Even after long-term asbestos exposure, individuals who quit smoking significantly decrease their chances of dying from lung cancer, according to research published in the American Journal of Respiratory and Critical Care Medicine.

A team investigated the contributions of asbestos exposure, asbestosis, smoking and their interactions to lung cancer risk. They found that asbestos increases lung cancer mortality among non-smokers, asbestosis increases the risk further, and smoking creates a supra-additive effect.

“In our study of a large cohort of asbestos-exposed insulators and more than 50,000 non-exposed controls, we found that each individual risk factor was associated with increased risk of developing lung cancer,” said lead author Steven B. Markowitz, MD DrPH, professor of occupational and environmental medicine at the School of Earth & Environmental Sciences at Queens College in New York. “The combination of two risk factors further increased the risk and the combination of all three risk factors increased the risk of developing lung cancer almost 37-fold.”

The good news is among study participants who quit smoking, lung cancer morality dropped. Among those who kicked the habit, deaths in the 10 years following smoking cessation dropped from 177 per 10,000 (among current smokers) to 90 per 10,000 (among those who quit). Lung cancer rates among participants who had stopped smoking more than 30 years earlier were similar to those who had never smoked.

“Our study provides strong evidence that asbestos exposure causes lung cancer through multiple mechanisms,” said Markowitz. “Importantly, we also show that quitting smoking greatly reduces the increased lung cancer risk seen in this population.”