Environmental Risk factors

Tobacco

▪ Multipotent carcinogenic mixture

▪ Linked to many cancers

– Oropharynx, larynx, esophagus, lung, stomach, liver, pancreas, kidney

– Acute myeloid leukemia

– Cervix, bladder colorectal

▪ Second-hand smoke contains many toxic chemicals (7000)

▪ Cigar and pipe smoking are equally harmful

Diet

▪ ~30% of the overall risk factors for cancer

▪ Mutagens found in human diet as a result of industrial/environmental contamination (pesticide/water)

▪ Aflatoxins and liver cancer

– Aspergillus flavus; fungus infecting peanuts, tree nuts and grains. This can produce animal food-products that contain aflatoxins. Women can pass in aflatoxin to infants through breast milk

▪ Carcinogenic chemicals. In food

▪ May influence epigenetics

Obesity

▪ Based on BMI

▪ Related to increased incidence of several cancers

– Examples: esophagus, gastric, colorectal, liver, gallbladder, pancreatic, breast, uterine, cervical, ovarian and kidney

▪ Casual relationship to cancer is unclear

▪ Gender differences in obesity-related cancers

▪ Abdominal obesity can be associated with insulin resistance, hyperinsulinemeia and increased steroids, all of which increase risk for cancer development

Alcohol

▪ Risk factor for oral cavity, pharynx, hypopharynx, larynx, esophagus, and liver cancers

▪ Substantial alcohol consumption (e.g. 3 or more drinks per day) has been associated with high risk

▪ Cigarette/alcohol combinations increases a person’s risk for cancer

▪ Genetic factors involved

Ionizing radiation

▪ X-rays, radioisotopes and other radioactive sources

▪ Exposure causes cell death, mutations, chromosome aberrations (disorder)

▪ Mutations in germ cells are heritable

▪ Increased use of diagnostic testing is of concern

– CT scans provide 50x more radiation to

stomach compaired to an x-ray.

UV radiation

▪ Principle source is sunlight (ultraviolet)

▪ Causes basal cell carcinoma, squamous cell carcinoma and melanoma (increased incidence)

▪ Produces ROS and other free radicals

▪ Promotes skin inflammation

▪ UVC rays do not enter the earth’s ozone (shortest wavelength = 100-290 nm)

▪ UVB rays reach the skins surface – cause surface tanning, burns, signs of aging (medium wavelength = 290-320 nm)

▪ UVC rays penetrate deep into the skin’s layers and release free radicals and cause DNA changes that can result in skin cancers. Wavelength is the longest (320-400 nm)

Electromagnetic radiation (EMR)

▪ Non-ionizing, low-frequency radiation

▪ Microwaves, cell phones, and power frequency radiation associated with electricity and radio waves, fluorescent lights, computers and other electrical equipment

▪ USA recommended that low-frequency EMFs be classified as possible carcinogens

Physical activity (30 mins a day)

▪ Reduces cancer risk (post-menopausal breast, colorectal, endometrial)

– Decreases insulin and insulin-0like growth factors

– Decreased obesity

– Decreased inflammatory mediators and free radicals

– Increased gut motility

o Less exposure of gut to dietary carcinogens

Sexual/reproductive behavior

▪ Carcinogenic types of human papillomavirus

– 99.7% of women with cervical cancer

– HPV vaccination

Occupational hazards

▪ Upper respiratory passages, lung, bladder, peritoneum

▪ Substantial number of occupational carcinogenic agents:

– Asbestos (mesothelioma and lung cancer)

– Dyes, rubber, paint, explosives, rubber cement, heavy metals, air pollution

Air pollution

▪ Outdoor

– Heavy metal and aromatic hydrocarbon emissions from industry

▪ Indoor

– Environmental tobacco smoke (ETS)

– Radon gas

– Heating and cooking combustion sources

– Asbestos

– Inorganic arsenic

Nutrition

▪ Foods that decrease cancer risk

– Fruits/vegetables; fiber; foods containing vitamins A, B6, C, D, E and folate; whole grains; legumes/nuts

▪ Foods that increase cancer risk

– Fat (especially omega-6 fatty acids), high glycemic index carbs; high preservatives; alcohol; grilled/blackened foods; fried foods, high calcium (>2000mg)

End of Module