Introduction
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According to the American Cancer Society,1 there are more than 11 million cancer survivors in the U.S. 2 Many cancers are linked to the environment in which we live, which means that many cancers that are linked to environmental exposures, can be prevented. An exhaustive review of this topic is beyond the scope of this chapter so we will focus on a definition of toxics; a brief orientation to the prevention principle; a brief review of the most common types of cancer by gender; a short section on toxins associated with cancers, mixtures of toxins, and industrial and environmental exposures; summaries of environmental toxins, which can affect the population and cancer survivors, and their relationship to common types of cancer; and what you can do to reduce the risk of cancer. Websites that provide additional information are listed throughout the sections.
For purposes of this chapter, toxins are considered to be any substance that causes biological injury. Generally, they can be thought of as poisons, which can vary in severity and can be delivered to the body in a variety of ways. Common routes of exposure are breathing, ingesting orally, or through the skin.
Precautionary Principle. The precautionary principle encourages the use of caution and foresight in the face of uncertainty. It attempts to avoid irreversible harm when the cause and effect relationships are not well understood. The precautionary principle has become a major tenant of environmental law, governance, natural resources management, and public health. One example of applying the precautionary principle is found in smoking and lung cancer. When scientists first found the associations between smoking and lung cancer, the precautionary principle would argue for avoiding smoking, and exposure to cigarette smoke, prior to understanding the molecular causality mechanisms by which the toxics in cigarettes cause lung cancer. From the time of the original observations and associations, it took decades to start to understand these molecular mechanisms that link cause and effect.
Exposure to tobacco, chemicals, some viruses and bacteria, certain hormones, alcohol, poor diet, and sunlight can increase the risk of cancer. Below are some lists of known carcinogens and their relationship to cancer(s). Some of the toxin exposures may be hard to avoid, especially if they are in or around the environment where someone lives or works (such as traffic pollution, or contaminated water). However, through advocacy and raising awareness more stringent regulation of environmental toxins can lead to decreases in carcinogens and cancer-causing exposures.
Studying carcinogens is challenging because it is hard to control for specific toxin exposures in retrospective studies. Studies that use people who have been diagnosed with cancer are not as reliable as prospective studies, which track a group of people through time, since each person in a retrospective study will have a lifetime of different exposures and different genes that could have contributed to the cancer.
Cancer Statistics
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- The Four most commonly detected cancers by gender, by 2008 estimates are:
Women
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1. Breast 182,460 (26%);
2. Lung & Bronchus 100,330 (14%);
3. Colon & Rectum 71,560 (10%);
4. Uterine Corpus 40,100 (6%);
- Men
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1. Prostate 186,320 (25%);
2. Lung & Bronchus 114,690 (15%);
3. Colon & Rectum 77,250 (10%);
4. Urinary Bladder 51,230 (7%).
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The American Cancer Society predicts about 1,437,180 new cancer cases to be diagnosed in 2008, and the survival rate for those diagnosed with cancer between 1996 and 2003 was 66%.2
Primary prevention with screening and secondary prevention with prevention strategies can reduce colorectal and breast mortality by 15-20%.3,4
Cancer-causing toxins
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- The most frequently occurring known cancer-causing toxins according to type of cancer are listed below:
- Lung cancer related to radon exposure;
Breast cancer related to traffic emissions;
Prostate cancer related to pesticides;
Malignant mesothelioma related to asbestos;
Lung and colon-rectum cancer related to tetrachloroethylene-contaminated drinking water.
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A list of updated cancer toxins as they are classified in the United States can be found on the National Health Institutes website and the International Agency for Research on Cancer.6
The most recent Report on Carcinogens from the National Toxocology Program in Research Triangle, North Carolina lists known and reasonably anticipated human carcinogens.7 Since the research on toxics is evolving, it is prudent to check web-based reports, which may be updated more frequently than written materials. Reporting upon this extensive list is beyond the scope of this chapter, which lays out information on the most common types of environmental toxics and potential ways to reduce exposures. 8
Additional common human carcinogens include:
- Asbestos
Benzene
Benzidine
Cadmium and Cadmium Compounds
Nickel Compounds
Vinyl Chloride
- Mixtures:
The following mixtures of toxins, listed alphabetically, have been found to be carcenogenic.
- Alcoholic beverages
Analgesic mixtures containing phenacetin
Areca nut
Betel quid with tobacco
Betel quid without tobacco
Coal-tar pitches
Coal-tars
Mineral oils, untreated and mildly treated
Salted fish (Chinese-style)
Shale-oils
Soots
Tobacco products, oral tobacco products
Wood dust
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Industrial and Environmental Exposures:
The following types of industrial, occupational, or environmental exposures, listed alphabetically, have been identified as carcenigenic.
- Aluminum production
Arsenic in drinking water
Auramine, manufacture of
Boot and shoe manufacture and repair
Coal gasification
Coke production
Furniture and cabinet making
Hematite mining (underground) with exposure to radon
Involuntary smoking (second-hand smoke)
Iron and steel founding
Isopropanol manufacture (strong-acid process)
Magenta, manufacture of
Painting (occupational exposure)
Rubber industry
Strong inorganic acid mists containing sulfuric acid (occupational exposure to)
Tobacco smoking
Environmental Substances that are known or likely to cause Cancer in Humans
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The section below outlines some of the toxics and risk factors that are in the forefront of the public's attention as cancer-causing or suspected- of- causing cancer agents. We drew heavily on the Cancer and the Environment: What You Need to Know, What You Can Do Report from the National Institutes of Health.
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Tobacco:
- approximately one-third of U.S. deaths from cancer are associated with tobacco. Types of cancer: lung, mouth, bladder, colon, kidney, throat, nasal cavity, voice box, sepophagus, lip, stomach, cervix, liver, and pancreas, leukemia.
- Being overweight:
- breast cancer in older women, cancer of endometrium, kidney, colon, and esophagus.
- Red and preserved meat, salt-preserved foods:
- stomach and colorectal cancers.
- Ionizing radiation:
- x-rays during pregnancy poses an increased risk of childhood leukemia and other cancers.
- Medications:
- some medications increase the occurrence of cancer or second cancers. It is important to discuss medications and their dosages with your physician(s).
- Pesticides:
- ethylene oxide, amitrole, some chlorophenoxy herbicides, DDT, dimethylhydrazine, hexachlorobenzene, hexamethylphosphorzmide, chlordecone, lead acetate, lindane, mirex, nitrogen, toxaphene. (For more information, check www.sghealth.org).
- Estrogen:
- can increase endometrial cancer and some studies indicate an increase of breast cancer; reduces risk of colon cancer. Progesterone can reduce the association with endometrial cancer when taken with estrogen; however, it increases the risk of breast cancer, heart disease, stroke, and blood clots.
- Solvents:
- benzene, carbon tetrachloride, chloroform, dichloromethane (methylene chloride) tetrachloroethylene, and trichloroethylene can be found in paint thinners, paint and grease removers, and in the dry cleaning industry and are suspected of causing cancer. Sources that people are frequently exposed to are gasoline stations, automobile exhaust, and cigarette smoke, which is estimated to expose approximately half of the U.S. population.
- Fibers, fine particles, and dust:
- these exposures can occur in industrial and non-industrial settings. Asbestos is a human carcinogen, and smokers are a high-risk sub-population among those exposed. Ceramic fibers, used in insulation materials, silica dusts, and wood dust are also known carcinogens.
- Dioxins:
- a byproduct of chlorine and hydrocarbon chemical processes, are toxic to humans. These occur in the production of paper, incineration of municipal and hospital waste products, electrical fires, and ore extraction. Insecticides, herbicides, and wood preservatives may also contain dioxins. Modifications of industrial processes such as bleaching and incineration have resulted in reduced dioxin emissions and have lowered dioxin levels in people.
- Polycyclic aromatic hydrocarbons:
- these are produced in burning carbon compounds, including wood and fuel for homes, gasoline and diesel exhaust, soot, coke, cigar and cigarette smoke, and foods that are charcoal broiled.
- Metals:
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- Arsenic:
- (sometimes found in drinking water), found in mining and copper smelting, wood preservatives, glass, herbicides, insecticides, and pesticides. Arsenic is associated with skin, lung, bladder, kidney, and liver cancers.
- Beryllium compounds:
- found in nuclear weapons, rocket fuel, ceramics, glass, plastic, and fiber optic products. Beryllium compounds are associated with lung cancer.
- Cadminum:
- these are found in metal coatings, plastic products, batteries, and fungidices and are associated with lung cancer.
- Chromium:
- found in automotive parts, floor covering, paper, cement, asphalt roofing, anti corrosive metal plating and associated with lung cancer.
- Lead:
- considered a probable carcinogen, is found in cotton dyes, metal coating, drier in paints, varnishes, pigments in ink, certain plastics, and specialty glass. It is associated with kidney and brain cancers.
- Nickel:
- nickel metal is considered a probable carcinogen and nicket compounds are a human carcinogen. These may be found in steel, dental fillings, copper and brass, permanent magnets, storage batteries, and glazes. Nickel is associated with nasal cavity and lung cancers.
- Chromium compounds:
- found in auto parts, electroplating, nuclear and high-temperature research; textile and tanning industries, pigments in floor coverings, paper, cement, asphalt roofing, and emerald-colored glass. Chromium compounds are associated with lung cancers.
- Lead acetate and lead phosphate:
- Lead acetate is found in colon dyes, coatings for metals, in paints, varnishes and pigment inks, permanent hair dyes, in explosives, and in washes to treat poison ivy. Lead phosphate is found in certain plastics and specialty glass. Both metals are associated with kidney and brain tumors in laboratory studies on animals.
- Nickel and Nickel compounds:
- found in steel, dental filings, copper and brass, permanent magnets, storage batteries, and glazes. Both are associated with several types of cancers in research on animals. Human exposures are linked with nasal cavity, lung, and possibly larynx cancers.
- Diesel and exhaust particles:
- Elevated lung cancer rates are found in workers on railroads, in mines, in bus garages, in trucking companies, in car mechanic shops, and around diesel generators.
- Vinyl chloride:
- in the U.S. the primary exposure is living near a plastics production plant or being a worker in such a plant. Exposure is linked to lung, blood vessel, liver, and brain cancers.
- Benzine:
- found in benzene-based dyes, which are considered toxic only in the vicinity of the dye and pigment plants. Benzine is associated with bladder cancer.
- Diethylstilbestrol (DES):
- a synthetic form of estrogen used in the U.S. between 1940 and 1971. Daughters whose mothers were prescribed DES during pregnancy have an increased risk of cervical and vaginal cancer. Their mothers have an increased risk of breast cancer. DES has been banned in the US, including its use in cattle feed.
Action: What can you do?
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Avoiding chemical and other toxics sometimes can be accomplished by individuals in their choice of exposures to specific environments and occupations. Since at least two-thirds of carcinogens are environmental in nature, many consider that the role of the government is a critical component of assuring that the air, water, soil, and food in our communities are safe and that exposures from industry and other activities do not pose risk to individuals and families.
Suggested activities include:
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Join cancer advocacy groups. Advocates and survivors are in a unique position to present data and individual stories that persuade legislative bodies and elected officials to implement safeguards against toxics.
Elect political representatives that believe in the regulation of toxics to protect the public from poisons.
Let your elected representatives know that you and your community hold them accountable for toxics that can affect the public's health. The U.S. has a history of regulating toxic substances that are detrimental to individuals' health. This record can be built upon to continue regulating substances that are toxic to individuals in their communities, in the market place, and the work place.
List of Common Cancers and some Toxins associated with them:
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Type of Cancer
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Toxic Substance/Material
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Common Places where the Toxic is Found
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Factors associated with Increased Risk |
| Breast Cancer |
Organochlorine** this is still controversial
Ionizing radiation exposure
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Insecticides
Nuclear Fallout
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Hormone replacement therapy
Obesity
Alcohol |
| Cervical Cancer
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Cigarette Smoke
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Cigarettes, second hand smoke |
Long-term use of oral contraceptives
High parity
Human Papillomavirus |
| Colon and Rectal Cancer
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|
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Obesity |
| Endometrial Cancer
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|
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Obesity |
| Esophageal Cancer |
Cigarettes, chewing tobacco |
Gastroesophageal reflux/Barrett esophagus |
Obesity
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| Kidney Cancer |
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Obesity |
| Leukemia |
Benzene
Pesticides |
Gasoline, chemical and drug industries, and traffic pollution
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| Lung Cancer |
Cigarette Smoke
Beta Carotene
Radon
Asbestos
Silica Dusts |
Cigarettes, second-hand smoke
Pharmocological doses, combine with high-intensity smoking
In homes/ rocky soil
Insulation
Mines, mills, quarries |
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| Melanoma |
|
Sunlight exposure |
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| Oral Cancer |
Tobacco
Alcohol
Pesticides
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Cigarettes, pipes, cigars, smokeless tobacco |
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| Ovarian Cancer |
|
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Obesity
Gene mutations
Age
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| Prostate Cancer |
Pesticides |
|
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| Skin Cancer |
Ultraviolet radiation
Pesticides |
Sun |
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| Information in this table from: National Cancer Institute (http://www.cancer.gov) |
- References:
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1. http://www.cancer.org/docroot/home/index.asp
2. American Cancer Society. Cancer Facts & Figures 2008. Atlanta: American Cancer Society; 2008
3. "Improving Organochlorine Biomarker Models for Cancer Research",
Mary S. Wolff, Julie A. Britton, Susan L. Teitelbaum, Sybil Eng, Elena Deych, Karen Ireland, Zhisong Liu, Alfred I. Neugut, Regina M. Santella and Marilie D. Gammon,
Cancer Epidemiology Biomarkers & Prevention, Vol. 14, 2224-2236, September 2005
4.
Recommendations of the US Preventive Services Task Force. http://www.ahrq.gov/clinic/pocketgd.htm. Accessed June 16, 2008.
5.National Health Institutes website (www.niehs.nih.gov/health/docs/cancer-enviro.pdf) and the International Agency for Research on Cancer (monographs.iarc.fr/ENG/Classification/index.php).v,vi
6. International Agency for Research on Cancer (monographs.iarc.fr/ENG/Classification/index.php)
7. http://ntp.niehs.nih.gov/ntp/roc/eleventh/known.pdf
8. http://ntp-server.niehs.nih.gov/index.cfm?objectid=32BA9724-F1F6-975E-7FCE50709CB4C932
9.http://www.cancer.gov/images/Documents/5d17e03e-b39f-4b40-a214-e9e9099c4220/Cancer%20and%20the%20Environment.pdf
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