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Both mechanistic and epidemiology studies indicate chrysotile asbestos has a threshold below which it does not cause mesothelioma or lung cancer. We conducted a critical review to determine whether electricians are at increased risk for these cancers and, if so, whether their exposure to chrysotile in electrical products could be responsible. We found that most, but not all, epidemiology studies indicate electricians are at increased risk for both cancers. Studies that evaluated electricians' exposure to asbestos during normal work tasks have generally reported low concentrations in air; an experimental study showed that grinding or drilling products containing encapsulated chrysotile resulted in exposures to chrysotile fibers far below the OSHA permissible exposure limit and the cancer no observed adverse effect level. Studies of other craftsmen who often work in the vicinity of electricians, such as insulators, reported asbestos (including amphibole) exposures that were relatively high. Overall, the evidence does not indicate that exposure to chrysotile in electrical products causes mesothelioma or lung cancer in electricians. Rather, the most likely cause of lung cancer in electricians is smoking, and the most likely cause of mesothelioma is exposure to amphibole asbestos as a result of renovation/demolition work or working in the proximity of other skilled craftsmen., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Following exposure to a substance, several biological events can occur that may eventually, depending on the exposure dose and duration, lead to adverse effects. We developed a framework to evaluate whether an exposure is causally related to an effect and whether that effect is adverse. An exposure is not likely to be causal if an effect is: not statistically significantly different in exposed and non-exposed study subjects; isolated or independent; secondary; observed because of study limitations; or unrelated to the apical effect and not associated with functional impairment. Adaptive effects are not adverse and, although effects that overwhelm homeostasis often are, this may not be the case if they are transient, early precursors of an apical effect, reversible, or of low severity. We applied the framework to a case study of sulfur dioxide (SO(2)) and conclude that the available evidence supports a short-term exposure threshold of 400 ppb SO(2) for adverse effects on lung function in sensitive individuals. At this concentration, effects are transient, reversible, and of low severity. Below this concentration, effects are isolated or independent and not statistically different in exposed and unexposed subjects in clinical trials, and study limitations affect interpretation of observational studies., (Copyright © 2010 Elsevier Inc. All rights reserved.)