Definition and Identification
Definitively, human carcinogens are substances, chemicals, or exposures that increase the risk of contracting cancer in humans. In essence, some of these chemicals do not cause cancer by directly interfering or altering the DNA’s blueprint but rather, through increased cell division above regular rates thereby increasing the chances of DNA alteration culminating in cancerous cells. While there is a myriad of carcinogens that increase the risk of developing cancer, the Environmental Protection Agency (EPA), National Toxicology Program (NTP), International Agency for Research on Cancer (IARC), and the American Cancer Society (ACS) have been fundamental in categorizing the chemicals or exposures according to their severity and level of cancer-causing potential. These categories include
Group 1: Carcinogenic to humans
Group A: Probably carcinogenic to humans
Group 2B: Possibly carcinogenic to humans
Group 3: Unclassifiable as to carcinogenicity to humans
Group 4: Probably not carcinogenic to humans
On this accord, Friis (2019) in his chapter 7discussions highlights some of the main known carcinogenic compounds or chemicals to humans. From his discussions, three main compounds or human carcinogens stand out and make-up part of the top twenty hazardous substances list by the ATSDR. The three chemicals are dioxins, polychlorinated biphenyls, and pesticides.
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Dioxins : these are highly toxic chemically-related compounds produced as by-products of some manufacturing processes such as paper bleaching or production of herbicides. These not only cause cancer but also result in developmental and reproductive problems, interference with the hormonal system, as well as damage to the immune system. An example is Polychlorinated dibenzo-p-dioxins.
Polychlorinated biphenyls (PCBs) : these are human-made chemicals that are widely used as lubricants and coolants in capacitors, transformers, and other electrical equipment due to their resistance to burning easily and excellent insulation properties. PCBs build up in the environment with some taking dioxin-like characteristics thereby increasing the risk and incidence of cancer primarily because of their high Toxicity Equivalency Factor ranging from 77 to 189, (American Cancer Society, 2016).
Pesticides : Friis as well identifies pesticides as carcinogenic to humans, especially those containing arsenic and inorganic compounds. Thus, pesticides are chemical substances or compounds used to destroy or control insects and other organisms that pose deleterious threats to animals and cultivated plants. Some of these substances and compounds include those that contain DDT, chlordane, and lindane which according to Dich, Zahm, Hanberg, & Adami (1997) are tumor promoters. Others such as phenoxy and herbicides have been linked with soft tissue sarcoma (STS).
Other health Effects upon Exposure
Short-term exposure to high levels of dioxins might result in skin lesions, particularly patchy darkening of the skin, as well as chloracne. Also, this exposure could result in an altered liver function. Long-term exposure could also result in impaired endocrine and nervous system. On the other hand, exposure to high levels of PCBs similarly results in skin conditions such as rashes and acne. Internally, exposure results in liver damage observed through changes in urine as well as blood. Ultimately, while some pesticides such as phenoxyl have been linked with STS, they as well have been linked with malignant lymphoma. Exposure to high doses of organochlorine insecticides has also been attributed to non-Hodgkin’s lymphoma (NHL), leukemia, and lung as well as breast cancers, (Dich, Zahm, Hanberg, & Adami, 1997). Ultimately, triazine herbicides result in ovarian cancer.
Examples of Accidents
Dioxins : In Italy 1976, an explosion occurred in a chemical plant which resulted in a massive airborne discharge of dioxins over Soveso. As such, more than 37, 0000 people living in the region were exposed to doses of dioxins. Luckily, there were no deaths from acute poisoning and exposure, (National Academies Press, 1995).
PCBs : On 3 rd August 1982, two massive explosions took place in the electricity room of a large paper mill in Imatra, Finland. Due to a lack of protective gear, more than 15 individuals were heavily exposed PCB with an average chlorine content of 42%, (Elo et al., 1985). The victims evidenced symptoms such as acute irritation of the respiratory tract.
Pesticides : The 2002 mass arsenic poisoning in Bangladesh where between 28-77million Bangladeshi were exposed to high levels of arsenic through drinking water from wells rich in arsenic. This exposure resulted in arsenicosis, (WHO, 2019).
Interventions
One of the critical interventions undertaken by organizations and institutions such as ACS and EPA to reduce exposure to the three chemical compounds is advocating for environmental health on local, state, and federal levels. This has further been achieved by creating awareness and educating the public regarding the various forms of dioxins, pesticides, and PCBs and their health effects. The organizations further put in efforts in educating individuals regarding how to reduce their risks of getting cancer beyond exposure to the three carcinogens but also other compounds in the ATSDR list. Dioxins mainly bioaccumulate in the food chain, and thus, the main route of human exposure is through food consumption, especially meat, fish, and dairy products. Therefore, the FDA has restricted consumption of some of the food products, especially those known to be contaminated with dioxins such as TCDD.
On the other hand, EPA has removed and banned some of the herbicides, especially 2,4,5-T from the commercial market as well as other heat-transfer agents that use PCBs. Through research, EPA continues to identify and eliminate these compounds further giving recommendations to less harmful ones. Also, to reduce harmful exposure, professional individuals such as firefighters, incinerator workers, and workers in herbicides, germicides, and organic solvents manufacturing industries are being rallied and enforced through the OSHA regulations to put on protective gear when undertaking their duties.
Moreover, as much as OSHA proffers stringent regulations to employers regarding ensuring their workers’ safety, it also enforces strict regulations with the help of EPA regarding toxic waste disposal. Also, following the massive contamination in Bangladesh, WHO has been materialistic in undertaking water decontamination measures and recommending these measures to governments while setting acceptable standards of arsenic contamination in water to 10ppb, (WHO, 2019).
References
Dich, J., Zahm, S. H., Hanberg, A., & Adami, H. O. (1997). Pesticides and cancer. Cancer Causes & Control , 8 (3), 420-443. http://lcms.truni.sk/europa/media-for-preview/ZPE/pesticides_and_cancer.pdf
Elo, O., Vuojolahti, P., Janhunen, H., & Rantanen, J. (1985). Recent PCB accidents in Finland. Environmental health perspectives , 60 , 315-319.
Friis, R. H. (2019). Essentials of environmental health, third edition . Jones & Bartlett learning. ISBN-13: 978-1284123975
The American Cancer Society. (2016). Known and probable human carcinogens. Retrieved from https://www.cancer.org/cancer/cancer-causes/general-info/known-and-probable-human-carcinogens.html
The National Academies Press. (1995). Case Study 13: Dioxin Toxicity. Environmental Medicine: Integrating a Missing Element into Medical Education. Institute of Medicine doi: 10.17226/4795
WHO. (2019). Arsenic - Mass poisoning on an unprecedented scale. Retrieved from https://www.who.int/features/archives/feature206/en/
