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Objectives: This investigation studied possible neuropsychological effects among former chloralkali workers with past exposure to mercury vapor., Methods: Seventy-five formerly exposed workers who had been examined with an extensive neuropsychological test battery were compared with 52 referents frequency-matched for age. The tests measured general cognitive function, motor and psychomotor function, attention, memory, and learning. The groups were similar in educational level, age, and verbal comprehension. The mean exposure time to mercury vapor in the index group was 7.9 (range 1.1-36.2) years with an annual mean urinary mercury concentration of 539 (range 41-2921) nmol/(l x year). The mean time since the cessation of exposure was 12.7 (range 1.0-35.0) years., Results: Performance on the grooved pegboard (dominant hand 75.8 versus 70.9 seconds, P<0.05; nondominant hand 82.2 versus 76.3 seconds, P=0.02) and the Benton visual retention test (mean number of correct reproductions 6.9 versus 7.5, P<0.05) was poorer among the formerly exposed workers when compared with the referents. In addition the subjects who had experienced the highest intensity of exposure [cumulative urinary mercury index > or =550 nmol/(l x year)] had a poorer performance on the trailmaking test, part A and B, on the digit symbol test, and on the word pairs test (retention errors)., Conclusions: The presented results suggest a slight persistent effect of mercury vapor exposure on the central nervous system, mainly involving motor functions and attention, but also possibly related to the visual system. Previous exposure does not seem to have affected the workers' general intellectual level or their ability to reason logically.

Mercury vapour exposure was studied for 40 years in 419 chloralkali workers. The concentration of mercury was measured in the work room (stationary) from 1953 and in urine from 1948. There were major differences in the mean urinary concentrations between different types of job. The mean urinary mercury concentration, uncorrected for urinary dilution, for all subjects varied between 30 and 250 micrograms 1.(-1) during the study period. For workers in the cell-room the correlation (r) between urinary mercury and mercury in the work room was r = 0.74 (P < 0.001), and for repair men/mechanics it was r = 0.70 (P < 0.001). The introduction of new cells and stabilizing the volume of production may have been important for reducing air-Hg and U-Hg, whereas other changes in the production process, or actions to reduce the release of mercury to the work environment, had no detectable effect. The urinary mercury concentration among all workers was related to the relative energy consumption (r = 0.83, P < 0.001).

Objectives: The dental health of 73 workers previously exposed to mercury vapour at a chloralkali plant was studied and compared with that of 51 non-exposed referents., Methods: A record of oral, periodontal, gingival and mucosal conditions, including teeth, restorations, prostheses, and oral hygiene, was established during a 30 min examination. The participants' periodontal conditions were assessed according to the community periodontal index of treatment needs (CPITN). The results with the CPITN index were also compared with previously published data for another similar population., Results: There was no significant difference between the exposed workers and the referents with respect to the number of remaining teeth, amount of amalgam restorations, crowns, bridges, or endodontically treated teeth. The oral hygiene among the exposed workers was significantly better than among the referents, but the periodontal health conditions did not significantly differ between the two groups, nor from those of another Norwegian population., Discussion: The present results seem to contradict previous reports claiming tooth loss as a possible result of exposure to mercury vapour.

Urinary albumin concentration (U-alb) and N-acetyl-beta-D-glucosaminidase (U-NAG) and glomerular basement membrane antibodies (a-GBMs) in serum samples were measured in 77 chloralkali workers previously exposed to mercury (Hg) vapour and 53 age matched referents. The exposure ceased on average 12.3 (range 1-35) years before the study. The mean exposure time was 7.9 (range 1.1-36.2) years. The mean yearly urinary Hg concentration (U-Hg) was 531 nmol/l. The concentrations of the urinary isoenzymes NAG A (U-NAG A) and NAG B (U-NAG B) were determined in 30 highly exposed subjects and 30 referents. No differences in U-alb or U-NAG, U-NAG A, or U-NAG B were found between the groups. Higher concentrations of a-GBMs were found among subjects who stopped exposure a short time before the study, but there was no association between a-GBMs and U-alb. The U-NAG and U-NAG A were negatively correlated with storage time. The results may suggest that microalbuminuria and enzymuria reported in subjects with ongoing exposure to Hg vapour are reversible in most instances.

Incidence of cancer and mortality were studied among 674 men exposed to mercury vapour for more than one year at two chloralkali plants. Mercury excretion in urine had been monitored among the workers at the two plants since 1948 and 1949. An individual cumulative urinary mercury dose was calculated, based on about 20,000 urinary mercury measurements. The incidence of cancer and the mortality were followed up from 1953 to 1989 and 1953 to 1988 respectively. The general Norwegian male population served as a reference population. There was a lung cancer excess of borderline significance (standardised incidence ratio = 1.66, 95% confidence interval = 1.00-2.59). The introduction of a 10 year latent period before developing lung cancer did not increase the incidence ratio. The excess may be partly explained by the smoking habits in the cohort or possibly by exposure to asbestos. No excess of cancer was found in the target organs for mercury toxicity--namely, the kidney and the nervous system. No significant excess mortality was found for nephritis and nephrosis or nonmalignant diseases of the nervous system.