What subtypes of lung cancer are associated with pollutants?

A study led by the Barcelona Institute for Global Health (ISGlobal)center driven by ”la Caixa” Foundationin collaboration with the American Cancer Society (ACS), analyzes the relationship between different air pollutants and the main subtypes of lung cancer. The results have been published in Environmental Pollution.

He lung cancer It is mainly classified into two large types. The most common is non-small cell lung cancer, which includes adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. These subtypes are differentiated by the type of cells affected and their location within the lung, and represent the majority of diagnoses. The second major type is small cell lung cancer, less common but more aggressive, which has a strong relationship with smoking.

Numerous studies have pointed to the outdoor air pollutionespecially exposure to fine suspended particles (PM2.5), such as carcinogen for lung cancer —that is, an agent capable of causing this cancer. However, it is not completely known how it influences the incidence of the different subtypes of cancer, nor if it affects how it evolves after diagnosis. Specifically, few studies have been conducted on the impact of air pollution on lung cancer survival, and this study provides valuable information in this area.

Follow-up of up to 25 years

They were included in the study more than 122,000 people of the American Cancer Prevention Study-II (CPS-II) cohort, of the American Cancer Society, starting in 1992. The participants updated their personal data and cancer diagnoses every two years until 2017. For each participant, their annual exposure to different pollutants was estimated: fine particles PM2.5, PM10, ozone (O3), sulfur dioxide (SO2), nitrogen dioxide (NO2) and carbon monoxide (CO). The analysis took into account variation in exposure over time and adjusted the results for multiple individual factors, including a history of smoking. Between 1992 and 2017, 4,282 cases of lung cancer were detected in this cohort.

“We use national air quality data combined with satellite and land use information,” explains Ryan Diver, researcher at ISGlobal and first author of the study. “Thus, we were able to relate pollution exposure to the risk of developing different subtypes of lung cancer, as well as survival after diagnosis in specific subgroups of patients.”

Different pollutants, different lung cancer subtypes

The study confirmed that the Exposure to fine particles (PM2.5) increases the risk of developing lung cancerand that this effect is observed similarly in all histological subtypes, including adenocarcinoma, squamous cell carcinoma, and large cell carcinoma.

The analysis also revealed relevant associations with several gaseous pollutants—particularly NO2, O3, and SO2—particularly in non-small cell lung cancer. Within this group, nitrogen dioxide (NO2) showed a stronger relationship with adenocarcinoma, the most common subtype of lung cancer, while ozone (O3) was associated with a higher risk of large cell carcinoma. On the other hand, no consistent associations were found between the gaseous pollutants analyzed and small cell carcinoma, one of the subtypes most strongly linked to smoking.

Lower survival, but only in some groups of patients

Regarding survival after diagnosis, no clear associations were observed in all patients. However, in those with early-stage disease, SO2 was related to lower survival.

“We have observed that air pollution is not related to all types of lung cancer in the same way,” explains Michelle C. Turner, ISGlobal researcher and lead author of the article. “Our results reinforce the importance of integrating local air quality into healthcare plans, evaluating each patient’s environmental exposure to identify additional risks,” concludes Turner.