Neurobehavioral effects in occupational chemical exposure.

Neurobehavioral effects in 30 female workers (aged 18-41, mean 25.6) exposed to an average of 341 mg/m3 (SD 100) toluene for an average of 5.7 years (SD 3.3) compared with 30 matched controls (aged 18-48, mean 25.1), 24 male workers (aged 18-32, mean 24.7) exposed to 268 mg/m3 (SD 185) toluene equivalent of mixed solvent (82.2% toluene, 12.3% ethyl acetate, and 5.5% methyl ethyl ketone) for 2.3 years (SD 3.0) compared with 24 matched controls (aged 17-31, mean 24.3), and 94 dentists (aged 24-49, mean 31.7) exposed to 0.017 mg/m3 (SD 0.009) of elemental mercury for 7.4 years (SD 5.3) compared with 54 referents (aged 23-50, mean 33.6) were studied. The Z score (made up of Digit Span, Symbols Digit, and Grooved Peg Board) for the workers exposed to toluene was 0.79, for workers exposed to mixed solvents was 0.38, and for the dentists exposed to mercury was 0.42. The Z score for each group of exposed subjects was statistically poorer than that for its controls. Neurobehavioral performance was statistically related to exposure intensity for the toluene-exposed workers and to years of exposure or dose (exposure intensity x years of exposure) for mixed solvent- and mercury-exposed subjects. The type of chemical species and pattern of exposure appear to influence whether the adverse effects will be cumulative.

Metals in hair as biological indices for exposure.

Hair samples from three groups of occupationally exposed subjects were analyzed for their lead (Pb), manganese (Mn) and mercury (Hg) contents. For lead (number of subjects, n = 209), the hair Pb ranged from 0.93 to 3527 micrograms/g (geometric mean, GM = 641) and blood Pb from 33.3 to 774 micrograms/l (GM = 341); for manganese (n = 38), the hair Mn ranged from 0.20 to 52.97 micrograms/g (GM = 2.66) and urine Mn ranged from 1.70 to 17.9 micrograms/l (GM = 5.56); and for mercury (n = 85), the hair Hg from 1.79 to 12.8 micrograms/g (GM = 5.09) and the blood Hg from 0.63 to 57.3 micrograms/l (GM = 10.9). The hair Pb was significantly (P < 0.0001) correlated to blood Pb (r = 0.85); the hair Mn to urinary Mn (r = 0.45); and the hair Hg to blood Hg (r = 0.53). The average metal content at the distal end was not significantly (P > 0.05) different from that of proximal end. The GM levels for the distal end were 223 micrograms/g (95% CI 152-347) and 2.26 (95% CI 0.97-5.29); and those for the proximal end were 186 (95% CI 97-261) and 1.18 (95% CI 0.54-2.58) for Pb and Mn respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic neurobehavioural effects of elemental mercury in dentists.

Neurobehavioural tests were performed by 98 dentists (mean age 32, range 24-49) exposed to elemental mercury vapour and 54 controls (mean age 34, range 23-50) with no history of occupational exposure to mercury. The dentists were exposed to an average personal air concentration time weighted average (TWA) of 0.014 (range 0.0007-0.042) mg/m3 for a mean period of 5.5 (range 0.7-24) years and had a mean blood mercury concentration of 9.8 (range 0.6-57) micrograms/l. In neurobehavioural tests measuring motor speed (finger tapping), visual scanning (trail making), visuomotor coordination and concentration (digit symbol), verbal memory (digit span, logical memory delayed recall), visual memory (visual reproduction, immediate and delayed recall), and visuomotor coordination speed (bender-gestalt time), the performance of the dentists was significantly worse than that of the controls. The dentists scored 3.9 to 38.9% (mean 13.9%) worse in these tests. In trail making, digit span, logical memory delayed recall, visual reproduction delayed recall, and bender-gestalt time test scores were more than 10% poorer. In each of the tests in which significant differences were found and in the block design time, the performance decreased as the exposed dose (product of the TWA of air mercury concentrations and the years of exposure) increased. These results raise the question as to whether the current threshold limit value of 0.050 mg/m3 (TWA) provides adequate protection against adverse effects of mercury.

Epidemiologic study on the association between body burden mercury level and idiopathic Parkinson's disease.

A case-control study was conducted among the multiethnic population of Singapore to test the hypothesis that a high level of body burden mercury is associated with an increased risk of Parkinson's disease (PD). Selected factors investigated that could contribute to the body burden of mercury included dietary fish intake, ethnic over-the-counter medications, occupational exposures and possession of dental amalgam fillings. Detailed interviews were completed in 54 cases of idiopathic PD and 95 hospital-based controls, matched for age, sex and ethnicity, between July 1985 and July 1987. After adjusting for potential confounding factors, including dietary fish intake, medications, smoking and alcohol consumption, there was clear monotonic dose-response association between PD and blood mercury levels. The odds ratios (OR) and 95% confidence intervals (CI) for the approximate subject tertiles based upon blood mercury levels were 8.5 (CI = 2.2-33.2) and 9.4 (CI = 2.5-35.9), relative to the tertile with lowest blood mercury levels (less than 5.8 ng Hg/ml). Similar associations were revealed using scalp hair and urinary mercury levels. However, only the comparisons between the highest and lowest tertiles were statistically different from unity (p less than 0.05). When the body burden mercury indicators were mutually adjusted in addition to the four confounding factors, blood and urinary mercury levels showed ORs of 21.00 and 18.65, respectively. These ORs were statistically different from unity (p less than 0.05, 2-sided test). After adjustment, scalp hair mercury was shown to be a poor predictor of PD risk.

Mercury in scalp hair of healthy Singapore residents.

Two hundred and twenty-five hair samples (150 Chinese, 44 Malays and 31 Indians) from healthy residents not occupationally exposed to mercury were analyzed by cold vapour atomic absorption spectrophotometry to determine their total, inorganic and organic mercury levels. The arithmetic means of total mercury levels in hair were 6.1, 5.2 and 5.4 ppm for the Chinese, Malays and Indians, respectively. Factors contributing to the amount of mercury in hair, including consumption of fish and marine products, use of traditional ethnic medicines, artificial hair waving, age, sex and ethnicity were analyzed. Fish consumption, sex and ethnicity are factors found to contribute significantly (p less than 0.05) to mercury levels in hair.

Atomic absorption spectrophotometric microdetermination of total mercury in undigested biological samples.

The influence of reaction time upon stannous (II) chloride as a reductant in the cold-vapor atomic absorption spectrophotometric method was investigated. In this comparative study, virtually all operating conditions, including volumes and chemicals used, were made identical except for the redesigning of the reaction vessels. The use of a reaction mixing time of 2 minutes (TR method), rather than immediate bubbling with aspiration (IL method) of total mercury from undigested biological samples, has several advantages. There is an average 4.5-fold increase in sensitivity of peak height readings with virtually no loss of mercury vapor from the reaction vessel by diffusion. Using the TR method also eliminated interaction of mercury with the matrices investigated, viz., undigested blood, undigested saliva, undigested urine, and digested hair samples. The average recovery for the TR method was superior to the IL method, 99.3 +/- 3.2% vs. 84.7 +/- 3.3%, p less than 0.05. In addition, mercury concentrations determined with the TR method were identical using either peak area or peak height readings. It was also found that concentrations determined using either the formulae given by Magos and Clarkson (4) and Farant et al. (5) or an aqueous calibration curve were equivalent. Only 0.2-1.0 mL of biological samples was needed for each analysis in the study.

Epidemiologic study of dental emergencies among utilizers in an insured population in Washington, USA.

This is a study of the epidemiology of dental emergencies based on information abstracted from the microfilmed dental claim forms of a large American insurance program in 1981-82. Overall, about 4% of all dental visits were classifiable as emergencies. There were significant seasonal and age variations in dental emergencies. There was no variation with respect to geographic regions in the State of Washington (USA) or sex. Paradoxically, residents in regions having fluoridated water supplies were at equal risk of developing dental emergencies due to dental caries, relative to those residing in non-fluoridated regions. There was also no difference in risk associated with insurance deductibles, although generally deductibles are thought to deter first-contact visits.

Cyclopia: an anatomic and histologic study of two specimens.

The craniofacial complex of two neonatal, human, cyclopic specimens was studied in detail. Both specimens exhibited a single ocular opening and one had a prominent probosics positioned in the midline directly superior to the ocular aperture. No external nasal development was noted in the other specimen. The most remarkable finding was the lack of development of all skeletal derivatives of the ethmoidal cartilage(cribriform plate, perpendicular plate, superior and middle nasal conchae, medial orbital walls, and nasal septal cartilage) in both specimens. Since these bones normally form the medial, lateral, and superior walls of the nasal passage, this cavity was also absent. The two posterior halves of the maxillae were directed superiorly, medially, and with the vomer merged in the midline as a thick mass of bone. As a result the right and left alveolar portions of the maxillae were joined superiorly in the midline. With the absence of the nasal cavity, the right and left medial pterygoid plates merged medially with the palatal and pyramidal processes of the palatine bone to obstruct the junction between the oropharynx and nasopharynx(choanal atresia). The role of the skeletal parts of the ethmoid during maxillofacial growth and development is discussed.