Groundwater contaminants, exposure

Constan AA, Yang RSH, Baker DC, et al. 1995. A unique pattern of hepatocyte proliferation in F344 rats following long-term exposures to low levels of a chemical mixture of groundwater contaminants. Carcinogenesis 16 303-310. 

The fact that endrin is no longer produced or used in the United States greatly reduces the potential for human exposure. Future levels of endrin, endrin aldehyde, and endrin ketone in environmental media are expected to be low. The most significant route of exposure is most likely ingestion of imported foods contaminated with endrin however, there may also be some localized risks from exposures near waste disposal sites or from groundwater contaminated with endrin. 

Members of the general population with potentially high exposure to 1,2- dibromoethane include individuals living near the nine NPL sites currently known to be contaminated with the compound. The size of the population and the concentrations of 1,2-dibromoethane in all of the contaminated media to which these people are potentially exposed have not been completely characterized. Other populations with potentially high exposures to 1,2-dibromoethane include individuals in the six states with confirmed groundwater contamination, and workers involved in the manufacture and continued use of 1,2-dibromoethane. 

Exposure of the general population to fuel oils is most likely to occur as a result of the use of kerosene and other fuel oils in heaters, furnaces, and combustion engines. Spills of number 2 fuel oil in residential basements can pose a significant health risk a spill of 21 gallons would present a risk for 8 days or longer (Kaplan et al. 1993). Unintentional exposure to fuel oils may occur as a result of groundwater contamination from spilled fuel oils or contact with soils that have been contaminated with fuel oils. 

Hutchins et al. 1980 Oliveira and Sitar 1985 Ram et al. 1985 Sawhney and Kozlowski 1984 Stuermer et al. 1982 Weber and Matsumota 1987) only (sources of groundwater contamination include hazardous waste sites). Data describing the exposure levels in air and surface water are lacking. It is not clear whether monitoring studies were not performed, or were not found. Quantified levels of cresols in food are also lacking. Estimates of human intake are not available. 

Information on nickel exposure from hazardous waste sites is lacking. The most probable route of exposure from hazardous waste sites would be dermal contact, inhalation of dust, and ingestion of nickel-contaminated soil. Groundwater contamination may occur where the soil has a coarse texture and where acid waste, such as waste from plating industries, is discarded. People using this water may be exposed to high levels of nickel. 

Hsieh GC, Parker RDR, Sharma RP, et al. 1990. Subclinical effects of groundwater contaminants. III. Effects of repeated oral exposure to combinations of benzene and toluene on immunologic responses in mice. Arch Toxicol 64(4) 320-328. 

Risk is the probability of harm or loss and can be considered to be a product of the probability and the severity of specific consequences. Risk, as it relates to hazardous wastes and groundwater contamination, may be defined as the chance that humans or other organisms will sustain adverse effects from exposure to these environmental hazards. Risk is inherent in the life of all organisms—humans, animals, and plants. Tornadoes, landslides, hurricanes, earthquakes, and other natural disasters carry a risk of injury or death to any living thing in their path. Similarly, human-caused risks such as automobile accidents, plane crashes, and nuclear disasters occur with varying levels of severity. 

In some cases, direct measurements of contaminant exposure may be made, such as in the assessment of the steady-state release of an established hazardous waste source. Groundwater monitoring wells or air-sampling devices can be used to determine current exposure concentrations for exposed populations. Commonly, however, air, surface water, and groundwater sampling is neither a logical nor a practical choice. Typical situations in which sampling is not feasible include (i) the evaluation of future exposme and risk to potentially exposed populations and (ii) the potential risk from an event that has yet to occm (e.g. a hazardous waste spill). 

Cyfluthrin is a photosensitive compound and following exposure to sunlight, it readily breaks down. It is highly immobile in soil and unstable in water. On soil surfaces its half-life is 2-3 days. Under anaerobic conditions, its half-life in soils is 2 months. Cyfluthrin does not move through soils and is not a groundwater contaminant. It rapidly breaks down in surface waters as it floats on the surface where it is subject to photodegradation. 

Investigation of potential human exposure to groundwater contaminants through development of a water-distribution model specific to township of interest... 

A.D. Kligerman, R.E. Chapin, G.L. Erexson, D.R. Germolec, P. Kwanyuen, R.S.H. Yang. Analyses of cytogenetic damage in rodents following exposure to simulated groundwater contaminated with pesticides. Mutation Research, Vol. 300, pgs. 125-134,1993. 

EPA has regulated many pesticides on the basis of carcinogenic potential. Dietary residues command a great deal of attention, but other issues, such as groundwater contamination, consumer or worker exposure, and Agency resources, also profoundly... 

Table VII. Immune Functions in B6C3Fi Mice Affected by Exposure to a Chemical Mixture of Groundwater contaminants...

Table VIII. Enhancement of Carbon Tetrachloride Hepatotoxicity in Male Fischer 344 Rats by Prior Exposure to a Mixture of 25 Groundwater Contaminants... 

The transport of contaminants in soil gas and groundwater represent major pathways of contaminant exposure to humans or sensitive ecosystems. The vadose zone treatment methods discussed previously exert control over further contaminant release to soil gas when applied and monitored carefully. 

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