Sub-clinical neurobehavioral abnormalities associated with low level of mercury exposure through fish consumption.

In order to assess early neurotoxic effects associated with relatively low levels of mercury absorbed through fish eating, two groups of 22 adult male subjects, habitual consumers of tuna fish, and 22 controls were examined using a cross-sectional field study. The assessment included neurobehavioral tests of vigilance and psychomotor function, hand tremor measurements and serum prolactin assessment. Mercury in urine (U-Hg) and serum prolactin (sPRL) were measured in all exposed subjects and controls, whereas measurements of the organic component of mercury in blood (O-Hg) were available for only 10 exposed and six controls. U-Hg was significant higher among exposed subjects (median 6.5 microg/g of creatinine, range 1.8-21.5) than controls (median 1.5 microg/g of creatinine, range 0.5-5.3). The median values of O-Hg were 41.5 microg/l among the tuna fish eaters and 2.6 microg/l in the control group. Both U-Hg and O-Hg were significantly correlated with the quantity of fish consumed per week. Significant differences in sPRL were found between exposed (12.6 ng/ml) and controls (9.1 ng/ml). Individual sPRL were significantly correlated with both U-Hg and O-Hg levels. The neurobehavioral performance of subjects who consumed tuna fish regularly was significantly worse on color word reaction time, digit symbol reaction time and finger tapping speed (FT). After considering the education level and other covariates, the multiple stepwise regression analysis indicated that O-Hg concentration was most significantly associated with individual performance on these tests, accounting for about 65% of the variance in test scores.

trans,trans-Muconic acid excretion in relation to environmental exposure to benzene.

OBJECTIVES: Potential environmental sources of benzene exposure, and intake of foods and beverages susceptible to being preserved with sorbic acid, were investigated in relation to their contribution to the inter-individual variation in background urinary trans,trans-muconic acid ( t,t-MA) excretion among subjects non-occupationally exposed to benzene. METHODS: We measured urinary t,t-MA excretion in 65 subjects, 34 women and 31 men. A spot sample of morning urine was collected for each subject 10-12 h after they had consumed their last meal. Questionnaire information was collected on diet and possible sources of environmental benzene exposure in the surroundings of the subjects' residences. For each subject, an estimate of the average daily intake of sorbic acid with diet was calculated, based on questionnaire information and laboratory data on samples of local food items. RESULTS: The t,t-MA geometric mean was significantly higher among women (28.7 vs 11.5 microg/g creatinine, P<0.05) and among smokers (37.6 vs 15.6 microg/g creatinine, P<0.05), and increased by years of education among women, but not among men. In the multivariate analysis, smoking was the only significant predictor of elevated t,t-MA excretion. In our study, the average estimated daily sorbic-acid intake with diet was 0.33 ppm (standard deviation: 0.28), and it did not show a correlation with t,t-MA excretion. Urban traffic and residence within 100 m of a fuel station also did not show an association with elevated t,t-MA values. CONCLUSIONS: Our study confirms that, among subjects non-occupationally exposed to benzene, smoking contributes significantly to increased background t,t-MA excretion. Further studies should be addressed to confirm our observation of elevated t,t-MA levels among women.