Air Pollution a Key Reason for Lung Cancer Among Non-Smokers

Worsening air pollution globally is causing lung cancer rates to rise everywhere. A look at Taiwan, where a majority of new cases affect non-smokers, offers powerful lessons for the rest of the world.

Lung cancer among never-smokers is rising worldwide. In one US study of 12,000 lung cancer patients, the share of people who didn’t smoke rose from 8% to 15% over 20 years. A British study found similar results, with its never-smoking cohort jumping from 13% in 2008 to 28% in 2014.

While these trends are multifactorial, one key reason is air pollution, according to the International Association for the Study of Lung Cancer. Air pollution is the “new tobacco,” said Tedros Adhanom Ghebreyesus, the head of the World Health Organization (WHO).

One of the biggest culprits is PM2.5 – particulate matter that is 2.5 microns in size, or about 30 times smaller than a human hair. Much like cigarette smoke, these tiny pollution particles get sucked deep inside the lungs, damaging DNA inside cells, and increasing the risk of cancer.

Every year, more than 300,000 people die of lung cancer due to PM2.5, and research suggests these pollution particles not only initiate cancer-causing genetic defects but drive tumour formation. According to a 2023 study in the journal Nature, PM2.5 incites a flush of immune cells into the lungs, and the resulting inflammation “wakes up” the EGFR mutation, triggering uncontrollable cell growth.

The air in Taiwan contains 4 times the number of PM2.5 considered safe according to the WHO, with sources of air pollution ranging from vehicle emissions to coal-fired power plants to petrochemical factories. That doesn’t account for the toxic haze floating in from China or Taiwan’s mountainous geography trapping in pollutants, says Kuan-Hsun Lian, a thoracic surgeon at National Taiwan University (NTU) Yunlin Branch Hospital.

Is lung cancer different in never-smokers? “If you are a smoker, you can think of your lung as a bag of white marbles, and cancer is like putting a black marble in there,” says Daniel Boffa, chief of thoracic surgery at Yale. “The type of cancer a nonsmoker gets is more like putting in black sand.” Instead of a well-defined spot, it tends to be a little hazy.

These differences are not always so stark, but never-smokers have an advantage because in half the cases, their lung cancer can be treated with precision drugs, compared to 10% of smokers.

Doctors can thus better target specific mutations and block tumour growth in never-smokers, instead of having to rely on less effective carpet-bombing techniques like chemotherapy, according to Mong-Wei Lin, vice-chief of NTU’s medical school.

With such distinct characteristics and treatment, “lung cancer in never-smokers should be regarded as a different kind of disease,” he says.

With the common perception that lung cancer is only caused by cigarette smoking, never-smokers are often unaware of their disease until the latest stages. Since the lungs have almost no nerve endings, “the most common symptom in lung cancer is no symptom at all,” says Pan-Chyr Yang, a pulmonologist and former NTU president.

The Taiwanese government has prioritized screening, recognising that it’s not only a life-saving opportunity but a money-saving one.

Learn more about the connection between air pollution and lung cancer, how cases differ for non-smokers, and why early screenings are so important at https://on.natgeo.com/4eu2Qa4.

– edited excerpts from National Geographic (20 August 2024)