Cancer and The Environment
Photo by John Cameron on Unsplash
The “environment” includes the areas where people live, learn, work, worship, and play. It’s made up of the air they breathe, the water they drink, the food they eat, and other conditions they may not control, but which can affect their health. The most significant risks of developing cancer come from lifestyle factors. However, exposures to certain human-made and naturally occurring substances in the environment may contribute to an individual’s risk of developing cancer. The International Agency for Research on Cancer (IARC) has classified these substances (and many others) as known human carcinogens or possible or probable (suspected) human carcinogens.
Climate change is associated with increased cancer risk through a variety of mechanisms, including increased ultraviolet exposure, risk of exposure to air pollution and toxic chemicals, heat, and reduced access to cancer screening, and most notably through disruption in cancer care itself. Environmental pollution causes cancer. For example, tiny particles may build up in the lungs and damage the DNA in cells. This can change how cells divide, which can lead to cancer.[1]
Environmental Factors Associated With Cancer[2]
Air Pollution: Exposure to air pollution has been linked to an increased risk of certain cancers, particularly lung cancer. Fine particulate matter, nitrogen oxides, sulfur dioxide, and other pollutants released from vehicles, industrial facilities, and power plants can penetrate deep into the lungs and bloodstream, causing inflammation, oxidative stress, and DNA damage that may contribute to cancer development.
The most significant environmental risk factor for cancer is tobacco products like cigarettes, pipes, cigars, chewing tobacco, snuff or vaping, being exposed to secondhand smoke and asbestos. Asbestos occurs in rock and soil and is often found in building construction materials for insulation. The mineral fiber increases the risk of lung cancer, mesothelioma, laryngeal cancer and ovarian cancer. Asbestos exposure accounts for the largest percentage of occupational cancer risks, mainly workers who also smoke.
Water Pollution: Water is another key source of pollution. Water contaminated with high levels of arsenic is a cause of bladder cancer, and it's also been associated with skin and lung cancers. Contamination of water sources with chemicals, heavy metals, and carcinogenic substances poses a hidden yet significant risk to human health.
From industrial runoff to agricultural runoff and inadequate wastewater treatment, there are numerous sources of water pollution that can expose individuals to harmful substances. Arsenic, chromium, chlorination byproducts, and other contaminants found in drinking water have been associated with an elevated risk of cancer, including bladder cancer, kidney cancer, and gastrointestinal cancer.
Pesticides and Herbicides: The widespread use of pesticides and herbicides in agriculture presents another environmental challenge with potential health consequences. Exposure to these chemicals, whether through direct contact with agricultural workers or residues on food, has been linked to an increased risk of certain cancers, such as non-Hodgkin lymphoma and leukemia.
Food Contaminants: Food contaminants, including aflatoxins, polycyclic aromatic hydrocarbons (PAHs), and other carcinogenic substances, can pose a risk to human health when consumed in contaminated food products. Aflatoxins produced by molds in grains and nuts, PAHs formed during food processing or cooking at high temperatures, and other foodborne contaminants have been associated with an increased risk of liver cancer, stomach cancer, and other malignancies.
Radiation Exposure: Exposure to ionizing radiation, whether from medical imaging procedures, nuclear accidents, or natural sources such as radon gas, can increase the risk of cancer. While medical imaging plays a crucial role in diagnosing and treating diseases, excessive or unnecessary exposure to radiation should be minimized whenever possible.
Endocrine Disruptors: Endocrine disruptors are chemicals that interfere with the endocrine system, potentially disrupting hormone balance and increasing the risk of hormone-related cancers such as breast cancer, prostate cancer, and ovarian cancer. Found in plastics, pesticides, flame retardants, and other common household products, these chemicals pose a significant health threat, particularly during critical periods of development such as fetal development and puberty.
Factors That Are Known To Increase The Risk Of Cancer[3]
· Cigarette Smoking And Tobacco Use: The most significant environmental risk factor for cancer is tobacco, whether people are using products like cigarettes, pipes, cigars, chewing tobacco, snuff or vaping, or being exposed to secondhand smoke. In fact, tobacco accounts for 80 % to 90 % of all cases of lung cancer, which is the top most common cancer in both men and women. Scientists believe that cigarette smoking causes about 30% of all cancer deaths globally. Smoking cigarettes is the leading cause of the following types of cancer:
· Acute myelogenous leukemia (AML)
· Infections: Certain viruses and bacteria are able to cause cancer. Chronic infection with human papillomavirus (HPV), hepatitis B or hepatitis C virus is the most common risk factor for liver cancer. Both viruses are spread by sharing contaminated needles, unprotected sex and childbirth. Also, the Epstein-Barr virus, which causes mononucleosis, is linked to some types of lymphoma. Currently, there are no vaccines for hepatitis C or Epstein-Barr, barring hepatitis B. Examples of cancers caused by infections include:
· Human papillomavirus (HPV) increases the risk for cancers of the cervix, penis, vagina, anus, and oropharynx.
· Hepatitis B and hepatitis C viruses increase the risk for liver cancer.
· Epstein-Barr virus increases the risk for Burkitt lymphoma.
· Helicobacter pylori increases the risk for gastric cancer.
Two vaccines to prevent infection by cancer-causing agents have been developed and approved by the US Food and Drug Administration (FDA). One is a vaccine to prevent infection with hepatitis B virus. The other protects against infection with strains of human papillomavirus (HPV) that cause cervical cancer. Scientists continue to work on vaccines against infections that cause cancer.
· Ultraviolet (UV) rays from the sun, sunlamps or tanning beds may damage cell DNA and lead to melanoma or other forms of skin cancer. Skin cancer is the most common form of cancer, affecting more than 3.5 million people in globally including countries like US each year, and melanoma accounts for the most skin cancer deaths. And its incidence is on the rise. There are two main types of radiation linked with an increased risk of cancer:
· Ultraviolet radiation from sunlight
· Ionizing radiation including:
· Medical radiation from tests to diagnose cancer such as X-Rays, CT scans, fluoroscopy, and nuclear medicine scans.
· Radon gas in our homes.
Scientists believe that ionizing radiation causes leukemia, thyroid cancer, and breast cancer in women. Ionizing radiation may also be linked to myeloma and cancers of the lung, stomach, colon, esophagus, bladder, and ovary. Being exposed to radiation from diagnostic X-rays increases the risk of cancer in patients and X-ray technicians. Diagnostic radiation in children and adolescents has been linked with a higher risk of cancers at a young age. The growing use of CT scans over the last 20 years has increased exposure to ionizing radiation. The risk of cancer also increases with the number of CT scans a patient has and the radiation dose used each time. Ionizing radiation is thought to cause about 1 % of all cancers. It comes from cosmic rays that enter the earth’s atmosphere, the radioactive gas radon—found naturally at low levels in soil—and from certain medical procedures, such as X-rays and radiation therapy.
· Immunosuppressive Medicines : Immunosuppressive medicines are used after an organ has been transplanted from one person to another. These medicines stop an organ that has been transplanted from being rejected. These medicines decrease the body's immune response to help keep the organ from being rejected. Immunosuppressive medicines are linked to an increased risk of cancer because they lower the body's ability to keep cancer from forming. The risk of cancer, especially cancer caused by a virus, is higher in the first 6 months after organ transplant, but the risk lasts for many years.
· Diet: The foods that one eats on a regular basis make up his/her diet. Diet is being studied as a risk factor for cancer. It is hard to study the effects of diet on cancer because a person's diet includes foods that may protect against cancer and foods that may increase the risk of cancer. Some studies have shown that a diet high in fat, proteins, calories, and red meat increases the risk of colorectal cancer.
· Alcohol: Research has found that people who have three-and-a-half drinks or more a day are two to three times more likely to develop head and neck cancer. Alcohol increases cancer risk by damaging cell DNA and proteins, as well as the body’s ability to break down nutrients, and by increasing estrogen levels. People who use both alcohol and tobacco have much higher risks of developing head and neck cancer than those who use alcohol or tobacco alone. Studies have shown that drinking alcohol is linked to an increased risk of the following types of cancers:
· Breast cancer
· Colorectal cancer (in men)
· Colorectal cancer (in female)
· Physical Activity: Studies show that people who are physically active have a lower risk of certain cancers. It is not known if physical activity itself is the reason for this. Some studies show that physical activity protects against postmenopausal breast cancer and endometrial cancer.
· Obesity: Obesity is linked to 13 types of cancer, including two of the most common the breast and prostate. In fact, physical inactivity and obesity together account for 25 % to 30 % of the following types of cancer:
· Postmenopausal breast cancer
· Colorectal cancer
· Endometrial cancer
· Esophageal cancer
· Kidney cancer
· Pancreatic cancer
· Gallbladder cancer
· Liver cancer
· Diabetes: Some studies show that having diabetes may slightly increase the risk of having the following types of cancer:
· Bladder
· Breast
· Colorectal
· Endometrial
· Liver
· Lung
· Oral
· Oropharyngeal
· Ovarian
· Pancreatic
Diabetes and cancer share some of the same risk factors. These risk factors include the following:
· Being older
· Smoking
· Having obesity
· Not exercising
· Not eating a healthy diet
Because diabetes and cancer share these risk factors, it is hard to know whether the risk of cancer is increased more by diabetes or by these risk factors.
· Age and Cancer Risk: According to Surveillance, Epidemiology, and End Results (SEER) Program report of period 2013–2017 advancing age is the most important risk factor for cancer overall and for many individual cancer types. The incidence rates for cancer overall climb steadily as age increases, from fewer than 25 cases per 100,000 people in age groups under age 20, to about 350 per 100,000 people among those aged 45–49, to more than 1,000 per 100,000 people in age groups 60 years and older. But cancer can be diagnosed at any age. For example, bone cancer is most frequently diagnosed in children and adolescents (people under age 20), with about one-fourth of cases occurring in this age group. And 12% of brain and other nervous system cancers are diagnosed in children and adolescents.
Photo by National Cancer Institute on Unsplash
Vulnerable Population
Cancer is still most commonly diagnosed among people older than 65. Globally only about 12% of cancers are diagnosed among adults younger than 50. For certain types of cancer, the numbers are especially striking. Colorectal cancer is now diagnosed among young adults almost twice as often as it was in the 1990s. According to the JAMA Network Open Research, the scientists have found that many other types of gastrointestinal cancer are also on the rise among this population. According to a 2024 study early-onset breast cancer is becoming more common too, with its incidence rising by almost 4% among women every year from 2016 to 2019. Even lung cancer, a disease typically associated with older cigarette smokers, is now to a surprising degree affecting younger women, even those who have never smoked.
According to a recent study report, the overall cancer incidence rates are higher among men than women. Among racial/ethnic groups, there are more new cases among African American men and white women and fewer new cases among Asian/Pacific Islanders of both sexes. The rate of new cases per 100,000 of cancer of all races at any site was 478.7 for men and 416.7 for women per year. Cancer affects different groups differently. People in countries with a lower human development index may receive diagnoses later and have a lower chance of access to quality treatment. This can significantly increase the risk of poor cancer health outcomes.
Environmental Risk Factors & Prevention[4]
· Environmental risk factors account for at least two-thirds of all cancer globally, so knowing more about what to look out for, and what to avoid, may go a long way in protecting one’s health. Cancer develops when changes, or mutations, in a cell’s DNA cause the cell to grow out of control. Sometimes, the mutations are caused by chemicals and other toxic substances in the environment—classified as carcinogens because of their cancer-causing potential. While such chemicals are toxic, they don’t always cause cancer. One’s risk for developing the disease depends on several factors—including how long and how often one is exposed, People genetic makeup, their diet lifestyle, overall health, age and gender.
· To reduce the risk of lung cancer, avoid tobacco altogether—don’t start the habit, and if one has, quit as soon as possible, and steer clear of secondhand smoke. Alcohol increases cancer risk by damaging cell DNA and proteins, as well as the body’s ability to break down nutrients, and by increasing estrogen levels. People who use both alcohol and tobacco have much higher risks of developing head and neck cancer than those who use alcohol or tobacco alone so one must avoid. To help avoid obesity-related cancers, experts recommend one must lose excess weight through diet and exercise, if possible, and with the help of behavioral and dietary counseling, if necessary. To reduce Ultraviolet (UV) rays, limit exposure to sun and indoor tanning—and wear sunscreen and protective clothing when outdoors. Asbestos fiber increases the risk of lung cancer, mesothelioma, laryngeal cancer and ovarian cancer. If one is planning to remodel home, which may disturb building materials, or if home contains damaged materials, such as crumbling drywall or insulation, one must wear a mask and other protective gear while doing any of remodeling. Certain viruses are linked to several types of cancer. Human papillomavirus (HPV), for instance, is responsible for almost all cervical cancers. The Centers for Disease Control and Prevention recommends that upto12-year-old boys and girls must receive two doses of the HPV vaccine six months apart, and that young men and women ages 15 to 26 must receive three doses. Chronic infection with hepatitis B or hepatitis C virus is the most common risk factor for liver cancer. Both viruses are spread by sharing contaminated needles, unprotected sex and childbirth. Also, the Epstein-Barr virus, which causes mononucleosis, is linked to some types of lymphoma. Currently, there are no vaccines for hepatitis C or Epstein-Barr, but there is a vaccine for hepatitis B. Ionizing radiation is thought to cause about 1 percent of all cancers. It comes from cosmic rays that enter the Earth’s atmosphere, the radioactive gas radon—found naturally at low levels in soil—and from certain medical procedures, such as X-rays and radiation therapy. Today, some possible but unproven risk factors include fluoride in water, radiation from power lines and electrical devices, chemicals in certain hair dyes and cosmetics, lead, the mineral talc in talcum powder, diesel exhaust and the chemical BPA (Bisphenol A (BPA) is a chemical produced in large quantities for use primarily in the production of polycarbonate plastics. It is found in various products including shatterproof windows, eyewear, water bottles, and epoxy resins that coat some metal food cans, bottle tops, and water supply pipes). One must try to avoid or limit even these unproven risk factors now, especially if doing so doesn’t affect the quality of life.
· Understanding the relationship between the environment and genetics is vital to lowering the cancer risk. Every doctor should help his or her patient realize that a poor diet, excessive alcohol consumption and certain medications may affect chemical levels in the body that break down cancer-causing substances.
· Action can take place at many levels to improve access to screening and treatment.
· Various governments and medical organizations can help by raising awareness and increasing understanding of cancer risk. Countries should reexamine prioritizing cancer in health benefits packages.
· People should also take steps at the individual level to cut down on personal risk factors like quitting smoking, following a balanced diet, maintaining a healthy weight, and limiting alcohol use.
Preventive measures provide the only feasible approach to slow and ultimately reverse the global increase in cancer and its disproportionate impact on countries that can least afford it. National and international efforts are required to strengthen tobacco control and to make childhood vaccination against HBV and HPV universally available and affordable in countries where these infections are prevalent. Successful implementation of these programs will require both national leadership and international collaboration to overcome the economic and political barriers that often impede public health. It will also require action-oriented translational research to adapt programs that have proven to be effective in high-income countries to every setting in which they are needed.
References
1. IARC. (2008) World Cancer Report, 2008. Boyle,P. and Levin,B.E. (eds), IARC Press, Lyon.
2. Danaei G, Vander Hoorn S, Lopez AD, Murray CJ, Ezzati M (2005). "Causes of cancer in the world: comparative risk assessment of nine behavioural and environmental risk factors". Lancet. 366 (9499): 1784–93. doi:10.1016/S0140-6736(05)67725-2
3. Danaei G, Vander Hoorn S, Lopez AD, Murray CJ, Ezzati M (2005). "Causes of cancer in the world: comparative risk assessment of nine behavioural and environmental risk factors". Lancet. 366 (9499): 1784–93. doi:10.1016/S0140-6736(05)67725-2
4. Valle I, Tramalloni D, Bragazzi NL (June 2015). "Cancer prevention: state of the art and future prospects". Journal of Preventive Medicine and Hygiene. 56 (1): E21–7.