Earth Materials and Health Research Priorities for Earth Science and Public Health (2007) / Chapter Skim
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5 What We Eat
5 What We Eat
Pages 83-98
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From page 83... ...
focus on soils -- the major exposure pathway between earth science and the human health issues that are associated with eating. This chapter reviews the exposure pathways represented by direct ingestion of earth material and by indirect ingestion arising from both microbial activity in soil and the trace elements and metals present in soil and other earth materials.
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From page 84... ...
or with leafy vegetables. Although eating such large quantities of soil increases exposure to essential trace nutrients, it also significantly increases exposure to biological pathogens and to potentially toxic trace elements, especially in areas associated with mineral extraction or in polluted urban environments.
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From page 85... ...
Both of these symbiotic associations improve the nutritional content of plants, contributing nitrogen, phosphorus, and trace elements. In addition, some natural soil microbes suppress plant pathogens (Press et al., 2001; Zehnder et al., 2001)
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From page 86... ...
Another important example of indirect benefits of soil microbes, and the influence of the earth sciences on what we eat, is in the efficient break down of the various organic pesticides used to enhance agricultural yields (Corona-Cruz et al., 1999; Ragnarsdottir, 2000)
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From page 87... ...
HEALTH EFFECTS OF TRACE ELEMENTS AND METALS IN EARTH MATERIALS Both toxic and beneficial trace elements are naturally present in soils as a consequence of soil parent minerals and as a result of atmospheric deposition of natural materials (e.g., volcanic ash)
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From page 88... ...
classified trace elements in agricultural soils that received sewage sludge and other wastes according to their potential for risk. At a soil pH of 6-8, the low solubilities or strong adsorptions of silver (Ag)
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From page 89... ...
. The uptake of trace elements by earthworms is principally from soil solution, rather than from food or ingested soil particles (Saxe et al., 2001)
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90 EARTH MATERIALS AND HEALTH BOX 5.2 Use of Geochemical Models for Public Health A number of models are available to characterize the equilibrium spe ciation of soil solutions, and these models can also provide data for physi ological studies of metal toxicity. Among the commonly used models in such geochemical studies are PHREEQC (Parkhurst and Appelo, 1999)
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From page 91... ...
. Improved understanding of the synergistic and/or antagonistic trace element interactions in dietary constituents is needed.
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From page 92... ...
92 EARTH MATERIALS AND HEALTH BOX 5.3 Human Health Effects of Excess Cadmium in Soil Cadmium is a nonessential trace element that has been identified as the source of a number of human health problems. The exposure pathway is generally from foodstuffs grown on soil containing elevated levels of cad mium, principally as a result of emissions from mining and smelting of ores and from the application of sewage sludge and phosphatic fertilizers to agricultural land.
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From page 93... ...
. Many ecological studies have established an inverse correlation between soil selenium levels, prostate cancer mortality, and mortality from other cancers (Clark et al., 1991; Fleet, 1997; Shamberger and Willis, 1969)
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94 EARTH MATERIALS AND HEALTH Barnes, 2001; Nelson et al., 1999) , the effect of low-selenium bioavailability on the risk of prostate cancer or benign prostatic hyperplasia (BPH)
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From page 95... ...
To determine the influence of biogeochemical cycling of trace elements in soils as it relates to low-dose chronic exposure via toxic elements in foods and ultimately its influence on human health. For example, it is well known that zinc and cadmium compete for plant uptake in soils and that zinc protects against excess cadmium uptake.
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From page 96... ...
Selenium supplementa tion (organic forms of selenium) has been shown to be helpful against poisoning from arsenic and other toxic elements in mice (Andersen and Nielsen, 1994)
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From page 97... ...
Information on the modes of occurrence of potentially toxic elements, and the textural relations on the minerals and macerals in which they occur, may help scientists anticipate the behavior of the potentially toxic compounds and metals during coal use. This type of characterization offers an opportunity for geoscientists and public health professionals to directly contribute to the resolution of a major public health issue.
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From page 98... ...
In this research, earth scientists would characterize metal abundance and metal speciation in soils and the mobility and availability of these metals to the biosphere; microbiologists would characterize the microbial populations and mechanisms that are responsible for metal species transitions in soil environments; and public health specialists would use spatial information on the distribution of metal speciation to examine the incidence of specific disease
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