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Abstract and Introduction
Abstract
Background: Polychlorinated biphenyls (PCBs) may accelerate the cognitive and motor dysfunction found in normal aging, but few studies have examined these outcomes and PCB exposure among older adults.
Objective: We evaluated neuropsychological status and low-level PCB exposure among older adults living along contaminated portions of the upper Hudson River in New York.
Methods: A total of 253 persons between 55 and 74 years of age were recruited and interviewed, and provided blood samples for congener-specific PCB analysis. Participants also underwent a neuropsychological battery consisting of 34 tests capable of detecting subtle deficits in cognition, motor function, affective state, and olfactory function.
Results: After adjustment for potential confounders, the results indicated that an increase in serum total PCB concentration from 250 to 500 ppb (lipid basis) was associated with a 6.2% decrease in verbal learning, as measured by California Verbal Learning Test trial 1 score (p = 0.035), and with a 19.2% increase in depressive symptoms, as measured by the Beck Depression Inventory (p = 0.007).
Conclusions: The results suggest that exposure to PCBs may be associated with some measures of memory and learning and depression among adults 55–74 years of age whose current body burdens are similar to those of the general population. Although the results are useful in delineating the neuropsychological effects of low-level exposure to PCBs, further studies of whether older men and women are a sensitive subpopulation are needed.
Introduction
Considerable evidence links polychlorinated biphenyls (PCBs) to subtle neurodevelopmental deficits among neonates, infants, and children (Schantz et al. 2003). Relatively few studies, however, address neurotoxicity among adults exposed to PCBs (Faroon et al. 2002). The possibility that PCBs may interact with the neurodegenerative processes associated with aging underscores the need for more data on long-term neurologic effects of PCBs in adults (Seegal 2001). To date, only one study has examined these effects. In a study of aging Great Lakes fish consumers, Schantz et al. (2001) reported that PCB exposure was negatively associated with several measures of memory and learning, whereas other cognitive domains and motor function (Schantz et al. 1999) were unaffected. The present study assesses the neuropsychological status of older adults living along PCB-contaminated portions of the Hudson River in New York.
Over approximately 30 years, General Electric plants in Fort Edward and Hudson Falls, New York, used PCBs to manufacture electrical capacitors. Nearly 1 million pounds of PCBs were discharged from these facilities into the Hudson River, about 15% of the nationwide discharge at that time (Hetling et al. 1978). In a previous article (Fitzgerald et al. 2007), we reported that although some older long-term residents of Fort Edward and Hudson Falls ate fish from a contaminated portion of the Hudson River in the past, their current rates of consumption are low, apparently due to the fishing ban and advisories issued by state environmental and health agencies. After adjustment for age, body mass index (BMI), and cigarette smoking, the geometric mean serum total PCB concentration of Fort Edward and Hudson Falls residents was 3.07 ppb (wet weight) and 473 ppb (lipid basis), values that did not differ significantly from 3.23 ppb (wet weight) and 485 ppb (lipid basis) for residents of Glens Falls, a control community upriver from the PCB contamination. Despite low current consumption rates, serum PCB levels tended to increase with estimated cumulative lifetime exposure to PCBs from Hudson River fish consumption.
The current article extends the investigation by examining neuropsychological status in these populations to evaluate whether low-level PCB exposure is associated with nervous system function. This study builds on the work of Schantz et al. (1999, 2001) and extends the outcome assessment to include domains such as affective state and olfactory function that they did not investigate. Given the possible effects of PCBs on dopamine and serotonin (Morse et al. 1996; Seegal et al. 1991) and the impact of these neurotransmitters on cognition (Volkow et al. 1998), mood (Baldwin and Rudge 1995), and olfaction (Doty et al. 1992), it is hypothesized that serum PCB concentrations will positively associate with measures of depression and anxiety and negatively associate with learning, memory, and smell. In order for us to evaluate the neurotoxicity of specific congeners, the exposure assessment includes serum levels of individual PCB congeners as well as total PCBs.
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