The National Cancer Institute compiles an ongoing list of substances deemed to be probable carcinogens. Carcinogens are substances that trigger the onset of cancer. When a cell is exposed to a carcinogen, the genetic information encoded in its DNA is altered. There are some carcinogens that don’t affect DNA but they still cause cancer to develop by other means. They do this by accelerating the rate at which cells divide, upping the risk for DNA changes.
Substances listed as carcinogens can pose different cancer-causing threats—some are more likely to trigger cancer than others. Others may only lead to cancer after long and lengthy exposure. Then, too, there is the issue of an individual’s genetic response to a carcinogen and how they are exposed to this carcinogen.
Take, for example, the chemical trichloroethylene (TCE). TCE has recently been added to a list of potential carcinogens compiled by the National Cancer Institute. TCE is used as a cleaning agent in the dry cleaning industry. It is also used in various manufacturing processes as a degreaser.
In a recent study, researchers looked at the effects TCE had on workers exposed to the chemical in Finland, Sweden, and Denmark. This study was thorough and comprehensive, following the workers for 42 years. Before the conclusion of the study, TCE was linked to an increased risk for cervical and liver cancer. The chemical also played a smaller role in the development of kidney, esophageal, and non-Hodgkin lymphoma cancer.
The researchers stressed that the average person going to the dry cleaners doesn’t need to worry about their exposure. The study primarily points to the need to protect workers in the dry cleaning industry who experience long-term exposure to TCE.
The carcinogenic potential of TCE is going to continue to stir up controversy. More studies are needed to determine the exact threat of TCE. Unfortunately, the tests involved in proving the carcinogenic threat of a substance are often done on animals who are exposed to excessively high levels. It’s not always clear if the results from these animal studies will show similar results in humans. Then too, animal bodies can react differently to carcinogens than human bodies. Researchers also have difficulty determining the cancer risk of a carcinogen depending on whether it is inhaled or absorbed through the skin.
Researchers can test TCE through epidemiological studies, like they did in the case of the study conducted on workers in Finland, Sweden, and Norway. But even studies like these have their limits. People are exposed to different chemicals in the course of living their lives. If can be hard to determine the precise influence of any one chemical when it comes to cancer risk.
By performing multiple types of studies, a substance like TCE can be classified as a probable carcinogen if the combined results are conclusive. This would seem to be the case for TCE, especially since the National Cancer Institute has weighed in and added the chemical to its list of carcinogens.
Hansen, J., et al., “Risk of Cancer Among Workers Exposed to Trichloroethylene: Analysis of Three Nordic Cohort Studies,” J Natl Cancer Inst. May 30, 2013.
Karami, S., et al., “Occupational trichloroethylene exposure and risk of lymphatic and haematopoietic cancers: a meta-analysis,” Occup Environ Med. May 30, 2013.
Straif, K., et al., “Occupational exposure to trichloroethylene and perchloroethylene and the risk of lymphoma, liver, and kidney cancer in four Nordic countries,” Occup Environ Med. June 2013; 70(6): 393-401.