Contribution of air pollution to lung cancer
In her presentation, Dr. 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.
Dr. 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, Dr. 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 U.S. adults were smokers, and the air concentration of particular matter of 2.5 mcm was 9.6% mcg/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 Dr. 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. Dr. Berg has relationships with GRAIL and Mercy BioAnalytics. Dr. Aerts has relationships with Amphera, AstraZeneca, Bayer, BIOCAD, Bristol-Myers Squibb, Eli Lilly, and Roche.
A version of this article first appeared on Medscape.com.