The influence of environmental pollutants on nervous system function among older adults

Fitzgerald, Edward
Department of Epidemiology and Biostatistics
School of Public Health, University at Albany
Rensselaer, NY USA

It is well known that the fetus and infant are particularly sensitive to the adverse effects of many environmental contaminants. For example, metals such as lead and mercury and persistent organic pollutants such as polychlorinated biphenyls (PCBs) have been associated with cognitive and neurobehavioral deficits among newborns in numerous studies. There is growing evidence, however, that older adults may also be a sensitive subpopulation. That is, environmental pollutants may accelerate the neurodegenerative processes that normally occur with aging. This paper will summarize current studies suggesting that cumulative lifetime exposure to lead or PCBs adversely affect cognitive or motor function among adults. It also will include a detailed description of two studies recently conducted in New York State, USA. The first study evaluated neuropsychological status and PCB exposure among older adults living along contaminated portions of the upper Hudson River. A total of 253 persons between the ages of 55 and 74 were recruited, 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. After adjustment for potential confounders, the results indicated that an increase in serum total PCB concentration from 250 to 500 parts per billion (lipid basis) was associated with 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). In a parallel project of 241 former workers at a capacitor manufacturing facility, 241 men and women 50 to 87 years old were interviewed and underwent the same neuropsychological battery described above. Bone lead was determined from in vivo measurement of the tibia using K-shell X-ray fluorescence spectrometry. After adjustment for several covariates, bone lead was associated with five tests of memory and learning and with three tests of motor function (p < 0.05). Importantly, the levels of PCBs in serum and of lead in bone in these two studies were not greatly elevated. Hence, the results suggest that exposure to PCBs or lead may be negatively associated with some measures of cognitive or motor function among older adults whose current body burdens are similar to those of the general population.

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