Cumulative exposure to inorganic lead and neurobehavioural test performance in adults: an epidemiological review.

OBJECTIVES: To evaluate the current evidence that cumulative exposure to inorganic lead is associated with decreased performance in neurobehavioural tests in adults. METHODS: 21 unique studies were reviewed from 28 published manuscripts. An algorithm was developed to determine the usefulness of each study on the basis of exposure assessment, control of confounding variables, methods of subject selection, test conditions, and data analysis. Highest emphasis was placed on the use of cumulative measures of exposure or absorption. RESULTS: Only three studies used a measure of cumulative exposure to or absorption of lead, and two others used duration of exposure as a surrogate for cumulative exposure. All other studies used a measure that did not adequately estimate cumulative exposure to lead, most often current blood lead concentration. 20 of the studies controlled for age as a confounding variable, although in several studies the possibility for residual confounding by age remained. 16 studies controlled for intellectual ability before exposure; all of them used educational level for this purpose. Of the five studies that used direct or surrogate measures of cumulative exposure to or absorption of lead, two were thought to be of low usefulness because of inadequate duration of exposure. The three remaining studies found stronger associations of neurobehavioural performance with recent exposure measures than with those of cumulative exposure. CONCLUSION: The current scientific literature provides inadequate evidence to conclude whether or not cumulative exposure to or absorption of lead adversely affects performance in neurobehavioural tests in adults. The current evidence is flawed because of inadequate estimation of cumulative exposure to or absorption of lead and inadequate control for age and intellectual ability before exposure.

Investigation of a reported cluster of bladder cancer cases in the Pottstown/Phoenixville area of Pennsylvania.

A urologist in Phoenixville, Pennsylvania, noted an apparent excess of invasive bladder cancer cases in his practice area during 1988 and 1989. Background incidence data for the local area were derived from state Cancer Registry statistics. Seventeen additional cases were noted during review of local hospital tumor registry data. Exposure evaluation included complete occupational histories for 15 index cases and correlation of residential histories with a review of local industries, water quality data, and toxic waste sites. The data were compared with incidence data from 1984 and 1985, and no increase in bladder cancer incidence for this area in 1988 and 1989 was evident. There was, however, a higher bladder cancer incidence among white males in the study area and Chester County, compared with Pennsylvania as a whole. Residential histories and environmental analysis did not reveal a common environmental carcinogen. A high incidence of occupational exposure to suspected bladder carcinogens was noted. In addition, all but 4 of the index cases smoked cigarettes. The study was limited by an extreme paucity of water supply analysis data. Effective environmental monitoring would promote more effective research into environmental carcinogenesis.