Follow-up of cancer incidence associated with smoke-related PM_2.5 exposure due to a coal mine fire

The link between chronic exposure to ambient PM_2.5 and lung cancer is well established. However, there is limited evidence on the effects of acute, high-level exposure such as that resulting from the 2014 Hazelwood coal mine fire in regional Australia. We investigated the effects of PM_2.5 from this fire on cancer incidence 8.5 years later.

We obtained Victorian Cancer Registry data linked to 2,872 Hazelwood Health Study Adult Cohort members, from August 2014 to December 2022 and analysed all cancers combined and cancer subtypes. Individual fire-related PM_2.5 exposure was estimated by blending time-location diaries with spatial and temporal air pollution modelling data. To evaluate cancer risk from fire-related PM_2.5 exposure, we used a competing risks survival model, specifically the Fine-Gray subdistribution hazard model for deaths from causes other than the cancer outcome being analysed, and to adjust for confounders including demographics, occupational exposures, and socioeconomic factors.

In the post-mine fire period, 295 people (14.3/1000 person-years) were diagnosed with 332 new cancers (12.7/1000 person-years). No significant association was found between fire-related PM_2.5 exposure and the overall incidence of cancer (hazard ratio = 1.00, 95 % confidence interval: 0.90-1.11). Additionally, no associations were identified with any specific cancer subtypes, including lung cancer.

We found no evidence that this coal mine fire increased cancer incidence. However, it would be premature to rule out potential carcinogenic effects. Cancer has a long latency period, which means it will be necessary to analyse new data as they become available to more conclusively determine the effects of medium-duration, high-level smoke exposure.