January 28, 2015

Study by COPH researchers finds brain cancer more common in poultry workers

C O P H Professor Department of Epidemiology Eric Johnson, M B B S, P h D, M P H, D T P H

Eric Johnson, Ph.D.

Brain cancer has been found to be more common among poultry workers involved in the killing of chickens in an exploratory study published last year in Nutrition and Cancer by researchers at the Department of Epidemiology at the UAMS Fay W. Boozman College of Public Health (COPH) and their colleagues at the University of North Texas Health Science Center. The purpose of the study was to investigate brain cancer in occupational groups that typically have the highest known exposures to poultry and raw poultry products, as well as in other occupations in the meat industries.

Killing chickens was associated with a near 6-fold increase in risk for brain cancer compared with the risk in the comparison group. A 13-fold increase in risk for brain cancer was associated with working at a shellfish farm.

An extensive questionnaire asked of relatives of deceased workers as well as workers still alive delved into workers’ specific occupational tasks, lifestyle, and medical history. It was found that eating raw fish or shellfish is associated with an 8-fold increased risk of death, compared to a control group.

Workers in poultry slaughterhouse and processing facilities often handle thousands of chickens in a day, come in contact with poultry meat, organs and blood, and are at risk of injuries that provide a route for viruses and other microbial agents to enter the body. They also work in enclosed areas for extended periods of time, increasing the risk of inhaling airborne organisms. Researchers suspect that viruses known to cause cancer in poultry may be responsible for the increased incidence of cancer in poultry workers who kill chickens.

The study, entitled “A pilot case-cohort study of brain cancer in poultry and control workers,”builds on a large body of research, now spanning three decades, by Eric Johnson, M.D., Ph.D., MPH, DTPH, Professor and Chair of the college’s Epidemiology Department. His work has focused on the health of workers in the meat industries and related occupations.

A group of almost 47,000 poultry and non-poultry workers in Missouri, Maryland, and Illinois was the source population for the study, as well as many other studies by Dr. Johnson over the years. All of the workers were members of the United Food and Commercial Workers International Union between 1949 and 1989. Of those who died during the 14-year study period (1990-2003), 47 workers died of brain cancer, according to their death certificates. About 1,500 workers randomly selected from the base population comprised the comparison group.

For the study, interviews were conducted with next-of-kin for 26 of the 47 workers who had died of brain cancer and 152 of the controls or next-of-kin of those workers who had died. They answered a 646-item questionnaire that asked about where they had worked (e.g., working or living on a farm, working in meat industries other than poultry) and a range of non-work-related questions about lifestyle, medical history, diet, medication use and immunizations. The questionnaire asked very specific questions about tasks typically done by poultry workers, such as unloading chickens from trucks, killing and cutting them up, and hanging them on a conveyor line. Only workers who killed chickens were at a statistically significant (5.8 odds ratio) increased risk of dying from brain cancer.

The study’s findings are consistent with numerous other studies by Dr. Johnson and his group using the same large cohort of poultry workers. Occupational exposures for meat industry workers are associated with elevated risk for cancers of the pancreas, lung and liver. It is also consistent with studies by other researchers. However, this latest study emphasizes that it is only preliminary and that “results should be interpreted with caution,” in part because it has limited statistical power. Also, the fact that the brain cancer cases interviewed were all proxies, whereas controls were mostly the live subjects, could potentially be a source of response bias, authors noted.

Dr. Johnson has published more than 30 articles in peer-reviewed journals about elevated cancer risks for workers in the meat industry, and many of those are specific to poultry workers. Even so, he says that definitively linking cancer risk to those occupational exposures will require something more. In pursuit of that, he has developed and patented the only assay to date that can detect the presence of cancer-causing viruses in the genome of human subjects.

“The thing that will nail that these viruses cause cancer is to find them in the human genome by studying exposed people who actually developed the cancer,” Dr. Johnson said.

Full reference: Gandhi S, Felini MJ, Ndetan H, Cardarelli K, Jadhav S, Faramawi M, Johnson ES. A pilot case-cohort study of brain cancer in poultry and control workers. Nutrition & Cancer, April 2014. DOI: 10.1080/01635581.2013.878734.