10 facts you should know about occupational carcinogens

Transcription

1 10 facts you should know about occupational carcinogens Carcinogens are the time bombs of hazardous substances in the workplace. But many substances do not develop their deadly effect until years after exposure. It s a risk for the worker that is often underestimated and represents an enormous challenge for industrial hygienists. The good news is that occupational cancer can be prevented through monitoring and protective measures. Drägerwerk AG & Co. KGaA 1

2 1. Cancer in the workplace is twice as common as occupational accidents. Every year, 660,000 deaths occur worldwide due to work-related cancer.* * Nenonen N., Hämäläinen P., Takala J., et al. (2014) Global estimates of occupational accidents and fatal work-related diseases in 2014, Singapore, Workplace Safety & Health Institute Plastic is a deadly threat. For many years, vinyl chloride was considered to be safe. This compound of carbon, hydrogen and chlorine is a raw material used in the production of PVC. In 1974, seven cases of severe (and very rare) liver cancer were found in individuals who worked at a PVC plant in Louisville, Kentucky. Five of the afflicted workers, all of whom had worked with vinyl chloride for 20 years, had already died. 1 It is only because of the efforts of the National Institute for Occupational Safety and Health (NIOSH) and the energetic probing of a few scientists that the connection between cancer and vinyl chloride became known. The authorities reacted quickly: In 1974 OSHA established a threshold limit for vinyl chloride that was 500 times more rigorous that before. As a result, liver tumors in workers as a result of vinyl chloride exposure have not occurred since. 3. Carcinogens are toxic to cells. Carcinogenic substances are a subgroup of toxic agents that have the potential to cause cancer in living tissues. Carcinogen exposure can occur from the inhalation, ingestion, or absorption of many different types of substances in our bodies. Carcinogens may increase the risk of cancer by altering cellular metabolism or damaging substances such as proteins, ribonucleic acids, and especially DNA directly in cells which interferes with biological processes. This causes genetic abnormalities to develop in the normal cell. With cancer, cells go out of control, multiply without order, and invade and destroy the surrounding tissue. The changes in a cell s DNA are called genetic blueprint. Some of these changes may be inherited from our parents and grandparents. If, and to what degree, a carcinogen actually causes cancer is highly dependent on each individual organism. Drägerwerk AG & Co. KGaA 2

3 4. Substances are acutely toxic at first, then carcinogenic. Exposure time is a critical factor for carcinogenic substances in the workplace. Most carcinogens do not develop their carcinogenic effect in a brief exposure. However, they can cause toxic effects in other ways. For instance, acute inhalation of chromium IV compounds starts by causing nausea, but can lead to caustic effects on the skin and mucous membranes. For the threat of cancer to exist, long-term exposure to a carcinogen is often necessary. For example, many workers who were exposed to asbestos for a prolonged period developed a particular form of lung cancer called mesothelioma. It takes at least 20 years and in many cases 40 years before the cancer appears. Since asbestos is no longer used in the construction industry, no new cases of occupational mesothelioma are expected to occur in the United States after Carcinogens pose a lifelong risk. Carcinogens do not cause cancer in every case. Substances labeled as carcinogens may have different levels of cancer-causing potential. It is true that a large amount of a cancer-causing substance leads to cancer much more frequently. But even very small doses can develop a harmful effect although the probability is clearly lower. The risk of developing cancer due to contact with a carcinogen remains throughout one s lifetime, since in many cases cell damage does not develop until years after contact with the substance. And for any particular person, the risk of developing cancer depends on many factors including how they are exposed to a carcinogen, the length and intensity of the exposure, and the person s genetic makeup. 6. Occupational cancer is more common than previously thought. Approximately 3 to 6% of all cancer cases are due to substances in the workplace 3,4 Europe: More than 100,000 deaths every year are due to job-related cancer 5 USA: Each year, there are as many as 90,000 new cases of cancer and 30,000 work-related deaths globally 6 7. A mouse is not a human, and vice versa. Detecting the cancer-generating property of a chemical agent is often very difficult. It is not ethical to test a substance by exposing people to it and seeing if they get cancer. That s why scientists must use other types of tests which may not always give clear answers. For example, it is not easy to deduce whether or not a substance is carcinogenic from animal testing. Rodents and humans often react to chemical substances in entirely different ways. 19 out of 20 test substances that are considered safe for humans cause cancer in rodents. 7 However, of 19 sub- stances known to cause cancer in humans, only seven prove to be carcinogenic in rodents. 8 Here s another example: The artificial sweetener saccharine gives rise to bladder cancer in male rats, but not in female rats or humans. 9 This is why multiple sources should be used and combined, such as: Lab studies in animals and examinations Tests and lab studies of human cell cultures Human case and epidemiologic studies and observations from practice Drägerwerk AG & Co. KGaA 3

4 8. The chemical industry is subject to a particularly high risk. In the United States, most occupations don t present a major risk for developing cancer. However, there are some industries such as certain types of chemical manufacturing, mining, coal production, and iron and steel founding in which cancer risk is higher for certain workers. WHEN IS A SUBSTANCE CALLED CARCINOGENIC? When the evidence is conclusive, the substance is labeled as a carcinogen. When the available evidence is compelling but not felt to be conclusive, the substance may be considered to be a probable carcinogen. But in some cases, there simply isn t enough information to be certain one way or the other. Lung Asbestos, crystalline silica, diesel engine exhaust, arsenic, chromium, nickel Liver and biliary tract Trichloroethylene, vinyl chloride Bladder Aromatic amines Nasopharynx Formaldehyde Larynx Acid mists, asbestos Mesothelioma Asbestos Ovary Asbestos Skin mineral oils, polycyclic aromatic hydrocarbons Leukemia Benzene, formaldehyde Non-hodgkin lymphoma trichloroethylene Graphic modified according to Siemiatycki, J, et al. Listing occupational carcinogens. Environmental Health Perspectives, Vol. 112, no. 15 (2004). p Drägerwerk AG & Co. KGaA 4

5 9. Carcinogens are classified according to potential harm. Various organizations test chemicals for their cancer-causing potential. Chemicals, mixtures, substance groups, and other carcinogens are divided into different groups, as follows: IARC* ACGIH* Group 1: Carcinogenic to humans Group A1: Carcinogenic to humans Group 2A: Probably carcinogenic to humans Group A2: Probably carcinogenic to humans Group 2B: Group 3: Possibly carcinogenic to humans Not classifiable with regard to carcinogenicity to humans Group A3: Group A4: Confirmed carcinogenic to animals, unconfirmed relevance to humans Not classifiable as human carcinogen Group 4: Probably not carcinogenic to humans Group A5: Not carcinogenic to humans * International Agency for Research on Cancer (IARC)/Division of the World Health Organization * American Conference of Governmental Industrial Hygienists (ACGIH) 10. Binding occupational exposure limits bring greater safety. Most people know that asbestos is a potential cancer threat in the workplace. But what about trichloroethylene, benzene, or the various chromium compounds? The European Trade Institute has listed 71 cancer-causing substances that constitute 80% of the carcinogens to which people may be exposed in the workplace. Binding occupational exposure limits are being mandated for at least 50 substances that cause work-related cancer. 10 Conclusion: Occupational cancers can be prevented. All types of occupational cancer are preventable. To minimize the risk of cancer caused by on-the-job exposure, substances considered to be carcinogenic should not be used at all. But that is not always possible. However, taking appropriate measures can significantly reduce the health danger to workers. Strong regulatory control including occupational exposure limits, worker education, and constant attention to safe practices are needed to minimize workplace exposure to carcinogens. However, occupational exposure limits are only one component of better work and health safety because these substances can still represent a threat to health. Besides minimizing exposure to potentially carcinogenic substances, appropriate protective and safety gear is important. In addition, all employees who handle carcinogenic substances should have occupational training and medical supervision. Drägerwerk AG & Co. KGaA 5

6 Occupational cancer was known about as far back as : Identification of 2-naphthylamine as cause of bladder cancer in dye plant workers 2011: Classification of formaldehyde as carcinogenic 1755: Recognition of testicular cancer in chimney sweeps as an occupational cancer 1974: Recognition of vinyl chloride as the cause of liver tumors in the plastics industry IMPRINT USA Dräger Safety AG & Co. KGaA Revalstraße Lübeck Drägerwerk AG & Co. KGaA 6

7 SOURCES: 1 Mundt, KA, Dell, LD, Austin, RP et al. Historical cohort study of 10,109 men in the North American vinyl chloride industry, : update of cancer mortality to 31 December Occup Environ Med. 2000; 57: Price B, Ware A. Time trend of mesothelioma incidence in the United States and projection of future cases: an update based on SEER data for 1973 through Crit Rev Toxicol. 2009;39(7): Straif K. The burden of occupational cancer. Occupational and Environmental Medicine. 2008;65(12): Driscoll T, Takala J, Steenland K, et al Review of estimates of the global burden of injury and illness due to occupational exposures. Am J Ind Med 48: Figures of the European Trade Institute (ETUI) at (Accessed: October 31, 2016) 6 Centers for Disease Control and Prevention. U.S. Cancer Incidence Statistics: an Interactive Atlas. gov/dcpc_inca/. (Accessed October 29, 2015) 7 Ennever FK, Noonan TJ, Rosenkranz HS. The predictivity of animal bioassays and short-term genotoxicity tests for carcinogenicity and non-carcinogenicity to humans. Mutagenesis Mar;2(2): Salsburg, D. The Lifetime Feeding Study in Mice and Rats - An Examination of Its Validity as a Bioassay for Human Carcinogens. Fundamental & Applied Toxicology 1983;3: National Cancer Institute: What have studies shown about a possible association between specific artificial sweeteners and cancer? At (Accessed: October 31, 2016) 10 Wriedt H. Carcinogens that should be subject to binding limits on workers exposure At Publications2/Reports/Carcinogens-that-should-be-subject-to-binding-limits-on-workers-exposure (Accessed: October 31, 2016) For an extensive list of potentially carcinogenic substances that includes IARC, ACGIH and OSHA classifications, go to: Drägerwerk AG & Co. KGaA 7