products, such as greases, oils, or other organic chemicals that come into contact with animals or animal feeds, may present additional opportunities for point-source contamination. Inadvertent or purposeful contamination of high- fat animal feeds has been reported. For example, inadvertent DLC production was recently discovered in the chelation process of a mineral supplement (Per- sonal communication, H. Carpenter, Minnesota Department of Health, April 2, 2002~. Such occurrences illustrate the spectrum of potential point-source con- tamination events that must be considered in DLC reduction efforts. The contamination levels found in deposits of ball clay used in animal feeds from one region demonstrate that DLCs can appear in a wide range of natural environments (Hayward et al., 1999), which represent another inadvertent point source of contamination. These deposits, the result of natural combustion pro- cesses that occurred centuries ago, remain as a reservoir until uncovered.

78 DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY Management Practices The relative importance of the various pathways of exposure for animals is influenced by the production system under which the animals are raised. As described earlier, animals have direct access to soils during their residence in an extensive production system (which includes unpaved feedlots), and animals are limited to facilities or are under conditions where direct access to soil is elimi- nated in an intensive production system. The percentage of products in each category (beef, lamb, pork, poultry, eggs, and dairy) produced under the two management systems varies, based on economic conditions, resources available, market opportunities, geography, and animal health and management concerns. Ruminants (e.g., cattle and sheep) are the species most likely to be produced in extensive systems. Extensive systems are expected to generate greater DLC ex- posure to food animals than intensive systems, due to direct contact with soil and greater consumption of forage products by the animals, however, there are lim- ited data regarding geographic variations in soil contamination levels with which to quantify the differences. Extensive Production In extensive production systems, environmental media are potential sources of DLC contamination. The levels of DLC contamination in these sources, and in grazing livestock, will reflect the local history of environmental releases. Soils and vegetation may accumulate DLCs on their surfaces, but little migration or absorption into the plants is expected to occur. Sediments in ponds and streams may be DLC sources to the extent that livestock have direct access to these waters and are able to stir and ingest sedi- ment while drinking. Forage and grasses harvested and supplied as supplemental animal feeds may also contribute to DLC contamination levels; however, since soil ingestion is reduced, so is the total daily DLC exposure. Thus, poultry, swine, and other animals that ingest soil during food foraging activities will have higher DLC exposure potentials than those not exposed to soil. Intensive Production Intensive operations remove an animal's access to soils and ground water sources and thus limit their opportunities for DLC exposure. Thus, both aerosol exposure and surface water contact are minimized by the facilities in which the animals are raised. In most intensive animal production operations, feeds are provided in processed forms, and, for monogastric animals, are primarily grain- based in composition. Because of these factors, environmental DLC contamina- tion is less likely to occur in intensive than in extensive operations. As analytical methods improve and costs are reduced, air and water quality sampling will

ANIMAL PRODUCTION SYSTEMS 79 permit more precise comparisons of exposure between intensive and extensive operations. If the rations fed to animals do not include forages or grasses, expo- sure is further reduced. However, a shift in animal production practices from extensive to intensive to reduce exposure may have economic, sustainability, and animal welfare consequences that are beyond the scope of this report. ANIMAL HUSBANDRY PRACTICES As discussed in the previous section, foods of animal origin in commercial channels may be derived under either extensive or intensive production systems. In many cases, the production system will not be readily identifiable at the meat counter, although specialized or niche products may offer this information to differentiate themselves from other suppliers. When this is not the case, a general knowledge of the dominant production types for these products may provide guidance as to the likely production system, which will in turn enable a better evaluation of the relative risks of DLC contamination from various animal food sources. The paucity of analytical data to characterize DLC contamination within food animal species, however, makes the assessment of risks difficult, but based on general production systems risks, it can be expected that a range of DLC exposures exists within each class of meats, milk, fish, and eggs. Ruminants Beef and Lamb Production Grazing livestock and those fed contaminated forages can be expected to reflect the environmental burdens for these localized areas of access. This obser- vation has a direct impact on beef production at the cow-calf and stocker-calf stages where the primary source of nutrients is forage. Similar concerns can be raised with range-lamb production. Since DLCs are not readily taken up by plants and deposited onto grains and other edible plant parts, it is possible for beef and lamb feeder animals placed on predominately grain diets in an extensive feedlot system to reduce DLC intake levels after pasture exposures (Lorber et al., 1994~. Removal of known point-source contaminants, reduced atmospheric DLC pro- duction, and the subsequent reduced soil contamination levels will, in turn, re- duce expected DLC levels in extensively managed animals. However, because animal-based fats and protein ingredients may be added to the diets of animals in intensive production systems, DLCs can accumulate in the animals' tissues, al- though DLC levels are likely to be much lower than those found in animals on pasture-based diets. The second major source for contamination for beef and lamb is feeds and feedstuffs. As discussed previously, forages are the major source of DLC expo- sures for ruminant species. Nearly 35 percent of U.S. land area (788 million

80 DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY acres) is devoted to grazed forest land, grassland pasture and range, or cropland pasture (Vesterby and Krupa, 2001~. Because of the great expanses of land in the western United States, grazing is the predominant agricultural land use in this area (Figure 4-2~. Intensive forage production can be found throughout the midwestern and eastern regions and primarily on irrigated lands in some western areas of the United States. More concentrated grazing and forage production practices are found in southern, midwestern, and eastern regions. Cow-calf, sheep, and lambs are predominantly raised under extensive condi- tions in all regions (Figures 4-3, 4-4, and 4-5~. Large feedlots for finishing cattle and sheep are found predominately in the plains states of Texas, Oklahoma, Nebraska, and Colorado (Figure 4-6~. These feedlots are extensive but concen- trated operations. Forage supplies are generally of local origin, but grains may be imported into the area. Smaller feedlots are found predominately in the states east of the Missouri River and in California. A few intensive (total confinement) finishing lots can be found in the midwestern and eastern regions, but they repre- sent a minimal percentage of total beef and lamb production. These smaller feedlot operations, irrespective of production system, use locally produced feed- stuffs. g~:~ ~ . .~ (. {I-.? ^N Otis; it: ~ f '+77 ~ l ~ ' _- ~ ~ ~ . A ~ ~ . {, 1 2 ~ 3 ~ '~ .) - ... . ,, ,~ ?x' . ~ ~ ~ ~ C At.' ~~ j - .; . ~ < ~t Is ~ L'~''^^.''~ a'- ~) I- ~ ~ as, ~ _ ~ , , .,.4 ~ , , it, ~ ~ , ; , i, <, ~ , ~ ~ ~~ ~ A - ~ -t ~ ~ 1 < C , ,~~ ·~., ~ , ~,~ ~ V ~ · ~ ~~m A ~ . ~ ~ . . ~ . A ~ ., ~ _ , . , . , · ~ · ~ . L. , ~ \~ ~ _ · ~ . . . ' {'. S ~ 2 ' he ~ ~ . ~ · 3 \ ~ ,< ,~,~2 28 ~ ' < ~ ' ~ ~~ ~ . i ~ ~ 3 i ~ > 4,~, i ~ t ~ ·, ~ ~.2S,,.i, . ,,. ~ 5w~ ~ ~ ~ ~ twit .—Hi ~~ ''an '_' ~ ? " it [~ ?- ~~ lip ~ 4 Y A:- : —~~ ~ ~ ' -~ 2 ~ ~ i {~ 22 ~2 l~ ~ ~, g > ~ D t ~ ~ , 5 ~ A I, — , . 5 2 ~ ~ ~ ~ . ~ _ ~ _ ~ jam t ~ . 3 ~ . . .~ ~ . in. .~ ..~ (~ ~ I3. ' ~ ~ 5~ . . ~—~ ~ ~ —~~ <¢L~ ~5~ ~ ~~} Van ~ ~ ~ . A ~ ~5~ ·2 ,· 'it .-'i'5.>2 -'-I ~ - ~ >.z~ 5 ~~ I. . ~—A,; . Z 'S . — ~ · ~ · j · ~ · · — ~ h ~ it? ~ 2 . ~ L _ ~ ~ ~~ j3~2~ S ~ 4 ~ ·~ ~ ~ ~ _t ~ 5P~i?3~Www i004000 ~,~zp~- ~ ~ i ~ Z ~ ~ ~ ~ ~ ,~ ~ .( ~ ~~ < = C ~ ~ ~ A- ~ r ~ ~ ~ are. ~ . s ~ "I,W2~ ~ Z ~ ' ~ ~ ' J ~ V ~ ~ ~ ~[ off ~ ~ 2~ x<~ ,~ ~ f ~ ei, ~ ~ i~j~ ~5~ , ~ , ~ ~<3 ~ 1~ ~ ~ S. 1~ ilk 5 ·-~ 5P ~ ~ · · —~~ SS Hi_ ~~. |~A ~ ~ ~ ~ ~ · ~ ', me. ' .; ' P ~ ~ A ~ ~ ~ ~ ~ \~ '' 2/ ~ ~~d 1 ~\ ~ ~ Z' ill 7],y,~p ~—\5 ~~ LIZ 1~*~ ~ ~5lt~ FIGURE 4-2 Geographic distribution of pastureland in the United States, 1997. SOURCE: NASS (19991.

---a ~ ~ > ~7 FICORE 4-3 Ceogr~bic ~s~ibuUon of beef cows in me United Stags, 1997. SOWS: BASS (1999, am. United ages gal ~,~4 FICORE 4-4 Ceogr~Nc ~s~ibuUon of came ad caves in me United Stags, 1997. SOME: BASS (19997

82 DIOXINS AND DIOXIN-~IKE COMPOUNDS IN THE FOOD SUPPLY ~~ ~~ ~1 ~ `~2 ~ `$~5 FIGURE 4-5 Geographic distribution of sheep and lambs in the United States, 1997. SOURCE: NASS (1999). - . ., ~ ax_ - al ) - as UntIed ~~s Tom! Ail, 13}) FIGURE 4-6 Geographic distribution of fattened cattle sold in the United States, 1997. SOURCE: NASS (19991.

ANIMAL PRODUCTION SYSTEMS Dairy Cattle 83 Dairy operations have two routes through which they may contribute DLCs to the human food supply: milk and meat. Milk levels reflect the DLC body burden of the herd and the fat content of the milk. Mobilization of body fat during lactation likely causes variances in milk DLC levels, but these differences may be leveled through the practice of staggered lactations of individual cows, which is designed to maintain a steady daily herd production level. One exception to this staggered production is selected herds, where the entire herd is brought into simultaneous lactation to take maximum advantage of pasture grass growth to sustain production levels. As in beef operations, a higher proportion of grains in the ration may reduce the total DLC exposure potentials, irrespective of the type of operation. Dairy operations in the western, southwestern, and plains states are primarily concentrated operations (Figure 4-7~. Many of these operations import feedstuffs, both forage and grains, as well as replacement animals from outside the immediate area. Therefore, DLC exposure from meat and milk contamination is predominately a function of DLC levels in these source areas. Large intensive dairy operations increasingly are found in the Midwest and parts of the Southeast, where forages are grown locally and grains may or may not be imported from outside the immediate area. Water supplies for these inten- fC) ~ . i ~ L · ~~ J. 1_' ' ~ ~ W IF '. t'N ~ ~ a) ~ AN f I,,, ~ At. ~~ ~ i_ I'm ~~\ ,..' 2 .~ United $t~$ Tabs 310954439 FIGURE 4-7 Geographic distribution of lactating dairy cattle in the United States, 1997. SOURCE: NASS (19991.

84 DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY sive units are generally from wells or filtered sources, rather than from surface water. In these same areas, as well as in the Northeast, smaller extensive dairies have traditionally predominated. In these extensive operations, cows graze pas- tures during the summer months, but are confined during the winter. In all cases, rations maintain a forage-grain configuration, based on production needs. Intensive operations are more inclined to feed increased proportions of grains, grain and animal by-products, and other supplements in an attempt to achieve higher production targets. The foodstuffs and replacement animals for intensive and extensive groups are generally locally raised. Therefore, DLC levels in these operations are more reflective of local environmental conditions. Veal Veal production is a specialized program that places approximately 750,000 calves annually into intensive production systems. Veal production is concen- trated in the eastern Midwest and the Northeast, and is largely a method for utilizing the male dairy calves for a specialty market. These calves receive colos- trum prior to placement and are generally maintained in individual crates for the feeding period. Veal calves are fed a commercial milk-based liquid diet for the 16 to 21 weeks of production. These animals receive no forage during the feeding period and have limited access to soils to maintain the pale meat color desired by consumers. Thus, the level of DLC exposure to these calves is dependent upon the DLC levels in the milk used to formulate their diet. Swine and Poultry Swine and poultry (monogastric) food animals are fed predominately grain- based diets. Additional animal fats and meat products, fish meal, grain by-prod- ucts, and other supplements may be added to the diets to meet nutritional or best- performance production goals, and DLCs may accumulate in animal tissues that are utilized as feed. Minimal access to grasses or forages occurs except in some extensive production situations where soil access is a major source of DLC contamination. Swine consume soil as a part of their normal rooting activities when given access to extensive systems. Fries and coworkers (1982) estimated that swine consume from 3.3 to 8 percent of their diet in pastures. Similarly, poultry with soil access ingest DLCs from the environment during their normal feeding behav- iors. Geese were found to consume 8 percent and wild turkey 9 percent of their diets as soil (Beyer et al., 1994~. Free-range poultry may exhibit similar behavior. Laying hens exposed to soils produce eggs with DLC contamination levels that are reflective of the soil contamination levels (Schuler et al., 1997~.

ANIMAL PRODUCTION SYSTEMS S. wine 85 Swine operations are concentrated in the midwestern areas east of or imme- diately west of the Missouri River and in North Carolina (Figure 4-8~. Swine operations are predominantly intensive throughout these regions. Intensive op- erations raise swine in enclosed facilities on concrete, wire, or other slatted materials to separate them from their manure. In some midwestern areas, the use of intensive but bedded systems for finishing swine is increasingly popular. These bedding materials range from wood chips to mixtures of corn fodder and recycled paper products. Bedding materials are produced locally and generally are re- placed after each group of swine is marketed. Feed supplies may be produced locally, or in the case of the southern and mid-Atlantic states, shipped from the Midwest. Feeds are predominately veg- etable and grain-based diets. Water sources are generally from wells or other controlled sources, rather than surface waters. Therefore, exposures are primarily limited to dietary introductions. A small but growing population of swine is raised in extensive production systems. Many of these operations are small producers with local or specialty markets that desire to have free-range products. These animals have access to ): ~ ~ ~' ~ ~ ~ ' 1~ ~ ~ in.' . i. - , _~, ,~, a,_ Act 1 ~ W~ 4~ 7 ~ \: ~ 'me ~ ~ ,( :~ G] __ ~ ~ : W~ dr'`ted ~~s T`:~f `1 42 '6 ~ ~ '882 FIGURE 4-8 Geographic distribution of hogs and pigs sold in the United States, 1997. SOURCE: NASS (1999).

86 DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY soils and pasture. They may have access to surface water sources, but are more likely to receive water from wells or other controlled sources. Their diets are grain-based, similar to the intensive operations, but DLC levels may vary as other sources of exposure (soil and forage) are introduced into their environment. Poultry Egg production is concentrated in scattered geographic regions (Figure 4-9~. Poultry operations (broiler, turkey, and egg production) are predominantly inten- sive production models. Broiler production is concentrated in the southern and mid-Atlantic states (Figure 4-101. Turkey production is found in these areas and in the upper Midwest states (Figure 4-111. Broiler and turkey operations, while intensive in production, are predomi- nantly litter-based systems. Litter materials include wood chips, ground corn- cobs, and other suitable bedding materials and may be used for several groups of animals before being recycled. Egg production predominantly occurs on wire structures or in cages that limit the bird's exposure to soil and fecal material. Feed supplies for all production types may be locally produced, or in the case of the southern and mid-Atlantic states, shipped from the Midwest. Feeds are predomi- nately vegetable and grain-based diets, supplemented with animal and grain by- products in best-cost formulations. ~ ~ ~ ~ ~ 2$- ,,2, ~~ A <52 ~ _L to ~~ ~ —' .~-'' ~ ~~ I, ~ ~ 2~ - $, .'~'$'~ 2' _~ ~15 'at ^.~ \~\,_~ e' t$202~ ~~ Arts FIGURE 4-9 Geographic distribution of layers and pullets in the United States, 1997. SOURCE: NASS (1999).

ANIMAL PRODUCTION SYSTEMS 87 ~ ~ ~--- ~ ~~?~— Urged ~~s Total 64~] t927 ~ 1 1 ~ FIGURE 4-10 Geographic distribution of broilers and other meat-type chickens sold in the Unite d S late s, 1 9 9 7 . SOURCE: NASS (1999). ~ At ~ - , ,~¢, FIGURE 4-11 Geographic distribution of turkeys sold in the United States, 1997. SOURCE: NASS (19991.

88 DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY As with swine, a small but growing population of broilers and layers are being housed in extensive production systems for the free-range markets. These animals have access to soil and, in some cases, to pasture. Feeds are predomi- nately grain-based diets, and water sources are generally from wells or other controlled sources. Rarely, however, do they have access to standing surface water. FISH AND SEAFOOD There are a number of ways in which aquatic organisms can accumulate persistent organic pollutants (POPs) such as DLCs. Two common scenarios that lead to the accumulation of POPs in aquatic organisms are presented below. Wild-Caught Seafood Persistent compounds accumulate in the wild populations of fish and shell- fish that are caught in freshwater, estuaries, and the open ocean. This is because of their lipophilicity, reliance on passive transport, and resistance to metabolism. In contaminated aquatic environments, POPs are generally associated with par- ticles that settle in sediment or are carried downstream to the delta or depositional areas, where they then are deposited. Fish or aquatic organisms may come in direct contact with POPs if they live near the bottom or have contact through their gills. The aquatic food chain, just as with the human food chain, is the predomi- nant route of DLC exposure for fish, with the DLCs accumulating in the larger fish that eat the small crustaceans or smaller fish. The most critical step in expo- sure is Resorption of the DLCs from particulate matter and subsequent entry into the food chain. Once in the food chain, the DLCs associate with lipids, where the rate of accumulation is directly related to lipid uptake. Once DLCs are ingested, they distribute to different tissues in fish, based primarily on tissue lipid content, and, to some extent, nonspecific binding pro- teins. The liver, gonads, and fat are the three highest fat tissues and the most highly contaminated. The muscle is generally less contaminated, but that is par- tially determined by the lipid content in the muscle tissue of a specific type of fish. In general, older, larger, and oily fish have higher DLC levels than other fish. In addition, different fish harvested from the same location may have differ- ent DLC levels. Wild fish are migratory and therefore may on one day eat food that is highly contaminated and then the next day, eat the same type of food from another location that is less contaminated. Different species also have preferred habitats or behaviors that may expose them to higher DLC levels. The major sources for aquatic DLC contamination are air deposition over large watersheds

ANIMAL PRODUCTION SYSTEMS 89 and regional point sources. Since their deep-water food sources have lower DLC levels, ocean fish have lower contamination levels than near-shore species. In the case of other seafood, such as crabs, crawfish, oysters, clams, and scallops, the environment in which they grow determines their DLC body burden. Lobsters that inhabit near-shore areas may accumulate DLCs in high concentra- tions. Unfortunately, the most productive lobster trapping areas are along the coasts, where watersheds drain and point sources are located. Regional variations in methods for preparing and eating fish can have a direct impact on the levels of DLCs to which the consumer is exposed. This is the reason that states such as New Jersey have developed recommendations for pre- paring fish that reduce the exposure to high-fat-containing tissues (i.e., fat under- lying the skin of the fish). If the fish is used whole, such as in some types of soups, the average exposure is higher than if just the filets are used. Soups made from whole organisms (e.g., lobster) contain both low-contamination muscle meat and high-contamination organ meats. Food preparation methods to decrease DLC exposure are discussed further in Chapter 5. Aquaculture Aquaculture in the United States and other countries supplies an increasing proportion of fresh fish and certain shellfish that is consumed in the United States. Some of the major aquaculture species sold include salmon, catfish, tila- pia, striped bass, crawfish, and prawns. Management practices in aquaculture are designed to maximize the animal' s growth and the quality of its meat. This is accomplished by modifying the com- position of the feeds used during different stages in an animal's life. Extensive research has been carried out on the nutrient requirements and feeding of catfish and salmonids, and consequently, their nutrient requirements and feeding charac- teristics are well understood. The diets for intensively cultured species provide, in a water-stable, readily digestible formulation, all known nutrients at required levels and energy necessary for their utilization. Because of the intensive culture conditions, the majority of the food is supplied by the producers. The feed pro- duced for fish includes protein, vitamins, minerals, lipids, and energy for normal growth and other physiological functions. As an example, the percent composition of feed for channel catfish at differ- ent times in the growth cycle is presented in Table 4-1. The composition of the feed is varied to meet the physiological requirements of the fish at each life stage. The higher the percentage of protein, the more rapid the growth target. At the fry stage, the highest amount of menhaden meal is used in the feed, allowing for rapid growth in the earliest stages of culturing. Because of this intensive management approach, even low levels of DLCs can accumulate into fish tissues. A reduction in the use of animal-based fats as an

9o DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY TABLE 4-1 Examples of Ingredient Composition of Typical Channel Catfish Fry, Fingerling, and Food Fish Feeds Ingredients Fry Feed (50%)a Fingerling Feed (35%) Food Fish (32%) Food Fish (28%) Soybean meal (48%)a 38.8 35.0 24.4 Cottonseed meal (41%) 10.0 10.0 10.0 Menhaden meal (61%) 60.2 6.0 4.0 4.0 Meat/bone/blood (65%) 15.3 6.0 4.0 4.0 Corn grain 16.1 29.9 35.5 Wheat middling 19.0 20.0 15.0 20.0 Dicalcium phosphate 1.0 0.5 0.5 Catfish vitamin mixb Included Included Included Included Catfish mineral mixb Included Included Included Included Fat/oilC 5.0 2.0 1.5 1.5 aValues in parentheses represent the percentage of protein. bCommercial mix that meets or exceeds all requirements for channel catfish. CFat or oil is sprayed on the finished feed pellets to reduce feed dust (fines). SOURCE: Robinson et al. (2001). ingredient in fish feeds would generally reduce the uptake of minor contaminants present in the fat. There is a need to examine all of the feed ingredients to ensure that DLCs are not being inadvertently introduced. In the case of pond-reared crawfish, catfish feed is often used. Similar concerns exist for salmonids and other finfish species raised under intensive culture conditions. Feeds that are dependent on animal fats are potential sources of DLC expo- sure. However, reformulation of fish diets requires the development of a defined diet that meets the nutritional needs of the fish and reduces the potential introduc- tion of DLCs into the food system. The use of defatted (rendered) fishmeal offers a potential means to reduce entry of DLCs into animal feeds. Diets for fatty fish also require formulations that include omega-3 fatty acids. WILD ANIMALS For some population subgroups such as Northern Dwellers (i.e., Native popu- lations living in Canada and Alaska) and Native American fishers, the consump- tion of wild-caught animals is an important source of nutrition, and hunting and fishing activities are important cultural activities. However, the consumption of food products from wild-caught animals may result in increased DLC exposure. As with commercial extensively raised livestock, wild animals are exposed to DLCs through the plants and animals they eat. Exposure may be due to either the generalized presence of DLCs in the environment, as is the case throughout much of the Arctic region (Arctic Monitoring and Assessment Programme, 2001),

ANIMAL PRODUCTION SYSTEMS 91 or to the presence of environmental hot spots. DLC levels in animal tissues vary, depending on the animal's fat content and its length of exposure. Arctic animals may be of special concern because of their high fatty makeup (e.g., seals). Ani- mals in other areas of the United States (e.g., deer in Michigan) may be of lesser concern because products from them are relatively low in fat. DLC exposure may also vary due to the migratory habits of animals and to the contamination levels in areas through which they migrate. For example, in the Arctic region, birds that migrate south along the Eastern seaboard of the United States have higher levels of several POPs than do birds from farther west (Arctic Monitoring and Assessment Programme, 2001~. Exposure of wild animals, and of humans who consume them, to DLCs is also affected by point sources of pollution, as is the case among the Akwesasne people living along the St. Lawrence River. As a result, DLC levels found in particular animals (e.g., deer, elk, caribou, seals, and salmon) may vary considerably, resulting in localized hot spots. In contrast to commercially produced animals, the "production" of wild animals is relatively unmanaged and unregulated and has few intervention points that can significantly affect DLC loads. Reduction of DLC levels in wild animals is almost entirely dependent on reductions in environmental DLC loads. ANIMAL FEEDS As discussed in previous sections, for livestock raised intensively and sea- food produced by aquaculture, animal feeds used to supplement or replace natu- ral dietary components may be an important source of DLC exposure. Feeds are carefully formulated to provide complete and balanced nutrition to animals with the greatest efficiency. Not all feeds contain DLCs, but when they do, it is likely due to isolated ingredients and is often, but not exclusively, limited to feeds that contain animal products. Feed Ingredients Collective terms are classes of feed ingredients grouped by ingredient origin, as jointly defined by the Association of American Feed Control Officials and the Food and Drug Administration (FDA) (AAFCO, 2002~. Collective terms are permitted on all animal feed labels (rather than the listing of each individual ingredient within that feed term) in all states except for California and Florida. In California, each individual feed ingredient must be listed in the ingredient state- ment in descending order of relative presence. In Florida, the collective terms can only be used on the feed labels of certain species. Table 4-2 presents the collec- tive terms and the ingredients most commonly used in them (AAFCO, 2002~. Many other feed ingredients that are used in animal feeds are not classified into the collective terms. These ingredients are listed individually in the ingredi-

92 DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY TABLE 4-2 Animal Feed Collective Terms and Illustrative Ingredients Collective Term illustrative Ingredient Animal protein products Forage products Grain products (i.e., whole, ground, cracked, flaked) Plant protein products Processed grain by-products Roughage products Molasses products Fish meal Meat and bone meal Milk, dried, whole Poultry by-product meal Whey, dried Hydrolyzed poultry feathers Animal blood, dried Casein Alfalfa meal, dehydrated Corn plant, dehydrated Soybean hay, ground Barley Corn Grain, sorghum Oats Wheat Rice Canola meal Cottonseed meal Peanut meal Soybean meal Sunflower meal Yeast, dried Aspirated grain fractions Brewers dried grains Corn gluten meal Corn distillers dried grains Wheat bran Wheat middling Apple pomace, dried Beet pulp, dried Citrus pulp, dried Corn cob fractions Cottonseed hulls Oat hulls Peanut hulls Rice hulls Soybean mill run Straw, ground Beet molasses Cane molasses

ANIMAL PRODUCTION SYSTEMS 93 ent statement on the animal-feed product label, but can be grouped into feed ingredient categories, as shown in Table 4-3. The potential for DLC exposure varies for each of the categories shown, although animal fat is considered to have the greatest potential for containing DLCs. Forage and roughage products vary geographically depending upon air exposure to DLCs and the season of the cut, although more data is needed to confirm which regions are likely to have high DLC levels. Processed grain by-products may contain DLCs depending upon the type of processing. Some animal medications used in the past may have had DLC contaminants (nitrofurans), but none of the presently approved medications are known to have DLC contaminants. The annual production of animal fats (white and yellow tallow, greases, and poultry fat) is estimated to be 3.6 billion pounds of inedible tallow, 3 billion pounds of grease, and 1.4 billion pounds of recycled fat (PROMAR International, 1999~. Animal fats have been identified as the greatest potential source of DLC contamination; however, removal of this by-product from feed formulations may create secondary problems with disposal of the unused fat. Implementation of appropriate and efficient disposal routes for contaminated fat would serve as an acceptable alternative to eliminating the recycling of fat, permanently or tempo- rarily. The transformation of unused fats and oils into alternative uses, such as biofuels (Pearl; 2002, Tyson, 1998; Wiltsee, 1998), is an intriguing alternative that may become more important as the technology develops. In 2000, prompted by the 1997 findings of the entry of DLCs into animal feed products through contaminated ball clay (described in Ferrario et al., 2002; see also Box 4-1), FDA's Center for Veterinary Medicine initiated the Prelimi- TABLE 4-3 Animal Feed Categories and Illustrative Ingredients Category illustrative Ingredient Fats and oils Microingredients Medication Fermentation products Enzymes and herbals Animal fat Vegetable fat or oil Fat product, feed grade Vitamin A supplement Vitamin E supplement Calcium oxide Cobalt carbonate Amprolium Carbadox Cereals/grain fermentation solubles, condensed Direct-fed microorganisms, such as Aspergillus niger Lactase Phytase

94 DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY nary National Survey of DLCs in Animal Fats, Animal Meals, Oilseed Deodor- izer Distillates, and Molasses (CVM, 2000), with a follow-up survey in 2001 (CVM, 2001~. The purpose of the surveys was to determine background levels of DLCs in fatty and other ingredients commonly used in animal feeds. The results, expressed as TEQ parts per trillion (ppt) dry weight, showed the following conge- ner concentrations for groupings of samples:

ANIMAL PRODUCTION SYSTEMS 95 1. Fish meal (used as an ingredient in animal diets) samples varied by species. Meal derived from Pacific whiting had the lowest DLC values (< 0.5 ppt), whereas menhaden had the highest values (average 0.9 ppt). The DLC levels in fish from the Atlantic and Gulf areas are considered to be uncontrollable in that there is presently no known intervention that can lower the DLC levels in these fish. 2. Deodorized distillates showed DLC values of 1.4 to 7.1 ppt (average 4.4 ppt). Oil from fish-oil distillates is used as a feed ingredient (and is also used in the manufacture of dietary supplements intended for consumption by humans). 3. Other animal feed ingredients, including carcass-animal fat (including pork, beef, and mixed species) showed DLC values of 0.2 to 3.95 ppt (average 0.5 ppt), while meat and bone meal from mixed species, by- product meal from poultry, and eggs showed < 0.3 ppt. For animal diets, the DLC level found in rendered fat may represent a small percent of the total dietary fat because the final diet likely contains a mixture of both animal and vegetable fats. However, animal fats are a significant source of recycled DLCs, and can be removed from animal diets. For example, meat and bone meal (a protein source derived from the same rendering process), can be defatted to reduce the risk for DLC contamination (Ferrario et al., 2002~. 4. Results are pending for mineral additives such as copper sulfate. DLCs have been found where kelp and heat are used in manufacturing and processing. The DLCs produced in this process are considered to be controllable through the drying process during manufacture. 5. Anti-caking agents (from a 1998 survey) showed DLC values of 0.4 to 22.5 ppt. The broad range of DLC levels may indicate hot pockets of environmental contamination. There also may be other clays contami- nated with DLCs in addition to the ball clay that has already been banned from animal feeds. Some of these clays are used for bleaching in both animal and human food processing. Although there have sporadic events in which very high levels of DLCs have been detected as shown in Boxes 4-1 and 4-2, more representative analytical results for specific DLC congeners are shown in Table 4-4. Feed Formulation The feeding objective in food animals is weight gain in the shortest period of time at the lowest cost. There are breeding issues that are also addressed with feed formulations, but formula cost is the driver of the feed formulation consis- tent with the feeding objective.

96 DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY Least-Cost Formulations In the least-cost formulation process, the goal is to select ingredients for a formulation that will provide the desired nutritional characteristics at the lowest cost. The complexity of the various systems available for developing formula- tions range from a simple percentage system to extremely complicated systems with many ingredients and ingredient constraints. Using computer software, information about each available ingredient in a formulation is entered into the system, including the nutritional value of the ingredient (e.g., protein, fat, vitamins, minerals, fiber), the ingredient cost, and amount to be used (depending on species and age). Other factors may be included in the ingredient selection process, depending upon the sophistication of the system being used. Most systems include: ingredient profiles commodity prices nutrient specifications for the products manufacturing capabilities interface with tagging/labeling systems links with feed-manufacturing plants updates on the nutrient content of the ingredients (some systems automatically update changes) drug validation allocation of limited or excess available ingredients history storage systems links with pricing systems links with accounting systems links with purchasing systems

ANIMAL PRODUCTION SYSTEMS 97 TABLE 4-4 Summary Data of Dioxins and Dioxin-like Compounds Congener Concentrations (ppt) for Feed Ingredients Animal-Based Ingredientsb Descriptiona AF- AF- SL MX Plant-Based IngredientsC MBM- PBM FM- FM- FM- MX & E WHI CAT MEN DD MOL Number of samples 6 2,3,7,8-TCDD 0.04 1,2,3,7,8-PeCDD 0.12 1,2,3,4,7,8-HxCDD 0.13 1,2,3,6,7,8-HxCDD 0.61 1,2,3,7,8,9-HxCDD 0.19 1,2,3,4,6,7,8-HpCDD 3.17 OCDD 12.03 2,3,7,8-TCDF 0.04 1,2,3,7,8-PeCDF 0.06 2,3,4,7,8-PeCDF 0.11 1,2,3,4,7,8-HxCDF 0.13 1,2,3,6,7,8-HxCDF 0.11 2,3,4,6,7,8-HxCDF 0.06 1,2,3,7,8,9-HxCDF 0.06 1,2,3,4,6,7,8-HpCDF 0.17 1,2,3,4,7,8,9-HpCDF 0.17 OCDF 0.50 PCB 77 PCB 126 PCB 169 TEQ-D TEQ-F TEQ-P TEQ-DF TEQ-DF; ND = 0 TEQ-DFP TEQ-DFP; ND = 0 Min TEQ-DFP Max TEQ-DFP 2.06 22.15 1.62 6.60 0.54 1.29 0.28 1.02 0.10 0.40 0.17 0.68 0.38 1.43 0.26 1.41 0.54 2.10 0.43 2.09 0.08 1.07 1.49 3.95 3 0.08 0.01 0.36 0.03 0.53 0.03 2.99 0.10 0.66 0.06 16.26 1.66 76.74 15.06 0.73 0.04 0.11 0.02 0.32 0.02 0.63 0.04 0.42 0.02 0.22 0.04 0.06 0.02 2.87 0.24 0.25 0.07 2.25 0.42 1.68 0.32 0.04 0.04 0.03 0.03 0.11 0.07 0.14 0.10 0.13 0.16 0.05 0.15 0.11 0.15 0.01 0.11 0.16 0.29 0.06 0.26 0.09 0.20 0.30 0.44 5 3 1 4 11 0.01 0.01 0.09 0.37 0.23 0.02 0.04 0.04 0.46 0.62 0.92 0.04 0.04 0.03 0.61 0.17 1.31 0.04 0.04 0.08 0.91 0.66 3.27 0.04 0.04 0.03 0.64 0.46 3.45 0.04 0.61 0.29 6.62 3.11 62.55 1.12 7.29 2.80 47.84 54.07 511.15 11.61 0.01 0.20 0.05 2.32 0.68 0.02 0.04 0.03 0.02 0.31 0.40 0.04 0.04 0.08 0.04 0.58 0.77 0.04 0.04 0.03 0.02 0.12 0.70 0.04 0.04 0.03 0.02 0.06 0.51 0.04 0.04 0.04 0.05 0.12 0.65 0.04 0.04 0.03 0.02 0.02 0.24 0.05 0.19 0.09 0.06 0.28 6.54 0.50 0.11 0.08 0.05 0.06 0.57 0.12 0.27 0.25 0.02 0.33 10.55 1.63 119.06 2.01 2.37 82.10 133.70 0.71 0.50 1.42 0.37 11.63 9.73 0.02 0.13 0.40 0.08 1.97 0.44 0.04 0.07 0.07 0.84 1.15 2.63 0.08 0.04 0.07 0.04 0.57 0.76 0.05 0.04 1.19 0.99 <0.01 0.87 1.72 3.38 0.13 0.87 1.72 3.35 0.02 0.91 2.91 4.39 0.13 0.91 2.91 4.34 0.02 0.91 2.14 1.43 0.02 0.91 3.33 7.08 0.18 aTCDD = tetrachlorodibenzo-p-dioxin, PeCDD = pentachlorodibenzo-p-dioxin, HxCDD = hexachlor- odibenzo-p-dioxin, HpCDD = heptachlorodibenzo-p-dioxin, ACED = octachlorodibenzo-p-dioxin, TCDF = tetrachlorodibenzofuran, PeCDF = pentachlorodibenzo-p-furan, HxCDF = hexachlorodi- benzo-p-furan, HpCDF = heptachlorodibenzo-p-furan, 0CDF = octachlorodibenzo-p-furan, PCB = polychlorinated biphenyls. bAF-SL = animal fat from slaughtered animals, AF-MX = animal fat from mixed animal species, MBM-MX = meat and bone meal from mixed animal species, PBM&E = poultry by-product meal and eggs, FM-WHI = Pacific whiting meal, FM-CAT = catfish meal, FM-MEN = menhaden meal. CDD = deodorizer distillates, MOL = molasses, corn oil, and canola meal. NOTE: Nondetects (ND) = I/2 limit of detection (LOD); levels of 0.01-0.04 ppt indicate ND for all or most samples; average toxicity equivalents (TEQ) concentrations in ppt when ND = I/2 detection limit and at ND = 0. SOURCE: Ferrario et al. (2002).

98 DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY Through the use of such least-cost formulation systems, limits on DLC levels for individual ingredients can be set. The major obstacle in the use of a computer system for DLC-level control is obtaining the level of DLCs in an ingredient because of sampling, assay, and timing issues. In addition, as more limitations are placed on ingredients during the selection process, the cost of the animal feed increases. If the use of a cost-effective feed ingredient is limited or eliminated because of a concern for DLC contamination, then the computer must select alternate ingredients. Such alternate selections may come at a high price and may trigger other undesirable effects, such as adverse impacts on food quality, quan- tity, or production duration. For example, different sources of fat may affect the meat quality of swine or may decrease milk production in dairy animals. Typical Feed Formulations Animal diet formulations are based on the species and stage of life of the animal. Tables 4-5 and 4-6 provide two least-cost feed formulations. These for- mulations include the typical feed ingredients used as the primary animal diet fed in the United States at each stage of life and the effect on costs if animal products were removed. Replacement of animal products can cause either an increase or decrease in feed cost. This can also cause increases or decreases in secondary costs, such as the relative costs of ingredients due to changes in demand and the time it takes to raise an animal to term. Replacement of animal products in feeds may also cause an unacceptable decrease in the nutrient content or quality of the final food animal product (Cameron and Enser, 1991~. TABLE 4-5 Example of a Least-Cost Feed Formulation for Dairy Cattle Ingredient Typical Amount (%) Amount Without Animal Products (%) Corn or grain Midds or ground soybean hull Cottonseed meal Soybean meal (could be some sun meal) Calcium carbonate Salt Animal fat Molasses Trace minerals and vitamins pack Total Total ingredient cost 22.0 53.5 4.0 10.0 2.0 1.0 2.0 5.0 0.5 100.0 $106.00 32.5 42.0 7.0 10.0 2.0 1.0 0.0 5.0 0.5 100.0 $107.50

ANIMAL PRODUCTION SYSTEMS TABLE 4-6 Example of a Least-Cost, Starter-Phase Feed Formulation for Hogs 99 Ingredient Typical Amount (%) Amount Without Animal Products (%) Corn Wheat byproducts Soybean meal Fish meal Calcium carbonate Dical or mono dical phosphate Salt Animal fat Trace minerals and vitamins pack Corn Total percent Total ingredient costa 51.5 11.0 30.0 1.0 1.0 1.5 0.5 3.0 0.5 51.5 63.0 0.0 33.0 0.0 1.0 2.0 0.5 0.0 0.5 63.0 100 100 $127.00 $126.00 aA hog-starter product without animal fat or other animal products is much lower in protein so the time to complete grow-out will be increased. Certification Programs The U.S. Department of Agriculture (USDA) has some certification pro- grams for various feed ingredients, although none are specific to DLCs. Distribution The distribution mode for feed ingredients and products should be consid- ered as a potential means for distributing DLCs. The distribution conveyances used for animal-feed ingredients require that all containers be cleansed and se- quenced to protect feed ingredients from harmful contaminants, including DLCs. FOOD PROCESSING AND PACKAGING Most food sources have the potential to contain some level of DLC contam~ . nation, depending on the area from which they originated and the agricultural practices under which they were grown or raised. Once these foods sources are destined for the food supply (e.g., harvested, collected, slaughtered, caught), they are prepared for market and then for consumption. For some foods, this requires minimal processing and packaging; for others, significant opportunities for addi- tional DLC contamination exist.

100 DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY Composite and Processed Foods Processed foods, including foods containing significant levels of animal fat, such as sausage, bacon, fondues, and products fried in animal fat (e.g., fried snack foods), contribute to DLC intakes. Processed foods may contain varying levels of DLCs depending on the DLC content of each ingredient in the compos- ite food. Therefore, all mixtures of processed foods containing animal, dairy, or fish fats should be considered as potential sources of DLCs. Water, used in processing and contained in the products themselves, prob- ably does not contribute to the overall DLC load. In a study of the persistence of TCDD metabolites in lake water and sediment (under laboratory conditions), Ward and Matsumura (1978) determined that most of the TCDD spiked into a mixed water-sediment sample is partitioned with the sediment, leaving less than 4 percent of the metabolites in the water itself. Food Processing and Packaging Information on the entry or generation of DLCs in the processing and pack- aging of foods is limited. However, analysis of current practices and procedures may be useful in predicting potential sources of entry of DLCs into the food supply by these routes (Table 4-7~. Processing There are numerous ways that food is processed, some of which may alter the DLC content in foods, and some of which may not. The processes that are not likely to alter the DLC content in foods are: . Processing, mixing, and blending foods (e.g., a blend of cereal grains), and forming and molding foods (e.g., bread, pie crusts, biscuits, confec- tions) at ambient temperatures (although much higher temperatures have been found to decompose DLCs) (Zabik and Zabik, 1999) Other ambient processing techniques such as sorting, cutting, and sepa- rating debris The process of flame peeling used in onion processing may generate DLCs due to the high processing temperature, but they may also be washed away in the process Blanching, pasteurization, heat sterilization, baking, and roasting Freeze processing products sold and maintained as frozen foods (e.g., frozen fruits, vegetables, and meat products) (Larsen and Facchetti, 1989) and chilled and refrigerated storage of fresh and processed foods (freeze- drying or freeze-concentration of certain substances may increase the ratio of DLCs relative to the mass of the resulting processed food)

ANIMAL PRODUCTION SYSTEMS TABLE 4-7 Effects of Food Processing Methods on Levels of Dioxin and Dioxin-like Compounds (DLCs) 101 Processing Methods Effect on DLC Levels Raw material preparation Cleaning Wet cleaning Dry cleaning Removing contaminants/foreign bodies Sorting Shape and size sorting Color sorting Weight sorting Peeling Flash steam peeling Knife peeling Abrasion peeling Flame peeling Mixing and forming Mixing Solids mixing Liquids mixing Forming Bread molders Pie and biscuit farmers Confectionery molders Separation and concentration of food components Centrifugation Filtration Expression Extraction using solvents Membrane concentration May reduce or remove DLCs No effect on DLCs No effect on DLCs No effect on DLCs No effect on DLCs No effect on DLCs May reduce or remove DLCs (adsorbed to surface) May reduce or remove DLCs (adsorbed to surface) May reduce or remove DLCs (adsorbed to surface) Process used for onions, may generate DLCs, but may also be washed away during process, no fat content in onions to hold DLCs No effect on DLCs No effect on DLCs No effect on DLCs No effect on DLCs No effect on DLCs Could concentrate and reduce existing DLCs in lipid and aqueous phases, respectively (e.g., milk separation, more concentrated in cream, less concentrated in skim milk) May concentrate or reduce existing DLCs May concentrate or reduce existing DLCs May concentrate existing DLCs as in fish-oil production May concentrate existing DLCs or introduce DLCs from solvent residues May concentrate existing DLCs continued

102 TABLE 4-7 Continued DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY Processing Methods Effect on DLC Levels Fermentation and enzyme technology Fermentation Enzyme technology Blanching Theory Effect on foods Pasteurization Theory Heat Sterilization In-container sterilization Ultra high-temperature (UHT)/aseptic processes Evaporation and distillation Evaporation Distillation Baking and roasting Theory Frying Shallow (or contact) frying Deep-fat frying Chilling Fresh foods Processed foods Cook-chill systems Chill storage Freezing Theory Freeze drying and freeze concentration Freeze drying (lyophilization) Freeze concentration Packaging Interactions between packaging and foods Printing Filling and sealing of containers Filling Sealing Labeling No effect on DLCs No effect on DLCs No effect on DLCs No known effect on DLCs No effect on DLCs No effect on DLCs No effect on DLCs May concentrate existing DLCs No effect on DLCs No effect on DLCs No effect on existing DLCs, could be introduced from contaminated oils or fats No effect on existing DLCs, could be introduced from contaminated oils or fats No effect on DLCs No effect on DLCs No effect on DLCs No effect on DLCs No effect on DLCs May concentrate existing DLCs May concentrate existing DLCs May introduce DLCs from packaging May introduce DLCs from inks and pigments No effect on DLCs No effect on DLCs No effect on DLCs

ANIMAL PRODUCTION SYSTEMS . . . . 103 Frying meats, fruits, or vegetables, unless DLCs are introduced into the food by contaminated fats and oils during frying. Processes that may alter DLC content of foods are: Heat processing of meats, which has been shown to reduce DLC levels through the loss of fats (Petroske et al., 1998; Stachiw et al., 1988~. (However, because high temperatures and other favorable conditions can produce DLCs, research should be undertaken to determine if high-tem- perature processing in baking, extrusion, puffing, and short-time, high- temperature pasteurization has an impact on DLC levels in the finished food product.) Extraction and drying during food processing, specifically, the extraction of fat or moisture. For example, a food that had its moisture content reduced would exhibit an increased DLC content as a percent by weight, even though it would contain the same total DLC content as the original food (e.g., dehydrated peas); expression of oils from food products may concentrate DLCs from the original intact food into the oil intended for consumption (e.g., fish oil production); and certain forms of extraction using solvents may concentrate existing DLCs or may introduce them from solvent residues. Separation of raw milk, during which existing DLCs will be reduced in the skim milk (aqueous phase) and increased in the cream (lipid phase). (Products made from skim milk and standardized low-fat milk will have lower DLC concentrations than those produced with full-fat milk or cream. Products with a higher fat content, such as cheese, in which much of the aqueous content has been removed in the form of whey, would have a relatively higher DLC concentration than the same volume of food with more water and less fat content.) Trimming and cutting fat from meat products, similar to extraction, re- duces the DLC content of the prepared food. Filter processing may involve the use of filtering agents that contain DLCs and therefore could become a source of food contamination. Ex- amples include the frequently cited ball-clay incident in chicken feeds (Hayward et al., 1999) and the identification of 1,2,7,8-tetrachlorodi- benzofuran (TCDF) and 2,3,7,8-TCDD as low-level contaminates intro- duced into coffee filter papers in Japan (Hashimoto et al., 1992~. (Cur- rently, maximum levels of PCDDs and PCDFs in filter paper have been established at 0.00038 to 3.6 pg TEQ/g of paper, with about one-third of the total PCDD and PCDF contamination being eluted from the filter paper during coffee brewing. Hot water elutes low levels of DLCs; there- fore, the existing low level of contamination could be avoided by rinsing the filter prior to use.)

104 DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY Food safety food-processing procedures such as irradiation, ozonation, ultra- violet light, sunlight, and chlorination have not been examined for their impacts on DLC levels. Packaging With the exception of fresh vegetables, virtually all foods sold to the public are packaged. Generally, the packaging material is glass, metal, paperboard, or films. Paperboard may also have a film layer. Films may be made from various density polymers or flexible metals of several layers, which support moisture control, migration of specific molecules, gas barriers, physical support, and pack- age labeling and graphics. There are no reported incidences of glass or metal packaging that alter DLC levels in the products they contain. Furthermore, there is no reason to suspect they would alter DLC levels given their composition and stability. There have been incidences of chemicals migrating from paperboard pack- aging to foods (Cramer et al., 1991; Garattini et al., 1993; LaFleur et al., 1991; Ryan et al., 1992~. Other researchers have attempted to predict this migration (Chung et al., 2002; Franz, 2002; Furst et al., 1989~. The Dow Chemical Com- pany has undertaken the development of analytical methodology capable of de- tecting the presence of 2,3,7,8-TCDD and 2,4,7,8-TCDF in low-density polyeth- ylene matrices at concentrations between the range of 200 and 400 parts per quadrillion (Nestrick et al., l991~. Other analytical methods, currently in use, are discussed in Chapter 2. While attention regarding human exposure to DLCs has concentrated on the ingestion of animal products as the most likely source of human exposure, food processing and packaging might play a minor role DLC contribution. IMPORTED FOODS Food imports to the United States have increased steadily in the last two decades (see Table 4-8~. The average share of imports in U.S. food consumption has risen from 6.8 percent to 8.8 percent. Consumption of imported cereal, fruits, and vegetables has risen from 10 to 12 percent since the early 1980s, and im- ported animals product (including fish and seafood) consumption has risen from 3 to 4 percent (Jerardo, 2002~. More reliable sources, reversed seasonality, im- proved shipping and storage technology, wider ethnic food preferences, and vari- ous economic factors have contributed to these trends. As import shares increase, ensuring the safety of the U.S. food supply be- comes more challenging. The U.S. government regulates and monitors, from farm to table, the production, processing, and transportation of foods produced in the United States. The targeted monitoring and regulation of the overseas produc- tion of foods destined for the United States, while theoretically possible, would

ANIMAL PRODUCTION SYSTEMS TABLE 4-8 Summary of Import Shares of U.S. Food Consumption (%)a 105 Years Food Groups 1981-1985 1986-1990 1991-1995 1996 1997 1998 1999 2000 Total food consumption 6.8 7.3 7.4 8.1 8.5 8.8 8.8 8.8 Animal productsb 3.2 3.4 3.2 3.2 3.2 4.0 4.2 4.2 Red meat 6.7 8.1 7.3 6.4 7.1 7.7 8.2 8.9 Dairy products 1.9 1.8 1.9 2.0 1.9 2.9 2.9 2.7 Fish and shellfish 50.9 56.0 56.0 58.5 62.1 64.7 68.1 68.3 Animal fat 0.5 0.7 1.4 1.4 2.3 2.3 2.5 2.8 Crops and productsC 9.9 10.6 10.6 11.9 12.5 12.4 12.1 12.3 Fruits, juices and nuts 12.0 16.5 15.5 14.9 16.7 16.9 18.2 18.7 Vegetables 4.8 6.1 5.9 7.8 8.0 9.0 8.9 8.8 Vegetable oils 15.7 19.7 19.3 19.2 20.9 21.0 17.9 20.2 Grain cereals 1.6 3.1 6.7 7.2 7.0 7.4 6.5 6.3 Sweeteners and candy 19.8 9.8 9.1 14.8 14.8 10.4 8.5 8.0 aCalculated from units of weight, weight equivalents, or content. bImport shares of poultry and eggs are included, but negligible. Red meats are estimated from carcass weights. CIncludes coffee, cocoa, and tea for which import shares are 100 percent. Also includes crop content of beer and wine. DATA SOURCE: Jerardo (2002). tax the system beyond its capacity. There is significant variation in DLC environ- mental contamination levels and agricultural, processing, and packaging prac- tices among countries. Some monitoring programs, such as FDA's Total Diet Study, may include some imported foods; however, the country of origin is not currently documented. As a result, current food safety laws require that imported foods meet the same safety standards as domestically produced foods, although it is difficult to specu- late on the relative levels of contaminants in imported foods. Mirroring the differences in their domestic control programs, FDA and USDA's Food Safety and Inspection Service (FSIS) rely on different systems to reach food safety goals. FDA relies primarily on physical inspection and chemi- cal analysis of port-of-entry samples of a small proportion of imported foods, particularly from those countries where food safety systems do not meet U.S. standards. FSIS enforces the Federal Meat Inspection Act, the Poultry Products Inspection Act, and the Egg Products Inspection Act. These laws are applicable to domestic and imported products, which must meet the same standards for safety, wholesomeness, and labeling. Meat, poultry, and egg products may be imported into the United States only from countries that FSIS has evaluated and found to have equivalent science- based systems of food inspection that include mandatory HACCP processing

106 DIOXINS AND DIOXIN-LIKE COMPOUNDS IN THE FOOD SUPPLY systems. The equivalence evaluation process has two parts: analysis of an appli- cation from a prospective exporting country followed by an on-site audit in the applicant country. Once a country is deemed to be equivalent, it may certify establishments for export to the United States. FSIS verifies the continuing equivalence of exporting countries through annual on-site audits of foreign in- spection systems and daily port-of-entry inspections in the United States. All shipments of imported meat, poultry and egg products are reinspected by FSIS at ports-of-entry. Each shipment is inspected for proper documentation and condition of containers. Additional types of inspection may be made on randomly selected individual lots of product, including product examinations for physical defects or laboratory analyses for chemical residues or microbiological contami- nation. Products that fail FSIS inspection are refused entry to the United States and must be reexported, reconditioned (if approved by FSIS), converted to non- human food use (if approved by FDA), or destroyed under FSIS supervision. Absent a system for monitoring DLCs in imported foods, reduction of expo- sure from this food source will be difficult to achieve. Testing for DLCs, espe- cially in animal products, must rely on the standard domestic surveillance pro- grams. Since there are no current standards for allowable DLC levels in foods, rejection of those sampled foods that are determined to be high in DLCs can only be based on pesticide limits set in or on raw agricultural commodities. Other potential interventions are not applicable to imported foods. SUMMARY As stated in the introduction, DLCs are undesirable contaminants in the environment that serve no beneficial purpose and have a number of adverse biological effects in a wide variety of organisms, including humans. The focus of this chapter has been on identifying and describing DLC entry into agricultural pathways and subsequent exposure of the general U.S. population, as illustrated in Figure 4-1. Individuals or specially identified groups may be exposed to higher or lower DLC levels through alternative pathways, and it is possible that an unintended release or production of DLCs could result in high levels of contami- nation in any one of these pathways. Terrestrial and aquatic animal management practices, animal feed formula- tions, and food processing and packaging present the primary potential interven- tion opportunities. Because of the reuse of animal products through feed manu- facturing and the potential for bioconcentration of DLCs, animal feed practices may be especially important in reducing exposure to DLCs through foods.

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Dioxin and dioxin-like compounds, or DLCs, are found throughout the environment, in soil, water, and air. People are exposed to these unintentional environmental contaminants primarily through the food supply, although at low levels, particularly by eating animal fat in meat, dairy products, and fish. While the amount of DLCs in the environment has declined since the late 1970s, the public continues to be concerned about the safety of the food supply and the potential adverse health effects of DLC exposure, especially in groups such as developing fetuses and infants, who are more sensitive to the toxic effects of these compounds.

Dioxins and Dioxin-like Compounds in the Food Supply: Strategies to Decrease Exposure, recommends policy options to reduce exposure to these contaminants while considering how implementing these options could both reduce health risks and affect nutrition, particularly in sensitive and highly exposed groups, if dietary changes are suggested.

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