Fish consumption advisories

While methylmercury occurs naturally in tlie environment, it is reasonable to expect that methylmercury levels have increased in modem times as a result of increased inorganic mercury concentrations. Whether methylmercmy concentrations have increased to a similar extent as inoiganic mercuiy is not known. It is clear, however, that elevated fish mercuiy concentrations can currently be found in remote lakes, rivers, reservoirs, estuaries, and marine conditions, typically in predators such as sportfish at the top of food webs. As of 2003, 45 states had fish consumption advisories related to mercuiy, and 76% of all fish consumption advisories in the United States were at least partly related to mercury (USEPA 2004a). The number of advisories is increasing with time, although this is due at least partly to more sites being sampled (Wiener et al. 2003). 

Relevance. A key criterion in the selection of biological indicators is relevance to human and ecological health and to the development of policy. Fish are directly relevant, for example, given that consumption of fish is the primary pathway for exposure to MeHg. The concentration of MeHg in fish is also a key variable in the issuance of fish-consumption advisories. 

In the United States, the threshold mercury concentration for commercial sale of fish is determined by the Food and Drag Administration, whereas consumption advice for recreational (noncommercial) fish is developed by individual states and tribes. Mercury data collected for development of fish-consumption advisories are typically from analyses of filets (axial muscle tissue, with or without skin) for total mercury, with concentrations expressed on a wet-weight basis. Analysis of filets for total mercury yields a valid estimate of MeHg concentration (Grieb et al. 1990 Bloom 1992), whether the analyzed sample consists of a large filet or a small mass of tissue obtained with a biopsy needle (Cizdziel et al. 2002 Baker et al. 2004). 

Long-range atmospheric transport of Hg from fossil fuel combustion and solid waste incineration has increased Hg in freshwater and biota. In the United States, combustion of fossil fuels for power generation is estimated to generate about 30% of the total release of Hg into the atmosphere (Harriss and Hohenemser, 1978). One in every three lakes in the United States and nearly one-quarter of the nation s rivers contain various pollutants, including Hg (CNN, 2004). Forty States in the U.S. have issued advisories for methylmercury on selected water-bodies, and 13 states have statewide advisories for some or all sportfish from rivers or lakes (USGS, 2000). Fish consumption advisories for methylmercury account for more than three-quarters of all fish consumption advisories. 

Fish consumption advisory (mg total Hg/kg FW edible aquatic product) ... 

EPA. 1995b. The national listing of fish consumption advisories and bans. Washington DC U.S. Environmental Protection Agency, Office ofWater. EPA-823-C-95-001. 

The high BCF values observed for chlordecone (>60,000) indicate that the compound will be found in high concentrations in aquatic organisms that dwell in waters or sediments contaminated with chlordecone. Chlordecone has been detected in fish and shellfish from the James River, which empties into the Chesapeake Bay, at levels in the pg/g (ppm) range. There is currently a fish consumption advisory in effect for the lower 113 miles of the James River. Chlordecone residues were detected in foods analyzed from 1978-1982 and 1982-1986 as part of the Food and Drug Administration (FDA) Pesticide Residue Monitoring Studies. Chlordecone was detected in one of 27,065 food samples analyzed by 10 state laboratories, but was not detected in the more recent FDA Pesticide Residue Monitoring Studies from 1986 to 1991. No information on the specific foods in which residues were found or levels detected was located. 

Mirex contamination has triggered the issuance of several human health advisories nationwide. As of September 1993, mirex was identified as the causative pollutant in eight fish consumption advisories in three different states. This information is summarized below (RTI 1993) ... 

Shubat, P.J., Raatz, K.A. and Olson, R.A., Fish consumption advisories and outreach programs for Southeast Asian immigrants, Toxicol. Ind. Health, 12, 3-4, 427, 1996. 

Since chloroform is highly volatile and shows little tendency to bioconcentrate or bioaccumulate in higher life forms such as fishes, it is not ordinarily included in the types of persistent pollutants that are the focus of state fish consumption advisory programs. Information from HazDat (1996) does document detections of chloroform in tissues from fishes from at least 3 current or past NPL sites. 

In addition to individuals who are occupationally exposed to 3,3 -dichlorobenzidine (see Section 5.5), there are several groups within the general population that have the potential for exposures to 3,3 -dichloro-benzidine at levels above those of the general population. These groups include individuals living in proximity to sites where 3,3 -dichlorobenzidine was produced or sites where 3,3 -dichlorobenzidine was disposed, and individuals living near one of the 32 NPL hazardous waste sites where 3,3 -dichloro-benzidine has been detected in some enviromnental media (HazDat 1998). 3,3 -Dichlorobenzidine was not detected in fish samples obtained from rivers near nine textile dyestuff manufacturers known to use 3,3 -dichlorobenzidine-based pigments (Diachenko 1979), nor were there any fish consumption advisories for 3,3 -dichlorobenzidine in 1996. Therefore, recreational and subsistence fishers are not at risk. 

More recently, several authors studied the possible association between fish consumption and levels of PFCs in human blood [138], as well as the evaluation of the risk associated with fish consumption [73, 139]. In recognition of the potential for human exposure to PFCs via fish consumption, the Minnesota Department of Health has issued fish consumption advisories for contaminated sections of the Mississippi River (Minnesota Department of Health 2007). This advisory suggests that people limit their intake of fish to no more than one meal a week if PFOS levels in fillet exceed 38 ng/g. 

The primary concern with organic mercury is methyl mercury in fish. Children and women of childbearing age should be cautious about consuming fish known to accumulate mercury such as tuna, shark, swordfish, and pike. Local fish consumption advisories should be followed. 

The primary human exposure to methyl mercury is from consumption of contaminated fish. The most sensitive population is the developing fetus or infant due to the effects of methyl mercury on the nervous system (neurotoxic) and developmental effects. Exposure limits and fish consumption advisories are directed at pregnant women, women of childbearing age, and children. All agencies also recognize that fish consumption has many nutritional benefits and is an important part of many people s diet. Nevertheless, the widespread distribution of mercury and subsequent bioaccumulation of methyl mercury requires that many agencies have developed recommendation for levels of mercury in fish. Below is a list of some of these recommendations, but it is very important to consult the local fish consumption advisories. 

Much of our current understanding of these impacts arose from research on wildlife and human populations within the Great Lakes basin. Despite being banned in North America more than 25 years ago, the toxicological risks from PCB exposure are still a present-day concern. For example, current PCB concentrations in fish in the Great Lakes are sufficiently large as to drive the need for fish consumption advisories for sport fish and to restrict commercial fisheries. 

The continued elevated concentrations of PCBs in sport fish in the Great Lakes necessitates that fish consumption advisories be issued by all of the US Great Lakes states and the Canadian provinces of Ontario and Quebec. Unlimited consumption is not advised until fish tissue concentrations decline below 0.05 igg 1 (ww), a level not expected to be reached for many decades (see Sect. 8). Thus PCBs will be of significant concern well into the future. 

The elevated toxaphene levels in Lake Superior have social and economic impacts as well. The 2003 Guide to Eating Sport Fish published by the Ontario Ministry of Environment and Energy [158] indicates fish consumption advisories for Lake Superior lake trout due to toxaphene levels. As a result of the high toxaphene levels, the Ontario Ministry of Natural Resources has restricted sale with Ontario (but not the export) of large lake trout harvested from Lake Superior as of 1995. An assessment of toxaphene levels in Lake Superior fish fillets by Health Canada concluded that consumption of lake trout, salmon, longnose sucker and whitefish muscle from northwestern areas of the lake should be limited to one or two meals per month (55-135 g/week) based on a provisional tolerable daily intake of 0.2 pg/g body wt/day [159]. 

These results have significant economic implications for commercial fishers and for aboriginal peoples in the region who depend on the fishery as a major food source. In the United States no consumption of fish with greater than 4.8 xg/g wet weight is recommended based on noncancer health endpoints or 0.18 xg/g (ww) based on cancer endpoints [160]. As of December 1998 there were six fish consumption advisories for toxaphene in the USA, but they were all for locations in the southern states [ 160]. No toxaphene advisories for Great Lakes fish consumption have been issued by the Great Lakes states. 

Ginsberg, G.L., and B.F. Toal. 2000. Development of a single meal fish consumption advisory for methyl mercury. Risk Anal. 20(l) 41-47. 

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