Air Pollution ― Second Leading Cause of Lung Cancer

Liam Davenport

September 13, 2021

Air pollution is the second leading cause of lung cancer in the world, after smoking, results of a novel analysis suggest. The researchers call for concerted action.

The new data show that the rate of lung cancer deaths attributable to air pollution varies widely between countries. Serbia, Poland, China, Mongolia, and Turkey are among the worst affected. The analysis shows an association between deaths from lung cancer and the proportion of national energy that is produced from coal.

"Both smoking and air pollution are important causes of lung cancer," said study presenter Christine D. Berg, MD, former co-director of the National Lung Screening Trial, and "both need to be eliminated to help prevent lung cancer and save lives.

"As lung cancer professionals, we can mitigate the effects of air pollution on causing lung cancer by speaking out for clean energy standards," she said.

Berg presented the new analysis on September 9 at the World Conference on Lung Cancer (WCLC) 2021, which was organized by the International Association for the Study of Lung Cancer (IASLC).

She welcome the recent statement issued by the IASLC in support of the International Day of Clean Air for Blue Skies, which took place on September 7. It was a call for action that emphasized the need for further efforts to improve air quality to protect human health.

The findings from the new analysis are "depressing," commented Joachim G. J. V. Aerts, MD. PhD, Department of Pulmonary Diseases, Erasmus University Medical Center, Rotterdam, the Netherlands.

It is now clear that air pollution has an impact not only on the incidence of lung cancer but also on its outcome, he added.

Indeed, previous research showed that each 10 µg/m3 increase in particular matter of 2.5 µg in size was associated with a 15% to 27% increase in lung cancer mortality. There was no difference in rates between women and men.

A key question, Aerts said, is whether reducing air pollution would be beneficial.

Efforts to reduce air pollution over recent decades in the United Kingdom have not led to a reduction in lung cancer deaths. This is because of the increase in life expectancy ― individuals have been exposed to pollution for longer, albeit at lower levels, he pointed out.

Because of lockdowns during the COVID pandemic, travel has been greatly reduced. This has resulted in a dramatic reduction in air pollution, "and this led to a decrease in the number of children born with low birthweight," said Aerts.

Hopefully, that benefit will also be seen regarding other diseases, he added.

The call to action to reduce air pollution is of the "utmost importance," he said. He noted that the focus should be on global, national, local, and personal preventive measures.

"It is time to join forces," he added, "to 'clean the air.' "

Berg's presentation was warmly received on social media.

It was "fabulous," commented Eric H. Bernicker, MD, director of medical thoracic oncology at Houston Methodist Cancer Center, Houston, Texas.

"Thoracic oncologists need to add air pollution to things they advocate about; we have an important voice here," he added.

It is "so important to understand that air pollution is a human carcinogen," commented Ivy Elkins, a lung cancer survivor and advocate and co-founder of the EGFR Resisters Lung Cancer Patient Group.

"All you need are lungs to get lung cancer!"

Contribution of Air Pollution to Lung Cancer

In her presentation, Berg emphasized that lung cancer is the leading cause of cancer death worldwide, although the distribution between countries "depends on historical and current smoking patterns and the demographics of the population."

Overall, data from GLOBOCAN 2018 indicate that annually, there are approximately 2.1 million incident cases of lung cancer and almost 1.8 million lung cancer deaths around the globe.

A recent study estimated that, worldwide, 14.1% of all lung cancer deaths, including in never-smokers, are directly linked to air pollution.

Berg said that this makes it the "second leading cause of lung cancer" behind smoking.

The figure is somewhat lower for the United States, where around 4.7% of lung cancer deaths each year are directly attributable to pollution. However, with "the wildfires out West, we're going to be seeing more of a toll from air pollution," she predicted.

She pointed out that the International Agency for Research on Cancer classifies outdoor air pollution, especially particulate matter, as a human carcinogen on the basis of evidence of an association with lung cancer.

It is thought that direct deposits and local effects of particulate matter lead to oxidative damage and low-grade, chronic inflammation. These in turn result in molecular changes that affect DNA and gene transcription and inhibit apoptosis, all of which lead to the development of cancerous lesions, she explained.

Synthesizing various estimates on global burden of disease, Berg and colleagues calculated that in 2019, the rate of lung cancer deaths attributable to particular matter in people aged 50–69 years was highest in Serbia, at 36.88 attributable deaths per 100,000.

Next was Poland, with a rate of 27.97 per 100,000, followed by China, at 24.63 per 100,000, Mongolia, at 19.71 per 100,000, and Turkey, at 19.2 per 100,000.

The major sources of air pollution in the most affected countries were transportation, indoor cooking, and energy sources, she said.

In Serbia, 70% of energy production was from coal. It was 74% in Poland, 65% in China, 80% in Mongolia, 35% in Turkey, and 19% in the United States.

At the time of the analysis, only 17.3% of US adults were smokers, and the air concentration of particular matter of 2.5 µm was 9.6% µg/m3. Both of these rates are far below those seen in more severely affected countries.

"But 40% of our energy now comes from natural gas," noted Berg, "which is still a pollutant and a source of methane. It's a very potent greenhouse gas."

No funding for the study has been reported. Berg has relationships with GRAIL Inc and Mercy BioAnalytics, LLC. Aerts has relationships with Amphera, AstraZeneca, Bayer, BIOCAD, BMS, Eli-Lilly, and Roche.

World Conference on Lung Cancer (WCLC) 2021: Abstract PL02.07. Presented September 9, 2021.

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