The persistent environmental pollutants found in the Hudson River watershed include chemicals with potential to disrupt development of the human nervous system and to interfere with human reproduction. Pollutants of greatest concern in this region are the polychlorinated biphenyls (PCBs), organochlorine pesticides, dioxins, and methylmercury. The potential risks from exposures to these chemicals are greatest for sensitive subgroups within the population, in particular, infants, young children, and pregnant and nursing women, and more generally for people who are chronically and heavily exposed (Rice, 1995; Long-necker, Rogan, and Lucier, 1997). Exposure of the developing brain to PCBs or mercury during critical early periods of vulnerability can produce serious and possibly irreversible decrements in cognitive and behavioral function (Kurland, Faro, and Siedler, 1960; Bakir, Damlogi, andAmin-Zaki, 1973; Chen, Guo, and Hsu, 1992; Schantz, Moshtaghian, and Ness, 1995; Jacobson and Jacobson, 1996b). Prospective epidemiologic data from environmentally exposed populations in the United States and Europe suggest that even relatively low levels of exposure may have detectable adverse effects on the developing nervous system (Gladen and Rogan, 1991; Patandin et al., 1999).

The Hudson River watershed and New York Harbor complex are home to about 17 million people, approximately 6 percent of the population of the United States. The watershed has been densely populated for more than 350 years and industrialized for over 200 years and encompasses hundreds of hazardous waste disposal sites. Twenty-one of these sites in New York as well as seventy in New Jersey have been placed by the United States Environmental Protection Agency (USEPA) on the National Priorities List (NPL) and thus are designated as Superfund sites (USEPA, 1992). Most important among the hazardous waste sites in the Hudson River watershed are:

1. The Hudson River itself, the nation's longest Superfund site, is contaminated for over 300 kilometers of its length by PCBs principally derived from the General Electric transformer manufacturing plants in upstate New York (USEPA, 2002a).

2. The 80 Lister Avenue site in Newark, New Jersey, is located on the western edge of New York Harbor. The herbicide Agent Orange, a 50:50 mix of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), was manufactured there for use in the Vietnam War. Dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin), formed as a byproduct of 2,4,5-T synthesis, has leached into soil and into adjacent sediments of the western Harbor and has moved north up the tidal Hudson as far as the George Washington Bridge. The organochlorine insecticide 2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane (DDT) was also produced at 80 Lister Avenue, and DDT-derived residues are found in adjacent soils and harbor sediments (USEPA, 2002b).

3. The Hudson River below Glens Falls, New York, contains a complex mixture of lead, chromium, and cadmium downstream of a pigment plant (USEPA, 2001).

4. The Hackensack Meadowlands estuary in northern New Jersey has been rated by the National Oceanic and Atmospheric Administration as among the worst areas of mercury contamination in the United States (USEPA, 2002c).

Non-point sources of environmental pollutants, for example, pesticide applications, are also prevalent in this region. In 1997, 16.7 million pounds of pesticides were used by commercial applicators and farmers in New York state, and additional, unquantified amounts of pesticides were applied privately. Continued leaching, runoff, or illegal disposal of commercial and residential organochlo-rine insecticides that were banned from use in the United States since the 1970s - including chlordane, dieldrin, and DDT - have prolonged the contamination of the sediments and the food chain of this aquatic ecosystem (Bopp et al., 1998). Organochlorine pesticides are extant in both the aquatic and the terrestrial chains. As was discussed elegantly by Clarkson (1995), some control exists over the quality of crop production and animal husbandry in terrestrial food chains (plants, meat, poultry, and dairy products) because these foods are monitored through a series of governmental inspections and regulatory checks. In contrast, in aquatic food chains, there exists little if any control over the environments in which fish develop and grow or on the contaminant burdens that are ultimately consumed by those who eat the fish.

Despite numerous advisories andfishing bans by public health officials, several questionnaire surveys of anglers indicate that residents of the lower Hudson watershed, including women and children, continue to eat fish from the Hudson River, its tributaries, and New York Harbor (Barclay, 1993; Burger, Staine, and Gochfeld, 1993;MayandBurger, 1996; Burger et al., 1999; NYSDOH, 1999; Pflugh et al., 1999). These studies found that poor people and people of color are most likely to consume locally caught fish and shellfish. White, middle-class anglers typically release many of the fish that they catch, while poorer anglers of color are more likely to keep their catch and share it with family and friends (Burger et al., 1999).

In this chapter, we will review the current evidence regarding the toxicity and human health impacts of the major persistent environmental pollutants found in the Hudson River watershed.

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