An Evaluation of Trends for Mesothelioma Mortality in American Workers
Mesothelioma, a rare and aggressive form of cancer, continues to be a persistent public health concern in the United States. This malignant neoplasm is primarily associated with occupational and environmental exposure to asbestos fibers and other elongate mineral particles (EMPs). Despite regulatory actions and the declining use of asbestos, the annual number of mesothelioma deaths has remained substantial, underscoring the need for ongoing vigilance and surveillance.
Epidemiology of Mesothelioma
Mesothelioma is a relatively uncommon cancer, with a median survival of approximately 1 year from the time of diagnosis. However, its incidence has been steadily increasing, likely due to the long latency period between initial exposure and disease development, which can range from 20 to 71 years.
Mesothelioma Incidence: The Centers for Disease Control and Prevention (CDC) reported that during 1999-2015, a total of 45,221 deaths with malignant mesothelioma mentioned on the death certificate were recorded in the United States. The annual number of mesothelioma deaths increased from 2,479 in 1999 to 2,597 in 2015, suggesting an ongoing public health concern.
Mesothelioma Risk Factors: Occupational exposure to asbestos fibers and other EMPs is the primary risk factor for mesothelioma development. Hazardous exposures have historically occurred in a variety of industrial operations, including mining, manufacturing, shipbuilding, and construction. Current exposures primarily arise during maintenance activities and the remediation of older buildings containing asbestos.
Mesothelioma Demographics: The burden of mesothelioma mortality has been disproportionately higher among certain demographic groups. During the study period, 79.8% of mesothelioma deaths occurred in males, 94.6% in individuals of white race, and 95.8% in non-Hispanics. Notably, the number of deaths increased among those aged 85 years and older, suggesting prolonged latency and ongoing exposures.
Occupational Exposure to Asbestos
Asbestos-related industries have been the primary drivers of mesothelioma mortality in the United States. The construction industry, in particular, has been a major contributor, accounting for a significant proportion of asbestos consumption throughout the 20th century.
Asbestos-Related Industries: According to the CDC analysis, industries with the highest proportionate mortality ratios (PMRs) for mesothelioma included ship and boat building, petroleum refining, and industrial chemical manufacturing. These findings underscore the historical legacy of asbestos use in these sectors.
Occupational Asbestos Exposure Levels: The Occupational Safety and Health Administration (OSHA) has progressively reduced the permissible exposure limit for asbestos, from 12 fibers per cubic centimeter (f/cc) in 1971 to the current limit of 0.1 f/cc. However, a significant proportion of air samples in the construction industry still exceed these standards, indicating that ongoing exposures remain a concern.
Occupational Asbestos Regulations: OSHA and the Environmental Protection Agency have implemented a range of regulations to limit asbestos exposure, including mandating engineering controls, work practice controls, and the use of personal protective equipment. However, the continuing occurrence of mesothelioma cases, particularly among younger workers, suggests that these efforts may not be sufficient to completely eliminate the risk.
Trends in Mesothelioma Mortality
The analysis of mesothelioma mortality data reveals several concerning trends, both temporally and geographically.
Temporal Patterns of Mesothelioma Mortality: While the age-adjusted mesothelioma death rate decreased by 21.7% from 1999 to 2015, the annual number of deaths increased by 4.8% during the same period. This discrepancy is likely due to the aging of the population and the long latency period associated with mesothelioma development.
Geographic Variations in Mesothelioma Mortality: The CDC’s analysis found that the annualized state-level, age-adjusted mesothelioma death rate exceeded 20 per million per year in two states: Maine (22.06) and Washington (20.10). These regional differences may reflect variations in industrial activity, asbestos use, and exposure patterns.
Demographic Differences in Mesothelioma Mortality: Mesothelioma deaths increased among individuals aged 85 years and older, as well as across all racial and ethnic groups. However, the disease burden remained disproportionately higher among males, whites, and non-Hispanics, consistent with historical patterns of occupational asbestos exposure.
Evaluation of Mesothelioma Mortality Data
The CDC’s analysis of mesothelioma mortality data provides valuable insights, but it is essential to consider the limitations and potential sources of bias inherent in the data.
Data Sources for Mesothelioma Mortality: The study relied on death certificate data from the CDC’s multiple cause-of-death mortality files, which may underestimate the true burden of mesothelioma due to misdiagnosis or coding errors.
Limitations of Mesothelioma Mortality Data: The available data lacked detailed information on individual exposure histories and the specific sources of asbestos or EMPs. Additionally, the industry and occupation data were only available for a subset of the decedents, potentially limiting the generalizability of the findings.
Strategies for Improving Mesothelioma Mortality Surveillance: To better understand the epidemiology of mesothelioma and inform prevention efforts, enhanced surveillance strategies are needed. This may include integrating data from multiple sources, such as cancer registries, workers’ compensation claims, and occupational health surveillance programs.
Public Health Implications
The persistent burden of mesothelioma mortality in the United States underscores the continued need for comprehensive public health interventions and policy actions.
Occupational Health Interventions: Employers must diligently implement the exposure control strategies recommended by OSHA and the National Institute for Occupational Safety and Health (NIOSH), including the use of engineering controls, work practice controls, and personal protective equipment.
Clinical Management of Mesothelioma: Healthcare providers should remain vigilant in the early detection and treatment of mesothelioma, as the disease often presents at advanced stages with a poor prognosis. Innovative therapeutic approaches, such as multimodal treatment and targeted therapies, may offer improved outcomes for patients.
Mesothelioma Prevention Policies: Policymakers should continue to strengthen regulations governing the use, handling, and removal of asbestos to further reduce the risk of exposure among workers and the general public. Ongoing surveillance and research are essential to monitor the effectiveness of these interventions and identify emerging trends.
Conclusion
The analysis of mesothelioma mortality data in the United States paints a concerning picture. Despite regulatory actions and the declining use of asbestos, the annual number of mesothelioma deaths remains substantial, with ongoing exposures and a continued public health burden. Sustained efforts to prevent asbestos exposure, enhance surveillance, and improve clinical management are crucial to mitigate the impact of this devastating disease. By addressing the occupational and environmental factors contributing to mesothelioma, public health professionals can work towards a future with fewer preventable deaths and improved outcomes for those affected.