Occupational mercury exposure and its consequences for behaviour

Abstract

Mercury is a known neurotoxin. Evidence from animal studies show behavioural impairment which can be long-lasting, after low-level exposure to mercury. Human research, however, has not been conclusive. Chronic, high-level mercury exposure such as occurred in Japan, and the Middle East, Causes long-lasting and profound neurological damage. However the effects of low-level exposure, such as occurs in occupational exposure, are far from clear. This study used a comprehensive test battery based on an information processing framework to compare a group of twelve chronically mercury-exposed workers with a matched control group. The mercury-exposed group showed poorer psychomotor co-ordination and premature fatigue, although simple motor responses were not affected. General arousal levels also remained unaffected but mercury-exposed workers were superior in sustaining attention. In spite of this, the mercury-exposed group showed clear deficits in short-term memory.

Neurobehavioural test results and exposure to inorganic mercury: in search of dose-response relations

“…These three functions were selected for the following assessments. To obtain a conclusive set of data, those studies which did not provide test results for each of these domains (Camerino et al 1981;Williamson et al 1982;Roels et al 1985;Gonzalez-Ramirez et al 1995;Ritchie et al 1995;Lucchini et al 2002) had to be excluded. The reduction resulted in a total of 11 studies providing averaged effect sizes for each of the three functions (Table 3).…”

“…1 depicts the total of effect sizes. Most of the studies obtained effect sizes in accordance with a hypothesis of an impairment due to mercury exposure (positive effect size), but several of the studies-especially those investigating lower levels of exposure-resulted in effect sizes displaying a superior Table 1 Details on studies meeting the criteria of inclusion for the analysis 1 Currently no longer exposed 2 Calculated from mercury concentration in blood 3 Estimated by using information about mean exposure for dentists in the year of the study and information from Echeverria et al (1995) 4 Similarity of groups was assured by parallelizing groups or by testing for differences between groups 5 Groups differed with respect to verbal intelligence/school years Williamson et al 1982Williamson et al , 1990 133 Similarity of groups performance of exposed groups (negative effect size). However, the overall tendency of a positive relationship between exposure and effects is clearly visible and can be tentatively estimated (use of statistically dependent data, see methods) by a coefficient of correlation amounting to r effsize, exp =0.48.…”

Does Inorganic Mercury Play a Role in Alzheimer's Disease? A Systematic Review and an Integrated Molecular Mechanism

“…Studies on current exposure of workers to mercury [57][58][59][60][61][62][63][64][65][66][67][68][69] were mostly conducted on workers in industry (chlorine-alkaline factories, thermometer factories, mercury extraction plants), and in one case on gold miners in the Philippines who use large amounts of mercury without any protection [59]. Correlations between the amount of Hg excreted in urine and measures of cognitive abilities (memory tests, attention span) were always significant and negative, i.e., the more mercury excreted the worse the test results.…”

Subjective symptoms and psychological performance of chlorine-alkali workers.

“…Nonspecific subjective symptoms such as fatigue, weakness, loss of memory, insomnia, and increased irritability have been characterized as micromercurialism in subjects exposed for long periods of time to low concentrations of mercury vapor (3,4). In psychological tests disturbances of cognitive and psychomotor functions have been associated with low levels of mercury exposure (5)(6)(7)(8)(9). However, conflicting data have also been reported for workers at similar levels of exposure (l0, 11).…”