[Neurotoxic effect of exposure to low doses of mercury].
OBJECTIVE
To assess early effects on the Central Nervous System due to occupational exposure to low levels of inorganic mercury (Hg) in a multicenter nationwide cross-sectional study, including workers from chloro-alkali plants, chemical industry, thermometer and fluorescent lamp manufacturing. The contribution of non-occupational exposure to inorganic Hg from dental amalgams and to organic Hg from fish consumption was also considered.


METHODS
Neuropsychological and neuroendocrine functions were examined in a population of 122 workers occupationally exposed to Hg, and 196 control subjects, not occupationally exposed to Hg. Neuropsychological functions were assessed with neurobehavioral testing including vigilance, motor and cognitive function, tremor measurements, and with symptoms concerning neuropsychological and mood assessment. Neuroendocrine functions were examined with the measurement of prolactin secretion. The target population was also characterized by the surface of dental amalgams and sea fish consumption.


RESULTS
In the exposed workers the mean urinary Hg (HgU) was 10.4 +/- 6.9 (median 8.3, geometric mean 8.3, range 0.2-35.2) micrograms/g creatinine, whereas in the control group the mean HgU was 1.9 +/- 2.8 (median 1.2, geometric mean 1.2, range 0.1-33.2) micrograms/g creatinine. The results indicated homogeneous distribution of most neurobehavioral parameters among exposed and controls. On the contrary, finger tapping (p < 0.01) and the BAMT (Branches Alternate Movement Task) coordination test (p = 0.05) were associated with occupational exposure, indicating an impairment in the exposed subjects. Prolactin levels resulted significantly decreased among the exposed workers, and inversely related to HgU on an individual basis (p < 0.05). An inverse association was also observed between most neuropsychological symptoms and sea fish consumption, indicating a "beneficial effect" from eating sea fish. On the contrary, no effects were observed as a function of dental amalgams.


CONCLUSIONS
In conclusion, this study supports the finding of early alterations of motor function and neuroendocrine secretion at very low exposure levels of inorganic Hg, below the current ACGIH BEI and below the most recent exposure levels reported in the literature.
Cattedra di Medicina del Lavoro, Università di Brescia, P.le Spedali Civili 1, 25125 Brescia.
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Lucchini
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Cortesi
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Facco
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Benedetti
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Camerino
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Carta
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Urbano
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Zaccheo
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Alessio
D000328:Adult; D000339:Affect / Q000187:drug effects; D000395:Air Pollutants, Occupational / Q000009:adverse effects; D000818:Animals; D002617:Chemical Industry; D003430:Cross-Sectional Studies; D003723:Dental Amalgam / Q000009:adverse effects / Q000493:pharmacokinetics; D004305:Dose-Response Relationship, Drug; D004781:Environmental Exposure; D004785:Environmental Pollutants / Q000009:adverse effects; D005247:Feeding Behavior; D005260:Female; D005399:Fishes; D005506:Food Contamination; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D008452:Maximum Allowable Concentration; D008628:Mercury / Q000008:administration & dosage / Q000009:adverse effects* / Q000493:pharmacokinetics / Q000652:urine; D020262:Mercury Poisoning, Nervous System / Q000453:epidemiology* / Q000209:etiology; D008875:Middle Aged; D009043:Motor Activity / Q000187:drug effects; D009483:Neuropsychological Tests; D009490:Neurosecretory Systems / Q000187:drug effects; D009784:Occupational Diseases / Q000453:epidemiology / Q000209:etiology; D016273:Occupational Exposure; D011388:Prolactin / Q000097:blood; D011597:Psychomotor Performance / Q000187:drug effects; D011930:Reaction Time / Q000187:drug effects; D017747:Seafood / Q000009:adverse effects
D000395:Air Pollutants, Occupational; D004785:Environmental Pollutants; D003723:Dental Amalgam; D011388:Prolactin; D008628:Mercury