Environmental risk of mesothelioma in the United States: An emerging concern-epidemiological issues

Our plain-English summary of Environmental risk of mesothelioma in the United States: An emerging concern-epidemiological issues, by F. Baumann, M. Carbone (Journal of Toxicology and Environmental Health. Part B, Critical Reviews, 2016).

The study

• Authors: F. Baumann, M. Carbone
• Journal: Journal of Toxicology and Environmental Health. Part B, Critical Reviews
• Published: 2016;19(5-6):231-249
• Cited by: 41 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Despite predictions of decline in mesothelioma following the ban of asbestos in most industrial countries, the incidence is still increasing globally, particularly in women. Because occupational exposure to asbestos is the main cause of mesothelioma, it occurs four- to eightfold more frequently in men than women, at a median age of 74 years. When mesothelioma is due to an environmental exposure, the M:F sex ratio is 1:1 and the median age at diagnosis is ~60 years. Studying environmental risk of mesothelioma is challenging because of the long latency period and small numbers, and because this type of exposure is involuntary and unknown. Individual-based methods cannot be used, and new approaches need to be found. To better understand the most recent trends of mesothelioma in the United States, all mesothelioma deaths reported to the Centers for Disease Control and Prevention (CDC) during 1999-2010 were analyzed. Among all mesothelioma deaths in the United States, the 1920s birth cohort significantly predominated, and the proportion of younger cohorts constantly decreased with time, suggesting a decline in occupational exposure in these cohorts. The M:F mesothelioma sex ratio fell with time, suggesting an increased proportion of environmental cases. Environmental exposures occur in specific geographic areas. At the large scale of a state, mesotheliomas related to environmental exposure are diluted among occupational cases. The spatial analysis at a smaller scale, such as county, enables detection of areas with higher proportions of female and young mesothelioma cases, thus indicating possible environmental exposure, where geological and environmental investigations need to be carried out.

In plain English

This article combined a review of earlier research on environmental (non-work) causes of mesothelioma with the authors' analysis of all 31,526 mesothelioma deaths reported to the US Centers for Disease Control and Prevention, 1999 to 2010. Yearly deaths rose from 2,486 to 2,748, but the age-standardized death rate fell from 8.18 to 7.08 per million. The authors reported that the rate fell only in men and stayed stable in women. Men accounted for 25,315 deaths (80.3%) and women for 6,211 (19.7%). The male-to-female ratio went from more than 4 to 1 before 2004 to less than 4 to 1 after 2006. About 65% of deaths were in people born from 1920 to 1939. In Kootenai County, Idaho, the standardized mortality ratio was 2.64 in men and 12.01 in women. The authors concluded that environment-related cases are diluted among work-related cases statewide, but that higher proportions of women and of people under 55, considered together at county level, may flag areas of possible environmental exposure needing further investigation. The data lacked tumor site (pleural or peritoneal) and residential history.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Review of earlier research on environmental mesothelioma, combined with the authors' own descriptive analysis of national death records: time trends and geographic patterns by gender, age, birth cohort, state and county
• Who was studied: All 31,526 deaths from malignant mesothelioma (listed as primary or secondary cause of death) reported to the US Centers for Disease Control and Prevention, 1999 to 2010
• Exposure: Exposure was not measured for individuals, and the authors' own data analysis did not look at fiber types. The authors used the male-to-female ratio and the proportion of deaths under age 55 as indicators of likely occupational versus likely environmental exposure.
• Main results:
  • For the whole United States, the age-standardized mesothelioma death rate fell from 8.18 per million in 1999 to 7.08 per million in 2010. The rate decreased only in males and remained stable in women.
  • The annual number of mesothelioma deaths rose from 2,486 in 1999 to 2,748 in 2010.
  • Mean age at death rose from 71.6 years in 1999 to 73.9 years in 2009. Deaths at age 85 or older rose from 8.6% of all mesothelioma deaths in 1999 to 15% in 2010.
  • 20,500 deaths (65%) were among people born between 1920 and 1939.
  • There were 25,315 (80.3%) male and 6,211 (19.7%) female deaths. The male-to-female ratio was more than 4 to 1 before 2004 and less than 4 to 1 after 2006.
  • By state, the male-to-female ratio ranged from 2.4 to 1 up to 9.0 to 1. The proportion of deaths under age 55 ranged from 1.57% in Delaware to 11.09% in Louisiana.
  • Among counties with the lowest male-to-female ratio, Kootenai County, Idaho, had a standardized mortality ratio of 2.64 in men and 12.01 in women.
  • None of the counties with the highest male-to-female ratio had more than 15% of cases under age 55.
  • The authors judged that neither a high proportion of young cases alone nor a lower male-to-female ratio alone was enough to identify counties with probable environmental exposure. Both were required.
• The authors' conclusion: The authors concluded that environmental risk of mesothelioma may be investigated only at a small geographic scale. They concluded that higher proportions of women and of people under 55 among cases may be used as indicators of environmental exposure to carcinogenic mineral fibers. They also concluded that cases related to environmental exposure are diluted among occupational cases at the state level.
• Limitations the authors state:
  • The database did not record the tumor site (pleura or peritoneum).
  • No residential history was available. Some people may have been exposed somewhere other than where they lived when they died.
  • The epidemiological data alone could not identify sources of exposure. The authors called for further epidemiological, geological and environmental investigations in the flagged areas.
  • Death records may undercount mesothelioma, because the diagnosis may not always appear on death certificates.
  • The short study period did not allow an age-period-cohort model.
  • Small numbers, especially in women, gave standardized mortality ratios wide confidence intervals that cannot be easily compared.
  • The age-group and birth-cohort trends ignore possible demographic changes between years.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Mesothelioma, Occupational Exposure, Environmental Exposure, Latency.

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