Environmental Cancer Causes
Environmental cancer causes are defined as causes that are modifiable or changeable. The World Health Organization suggests that up to 80% of all cancers fall under this category. Cancer arises principally from the exposure of individuals to carcinogenic (cancer causing) agents in the atmosphere and in what they eat and drink. Personal habits such as tobacco use and occupational exposure to carcinogens play significant roles in the etiology of cancer, according to WHO.
The following is a list of environmental cancer causes from the WHO.
Physical carcinogens: Both ionizing and non-ionizing radiation can cause cancer. Small amounts of ionizing radiation occur naturally, specifically in cosmic rays and in radioactive materials in the earth. Exposure may thus result from this background radiation, from medical and occupational contact with radiation, from accidents at nuclear power stations or from the use of nuclear weapons in war. Some types of leukemia and cancers of the breast, lung, and thyroid are specifically associated with exposure to ionizing radiation.
Chemical carcinogens: Extensive evidence of chemical carcinogenesis has come from studies of people whose occupations bring them into contact with various substances. Excessive alcohol use (IARC, 1988) and certain drugs (IARC, 1996) also increase the risk of some cancers. Vaginal cancer among young women was found to be due to diethylstilbestrol; a synthetic hormone that had been given to their mothers to prevent miscarriage during pregnancy (Lanier et al., 1973). Overshadowing all these is the critical role of tobacco smoking as a leading cause of cancer in many countries (IARC, 1986).
Biological carcinogens: Examples of cancer caused by living organisms include bladder cancer resulting from infection with the parasite schistosoma haematobium (IARC, 1994a), liver cancer following viral hepatitis B and C infection (IARC, 1994b), gastric cancer following infection with helicobacter pylori (IARC,1994a) and cancer of the uterine cervix following human papilloma virus infection (IARC, 1995).
Dietary factors: Several studies indicate that vegetables and fruits contain substances that provide protection against some cancers. Similarly, studies indicate that excessive amounts of animal products in the diet, such as red meat, increase the risk of colorectal and perhaps breast cancer and other forms of the disease (World Cancer Research Fund, American Institute for Cancer Research, 1997). Among the diet related factors overweight/obesity convincingly increases the risk of several common cancers such as colorectal and breast cancer (Joint WHO/FAO expert consultation on diet, nutrition and the prevention of chronic diseases, in preparation).
Occupation: The impetus for identifying occupationally-induced cancers has come from three principal factors:
- increased competence in recognizing and demonstrating occupational hazards;
- social pressures;
- the growing diversity of industrial processes and the concomitant exposure of workers to physical and chemical carcinogens.
- Among the industries in which there is evidence of carcinogenic risk are the following: agriculture, construction, demolition, shipbuilding, shipbreaking, petroleum, metal and rubber (Tomatis et al., 1990; IARC, 1990).
Air and water pollution: Throughout the world, carcinogenic agents are released into the air, and into surface and ground waters, as a result of industrial processes and the accidental or deliberate dumping of toxic wastes.
The role of medical services and care: Although rare, some incidence of cancer has been iatrogenically induced. For example, the routine use of X-ray fluoroscopy to follow the course of tuberculosis induced breast cancer in some patients (Miller et al., 1989). Further, some drugs used to treat cancer are carcinogenic, while estrogens used to counteract menopausal symptoms increase the risk of endometrial and breast cancer (IARC, 1999).
Source: World Health Organization