Cancer is the second leading cause of mortality today, resulting in more than half a million deaths each year.

If you or a loved one has been diagnosed with cancer, you may be feeling fear, anger, anxiety, sadness, or other emotions.

Want to know how cancer is caused, and what are the various factors that may influence the occurrence of cancer?

Karepedia is here to illustrate the influence of the environment, genes, and their interactions in the international variation reported in cancer incidence.

Cancer And Environmental Factors

A variety of linkages clearly exist between environmental exposures, diet, lifestyle factors, and cancer.

Environmental exposures, defined here as pathogens, chemicals, and additional external factors, have also been shown to contribute to disease.

While epidemiological studies can identify associative relationships between exposure to environmental factors and disease pathogenesis, not all individuals who are exposed to a specific environmental factor develop disease.

Likewise, not all individuals who inherit particular genetic variants develop disease.

Ageing:

• Most cancers occur in people over the age of 55, but also can occur in younger ages Both cancer and aging result from accumulating damage to the stem and progenitor cells.

• Certain genetic mutations cause the stem cells to divide out of control which lead to cancer.

• Environmental factors such as stress, social status, smoking and obesity can also accelerate telomere shortening due to reduced telomerase activity.

• In contrast to normal somatic cells, most human tumors have activated telomerase to achieve immortal growth.

Family history:

• Some genetic changes that increase the risk of cancer are passed from parent to child more often in some families than in the rest of the population. Like colon cancer, familial adenomatous polyposis hereditary non-polyposis colorectal cancer (HNPCC) or lynch syndrome.

• People with this syndrome usually have a higher risk of colorectal cancer. People with HNPCC have only a few polyps with a high risk of developing uterus, ovary, bladder, kidney and brain cancers. So they need to undergo regular screening.

• Also, inheriting a gene change does not mean that you will definitely develop cancer. It means that you have an increased chance of developing the disease.

• Following indications can increase the risk of developing cancers such as tumours on the same side of the family, some of the cancer linked inherited syndromes, two cases of rare cancers in the same family and family history of multiplicity of primary tumours.

Smoking:

Tobacco use is the most preventable cause of deathMore than 85% of all lung cancers and 30% of all deaths are caused by smoking. Second hand smoke can also increase 5% the risk of cancer.

Smokers most commonly develop cancers, like lung, larynx, mouth, oesophagus, bladder, kidney, throat, stomach, pancreas, cervix and acute myeloid leukaemia, leading to cardiovascular, brain stroke, pulmonary, congenital deformities and sudden infant death syndrome.

Alcohol:

Alcohol consumption causes 3.6 % of all human cancers.

• It has been classified by the World Health Organization (WHO) as group-1- carcinogen, having more than two drinks each day for many years will increase the chance of developing cancers of oral, throat, oesophagus, stomach, liver, colon, lymphomas, prostate, kidney, breast and ovaries.

• Liver can process 7 grams of ethyl alcohol each hour. When the liver processes alcohol, it will produce acetaldehyde which is carcinogenic.

• This will induce a defect in alcohol dehydrogenase gene and tumour suppressor gene (BRCA) inactivation that can lead to the upper gastrointestinal tract, breast and liver cancers.

• Liver cirrhosis leads to cancer, which includes liver cells replaced with scars due to chronic alcohol use.

Sunlight and ionising radiation:

Ultraviolet (UV) radiation comes from the sun, sunlamps, and tanning booths. It causes early ageing of the skin that can lead to skin cancer.

• You need to protect yourself from UV radiation which can penetrate light clothing, windshields, and windows.

• Avoid direct sunlight exposure between 10:00 a.m. and 3:00 p.m

• Wear long sleeves, long pants which mostly cover skin ,a hat and sunglasses with lenses that absorb UV.

• Sunscreen (Sun Protection Factor) prevents skin cancer when applied 30 minutes before exposure.

• Staying away from sunlamps and tanning booths.

• Regular self skin examination

Three types of sun radiations include the visible (colour), infrared (heat) and UV lights (UVA, UVB, UVC).

The UV light from sun and tanning can cause skin damages, such as; benign, pigmentation, discoloration, freckles, sunburn, cancers (Basal cell carcinoma, Squamous carcinoma and Melanoma) and destruction of elastin and collagen proteins.

Ionising radiation causes cell damage leading to cancer. This comes from outer space which includes radioactive fallout, radon gas, X-rays which can cause cancers of the blood, thyroid, breast, lung, and stomach.

Radon is a radioactive gas that you cannot see, smell, or taste. It forms in soil and rocks,exposed to radon are at increased risk of lung cancer. Doctors use low-dose radiation to take pictures to diagnose broken bones and use the high-dose radiation to treat cancer.

Exposure to solar ultraviolet radiation is the major cause of non-melanoma skin cancers, which are the most common malignancies in humans. At low doses, the cells repair the damage rapidly. At moderate and high doses, the cells may be changed permanently or die from their inability to repair the damage. These altered cells may become cancerous or lead to other abnormalities (e.g. birth defects).

Organic and Inorganic chemicals:

A number of chemical substances revealed to be dangerous at high concentration chemicals to our health. These cancer causing agents are called carcinogens.

Occupations such as; painting, construction, pesticide and petroleum workers,asbestos, benzene,cadmium, nickel, arsenic, radon and vinyl chloride in the workplace can cause cancer.

Many of the cosmetic products, such as; shampoos, hair conditioners, lotions,soaps,detergents,deodorant, lipstick, moisturisers, perfumes, facial creams

Viruses and bacteria:

• Human papilloma-viruses (HPVs): cervical cancer - vaccine conferred immunity results in a marked decrease in precancerous lesions.
• Hepatitis B and hepatitis C viruses: liver cancer.
• Human T-cell leukaemia/lymphoma virus-1 (HTLV-1): lymphoma and leukaemia (blood cancer)
• Human immunodeficiency virus (HIV): HIV is the virus that causes AIDS, lymphoma and Kaposi’s sarcoma cancers and immunodeficiency
• Epstein-Barr virus (EBV):Burkitt’s lymphoma
• Human herpesvirus-8 (HHV8):Kaposi’s sarcoma cancer
• Helicobacter pylori:bacterium causing stomach ulcers leading to stomach and esophageal cancers
• Salmonella typhi: bacterium can cause gallbladder cancer.
• Streptococcus bovis: bacterium can cause colon cancer

Hormone therapy:

Oestrogen and progestin are hormones that may increase the risk of breast and uterus cancers, heart attack, stroke, or blood clots.

Tamoxifen and aromatase inhibitors (letrozole and anastrozole) which are more superior than tamoxifen for breast cancer treatment.

When the function of aromatase is inhibited, oestrogen production reduces tremendously in postmenopausal women which ceases cellular proliferation.

Also, steroid hormones can induce gene expression in the nucleus of cancer cells which lead to reduced hormonal production and subsequent cellular growth arrest

Diet and obesity:

Obese people are at higher risk of coronary heart disease, stroke, high blood pressure, diabetes, and cancers (oesophagus, breast, uterus, colon, rectum and prostate).

Fat tissue produces high oestrogen and produces high amounts of insulin-like growth factor-1 (IGF-1) in their blood which may lead to certain cancers.

Sodium nitrite which has been used for meats to produce a fresh red color to the consumer can be converted to nitrosamines which are highly carcinogenic.

Air and water pollution:

This results in biological, biochemical and atmospheric particles which cause damage to our living environment. Air pollution is a significant risk factor for respiratory infections, cardiac disease and lung cancer.

The main cause of air pollution includes particulate matter, damaged ozone, nitrogen dioxide, sulphur dioxide, carbon dioxide, carbon monoxide, ammonia, radioactive decay of radon gas, methane, hydrofluorocarbons and chlorofluorocarbons.

Water pollution is caused by several factors:

• Microorganism infection; bacteria, viruses, protozoa and parasitic worms.
• Wastes that are decomposed by oxygen-requiring bacteria by oxygen reduction leading to fish death.
• Acids, salts and toxic metals which cause the death of aquatic life.
• • Nutrients like water-soluble nitrates and phosphates which cause excessive growth of algae by using water’s oxygen leading to fish death.
• Water is polluted by several organic compounds such as oil, plastics, detergents, chloroform, petroleum, polychlorinated biphenyl, fertiliser, sulphur oxide, pesticides and trichloroethylene which cause various human diseases including cancer.

Prevention and Lifestyle Management

• Prevention is defined as the reduction of cancer mortality by reduction in the cancer incidence.
• This can be accomplished by avoiding carcinogenic exposures, modifying lifestyle practices and early detection of cancerous lesions.
• Having one or more risk factors does not mean that you will get cancer. Some of the risk factors can be avoided. Others like family history and - ageing cannot be avoided.

Fast food side effects are obesity, worker exploitation and negative health outcome

Toxin removal, preservation, marketing, distribution, seasonal availability and transportation are the benefits of food processing. Using food preservers and heating can destroy the food texture prior to canning.

• Any method of cooking can destroy some of the food nutrients based on water content, cooking time and temperature.

• However, it has been well documented that microwave cooking retains most of the food micronutrients due to short exposure time. Since microwave radiation is non-ionizing rays, it does not increase the cancer risks, as it has been shown by ionizing radiation like X-rays.

• A healthy diet every day includes plenty of foods that are high in fiber, low in fat, vitamins, minerals, whole-grain breads, cereals, fruits and vegetables

• A good physical activity

• Antioxidant vitamins like vitamin C and E, citrus fruits , may protect against cancer based on the premise that oxidative damage to DNA leads to cancer progression.

FAQs

1. How can I reduce my risk of cancer?

Yes, while not all forms of cancer are preventable,there are actions you can take to help lower your risk for the most common types of cancer.

• Avoiding commercial tobacco, including e-cigarettes and vapes
• Eating a healthy diet
• Not drinking alcohol or doing so only in moderation
• Limiting processed meats
• Being physically active
• Protecting yourself from the sun
• Getting vaccinated against hepatitis B and human papillomavirus (HPV)
• Practising safer sex and not sharing needles
• Getting regular medical care including screenings for certain types of cancer and guidance on performing regular self-exams

2. I was exposed to a cancer contaminant: what do I do now ?

Exposures to a cancer contaminant at low levels may not be worrisome. If in high concern, contact your doctor right away Ongoing regular health check ups, screenings,physical exams can help detecting a cancer and other health conditions