Firefighters face numerous hazards in the line of duty. The risks of acute and potentially fatal injuries and stresses from the dangerous environment of a fire scene are well known. In addition to these hazards, fires generate toxic contaminants, including some agents known or suspected to cause cancer. Less is known about the potential long-term health effects firefighters may experience as a result of work-related exposures. In particular, do firefighters face a higher risk of cancer than is found in the general population?
In 2010, the National Institute for Occupational Safety and Health (NIOSH) embarked on a multi-year effort to conduct a large-scale study to better understand the potential link between firefighting and cancer. The research was a joint effort led by NIOSH researchers and conducted in collaboration with researchers at the National Cancer Institute (NCI) and the University of California at Davis Department of Public Health Sciences and supported, in part, by the U.S Fire Administration.
Higher Cancer Rates
The study found that a combined population of firefighters from three large U.S. cities showed higher-than-expected rates of certain types of cancer than the general U.S. population.
Other notable findings included:
- The number of firefighter deaths from all causes did not differ from the expected number of deaths based on death rates in the general population.
- The number of cancer diagnoses and cancer-related deaths were greater than that expected based on rates in the U.S. population. The overall excess was comprised mostly of digestive, oral, respiratory, and urinary cancers.
- There were about twice as many malignant mesothelioma cases than expected. Occupational exposure to asbestos in firefighting is the most likely explanation for the greater-than-expected incidence.
- Some cancers were elevated among firefighters under 65 years of age. For example, firefighters who were under 65 years of age had more bladder and prostate cancers than expected.
- Excess bladder cancer risk was evident among women firefighters. However, because bladder cancer is far less likely in women than in men and less than 4% of our study group were women, our results are based on only a few bladder cancer cases.
Our study method is sometimes referred to as a retrospective longitudinal study, meaning that we followed the health experience of a group of persons over a defined time period beginning at a point in the past. In this case, we studied nearly 30,000 career firefighters from Chicago, Philadelphia, and San Francisco who were employed at any time between 1950 and 2009. Participation by multiple fire departments and inclusion of all firefighters better represents the U.S. fire service as a whole; therefore, our results are generalizable to other firefighter populations. The large study group and lengthy follow-up (sometimes referred to as the observation period) improved our ability to observe rare health outcomes, like most cancers. By including the most recent time period, our study is largely informative on current firefighters; while extending observation to the 1950s allows us to look at temporal trends in risk.
Our study is records-based, meaning that only historical information (e.g., personnel records, death certificates and cancer registry data) comprised the study data. A records-based approach is usually best in retrospective studies of persons who may have relocated or are deceased prior to data collection. This approach also avoids a reliance on the recollection of participants for study data, which can differ among persons and over time.
The health outcomes of primary interest are cancers, although other outcomes were investigated. We examined the numbers of cancer deaths and cancer diagnoses among these firefighters and compared them to “expected” numbers based on rates in the U.S. population. Examining cancer incidence (i.e., diagnoses) in addition to deaths from cancer is preferable when assessing risks of cancers that tend to have higher survival rates, such as testicular, bladder, breast, and prostate cancers.
These findings add to a growing body of scientific evidence suggesting a cause-and-effect relationship between work-related exposures and cancer in firefighters. Our next steps will further investigate cause and effect by examining the relationship between “exposure” and cancer among these firefighters. Workplace exposures will be estimated from employment records of fire runs and station assignments.
Raised awareness and exposure prevention efforts are cost-effective means to reduce occupational cancer risk. Thus, the fire service should increase efforts to educate members about safe work practices. This includes proper training, proper use of protective clothing, and proper use of approved respiratory protection during all phases of fire fighting.
More information including study results, frequently asked questions and our firefighter cancer study newsletter can be found at http://www.cdc.gov/niosh/firefighters/ffCancerStudy.html.
Robert D. Daniels, PhD, CHP
Dr. Daniels is a Health Scientist in the NIOSH Division of Surveillance, Hazard Evaluations and Field Studies.