Exposure to wildfire smoke may increase lung cancer patients’ risk of dying from their disease, particularly among non-smokers, but the effect may be mitigated by certain cancer treatments, according to a large California study presented at a major medical meeting on Saturday.

Researchers tracked more than 18,000 people with non-small cell lung cancer – the most common kind – between 2017 and 2020. Those living in neighborhoods with the highest levels of wildfire-caused air pollution in the year after their cancer diagnosis were more likely to die from the disease, they found.

Patients who inhaled higher levels of tiny particulate matter with a diameter of 2.5 microns or less that can penetrate deeply into the lungs had a 20% greater risk of dying from lung cancer, researchers reported at the American Society of Clinical Oncology meeting in Chicago.

People with advanced stage 4 cancer who had never smoked were especially affected, researchers found. Their risk of dying from cancer was 55% higher if they were exposed to high levels of wildfire air pollution.