Worksite behavioral research: Results, sensitive methods, test batteries and the transition from laboratory data to human health

Ample evidence demonstrates that many chemicals, at some concentration, affect the nervous system. Disastrous incidents resulting from food adulteration, medical experiments and pharmaceutical errors, and industrial and environmental exposures warn of the serious potential for neurotoxicants to affect human health. This article identifies the approximately 185 epidemiological behavioral neurotoxicology studies published through 1989 of extended workplace exposures to chemicals. Approximately 250 different tests have been administered to exposed workers in primarily cross sectional studies, and statistically significant decrements were reported in 43% of the approximately 1100 test/population administrations (virtually all 185 studies employed several of the 250 tests). In this research, 28 different chemicals as well as multiple chemical exposures have been studied. The most extensive findings are seen in research on carbon disulfide, lead, mercury, and multiple solvent exposures, although three or more independent studies also have been reported on workers exposed to styrene and organophosphates. Analyzing the consistent findings in these studies, they reveal a broad spectrum of cognitive, motor, and affective or personality changes. The most frequently reported functional deficits are in tests of intelligence, memory, spatial relations, coordination, and speed plus coordination. Individual behavioral measurement methods and significant test batteries that have been employed to assess changes in human nervous system functions to determine the degree of risk posed by new and established chemicals are described; two of those human behavioral test batteries are predicted to dominate research at the onset of the 1990's. There is a lack of parallelism between the human test methods found in these batteries and the US Environmental Protection Protection Agency (EPA) and Food and Drug Agency (FDA) guideline methods for pre-production screening of chemicals and food additives in animals, and it appears unlikely that the widely employed human and animal behavioral test batteries, as currently evaluated, could identify disease complexes newly suspected of having a chemical etiology.