Residual neurologic deficits 30 years after occupational exposure to elemental mercury.

A battery of tests of peripheral and central nervous system function was administered to 205 former workers of a large heavy industrial plant, 104 of whom were previously exposed to inorganic mercury. The mean age of those examined was 71 years. Exposed subjects had participated in a urine-mercury exposure monitoring program during the time of operation of a process that required the use of mercury and its subsequent clean-up. Mercury exposure had been high (mean peak urine mercury concentration was >600 microg/l) and had ended 30 years or more prior to the investigation. Peripheral nerve function outcomes that were statistically significantly associated with cumulative mercury exposure after controlling for covariates included classification as having peripheral neuropathy, peroneal motor nerve conduction velocity, ulnar motor nerve conduction velocity, and peroneal motor nerve F-wave latency. Quantitative assessment of resting tremor was nearly significantly associated with cumulative mercury exposure (p=0.07). Among tests of central nervous system function, results of the Handeye Coordination test were significantly associated with cumulative mercury exposure after controlling for covariates. Cumulative mercury exposure was not observed to be associated with a quantitative measure of dementia or with a number of cognitive neurobehavioral test outcomes. The statistically significant associations with mercury exposure were observed in spite of greater mortality among the exposed group than the unexposed group. These results suggest that substantial occupational mercury exposure can have long-term adverse effects on the peripheral nervous system detectable decades after cessation of exposure. Such long-term adverse effects were not observed for a measure of dementia or other measures of cognitive function.

Infertility: from a personal to a public health problem.

The inability to conceive a child is most often viewed as a private matter, but public health perspectives and skills can contribute greatly to our knowledge about infertility, and the development of effective and rational public policy for prevention, access to health care, and regulation of new technologies. We offer a primer of public health aspects of infertility in an effort to encourage the broad spectrum of public health professionals to become more knowledgeable about these topics and join in the national debate about preventive strategies, cost-benefit assessment, resource allocation, and ethics.

Neurobehavioural effects of occupational exposure to organic solvents among construction painters.

A cross sectional study of 101 construction painters was performed to investigate the relation between exposure to mixed organic solvents and changes in central nervous system function. Solvent exposure was estimated using questionnaire data to derive an exposure index (a measure of intensity of exposure) and to estimate the duration and frequency of exposure. Adverse effects on the central nervous system were assessed by self reported questionnaires and eight tests of a computer administered neurobehavioural evaluation system. Factor analysis of both measures of effect yielded factors both biologically plausible and in agreement with other empirical evidence. A consistent positive association was observed between most measures of exposure and the occurrence of neurotoxic symptoms, notably dizziness, nausea, fatigue, problems with arm strength, and feelings of getting "high" from chemicals at work. Associations with exposure were found with the neurobehavioural evaluation system tests of symbol digit substitution and digit span; however, no consistent pattern of effect on neurobehavioural function was observed. This pattern of the occurrence of neurotoxic symptoms without clear evidence of function deficit is consistent with the type 1 toxic central nervous system disorder as classified by the World Health Organisation.

Estimation of long term exposure to mixed solvents from questionnaire data: a tool for epidemiological investigations.

Quantifying the exposure of construction painters to mixed organic solvents is difficult in the face of a lack of industrial hygiene data, the heterogeneity of the solvents used, and the variability in work practices which influences the amount of solvents to which a worker is actually exposed. This report describes an attempt to derive an estimate of airborne solvent exposure using questionnaire responses in a population of construction and maintenance painters. This exposure index (EI) is a weighted average of the total number of gallons used a year minus the fraction which would be absorbed by a respirator, where the weights are based on the method of application (spraying, rolling, brushing) and the presence of ventilation (per cent time inside v outside). An analysis performed to determine the sensitivity of the EI to variations in the values chosen for several parameters showed that the index is relatively insensitive to the underlying assumptions that we have used. One component of the EI (self report of hours worked) correlated well with union payroll records. The EI appears to provide a useful relative (not absolute) estimate of airborne exposure to organic solvent mixtures which may be used as a dose surrogate in epidemiological investigations.

A computer-based neurobehavioral evaluation system for occupational and environmental epidemiology: methodology and validation studies.

To facilitate the evaluation of populations at risk for nervous system dysfunction due to environmental agents, we have developed a computer-administered neurobehavioral evaluation system (NES). The system includes a set of testing programs, designed to run on a microcomputer, and questionnaires which are used to record symptoms, obtain exposure history, and characterize potential confounding variables. Standard tasks evaluating memory, visual/motor function, vocabulary ability, and mood were selected and adapted for computer presentation following the recommendation of a World Health Organization (WHO)-National Institute for Occupational Safety and Health (NIOSH) expert committee. After the performance of several pilot studies designed to refine our methodology, validation studies were initiated to assess comparability of selected computer tasks to existing standard ones administered and scored by an interviewer. A different aspect of validity, score stability, was addressed by repeated administration of tests to a small unexposed group. Comparability to existing tests was good (r = .42 to .76). Score stability was excellent over a 150 day interval, particularly for the digit span and continuous performance tests. From our experience, this approach appears to be a feasible, efficient, acceptable, and sensitive approach to evaluating central nervous system function in populations.