Exposure reconstruction for substances of interest to human health is a process that has been used, with various levels of sophistication, as far back as the 1930s. The importance of robust and high-quality exposure reconstruction has been recognized by many researchers. It has been noted that misclassification of reconstructed exposures is relatively common and can result in potentially significant effects on the conclusions of a human health risk assessment or epidemiology study. In this analysis, a review of the key exposure reconstruction approaches described in over 400 papers in the peer-reviewed literature is presented. These approaches have been critically evaluated and classified according to quantitative, semiquantitative, and qualitative approaches. Our analysis indicates that much can still be done to improve the overall quality and consistency of exposure reconstructions and that a systematic framework would help to standardize the exposure reconstruction process in the future. The seven recommended steps in the exposure reconstruction process include identifying the goals of the reconstruction, organizing and ranking the available data, identifying key data gaps, selecting the best information sources and methodology for the reconstruction, incorporating probabilistic methods into the reconstruction, conducting an uncertainty analysis, and validating the results of the reconstruction. Influential emerging techniques, such as Bayesian data analysis, are highlighted. Important issues that will likely influence the conduct of exposure reconstruction into the future include improving statistical analysis methods, addressing the issue of chemical mixtures, evaluating aggregate exposures, and ensuring transparency with respect to variability and uncertainty in the reconstruction effort.
The potential carcinogenicity of beryllium has been a topic of study since the mid-1940s. Since then, numerous scientific and regulatory bodies have assigned beryllium to various categories with respect to its carcinogenicity. Past epidemiologic and animal studies, however, have been marked with notable methodological shortcomings. Because it has been about 16 yr since IARC evaluated beryllium and approximately 50 relevant papers on the topic have been published since that time, we conducted a weight-of-evidence analysis of the historical as well as recent animal and human literature. We also assessed whether recently published studies improved upon methodological shortcomings or shed light upon uncertainties in prior studies. Thirty-three animal studies, principally designed to evaluate the cancer hazard or related mechanisms, and seventeen epidemiologic studies were considered in this assessment. Based on this analysis, the evidence for carcinogenicity of beryllium is not as clear as suggested by previous evaluations, because of the inadequacy of the available smoking history information, the lack of well-characterized historical occupational exposures and shortcomings in the animal studies. We concluded that the increase in potential risk of lung cancer was observed among those exposed to very high levels of beryllium and that beryllium's carcinogenic potential in humans at exposure levels that exist in modern industrial settings should be considered either inadequate or marginally suggestive.
Many years of exposures to flavoring chemicals in this workplace, including diacetyl, were not found to produce an increased risk of abnormal spirometric findings.
Talc has been used for over a century in a variety of cosmetic products. While pure cosmetic talc (free of asbestos) is not considered a risk factor for mesothelioma, it has been recently suggested that inhalation of cosmetic talc containing trace levels of asbestos is a risk factor for mesothelioma. Bulk analyses of cosmetic talcum products were performed in the 1960s and 1970s, however, the analytical methods used at that time were incapable of determining whether asbestos minerals were present in the asbestiform versus non-asbestiform habit. The distinction between these two mineral habits is critical, as non-asbestiform amphibole minerals do not present an asbestos-related cancer risk via inhalation. As such, we evaluated six historical talcum powders using modern-era analytical methods to determine if asbestos is present, and if so, to identify the mineral habit (asbestiform versus non-asbestiform) of the asbestos. Based on their labels, the products were produced by four manufacturers and sold between 1940 and 1977. The products were analyzed in duplicate by two laboratories using standard protocols. Laboratory A analyzed samples using X-ray diffraction (XRD) and polarized light microscopy (PLM), and Laboratory B analyzed samples using PLM and transmission electron microscopy (TEM) with energy dispersive X-ray analysis (EDX) and selected area electron diffraction (SAED). No asbestiform minerals were found in any of the products. Nonetheless, even if some historical cosmetic talcum products contained trace amounts (≤0.1%) of asbestiform minerals, any resulting asbestos exposure would be expected to be exceedingly low, and comparable to exposures from breathing ambient air.
The study of occupational exposure to asbestos has been an ongoing activity for at least 75 years, dating back to the papers of Merewether and Price (1930). Since that time, literally tens of thousands of air samples have been collected in an attempt to characterize the concentration of asbestos associated with various activities. Many of the individuals who developed diseases from the 1970s to the current day were often exposed to very high airborne concentrations because of direct or indirect exposure to either raw asbestos fiber or insulation during the approximate 1940-1970 time period. Often, these high exposures were associated with work in shipyards during and after World War II and the Korean War, as well as with decommissioning, which continued into the mid-1970s. This study reviews the historical asbestos concentrations measured in shipyards and presents a visual illustration of typical conditions and work practices. A majority of the photographs presented in this article depict work conditions at the Puget Sound Naval Shipyard, circa 1940-1965, which is representative of other military shipyards of the time.
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