Effects of occupational exposure to mercury vapour on the central nervous system.

Abstract

Possible effects of mercury on the central nervous system (CNS) were examined in a group of chloralkali workers exposed to mercury (n = 89) and compared with a control group (n = 75), by registration of subjective symptoms, personality changes, forearm tremor, and performance on six computerised psychometric tests in the two groups. The groups were similar in age, education, verbal comprehension, and work tasks. In the chloralkali group, median blood mercury concentration (B-Hg) was 55 nmol/l, serum mercury concentration (S-Hg) 45 nmol/l, and urine mercury concentration (U-Hg) 14-3 nmol/ mmol creatinine (25-4 pg/g creatinine). Corresponding concentrations in the control group were 15 nmol/l, 4 nmol/l, and 1P1 nmol/mmol creatinine (19 pg/g creatinine) respectively.The number of self reported symptoms, the scores for tiredness and confusion in the profile of mood states (POMS), and the degree of neuroticism in the Eysenck personality inventory (EPI), were significantly higher in the mercury exposed group compared with the controls. Performance on the psychometric tests and tremor frequency spectra did not differ significantly between the two groups. Dose-response calculations showed weak but statistically significant relations between symptom prevalence and current mercury concentrations in both blood and urine. Psychomotor performance, attention, and short term memory were tested using six computerised tests, which were selected and adapted from the neurobehavioural evaluation system.4 17 A personal computer equipped with a joystick and a special button panel was used. All test sessions were performed in a quiet room under guidance of the same test leader (OA). The test conditions were standardised as much as possible. Exposed subjects and controls were tested in a randomised order, and could not be identified by the test leader. In all tests the first trial was a practice run. The six tests are:(1) Hand-eye coordination (HEC) -This is a visual motor coordination test executed with a joystick. The task was to move a cursor as close as possible to a curved line on the screen. The average deviation from the line (mean absolute error based on a graphic measure) during five tests was used as test parameter.(2) Finger tapping-Motor speed function was tested by finger tapping with (a) dominant hand, (b) non-dominant hand, and (c) alternating hands. The subjects were instructed to tap a button with the index finger as fast as possible for 10 seconds. The average number of taps during five trials for each condition was used as test parameter.(3) Simple reaction time-In this attention test the subjects were required to press a button with the index finger of the preferred hand as quickly as possible when a symbol (a large "0") appeared on the display. Twelve stimuli were presented per minute with randomised time intervals between 2-5 and five seconds. The average reaction time (ms) and standard deviation (SD) during six minutes were calculated and used as test parameters.(4) Symbol-digit-In this test of perceptual...

Mercury exposure in a low-income community in South Africa

“…Below 40 µg/l, symptoms are thought to be unlikely. 6 However, a study in Sweden 18 reported central nervous system symptoms involving 96 occupationally exposed individuals with a median mercury level in urine of 25 µg/g creatinine. Another study found renal effects in workers with levels >20 µg/g creatinine.…”

Mercury vapour levels in dental practices and body mercury levels of dentists and controls

“…11,12 Low concentrations of urinary mercury reported in recent studies of DHCWs 3,13,14 contrast with those published a decade or so ago. [15][16][17] These reductions may be considered to be due to greater awareness of the possible problems caused by excessive mercury intake, the use of automated methods of amalgam preparation and improvements in mercury hygiene in dental surgeries. [18][19][20][21]  One hundred and eighty dental surgeries were tested for environmental mercury.…”

Mercury risk from fluorescent lamps in China: Current status and future perspective

“…Urine excretion of mercury occurs during and shortly after exposure, thus urine assay can be used to evaluate the mercury exposure and body burden. Although there is no consensus on safe mercury contents in urine, various adverse effects have been reported for workers with chronic mercury exposure who had urine mercury levels of 50 μg/L or less (Barregard et al, 1988;Langworth et al, 1992;Pogarev et al, 1997). Table 2 summarizes the results from an occupational hygiene investigation on replacement of liquid mercury by Ti 3 Hg alloy in mercury dosing at a fluorescent lamp plant in Tianjin, China (Wang, 1993).…”