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A risk assessment for ingestion of toxic chemicals in fish from Imperial Beach, California
Lushenko, Mallory Arden
Quintana, PjeGersberg, RichardBiggs, Trent
Contamination of fish by heavy metals, chlorinated pesticides, and polychlorinated biphenyls (PCBs) can compromise the health of recreational and subsistence anglers consuming the fish they catch. This investigation quantified chemical contaminants in fish muscle and liver tissue samples and followed methods of the U.S. Environmental Protection Agency (EPA) to estimate the hazard indices and cancer risks associated with consuming fish caught in the waters off the Imperial Beach Pier in Imperial Beach, California. Similar risk assessment studies have been performed for other areas of Southern California but no such investigations have been undertaken for Imperial Beach. All fish samples were donated by Imperial Beach Pier anglers participating in a fishing derby on August 30, 2008. A total of 8 fish samples (3 jacksmelt, 3 mackerel, 1 yellowfin croaker, 1 white croaker) were collected and frozen until they were transported to CRG Marine Laboratories, Inc. for analysis of chemical contaminants. Different instrumentation, per the U.S. EPA methodologies, was used for the specific analytes. A mean ingestion value of 31.2 g/day and a subsistence ingestion value of 142.2 g/day were used along with the mean and maximum concentrations, respectively, to estimate the risk values for each chemical contaminant in muscle tissue. The level of exposure resulting from the consumption of each chemical in the fish tissue was estimated in an average daily dose equation. For noncarcinogenic chemicals, the average daily dose was divided by the oral reference dose, as specified by the U.S. EPA, for each chemical to estimate the hazard index. Estimation of risk for carcinogenic chemicals was calculated by multiplying the average daily dose by the cancer potency factor, also designated by the U.S. EPA. Hazard indices were calculated for organic arsenic, cadmium, chromium (VI), methylmercury, nickel, selenium, and zinc while cancer risk calculations were done for total chlordane, total DDT, individual PCB congeners detected, and total PCBs. All noncarcinogenic chemicals yielded hazard index (HI) values below 1.0, with the exception of mean and subsistence level ingestion of organic arsenic, with HI values of 1.031 and 8.103, respectively, and subsistence level ingestion of methylmercury, which had a HI of 1.424. Cancer risk calculations exceeding the U.S. EPA's acceptable risk level of 1 in 1,000,000 (or 10-6) included total chlordane at the subsistence level ingestion (1.780 x 10-6), total DDT at the mean ingestion level (7.184 x 10-6), and each PCB congener at the subsistence ingestion level (2.034 x 10-6). Inorganic arsenic at mean and subsistence ingestion levels (5.154 x 10-5 and 4.053 x 10-4, respectively), total DDT at the subsistence ingestion level (7.538 x 10-5), and total PCBs at mean and subsistence ingestion levels (1.159 x 10-5 and 5.290 x 10-5, respectively) all exceeded the U.S. EPA acceptable cancer risk as well as the California EPA's less stringent acceptable risk level of 1 in 100,000 (or 10-5). Regarding the risks of fish liver tissue consumption, the mean mass of the livers collected was 2.48 g and an assumption was made that 3 fish livers of this mass were consumed per week, yielding a mean daily intake value of 1.06 g/day. The presence of metals was not analyzed in liver tissue samples, thus only cancer risk calculations for detected chlorinated pesticides and PCB congeners were performed using the arithmetic mean chemical concentration found in the samples. Of all carcinogenic chemicals detected in the liver samples, only the total PCBs concentration yielded a cancer risk exceeding the U.S. EPA acceptable risk level, with a risk value of 2.804 x 10-6. Some of the chemicals studied, such as arsenic and mercury, occur naturally in the environment and present a "natural" risk because of their behavior in the marine environment. Due to their ban in the U.S. and decreased use in Mexico, the concentrations of the "legacy" pollutants, such as DDT andPCBs, should continue to decline to within de minimus levels over the next decade or two. The results of this study have shown that some of the chemicals analyzed exert a marginal level of unacceptable risk at present, particularly when consumed at subsistence levels; thus, it is important that continued research be conducted to better establish fish consumption data and to aid in the creation of accurate fish consumption guidelines for anglers on the Imperial Beach Pier.
Health and Human Services
Master of Public Health (M.P.H.) San Diego State University, 2010
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