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Understanding Health Effects of Incineration
Pages 112-181

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From page 112...
... Of these tools, all of which contribute to our understanding, risk assessment methods have provided the most-detailed information for regulatory decisionmakers. Although past regulatory risk assessments have suggested that the risks posed by emissions from a well-run incinerator to the local community are generally very small, the same may not be true for some older or poorly run facilities.
From page 113...
... Particulate matter, CO, lead, and acidic gases and acidic particles have been under regulatory scrutiny for the longest period. Typically, there are well-defined statutory limits on their emission rates or allowable ambient concentrations or increments in ambient concentrations under federal or state statutes.
From page 114...
... TOOLS FOR EVALUATING HEALTH EFFECTS Whenever searching for small or subtle health effects of exposures to environmental contaminants, it is best to use a variety of approaches and to critically compare their results. The primary tools that have been used include epidemiologic studies and risk assessments.
From page 115...
... The procedures used to perform risk assessments vary widely, from a snap judgment to the use of complex analytic models. However, risk assessments of incineration or incineration facilities have become more structured and formalized, following the four-step paradigm described in previous NRC reports (NRC 1983, 1994~.
From page 116...
... . Most of the effort of individual risk assessments has gone into the evaluation of exposure, which is the third step in the risk-assessment paradigm.
From page 117...
... A complete risk characterization should also contain a full discussion of the uncertainties associated with the estimates of risk. Risk assessment of waste incineration facilities can involve the following aspects: Measurement or estimation of emission rates from specific facilities.
From page 118...
... . Because of the variability and uncertainty, most risk assessments have not been designed to quantify actual health risks; rather they have been designed solely for regulatory purposes to yield upper-bound estimates of health risks that may be compared to regulatory criteria.
From page 119...
... of Exposure or Effect There is now considerable interest in the use of biologic markers of exposures or effects in epidemiologic studies of the health risks posed by some occupational and environmental exposures (NRC 1989a,b, 1992a,b, 1995~. Some of these studies are relevant to likely exposures to substances emitted from incinerators for example, measurements of specific congeners of PCDDs and PCDFs in blood and adipose tissues of exposed workers (Schecter et al.
From page 120...
... In general, information is rather sparse on the relationship between human exposure to pollutants released to the environment by incinerators and the occurrence of health effects. Studies of Local Populations In one of the earliest epidemiologic studies of populations in the vicinity of waste incinerators, Zmirou et al.
From page 121...
... A positive methacholine-challenge test was found in 9 of the former and only 1 in the latter group. The authors concluded that "the high level of air-pollution" in the population close to the incinerator was associated with a detrimental effect on lung function in primaryschool children; however, they did not obtain data that would allow them to ascribe the measured air pollution to emissions from the incinerator, nor did they characterize other sources of air pollution in the target population.
From page 122...
... Concentrations of particulate matter, including PM~o and PM2 5, and of acidic gases, including SO2 and HC1, were monitored in each of the study areas and did not differ measurably between target and comparison communities, either on a daily-average or monthly-average basis. Results of baseline lung-function
From page 123...
... Thus, the few community-based epidemiologic studies reported to date have yielded no evidence that acute or chronic respiratory symptoms are associated with incinerator emissions. However, that conclusion is based on only two community studies, that of Gray et al.
From page 124...
... Exposures and cancer risks were assessed at the aggregate, or "ecological" level. No data were obtained that would allow linking of individual exposure to cancer risk.
From page 125...
... When urinary-mutagen frequency was adjusted for age, cigarette-smoking, fried-meat consumption, alcohol use, and use of a wood stove in the home, the frequency of urinary mutagens in incinerator workers was found to be a factor 9.7 times as high as the comparison group of water-treatment plant workers when the assay was performed without microsomal activation and 6.3 times as high with microsomal activation. Mutagens were present in urine of workers at 4 of the 7 incinerators and only 1 of the 11 water-treatment plants.
From page 126...
... The other is that exposures to mutagenic substances in incinerator plants was highly variable. The authors pointed out that the presence of mutagens in the urine does not establish that mutations are taking place in the cells of these workers, but they did recommend that measures be taken to reduce occupational exposures of incinerator workers to potential mutagens in their work environments.
From page 127...
... A1though the average blood-lead concentration (11.0 ,ug/dL) of the incinerator workers was not high relative to concentrations associated with clinical abnormalities, they were statistically significantly higher than the average (7.4 ,ug/dL)
From page 128...
... The results suggest that the presence of lead in combustion-chamber fly ash can increase the blood-lead concentrations of incinerator workers. Only two morbidity or mortality studies of waste-incinerator workers have been reported.
From page 129...
... RESULTS FROM RISK ASSESSMENT STUDIES There have been hundreds of risk assessments performed on incinerators of various types in many parts of the country. These assessments have taken various forms and followed various protocols.
From page 130...
... Risk assessments have as one of their bases an evaluation of the health effects observed for the materials examined in risk assessment. A fundamental tenet of risk assessment is the ability to perform extrapolations, including extrapolations of dose-response results for health effects observed at different concentrations, in differing exposure circumstances, and even in different species.
From page 131...
... Concern about airborne particulate matter in recent years has been driven largely by epidemiologic studies that have reported relatively consistent associations between outdoor particulate-matter levels and adverse health effects. However, assessing the specific health risks resulting from exposures to airborne particulate matter, and distinguishing these effects from those produced by gaseous copollutants, involves substantial scientific uncertainty about the influence of copollutants and weather, about whether some particulate-matter fractions (size or chemical)
From page 132...
... , particularly those with pre-existing respiratory disease, were found to have higher risks than younger adults (Thurston 1996~. Studies suggest that children are also at increased risk from the adverse health effects of air pollution.
From page 133...
... were reported, and only high concentrations of TSP or PM~o were associated with respiratory symptoms of asthma, chronic bronchitis, or emphysema. However, a more recent analysis using an additional 5 years of follow-up on this cohort and improved PM~o exposure estimates did predict significant PM-mortality associations among men in this cohort, who reportedly spent significantly more time outdoors than women (Abbey et al.
From page 134...
... Acidic Gases and Acidic Aerosols Nitrogen Oxides Nitric oxide (NO) is the major nitrogenous pollutant emitted from incineration facilities.
From page 135...
... 1994. Relative-risk estimates per 10 ,ug/m3 from these studies were 1.11 and 1.03, respectively.
From page 136...
... Concern with respect to present-day ambient concentrations of NO2 is focused primarily on increases in airway responsiveness of asthmatic people after short-term exposures and increased occurrence of respiratory illness among children associated with long-term exposures to NO2 (EPA 1993~. Hydrogen Chloride The irritating properties of hydrogen chloride (HC1)
From page 137...
... However, more recent studies provide evidence that strongly acidic aerosols can constitute a portion of PM that is especially associated with acute respiratory health effects in the general public (Thurston et al.
From page 138...
... , which occur roughly 2 or 3 times per year in eastern North America. The studies provide evidence that present-day strongly acidic aerosols might represent a portion of PM that is contributing to the significant acute respiratory health effects noted for PM in the general public.
From page 139...
... Asthmatic subjects appear to be more sensitive than healthy subjects to the effects of acidic aerosols on lung function, but reported effective concentrations differ widely among studies (EPA 1986b)
From page 140...
... Results of human and animal studies that examined the health effects of these metals are discussed below. It should be noted that for many of the health effects of concern, exposures are uncertain or unknown and are related not to incinerators but rather to occupational studies or case reports of accidental spills or releases.
From page 141...
... The major toxic effects are acute and chronic inflammation of the respiratory tract, renal tubular effects, and lung cancer. In general, respiratory effects occur after cadmium exposures that are usually seen only in occupational settings, and environmental exposures to cadmium are unlikely to result in acute or chronic respiratory disease.
From page 142...
... The health effects of cadmium compounds in humans are summarized in Table 5-2. Lead Lead has been studied more thoroughly than any of the other pollutants of concern in connection with waste incineration.
From page 145...
... 145 s ~ ^ me .
From page 146...
... No threshold for such effects can yet be demonstrated. Other well-documented effects of lead exposure at blood-lead concentrations above 40 ,ug/dL in humans are renal impairment, hematologic effects, cardiovascular effects (including high blood pressure)
From page 147...
... Several toxic effects appear to have different thresholds of exposure, and some have no clearly defined safe exposure (that is, no identifiable threshold exposure)
From page 148...
... Such toxic effects at high exposures might reflect the high affinity of mercuric mercury for sulfhydryl groups. Results of animal studies support a concern for the necrologic, renal, developmental and reproductive, and respiratory effects of mercury exposure in humans.
From page 151...
... Occupational exposures of humans to chromium mainly Cr(VI) compounds have caused ulceration and perforation of the nasal septum; respiratory tract irritation; sensitization of the respiratory tract, skin, and mucous membranes; and increased risk of lung cancer.
From page 153...
... 153 Cal ·_4 Cq C)
From page 155...
... Epidemiologic data have suggested an increased risk of lung cancer associated with occupational exposures to beryllium. Results of a recent study that accounted for smoking habits and used an appropriate unexposed comparison group showed an increased risk of lung cancer among exposed people (Steenland and Ward 1991~.
From page 157...
... 1991~. Specifically, an excess of respiratory cancer was reported, as was a suggested increased risk of connective, soft tissue, and lung cancers.
From page 158...
... A variety of animal studies have shown that TCDD and its structurally related compounds affect female reproduction (Kociba et al. 1976; Barisotti et al.
From page 159...
... Occupational studies have been inconclusive regarding the association of PCB exposure and cancer risk (ATSDR 1998c)
From page 160...
... Because of confounding factors, including exposure to DDT and other organochlorine pesticides, the adverse developmental effects reported in these studies cannot be attributed specifically to PCB exposure. Effects of PCBs observed in experimental animals are generally consistent with the human data.
From page 161...
... POPULATIONS AT RISK In this section, we discuss sensitive populations and worker populations, which may be at especially increased risk because of exposure to incinerator .
From page 162...
... Sensitive populations can include those whose health is already compromised. For example, asthmatics respond to SO2 at lower concentrations than nonasthmatics (see section on Acidic Aerosols and Gases)
From page 163...
... These factors can be highly variable within the human population. The genetic variability of AAH mediated metabolic rates in the liver, for example, is in a range of a factor of several thousand, possibly leading to variability in sensitivity to toxic effects from PAH exposure.
From page 164...
... The NIOSH health hazard evaluation was undertaken after a report of increased PCDD and PCDF concentrations in a pooled blood sample from 56 municipal incinerator workers, indicating that municipal incinerator workers suffer higher exposures on the job than the general population (Schecter et al.
From page 165...
... After additional information is obtained, it is possible that a degree of concern for a particular pollutant might change. Table 5-8 shows the committee's qualitative consensus judgments of the relative degrees of concern for potential health consequences generally posed by waste incineration facilities.
From page 167...
... 167 R o R ~ be.
From page 168...
... A Single Facility and a Local Population As discussed in Chapter 4, results of environmental monitoring studies around individual incineration facilities have indicated that the specific facilities studied were not likely to be major contributors to local ambient concentrations of the substances of concern, although there are exceptions. However, methodological limitations of those studies do not permit general conclusions to be drawn about the overall contributions of waste incineration to environmental concentrations of those contaminants.
From page 169...
... Before MACT Compliance The committee is aware that incinerator emissions are expected to decrease as a consequence of improved design and operations, modifications of the waste stream, improved emission control devices, and changing waste management practices. In reviewing incineration practices and emissions data, the committee found that the data typically have been collected from incineration facilities during only a small fraction of the total number of incinerator operating hours.
From page 170...
... The following sections provide additional discussion about the levels of concern for specific pollutants. Particulate Matter Given the possible health effects of typical environmental concentrations of PM and despite considerable scientific uncertainty, the committee has a substantial degree of concern for potential effects on local populations from exposure to PM contributed by high emitting (principally older)
From page 171...
... Dioxins The committee has a substantial degree of concern for the potential health effects from exposures of plant workers to highly potent pollutants such as dioxin. There is uncertainty as to whether there is any adequate margin of safety between typical background exposures to dioxins and those with measurable responses that might be related to health.
From page 172...
... Four scales of exposure are shown because no single exposure or dose measure is known to correlate with all toxic effects, and various measures have been used in human and animal studies. The four scales are ambient air concentration, long-term average intake, adipose-tissue concentration, and serum concentration.
From page 174...
... Therefore, at the local population level, the committee has substantial concerns regarding contributions to total lead exposure by incinerators operating prior to implementation of MACT controls. Incinerators operated under MACT are expected to emit only a negligible amount of lead locally, so the potential health effects in local populations from lead after the implementation of MACT are seen as minimal.
From page 175...
... For example, frank anemia occurs at blood concentrations of 80,ug/dL or above; reduced hemoglobin synthesis occurs in adults at 50 ,ug/dL and above, although this effect might occur in children at lower concentrations; loss of hearing acuity occurs above 30,ug/dL, but hearing loss has been measured down to 10 ,ug/dL; and while the effect of lead on diastolic blood pressure is clear above 50 ,ug/dL, some studies indicate effects on systolic blood pressure above 30 ,ug/dL, and effects below 10 ,ug/dL are seen in some studies. Several effects have no apparent threshold (for example, the effects on children's cognitive function, on blood pressure, and on heme synthesis)
From page 177...
... Mercury Because low concentrations of mercury can have toxic effects, exposure of workers to mercury is of substantial concern to the committee. MACT controls are unlikely to alter the committee's degree of concern, because MACT is not designed to reduce worker exposures.
From page 178...
... Particularly strong acidic aerosols, such as those containing H2SO4, however, more readily reach into the deepest recesses of the lung and are of greater health concern at ambient concentrations. Acids released from incinerators therefore warrant a varied degree of concern depending on the form of the acid (particulate or gaseous)
From page 179...
... However, such assessments of risk under normal operating conditions may inadequately characterize the risks or lack of risks because of gaps in and limitations of existing data or techniques used to assess risk, the collective effects of multiple facilities not considered in plant-by-plant risk assessments, potential synergisms in the combined effects of the chemicals to which people are exposed, the possible effect of small increments in exposure on unusually susceptible people, and the potential effects of short-term emission increases due to off-normal operations. · Reductions in emissions will certainly reduce public health risks from direct and indirect exposure to those emissions.
From page 180...
... There is evidence that incinerator workers have been exposed to high concentrations of dioxins and toxic metals particularly lead, cadmium, and mercury in the past. · The committee's evaluation of waste incineration and public health has been substantially impaired by the lack of an adequate compilation of the associated ambient concentrations resulting from incinerator emissions.
From page 181...
... In addition to using other exposure assessment techniques, worker exposures should be evaluated comprehensively through biological monitoring, particularly in combination with efforts to reduce exposures of workers during maintenance operations. · Assessments of health risks that are attributable to waste incineration should pay special attention to the risks that might be posed by particulate matter, lead, mercury, and the dioxin and furans, due to their toxicity and environmental prevalence.


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