Neurological and neuropsychological deterioration in artisanal gold miners from the town of Andacollo, Chile

Abstract

It is widely known that human exposure to mercury vapor can cause neurological and neuropsychological deterioration. We have investigated if a population of Chilean artisanal gold-mining workers heavily exposed to elemental mercury (Hg⁰) display neurological and neuropsychological impairment. Male volunteers occupationally exposed to Hg⁰ (“gold miners”, n = 35) were recruited and compared with a group of unexposed workers (n = 40). Blood specimens were obtained from both groups for total mercury quantification. Upon neurological examination, 71% of the “gold miners” group showed abnormalities expressed as frontal impairment, tremor, or simultaneously frontal impairment, parkinsonism, and pyramidal syndrome. In contrast, only 16% of the individuals in the control group displayed neurological abnormalities. The “gold miners” group also showed impairment of the neuropsychological performance and the distribution of abnormal scores for almost all the neuropsychological tests applied was significantly higher in this group compared to the control group. Educational level, alcohol intake, and smoking habits did not influence the outcome of the neurological or neuropsychological examinations. Finally, despite that the higher blood mercury concentrations were found in the “gold miners” group, they were not significantly different from the values obtained in the control group.

Keywords:

• elemental mercury
• cognitive impairment
• neuropsychological battery
• gold miners
• blood mercury

Acknowledgment

This work was supported by a grant from Fondo de Investigación en Salud (FONIS SA05i20032) to F.P. and D.M.

Notes

**: Significant differences (t-test; p < 0.01).

***: Extremely significant differences (χ ² test; p < 0.001).

ns: No significant differences (U-test).

¹Despite that several individuals were declared to have had direct contact with Hg⁰ among the unexposed workers living in the town of Andacollo, they were not asked about the years of exposure since their contact with Hg⁰ occurred several years ago.

0: normal; 1: borderline; 2: mild impairment and 3: moderate to severe.

*Significant differences (p < 0.05; χ ² test with Yates's correction).

***Extremely significant differences (p < 0.001; χ ² test with Yates's correction).

ns: No significant differences between groups.

* Significant differences between groups (p < 0.05).

** Highly significant differences between groups (p < 0.01).

*** Extremely significant differences between groups (p < 0.001).

* p < 0.05; **: p < 0.01; ***: p < 0.001; χ ² test with Yates’ continuity correction.

Variables were adjusted for exposure, age, educational level, alcohol intake, and smoking habits.

*p < 0.05; **p < 0.01; Logistic binary regression.

ns: No significant differences.

Variables adjusted for exposure, age, educational level, alcohol intake, and smoking habits.

*p < 0.05; **p < 0.01; Logistic binary regression.