Food chain and

CHLORINATED HYDROCARBONS Hydfoearbons containing ehlorine atoms, e.g. triehloroethylene. Some of these ehemieals aeeumulate in the food chain and do not readily degrade. Some plastics which contain certain chlorinated hydrocarbons release dioxins into the ah, when burnt at low temperatures. 

Generally, the main pathways of exposure considered in tliis step are atmospheric surface and groundwater transport, ingestion of toxic materials that luu c passed tlu-ough the aquatic and tcncstrial food chain, and dermal absorption. Once an exposure assessment determines the quantity of a chemical with which human populations nniy come in contact, the information can be combined with toxicity data (from the hazard identification process) to estimate potential health risks." The primary purpose of an exposure assessment is to... 

Fish from Lake Erie are generally the least contaminated of all the Great Lakes IS), It has been speculated that contaminants in a more advanced eutrophic system become masked or removed by sedimentation within the food chain and have less opportunity to reach higher trophic levels 24), The management implications of this interaction between nutrient and contaminants needs to be further elucidated. 

In Chapter 3, the distribution of enviromnental chemicals through compartments of the gross environment was related to the chemical factors and processes involved, and models for describing or predicting environmental fate were considered. In the early sections of the present chapter, the discnssion moves on to the more complex question of movement and distribntion in the living environment— within individuals, communities, and ecosystems—where biological as well as physical and chemical factors come into play. The movement of chemicals along food chains and the fate of chemicals in the complex communities of sediments and soils are basic issues here. 

Processing has become an important part of the food chain and many types of food products can be fonnd on the market, allowing the population to choose... 

Limitations need to be carefully considered before selecting this method for site remediation. These include the depth of contamination, the total length of time required for cleanup to below accepted limits, potential contamination of vegetation and the food chain, and difficulty in establishing and maintaining vegetation at some polluted sites.8... 

The fact that HBCD is found in fish indicates that it is also bioavailable. However, the low fish to sediment ratio (below 1) does not agree with the high ratios reported by Sellstrom et al. [29] for pikes from a Swedish River. Pike is a predator at the top of the food chain and the higher fish to sediment ratio in this specie could indicate the biomagnification of this compound through the aquatic trophic chain. 

Cadmium biomagnifies in terrestrial food chains and tends to accumulate in liver and kidneys of older apex organisms (Scheuhammer 1987). This process was documented in the chain of soil to vegetation to invertebrates to upper trophic level consumers, including roe deer (Capreolus capreolus), bam owls (Tyto alba), weasels (Mystela nivalis), and kestrels (Falco tinnunculus Gorree... 

No biomagnification of chromium has been observed in food chains, and concentrations are usually highest at the lowest trophic levels... 

Post, J.R., R. Vandenbos, and D.J. McQueen. 1996. Uptake rates of food-chain and waterborne mercury by fish field measurements, a mechanistic model, and an assessment of uncertainties. Canad. Jour. Fish. Aquat. Sci. 53 395-407. 

PAHs are widely distributed in the environment as evidenced by their detection in sediments, soils, air, surface waters, and plant and animal tissues. However, the ecological impact of PAHs is uncertain. PAHs show little tendency for bioconcentration despite their high lipid solubility (Pucknat 1981), probably because most PAHs are rapidly metabolized. Sims and Overcash (1983) list a variety of research needs regarding PAHs in soil-plant systems. Specifically, research is needed to establish the rates of PAH decomposition in soils the soil PAH levels above which PAH constituents adversely affect the food chain and enhancement factors that increase degradation rates of PAHs, especially PAHs with more than three rings. Once these factors have been determined, PAH disposal into soils may become feasible at environmentally nonhazardous levels. 

Although the sequestration by plants immobilizes As, it may also facilitate its entry into the food chain and provide an exposure pathway to animals. 

Biologically available organic contaminants may find their way into the food chain and be toxic, but they are also more easily decomposed and are thus removed from the environment. Slowly decomposed biologically available organic compounds, such as pesticides, may have long lifetimes in soil and thus pose a hazard to animals and humans. Biologically unavailable compounds, such as tars, produce undesirable characteristics in soil, such as water... 

The environmental impact of a new product needs to be assessed before it can be released for general use. Chemicals released into the environment can enter the food chain and be concentrated in plants and animals. Aquatic ecosystems are particularly sensitive, in this respect, since chemicals, when applied to agricultural land, can be transported in the ground water to rivers and then to the lakes, where they can accumulate in fish and plant life. The ecokinetic model presented here is based on a simple compartmental analysis and is based on laboratory ecosystem studies (Blau et ah, 1975). The model is useful in simulating the results of events, such as the accidental spillage of an agrochemical into a pond, where it is not ethical to perform actual experimental studies. 

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