Lung cancer rising among non-smokers — here's why

Cigarette smoking is by far the biggest risk factor for lung cancer, data shows — but in a surprising turn of events, the most common form of the disease is primarily found in non-smokers.

Researchers at the International Agency for Research on Cancer (IARC) analyzed global trends in four main lung cancer subtypes: adenocarcinoma, squamous cell carcinoma, small-cell carcinoma and large-cell carcinoma.

They found that adenocarcinoma has been the most "predominant subtype" in recent years, according to a press release summarizing the study. Younger females were found to be at a particularly high risk.

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The study was published in The Lancet Respiratory Medicine earlier this month, based on global cancer data from 2022.

Adenocarcinoma — which starts in the cells lining the air sacs in the lungs — is the most common type of lung cancer among people who have never smoked, comprising up to 50% of diagnoses in that group, per the Centers for Disease Control and Prevention (CDC).

Air pollution was cited as a key driver of this type of lung cancer, with the highest levels reported in East Asia, particularly China, the release stated.

Worldwide, adenocarcinoma made up more than 45% of lung cancer cases in males and nearly 60% of female cases.

"This population-based study seeks to better understand variations in lung cancer incidence by place and time according to its constituent subtypes. We examine changes in risk in different countries across successive generations and assess the potential burden of lung adenocarcinoma linked to ambient particulate matter (PM) pollution," said lead study author Dr. Freddie Bray, head of the Cancer Surveillance Branch at IARC, in the release. 

"The results provide important insights as to how both the disease and the underlying risk factors are evolving, offering clues as to how we can optimally prevent lung cancer worldwide."

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Dr. Marc Siegel, clinical professor of medicine at NYU Langone Health and Fox News senior medical analyst, was not involved in the study but discussed these lung cancer trends with Fox News Digital.

"The main reason for increasing rates in non-smokers is air pollution, which can lead to adenocarcinoma of the lung, which is almost 50% of lung cancers now," he confirmed.

Increased vaping rates are also associated with the ramp-up of lung cancer rates, the doctor noted.

"Secondhand smoke also continues to be a factor, even though smoking rates have fallen dramatically," Siegel said.

Genetic risk factors may also come into play and "need to be further explored," according to the doctor.

"Artificial intelligence can play a huge role here in terms of early diagnosis and pattern recognition, even before discrete lung nodules develop," he added. "However, lung CT scans remain the best diagnostic tool for those at risk."

Marianne Matzo, PhD, a certified advanced nurse practitioner in Dallas, Texas, agreed that poor air quality and pollution can contribute to lung cancer. 

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"Pollutants in the air, such as particulate matter and industrial emissions, can damage lung tissue and lead to cancer over time," Matzo, who was not part of IARC’s research, told Fox News Digital. "This complicates the diagnosis and treatment process."

Some veterans who have been exposed to hazardous materials may also face a higher risk of lung cancer, she noted.

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"Veterans based in the Middle East (in particular Afghanistan and Iraq) were exposed to burn pits," said Matzo, who worked in oncology at the VA hospital. 

"The waste included paints, solvents, human and medical waste, trash, and plastics that were ignited with JP-8 jet fuel, which contains benzene." 

"We are starting to see the effects of the pollution from those pits on young vets being diagnosed with lung cancer."

Exposure to high doses of radiation, as well as chemicals like asbestos and benzene, can also increase the risk of developing cancer, she cautioned. 

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"Bacterial and viral infections can also cause genetic mutations and chronic inflammation, which contribute to the development of cancer."

In some cases, lung cancer can develop seemingly at random with no direct cause.

"What people miss when they say, ‘I never smoked a day in my life, how could I have lung cancer?’ are the variables of chance and genetics," Matzo added. "We can’t control our genetics, and there can be genetic predispositions to cancer."

Ravi Salgia, M.D., Ph.D., medical oncologist and chair of the Department of Medical Oncology & Therapeutics Research at City of Hope in California, noted that there is "considerable variability" of lung cancer subtype based on geography and gender. 

"There are a number of potential causes of lung cancer — smoking, pollution, radon exposure and genetics, for example," Salgia, who was also not involved in the research, told Fox News Digital. 

"More research is needed to determine the exact causes of lung cancer and the progression of this cancer. It is indeed concerning that pollution can potentially lead to lung cancer. We truly need to understand how the disease develops and ultimately how to better prevent and treat it."

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