Portal de Periódicos da CAPES

No Increased Risk for Mesothelioma in Relation to Natural-Occurring Asbestos in Southern Nevada

2015; Elsevier BV; Volume: 10; Issue: 7 Linguagem: Inglês

10.1097/jto.0000000000000564

1556-1380

Paulo S. Pinheiro, Hongbin Jin,

Air Quality and Health Impacts

As cancer epidemiologists, we read the article by Baumann et al.1Baumann F Buck BJ Metcalf RV McLaurin BT Merkler DJ Carbone M The presence of asbestos in the natural environment is likely related to mesothelioma in young individuals and women from Southern Nevada.J Thorac Oncol. 2015; 10: 373-377Abstract Full Text Full Text PDF PubMed Scopus (88) Google Scholar with great interest. We praise Baumann for producing a body of literature on mesothelioma and exposure to natural-occurring asbestos (NOA).2Baumann F Maurizot P Mangeas M Ambrosi JP Douwes J Robineau B Pleural mesothelioma in New Caledonia: associations with environmental risk factors.Environ Health Perspect. 2011; 119: 695-700Crossref PubMed Scopus (62) Google Scholar, 3Baumann F Ambrosi JP Carbone M Asbestos is not just asbestos: an unrecognized health hazard.Lancet Oncol. 2013; 14: 576-578Abstract Full Text Full Text PDF PubMed Scopus (118) Google Scholar, 4Baumann F Rougier Y Ambrosi JP Robineau BP Pleural mesothelioma in New Caledonia: an acute environmental concern.Cancer Detect Prev. 2007; 31: 70-76Abstract Full Text Full Text PDF PubMed Scopus (19) Google Scholar The recent discovery of NOA in Southern Nevada has raised our interest in the surveillance of mesothelioma in the region. Unfortunately, in our opinion, the methodology used was inappropriate for the stated aim of the study: “to test that malignant mesothelioma is increased in Southern Nevada in a pattern consistent with environmental exposure.” The proper indicator of risk in a population or a subpopulation is the incidence rate (gender specific, age adjusted, and/or age specific). Proportions or sex ratios restricted to mesothelioma deaths are not appropriate measures of risk because they do not account for the underlying population pool (and the concept of risk in epidemiology) from which the cases arise. For instance, a male to female sex ratio can be elevated just by virtue of a low number of male cases rather than an actual increased absolute number among females. Likewise, a high proportion of cases in younger populations may be the result of lower numbers in the older groups because of low incidence, or simply because of a smaller population pool. We reviewed the references provided, and there is no scientific consensus on the use of the sex ratio and the proportion under 55 years of age as indicators of environmental (nonoccupational) exposure to asbestos or NOA. The authors presented proportions, ratios, incidence rates for 2006–2010, and then mortality rates for 1999–2010. Multiple comparisons follow but with an inconsistent lists of states, first with states of low incidence (45 states, excluding 5 states classified as high incidence states), followed by mortality comparisons with 35 states without asbestos industry. Only one state, Alaska, has both high incidence and asbestos industry. With this much information from various sources, it is difficult to fully understand the occurrence of mesothelioma in Nevada and in its southern counties (Clark and Nye). These proportions, ratios, and inconsistent comparisons are used as evidence, which is then summarized as “elevated rates,” thus conveying the notion of an increased risk of mesothelioma for Southern Nevada. Simultaneously, the text points to an ecological link between mesothelioma and increased environmental exposure in our region. In referring to a past study, causality (a strong concept epidemiologists reserve to studies using individual level data) is mentioned between NOA and mesothelioma, when the evidence provided is mostly ecological.2Baumann F Maurizot P Mangeas M Ambrosi JP Douwes J Robineau B Pleural mesothelioma in New Caledonia: associations with environmental risk factors.Environ Health Perspect. 2011; 119: 695-700Crossref PubMed Scopus (62) Google Scholar Also, the presented numbers do not add up correctly: a total of 31,526 deaths in the 50 U.S. states is mentioned, but in Table 2, the sum of 49 other states and Clark and Nye counties, 31,545, already exceeds the total sum. Mesothelioma is rare, and the low numbers with high variability across geographic region make the statistical analysis difficult. Because of its very poor prognosis, the incidence and mortality rates of mesothelioma are very similar. Using the in-state mortality files (192 deaths during 1999–2010) and the Centers for Disease Control and Prevention wonder data5United States Cancer Statistics 1999–2011 Mortality, WONDER Online Database. United States Department of Health and Human Services, Centers for Disease Control and Prevention, 2014Retrieved from http://wonder.cdc.gov/CancerMort-v2011.htmlGoogle Scholar (29,663 deaths), we measured the risk for mesothelioma, reproducing the categories Baumann refers as markers for NOA exposure (Table 1).TABLE 1Mortality Rates for Malignant Mesothelioma 1999–2010 with Corresponding 95% Confidence IntervalsAll Age Groups CombinedYounger Age Groups, Sexes CombinedMaleFemale0–49 Years Old0–54 Years Old0–59 Years OldUS-49aU.S. states except Nevada.1.60 (1.58–1.62)0.29 (0.28–0.29)0.04 (0.04–0.04)0.07 (0.06–0.07)0.11 (0.11–0.11)US-34bU.S. states excluding Nevada and 15 states with commercial asbestos production.1.57 (1.55–1.60)0.29 (0.28–0.30)0.04 (0.03–0.04)0.07 (0.06–0.07)0.11 (0.11–0.11)Nevada1.34 (1.12–1.59)0.30 (0.22–0.40)0.04 (0.02–0.08)0.09 (0.06–0.14)0.12 (0.08–0.17)Southern NevadacClark and Nye counties.1.16 (0.92–1.43)0.33 (0.23–0.47)0.05 (0.02–0.10)0.09 (0.05–0.15)0.11 (0.07–0.18)Other Nevada1.78 (1.33–2.33)0.21 (0.10–0.41)0.02 (0.00–0.10)0.09 (0.03–0.19)0.14 (0.07–0.26)Rates are per 100, 000 and age adjusted for the 2000 U.S. standard population.a U.S. states except Nevada.b U.S. states excluding Nevada and 15 states with commercial asbestos production.c Clark and Nye counties. Open table in a new tab Rates are per 100, 000 and age adjusted for the 2000 U.S. standard population. The risk for mesothelioma is not increased in Southern Nevada for any category analyzed. The low sex ratio found by Baumann results from a significantly lower than average mortality among males in Southern Nevada and not from an increased mortality or risk for females. Likewise, the risk is not significantly raised for those aged 0 to 54 years old. Moreover, the choice of 55 years as a cutoff to characterize younger cases is questionable. For the immediately younger (0–49) and older age groups (0–59), the risk in Nevada is fundamentally the same as in the United States. In conclusion, we have strong reservations over the evidence presented on the risk of mesothelioma in Nevada in this article and suggest the use of improved methodology to assess the relationship between NOA exposure and mesothelioma.