Delhi is now the world's most polluted capital, with levels regularly exceeding those in Beijing, China. Pollution is a slow but steady killer. The toxin levels people are exposed to today will likely shorten people’s life spans by several days or weeks. Air pollution, in particular, is linked to many health conditions, especially lung cancer.

“According to a recent report, lung cancer constitutes 6.9% of all new cancer cases and 9.3% of all cancer-related deaths in both men and women. It is imperative for each one of us to understand the effects that air pollution have on the lungs and on one’s health and overall well-being,” said Dr M Udaya Kumar Maiya, Medical Director, Portea Medical.

Lung cancer or lung carcinoma is a malignant lung tumor characterized by uncontrolled cell growth in tissues of the lung. This can spread further by a process known as metastasis into nearby tissue or other parts of the body. The two main types of carcinomas are: small-cell lung carcinoma (SCLC) and non-small-cell lung carcinoma (NSCLC). A majority of lung cancer cases are a result of long-term tobacco smoking. However, about 10% to 15% of non-smokers are also at risk.

Both SCLC and NSCLC have similar symptoms and include: lingering or worsening cough, coughing up phlegm or blood, chest pain that worsens with coughing or laughing, hoarseness, shortness of breath, wheezing, weakness and fatigue, loss of appetite and weight loss. Some people also experience respiratory infections such as pneumonia or bronchitis. When the cancer spreads, the symptoms also vary according to the area affected.

“Statistics indicate that air pollution is responsible for 3,000 premature deaths in Delhi every year which works out to 8 deaths a day. The effects of air pollution on human health are very complex. This is because there are different sources and each has a different effect on our health,” he said.

Air pollutants can have serious impacts on the lungs and the respiratory system. They are absorbed into the circulatory system and pumped all around the body. Further, these air pollutants can also get deposited on soil, plants, and in water, increasing the level of human exposure.

Biological pollutants are mostly allergens that can cause asthma, hay fever, and other allergic diseases. Volatile organic compounds irritate the eyes, nose, and throat. They can lead to headaches, nausea, and loss of coordination in the longer term and are also known to cause damage to the liver and other parts of the body. It is also associated with exacerbating respiratory disorders such as asthma and lowering resistance to common cold. Nitrogen oxide released from industrial and vehicular emissions makes children susceptible to respiratory diseases especially in winters.

Carbon monoxide can combine with hemoglobin and reduce the oxygen carrying capacity. Further, it is harmful to the brain and cardiovascular system. Smog is a mixture of dust, fumes, mist, and smoke. It is very dangerous to both lungs and the heart. High sulfur dioxide contents can precipitate chronic bronchitis.

The WHO’s International Agency for Research on Cancer has classified outdoor air pollution as a carcinogen (cancer-causing agent). This inference was a result of evaluating over 1,000 scientific papers and studies from five continents. Polluted air carries tiny dust-like particles called particulate matter (PM).

This is a combination of extremely small solid particles and liquid droplets that are found in the air, and are the riskiest. The smallest particles called PM2.5 are particularly harmful due to their extremely permeable nature due to which they can easily enter the lung tissue linings. Some sources of PM2.5 include emissions from diesel engines.

The situation is worse in winter as the formation of smog can make the delivery of pollutants to the end of lung airways even easier. Radon is a radioactive gas that can accumulate inside the house, exposure to which increases the risk of lung cancer.

Another common source of air pollution is that which occurs indoors. This is the smoke that results from burning coal, more commonly done for cooking in rural areas. Statistics indicate that women exposed to indoor coal smoke have about twice the risk of getting lung cancer.

About 2.4 billion people globally are susceptible to this risk with indoor air pollution accounting for about 1.5% of deaths due to lung cancer. In the urban areas, one of the commonest sources is the mosquito coils and even cigarette smoke.

“There are some ways in which air pollution can be reduced and thus, the chances of lung cancer as well. It should start at a personal level with the very first option being to choose active travel wherever possible. This includes walking and cycling. Try and venture out during that part of the day when the pollution levels are at the lowest,” added Dr M Udaya Kumar Maiya.

When it comes to masks, only the more sophisticated ones such as N95 can prevent the tiny particles from entering the lungs. Another way is to try and stay away from areas where the air quality is not very good.