World Cancer Day 2019: What Causes Cancer? Here Are The Top Factors According To Science
What causes cancer? (Photo Credits: File Image)

Cancer is one of the biggest killers in the world today, claiming millions of lives every year. A complex ailment with no one cause or cure, it has mystified medical science for decades. Today, even with a promise of a potential cure at arm’s reach, we are still groping in the dark, trying to understand the disease better. What could be causing cancer? Is it something we eat or inherit? If science could find the answer to these questions, millions of lives could be saved. On World Cancer Day 2019, let’s take a look at some of the top factors that cause cancer.

Our current understanding of the disease tells us that all cancers are a result of environmental and genetic factors. In other words, there are multiple external and internal genetic factors that lead to cancer in human beings. Years of research has helped us zero down some of the common causes of cancer.

Growing Old

The biggest risk factor for cancer is ageing. Although cancers occur in the young, people over the age of 55 are at greater risk. Cancer and ageing are results of accumulating damage to stem and progenitor cells. As you age, the telomeres, the caps at the end of your DNA strand, become shorter. Many cancers like pancreatic, bone, prostate, bladder, lung, kidney, and head and neck cancers are linked to the shortening of telomeres.

Family History

Genetic mutation is one of the causes of cancer. Some of these mutations can be passed down from the parent to the child. That’s why, some cancers are seen recurring in the family. Sometimes, certain environmental and lifestyle factors, like smoking, can cause a mutation to the DNA. These faulty genes can then be passed to the next generation, increasing their risk for cancer.

Tobacco Use

One of the most preventable causes of cancer, tobacco smoking is responsible for 85 percent of all lung cancers and 30 percent of all smoking-related deaths. Even passive smoking or second-hand smoking increases the risk of cancer by five percent. Smokers are more at risk than nonsmokers to develop lung, larynx, oesophagus, mouth, throat, stomach, kidney, bladder, pancreatic and cervical cancers. At least 400 chemicals in tobacco smoke are harmful to human health, and 40 of those – such as arsenic, benzene, chromium, nickel and formaldehyde – are all cancer-causing agents. 10 Facts About Cancer You Need to Know by World Health Organization (WHO).

Alcohol Consumption

According to WHO, alcohol is classified as a group-1 carcinogen. So if you thought that a drink or two a day is safe, think again. Consuming alcohol is one of the top cancer-causing factors, accounting for 3.6 percent of all human cancers. Having more than two drinks a day for years will increase your chances of cancers of the mouth, throat, oesophagus, liver, colon, prostate, lymph nodes, kidneys, breast and ovaries.


Sunlight can do your health a lot of good. But that doesn’t mean it’s safe to venture out without sunscreen, because the sun’s UV rays are the top causes of skin cancer. These rays can cause damage to your skin and increase the risk of basal cell carcinoma, squamous carcinoma and melanoma. Even the mellow winter sunlight can produce the same kind of damage. It can be prevented by avoiding direct exposure to sunlight between 10 am and 3 pm, using sunscreen 30 minutes before stepping out and undergoing regular skin examination.

Chemical Exposure

Chemical exposure in our everyday lives is one of the risk factors for cancer. We are exposed to at least 10,000 chemicals a day, many of which are carcinogens. The disease is also an occupation hazard for people exposed to substances like asbestos, benzene, cadmium, nickel, arsenic, radon and vinyl chloride at work. Groundwater is tainted with arsenic and chemicals such as dioxane, petrolatum, formaldehyde, synthetic fragrance, talc, parabens and phthalates used in cosmetics also contribute to increased cancer incidence.


Eighteen percent of cancers are caused by micro-organisms. The risk is much higher in developing nations than the developed. HPV or human papillomavirus is the main cause of cervical cancer. Hepatitis B and C viruses can result in liver cancer. Human T-cell leukemia/lymphoma virus is linked to lymphoma and leukaemia. HIV increases the risk of lymphoma and Kaposi’s sarcoma cancers. The H.pylori bacterium has been responsible for stomach ulcers, which lead to stomach and oesophagus cancer.


Excessive hormones such as oestrogen, androgens and progestogens in the human body has been linked to increased risk of breast, ovarian and uterine cancers. Hormone therapy and oral contraceptives have been linked to both increased and decreased risk of cancer. Other factors such as age of menstruation, age of first birth and obesity play a role in hormone production, which also dictate women’s cancer risk.


Diet, body weight and activity levels – these three factors are important in influencing cancer risks. Excessive consumption of red meat, fried food, etc. has been tied to increased cancer risk. Obesity has been tied to chronic low-level inflammation, which causes DNA damage and cancer. Having more fat tissues means higher production of oestrogen, tied to cancers in women.


Pollution is one of the biggest environmental factors that cause cancer. Air, water and soil pollution caused an estimated 1-4 percent of cancers all over the world. Around 3.5 million deaths are caused by indoor and outdoor pollution globally.

Food Contaminants

Contaminated food is also a small causative factor of cancer, although the burden of the disease cannot be estimated. Natural carcinogenic contaminants like mycotoxins produced by fungi are present naturally in grains and legumes, especially when they are stored in hot, moist conditions. The toxin is responsible for causing liver cancer in Africa, Asia and South America. Foods tainted with pesticides are also one of the biggest causes of human cancers worldwide.


A small group of powerful drugs – ironically, some of which are used for treating cancer – are carcinogenic in nature. Immunosuppressive drugs interfere in the natural working of the immune system, affecting its ability to destroy cancer cells. Drugs with hormonal activity also increase the risk for breast, uterine and ovarian cancers. However, these drugs have been shown to increase cancers only decades later and their immediate benefits outweigh their long-term risks.

Preventing cancer is perhaps our biggest weapon against the deadly disease. Although some of the factors that cause the disease are unavoidable, knowing them can help us mitigate it to a certain extent.