LaDou et al. Great Britain, 65,000 occurring after 2001 (Hodgson et al. 2005). Environmental exposures to asbestos. Nonoccupational, environmental exposure to asbestos from the use of construction materials that contain asbestos is also a serious and often neglected problem throughout the world. In developed countries, large quantities of asbestos remain as a legacy of past construction prac- tices in many thousands of schools, homes, and commercial buildings. In developing countries, where asbestos is used today in large quantities in construction, asbestos-contaminated dust is now accumulating in thousands of com- munities, with virtually all people burdened with asbestos fibers in their lungs and bodies (Brophy et al. 2007; Kazan-Allen 2005). Both community-based and industrial exposures to asbestos and asbestiform fibers increase risks for mesothelioma (Pasetto et al. 2005). In a study of women residing in Canadian asbestos-mining communities, Camus et al. (1998) found a 7-fold increase in the mortality rate from pleural cancer. In California, residential proximity to naturally occurring asbestos was significantly associated with increased risk of mesothelioma (Pan et al. 2005); the risk of mesothelioma decreased approximately 6.3% for every 10-km increase in residential distance from the nearest asbes- tos source. Driece et al. (2009) reported that environmental exposures to asbestos waste on the surfaces of roads and yards in a contami- nated community of 130,000 residents in the Netherlands result in several cases of malig- nant mesothelioma each year. The currently observed increase in female cases of mesothe- lioma in the United Kingdom, many with no occupational exposure to asbestos, sug- gests widespread environmental contamina- tion (Rake et al. 2009). In a study in Libby, Montana, (Vinikoor et al. 2010), respiratory symptoms were positively associated with the frequent handling of vermiculite insulation. Residents of this mining community who were children when the mine closed experienced respiratory symptoms associated with asbestos- contaminated vermiculite exposure. Science and Controversy Asbestos is a general term applied to certain fibrous minerals of two configurations: serpen- tine and amphibole. The only type of asbestos derived from serpentine minerals, chrysotile (also known as white asbestos), accounts for 100% of the asbestos used in the world today (Natural Resources Canada 2006). Amphibole minerals include five asbestos species: amosite, crocidolite, tremolite, anthophyllite, and actinolite. Two of these are the most com- mercially valuable forms: amosite, or brown asbestos, and crocidolite, or blue asbestos. Other minerals sometimes containing fibers that are not defined by industry as asbestos, 898 such as erionite, taconite, and talc, are clearly capable of causing asbestos diseases, as are cer- tain man-made fibers, including some nano- fibers (Dikensoy 2008; Ryman-Rasmussen et al. 2009; Sanchez et al. 2009). The thermal and chemical resistance and tensile strength of asbestos fibers gave rise to a burgeon- ing industry before their detrimental health effects—which often take years and decades to appear—became known. The asbestos industry has relied on scien- tific debates over the roles of fiber types, viruses, and genetics in the development of mesothelioma to obfuscate the problem of asbestos-related disease (Castleman et al. 1998). The risk of lung cancer among workers exposed to chrysotile asbestos increases slightly with exposure to longer and thinner fibers (Loomis et al. 2009). However, efforts to use statistical models to characterize relative can- cer potencies for asbestos fiber types and sizes have not been able to overcome limitations of the exposure data. Epidemiologic, experi- mental, and molecular evidence suggests that the arguments for the role of fiber size relative to dose, dose–response effect, and genetic sus- ceptibility are fraught with enormous uncer- tainties (Terracini 2007; Tomatis et al. 2007). Scientists from NIOSH (2010) contend that the uncertainties have been so great that these estimates should not be used to determine occupational and environmental health policy until the agency can perform further research. The U.S. EPA has rejected and discontinued work on its proposed methods for quantifying potency factors for partitioned asbestos fiber types and sizes (Silverstein et al. 2009). Concern has been raised that mesothe- lioma deaths might be partly attributable to poliovirus vaccines used during the 1950s and 1960s that were contaminated with simian virus 40 (SV40), a monkey virus that is tumori- genic in rodents (Leithner et al. 2006; Price et al. 2007). However, sex- and age-specific trends in pleural mesothelioma incidence rates were not consistent with an effect of exposure to SV40-contaminated poliovirus vaccine. In addition, studies reporting a high prevalence of SV40 DNA in human tumors were based on molecular assays that are prone to false-positive results (Lopez-Rios et al. 2004). Some researchers have suggested that sus- ceptibility to asbestos-related diseases is related to genetic differences between individuals within populations. A study of a mesothe- lioma clustering in Turkey advocated the role of genetic susceptibility and familial inheri- tance in the etiology of the disease (Roushdy- Hammady et al. 2001; Saracci and Simonato 2001). A genetic factor identified in three vil- lages in Cappadocia, Turkey, where 50% of individuals die of mesothelioma, may con- tribute to the high incidence of the disease. In these villages, genetic predisposition for mesothelioma works together with erionite (Carbone and Rdzanek 2004). However, in European studies the low proportion of famil- ial cases does not suggest the influence of a large genetic component for mesothelioma in blood relatives (Ascoli et al. 2007). Controversies such as these have helped to make the disease experiences of asbestos- exposed workers and people in asbestos- contaminated communities invisible and uncompensated, allowing the asbestos industry to escape accountability (Braun et al. 2003). The problem extends well beyond asbestos. “Product defense papers” are commissioned by a wide range of industries seeking to blunt regulators’ efforts and to defeat the cases brought by plaintiffs. Even physician-scientists reporting on hazards of asbestos have been dis- ciplined by their politically motivated govern- ments (Joshi et al. 2009). Industries have the resources to seed the literature with strategic science that is less likely to be subjected to the same scrutiny routinely applied to science that is explicitly case specific (Boden and Ozonoff 2008). Many articles, published primarily in toxicology journals, are termed “product defense” science articles and are frequently sponsored by asbestos interests such as the defendants in personal injury asbes- tos litigation in the United States (Axelson et al. 2003; Michaels 2008). These articles are distin- guished from other science papers in that they are written by scientific consultants and con- sulting firms that are approached and paid mil- lions of dollars to publish and promote articles used to try to defeat liability claims (Michaels 2006). General Motors, Ford, and Chrysler sponsored the writing of review articles and meta-analyses of previously published work, and paid almost $37 million between 2001 and 2008 to scientist-consultants at ChemRisk and Exponent, Inc., for presentations of these papers at scientific meetings and expert testi- mony on the articles (Dietz et al. v. ACandS Inc. et al. 2009). These companies were defen- dants in damage suits brought by mechanics over their asbestos exposures and disease arising from automotive friction materials. When there is consensus in the public health community about the health effects of a compound—particularly one that is as well researched as asbestos—government agen- cies and other funders are not interested in additional research that will merely demon- strate what is already known. The only people who have an incentive to continue to fund research on the health effects of chrysotile are those with an economic incentive to raise doubt about its harm. Sponsorship by parties involved in litigation leads to an imbalance in the literature (Michaels and Monforton 2007). As a result, subsequent literature reviews that report a predominance of articles reaching a certain conclusion may then mistakenly report ovlume 118 | number 7 | July 2010 • Environmental Health Perspectives