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The neurobehavioral effects of lead (organic and inorganic) and organic solvents were compared in 386 U.S. workers (52 reference, 190 lead, and 144 solvent workers). The association between neurobehavioral test performance and duration of exposure to lead or solvents was also examined and compared. The neurobehavioral test battery consisted of examiner and computer-administered neurobehavioral tests, a test of olfactory function, and questionnaires that assessed neuropsychiatric symptoms. Adjusted mean differences on the neurobehavioral test scores were estimated by comparing the exposed group to the referent group using linear regression and adjusting for premorbid intellectual ability, age, and race. Both lead and solvents were associated with diminished neurobehavioral performance in all neurobehavioral areas tested. Specifically, while lead and solvent exposure had the same magnitude of adverse effects on tests of manual dexterity, lead exposure was associated with greater adverse effects on memory and learning tests but with less adverse effects on executive/motor tests and on a test of olfaction than solvent exposure. An elevated number of neuropsychiatric symptoms was reported by 7% of the referent group, 43% of the lead group, and 15% of the solvent group. For exposure duration of < or = 10 years, more neurobehavioral decrements were found in the solvent group relative to the lead group. However, for exposure duration of > or = 18 years, the lead group showed more decrements than the solvent group. Overall, these data suggest differences in neurobehavioral functioning between the lead (organic and inorganic) and solvent exposed workers examined in this study.

Objectives-To determine if measures reflecting chronic occupational lead exposure are associated with performance on neuropsychological tests. Method-467 Canadian male lead smelter workers (mean (SD) age 43*4 (11.00) years, education 9-8 (3.18) years, years of employment 17'7 (7.43), and current blood lead concentration (B-Pb) 27-5 (8.4) ug dl-e) were given a neuropsychological screening battery. Time weighted average (TWA) and time integrated blood levels (IBL) were developed from B-Pb records obtained through regular medical monitoring (mean (range) TWA 40-1 (4-0-66.4) jg di-1, mean IBL 765*2 (0'6-1625-7) pg-y dl-1). 14 exposure measures may mask differences in neuropsychological functioning related to chronic, low dose exposure.'7 Measures of chronic exposure include time weighted average (TWA), a weighted average of B-Pb over the duration of exposure, and time integrated B-Pb (IBL), a measure of cumulative B-Pb concentrations over the period of exposure.Baker et al found a relation between TWA (for B-Pb) and verbal memory and motor dexterity.4 However, TWA reflected only the previous 15 months of exposure, and was not a weighted average over the entire duration of exposure. Parkinson and colleagues used current B-Pb, TWA, peak exposure, and proportion of B-Pb values greater than 60 mg/i 00 ml as exposure indices. These authors did not find a relation between exposure variables and neuropsychological measures after adjustment for the effects of age and education.5 Hogstedt et al found differences between exposed and non-exposed controls in reaction time, learning, and memory. However, when the exposed group was analysed by TWA terciles, no significant differences (dose-effect) were found.'A recent review noted that the relation of chronic exposure and neuropsychological functioning remains unexamined.8 Our study examined the effects of chronic occupational lead exposure on neuropsychological performance. Method PARTICIPANTSWe held small group informational sessions with all employees to describe the purpose and procedure of the study. The 467 Canadian men currently and previously employed in a lead smelter (370 current, 97 former; mean (SD) age 43-4 (11-00), years of education 9 8 (3.18), years employed 17-7 (7-43)) who agreed to participate, represented about 87% of current employees. No company records were available to measure the number of former employees. Participants were not paid for their involvement, and current employees completed the evaluation at the start of their shift. A consent form explaining the purpose of the study was reviewed with each participant. Because the smelter was in a bilingual area, workers chose to be tested in either French (n = 129) or English (n = 329). Nine men chose to be evaluated with a combination of French and English. PROCEDUREThe participants completed an individual two hour neuropsychological screening battery.

Anti-tick saliva antibody (ATSA) has potential as a biologic marker of exposure to tick bites. In 1989, we conducted a cross-sectional study of 304 outdoor workers in Monmouth County, New Jersey, to evaluate associations between self-reported tick exposure, ATSA status, and Lyme disease antibody status. ATSA levels 1) were correlated with an index of tick exposure on the basis of three self-reported measures of tick exposure and outdoor hours worked per week (p = 0.01); 2) were consistently higher in pet owners compared with persons without pets (p = 0.03); and 3) when examined by duration since last tick bite, peaked at 3-5 weeks after tick bite and then declined (p = 0.06). ATSA levels dichotomized at the 75th percentile (approximately two standard deviations above the mean ATSA optical density of 25 subjects who denied recent tick exposure) were associated with self-reported tick exposure: adjusted odds ratios for high ATSA levels were 4.2 (95% confidence interval (CI) 0.9-18.9) for moderate (versus none) tick exposure and 5.8 (95% CI 1.2-27.2) for high (versus none) tick exposure. Finally, high ATSA levels were associated with Lyme disease seropositivity, with an adjusted odds ratio of 3.2 (95% CI 1.3-7.6). The data suggest that ATSA is a biologic marker of tick exposure that is a risk factor for Lyme disease seropositivity.

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