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 They recommended instead that consideration be given to "implementing measures to prevent or reduce the frequency" of the reported effects.

Murray [1991] also conducted a review of the potential health effects of CCP exposure at the request of the Commission of the European Communities. He noted an absence of documented cases of skin disorders among workers in the manufacturing industry—despite the fact that workers in this industry would be expected to have much higher exposures than office workers. On the basis of both his review of the literature and his experiences as a consultant for a manufacturer of CCP, Murray concluded that although individual cases of sensitivity to CCP components would continue to be reported, a "negligible" threat is posed to the health of producers and users.

Since 1991, additional studies (including some that qualify as analytical epidemiology) have appeared in the scientific literature. The following review considers not only information published in the scientific literature but also information that was submitted to NIOSH in response to announcements in the Federal Register in 1987 and 1997. More than 14,000 pages of combined submissions were received in response to the 1987 and 1997 Federal Register notices. Most of the submissions were made after the latter notice. No materials were accepted or reviewed if the submitter considered the items to contain proprietary information that could not be made available to the public. Information that contained personal identifiers was blocked out unless the submitter wanted the information to remain public.

The following review of CCP health effects separately considers the information from human and animal studies.

Human studies of CCP have dealt mostly with exposures in office settings. Three types of human studies of CCP have been conducted: individual case studies or case series, cross-sectional studies, and laboratory studies in humans. The following sections separately review each type of study.

The case report is a detailed profile of a single subject; case series describe the characteristics of a number of patients with a given disease. Case reports and series document unusual features of a disease or a patient’s exposure history; they are a type of descriptive epidemiologic assessment. Case reports and series can present a major problem in interpretability because the presence of any risk factor may be simply coincidental. Their usefulness is generally limited by the lack of a comparison group (i.e., persons without such symptoms who had similar opportunity for exposure). The lack of a formal comparison group in these studies can make it difficult to determine whether the observed associations represent more than the normal background rate of disease. Lack of a comparison group is particularly problematic when the cases involve common diseases or symptoms and when the exposure is relatively common (which is clearly the case with these reports for CCP exposures). In the absence of a comparison group, case reports and series can provide the first clues to the identification of new diseases or exposure effects, and they are potentially useful for formulating research questions; however, the evidence usually cannot be used to test hypotheses [Buring and Hennekens 1991]. On the other hand, when characteristic symptoms and clinical signs vary over time in direct correspondence with