PllKIVI L, HANNINEN H. Subjective symptoms and psychologicalperformance of chlorine-alkali workers. Scand J Work Environ Health 1989;15:69--74. Subjective symptoms and psychological performances on a computer-administered test battery were studied among a group of 60 chlorine-alkali workers and their matched referents. The exposure time of the group exposed to inorganic mercury vapor had been about 14 years, and the estimated long-term average exposure had been about 25 ug/m' of air. The exposed workers had an actual mercury concentration of 51.9 (SD 25.0, range 15-150) nmolll in blood and 84.1 (SD 56.6, range 15-260) nmolll in urine. Neither perceptual motor nor memory nor learning abilities of the mercury-exposed workers showed any disturbances in a comparison with the referents. However, the exposed group reported statistically significantly more memory disturbances than the referents. Strain caused by three-shift work was a possible cofactor for other increased subjective symptoms, namely, for sleep disorders, fatigue, and confusion.

Scand j work environ health 10 (1984) 10 (1984) 35-41. In a cross-sectional study the psychological test performances of a group of 36 male chlorine-alkali workers were compared with the level of exposure to mercury and to the corresponding results of referents. The mercury exposure had lasted for at least 10 years and had been controlled by regular health examinations and urine analyses. Several dose indicators were calculated. The more heavily exposed workers performed more poorly on the verbal intelligence test (Similarities) than the referents did. Impairments in the memory tests showed a statistically significant correlation with the actual exposure level, especially with the actual concentration of mercury in blood. The monitoring of mercury in blood can be useful in health surveillance programs. The level of mercury in the air was calculated from the dose indicators. The results support the recommended exposure limit of 25 rg/m3 for metallic mercury vapor in the air as a level avoiding adverse effects in exposed workers.

The cerebral effect of long term (mean 15-6, SD 8-9 years) and low (about 25 pg/m3 air) exposure to mercury vapour was studied in a group of 41 workers in a chlor-alkali plant and in a group of matched referents by electroencephalography (EEG). In the visually interpreted EEGs only a tendency for an increased number of EEG abnormalities, especially focal ones, could be seen in the exposed subjects. In the computerised EEG (cEEG), however, the exposed workers had significantly slower and more attenuated EEGs than the referants. This difference was most prominent in the occipital region, became milder parietally, and was almost absent frontally. Our results suggest that cEEG may show early effects on the brain of exposure to mercury vapour.Symptoms from the central nervous system such as weakened memory, insomnia, dizziness, and tremor have been early findings in workers excessively exposed to metallic mercury (Hg) vapour. 2 In chronic poisoning caused by Hg vapour diffuse slowing of electroencephalograms (EEG) has been shown in five of nine patients by Vroom and Greer.' Furthermore, toxic effects of Hg on the EEG have been described as bradyrhythmia or diffuse changes.45 So far as we know, no computerised EEG (cEEG) studies showing the effects of exposure to Hg vapour have been published, even though the method has been frequently applied in pharmaceutical research.6The purpose of our study was to discover whether EEG, and especially cEEG, could show cerebral effects caused by long term low exposure to Hg vapour.This was indeed the case; we found slowing and attenuation of EEG especially in the occipital area of the brain. Subjects and methods STUDY GROUP AND STUDY DESIGNThe study had a cross sectional design in which the data from exposed subjects were compared with the data of their matched referents. The indicator of the long term Hg exposure was calculated from the retrospectively collected results of the blood Hg analyses. Accepted 23 May 1988The exposed group consisted of 41 men from a chlor-alkali plant with an exposure time of at least five years. Their mean age was 38-1 (SD 6-7, range years. The exposure time varied from five to 27 years (mean 15-6, SD 8 9). Subjects with neurological, psychiatric, and metabolic diseases, skull injuries, hypertension, and a history of mercury intoxication were excluded on the basis of previous documents of periodical health examinations performed twice a year as well as of possible case records. Five chlor-alkali workers were excluded from the study, three with hypertension medicated by beta-blockers and two with periodical excessive use ofalcohol. One subgroup (n = 21) had regular daywork. The second subgroup (n = 20) had varying three-shift work with periods of four workshifts and two rest days.One referent, matched for age (± 1 year) and sex, was chosen for every exposed subject. The 41 referents were employed in mechanical wood processing plants.Exclusion criteria from the reference group were earlier occupational exposure either to heavy metals, wood cons...

Renal function indicated by urinary albumin and N-acetyl-beta-glucosaminidase was studied among a group of male chlorine-alkali workers (N = 60) and their matched referents (N = 60). Exposure to mercury vapor had occurred at least 5 y (mean 13.7 y; SD 5.5 y). The estimated long-term exposure level calculated from the time-weighted average blood concentrations of mercury had been approximately 25 micrograms/m3 of air. Neither glomerular nor tubular effects were shown in the exposed workers.

Subjective symptoms related to autonomic dysfunction and quantitative non invasive tests measuring both sympathetic and parasympathetic functions of the autonomic nervous system were studied among a group of 41 chlorine-alkali workers with low long-term exposure to mercury (Hg degree) vapour and their matched referents. The test battery included measurements of pulse rate variation in normal and deep breathing, in the Valsalva manoeuvre and in vertical tilt as well as blood pressure responses during standing and isometric work. The exposure time had been 16 years on average, and the mean exposure to Hg vapour was estimated to have been about 30 micrograms/m3 of air. Only a tendency for a subtle reduction of cardiovascular reflex responses and a slight increase of subjective symptoms were seen in the exposed group, but no significant autonomic dysfunction was associated with the low level of exposure.