Environmental health perspectives
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Environ. Health Perspect. · Sep 1994
Generation of hydroxyl radical by chromate in biologically relevant systems: role of Cr(V) complexes versus tetraperoxochromate(V).
While Cr(V) species and. OH radicals have been suggested to play significant roles in the mechanism of chromate-related carcinogenesis, controversy still exists regarding the identity of the Cr(V) species and their role in the generation of. OH radicals. ⋯ OH radicals. (iii) The major Cr(V) species formed are complexes of Cr(V) with reductant moieties as ligands. (iv) These Cr(V) complexes generate. OH radicals from H2O2 via Fenton-like reaction. The present study thus disagrees with the recently proposed "tetraperoxochromate(V) theory of carcinogenesis from chromate." Instead, it suggests an alternative mechanism, which might be labeled as "the Cr(V)-complexation-Fenton reaction model of carcinogenesis from chromate.
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Environ. Health Perspect. · Jun 1994
ReviewAssessment of developmental toxicity: neuropsychological batteries.
Assessment of change in behavioral functioning in children as a function of neurotoxicity is not a trivial undertaking. Psychological tests, widely (though erroneously) considered to be the "gold standard" for measurement of behavior in humans, are not adequate for the task; they tap the structure of cognition, not the behavioral repertoire, and cannot (alone) address developmental change. ⋯ Measures of neuropsychological outcome are optimally characterized as they relate to behavioral domains specified in terms of the competencies of infants and children of different ages; relevant information is derived from demographic, socioeconomic, medical, developmental, and educational sources, as well as from detailed observational data and performance on psychological tests. Two levels of assessment are proposed.
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Carcinogenesis data for 315 chemicals were obtained from the National Cancer Institute-National Toxicology Program (NCI-NTP) bioassay programs and were analyzed to examine the shape of carcinogenesis dose-response curves. Tumor site data were more often consistent with a quadratic response than with a linear response, suggesting that the routine use of linear dose-response models will often overestimate risk. ⋯ It was found that there were no clear relationships between the shape of the carcinogenesis dose-response curve and the result of the short-term test. These observations argue against the concept that carcinogens that are positive in a short-term assay be regulated using a linear dose-response curve and those that are negative be regulated using a sublinear dose-response curve or a safety factor approach.
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Environ. Health Perspect. · Nov 1991
Complex mixtures in industrial workspaces: lessons for indoor air quality evaluations.
Acceptable occupational exposure levels for hundreds of airborne concentrations of dusts, vapors, fumes, and gases have been set by consensus organizations and regulatory bodies for decades. These levels have established tremendous precedent and are tempting reference values in the relatively new field of indoor air quality evaluations where validated criteria are greatly needed. The American Conference of Government Industrial Hygienists (ACGIH) has been the most visible and productive group setting these guidelines for industrial exposure. ⋯ The only guidance given by the ACGIH for synergistic effects is that such cases must be determined individually. Clearly, there are major drawbacks in using occupational standards and guidelines for evaluating the health effects of chemical agents that can be found in office settings, often in concentrations orders of magnitude less than what is routinely measured in the workplace. These guidelines are even less valuable when the concern is the complex mixing of chemicals in nonoccupational environments.