Contaminants in fish: risk-benefit considerations.

Fish provide a healthful source of dietary protein and are high in nutrients such as omega-3 fatty acids. There is evidence of beneficial effects of fish consumption in coronary heart disease, stroke, age-related macular degeneration, and growth and development. Yet, benefits may be offset by the presence of contaminants, such as methylmercury (MeHg), dioxins, polychlorinated biphenyls (PCBs) and several other halogenated persistent organic pollutants. MeHg is a known developmental neurotoxicant, as evidenced by several animal studies and episodes of human intoxication in Japan and Iraq. Fish represent the main source of exposure to MeHg for the general population, and large predatory fish (swordfish, tuna) have the highest levels of MeHg contamination. Provisional tolerable weekly intakes of 0.7 microg kg(-1) to 1.6 microg kg(-1) have been set by regulatory agencies. Concern for contamination of fish with dioxins and dioxin-like PCBs stems from their reported carcinogenicity, immunotoxicity, and reproductive and developmental toxicities. Farmed and wild-caught fish appear to have similar levels of contaminants. Advisories are in place that recommend limited consumption of certain fish in children, pregnant women and women of childbearing age. Careful risk-benefit considerations should foster fish consumption while minimizing exposure to toxic contaminants.