Cancer clusters difficult to prove

Concerns must be addressed

A cancer cluster is a greater than expected occurrence of cancer cases in a group of people in a given workplace or geographical area. Concern among members that there is a cancer cluster in their school or district is one of the most challenging health and safety issues a local association can face. Emotions are sure to run high, privacy issues concerning sensitive medical information abound, and “proving” that a cluster is work-related is virtually impossible. Nevertheless, working together with its UniServ field representative, a local association can direct the energy members have around a possible cancer cluster into positive outcomes.

We don’t usually know if work is affecting employee health. School districts do not monitor employee health. Most physicians don’t ask workers about their workplace exposures. Association members themselves may not recognize health problems as work-related. They may think they are related to aging or lifestyle. Or members may be afraid to report suspected work-related effects or hazards even if they do have questions or are seeing connections.

Occupational epidemiology studies are rarely done. A crude science, it can only detect huge increases in health effects in small populations like a school or school district. If the increase in the cancer rate is small, it will be statistically very difficult to detect. In the unlikely event that a cluster is proven, it will be virtually impossible to identify a single occupational cause, because if occupational exposures did cause cancer cases, those exposures will have taken place 10, 20, or even 30 years earlier and long forgotten.

A final obstacle is that some true clusters occur by chance, without any obvious exposure to carcinogens. A cluster is more likely to be “genuine” if the cases consist of one type of cancer, a rare type of cancer, or a type of cancer that is not usually found in a certain age group. Between 5 to 15 percent of suspected cancer clusters are statistically significant.

Action still possible

Because of all this, it is often best for the local association to focus on what can be done to improve the present school environment. Better housekeeping and ventilation, for example, will lower exposures to air pollutants that might contribute to future cancer cases.

Concerns about a cancer cluster can provide the inspiration to form a health and safety committee to work to reduce current exposure to carcinogens in the school. For example, the committee can monitor the asbestos management plan, review radon testing, and push for reducing pesticide use in the school by making sure the district complies with Integrated Pest Management (IPM) regulations. The NJEA Health and Safety Manual provides a blueprint for action.

Whatever course of action the local association takes, it is important not to invalidate members’ cancer concerns. Even if it can’t be proven, there really may be a cancer cluster with an occupational or environmental cause. Carcinogens that may be found in school environments include asbestos, radon, polychlorinated biphenyls (PCBs), certain viruses, tobacco smoke, wood dust, silica dust, diesel exhaust, arsenic wood preservatives, formaldehyde, and some pesticides. And there may be many others because most chemicals have not been tested to see whether or not they cause cancer.

When addressing cancer cluster concerns, it helps if everyone realizes these facts:

  • Cancer is very common and gets more common with age.
  • Cancer can be found among people at any workplace.
  • Almost half of U.S. men and over a third of U.S. women will get cancer at some time in their lives.
  • The most common cancers among U.S. men are prostate, lung, colon and rectal, urinary bladder, and skin. Among women in this country, the most common cancers are breast, lung, colon and rectal, ovarian, uterine, and skin.
  • Smoking, obesity, diet, and alcohol are the biggest culprits for most cancers with perhaps 5 percent having environmental causes.
  • In order to be a cluster, the cancer cases must be one or only a few types of cancer and the people must be concentrated in a particular job title or location.

A concern about cancer at work may be reported by calling the New Jersey Department of Health and Senior Services (DHSS) which may agree to collect basic information with the assistance of the person or organization that reports the possible cluster. After reviewing the initial data, most often a decision is made that additional investigation by the DHSS is not necessary.

For example, if there are many different types of cancer, a lengthy and expensive investigation cannot be justified. If a decision were made that additional investigation is appropriate, the person who reported the cancer concern would be asked to collect more detailed information. All of this information must be kept confidential by the person collecting the information and by the DHSS.

The following information must be gathered in order to begin an investigation:

  • The number of people with cancer and the time period during which the cases were diagnosed.
  • The types of cancer, the date of diagnosis, age, sex, and occupation of each of the individuals with cancer.
  • How many years the persons with cancer worked in their current jobs or at their current workplaces.
  • The type and size of the work unit (e.g., a school with 20 teachers).
  • Whether there is or was direct exposure to a specific hazard at work, especially anything that is known or suspected to cause cancer.