• Pei Yu, Rongbin Xu, Shanshan Li, Xu Yue, Gongbo Chen, Tingting Ye, Micheline Coêlho, Paulo Saldiva, Malcolm R Sim, Michael J Abramson, and Yuming Guo.
• School of Public Health and Preventive Medicine, Monash University, Melbourne, VIC, Australia.
• Lancet Oncol. 2022 Jul 1; 23 Suppl 1: S6.

BackgroundWith the increasing frequency and duration of wildfires over the past 10 years, the effects of wildfire on health need to be better understood. Long-term exposure to particulate matter less than 2·5 μm in diameter (PM2·5) has been linked to cancer mortality. However, the long-term effects of wildfire-related PM2·5 exposure on cancer mortality risk were unknown. The aim of this study was to assess the association between wildfire-related PM2·5 and cancer mortality in Brazil on the basis of nationwide death records for the period of 2010-16.MethodsNationwide cancer death records for the period of January 1 to December 31, 2010-16 were collected and linked with municipal-level, wildfire-related and non-wildfire-related PM2·5 concentrations at a 2·0° latitude by 2·5° longitude resolution. We applied a difference-in-difference approach with quasi-Poisson regression for data analysis. Relative risks (RRs) and 95% CIs for the exposure on specific cancer sites were estimated, and attributable fractions and cancer deaths were also calculated.Findings1 332 526 cancer deaths in adults (ie, individuals aged 20 years or older) from 5565 Brazilian municipalities covering a population of 136 million adults were included. The annual wildfire-related PM2·5 concentration was 2·38 μg/m3 and the non-wildfire-related PM2·5 was 8·20 μg/m3. The RR for mortality from all cancers was 1·02 (95% CI 1·01-1·03) per μg/m3 increase of wildfire-related PM2·5 concentration, which was higher than other sources of PM2·5 (1·01 [1·00-1·01]; p=0·0029). Wildfire-related PM2·5 was associated with higher mortality from cancers of the nasopharynx (RR 1·10 [95% CI 1·04-1·16]; p=0·0015), oesophagus (1·05 [1·01-1·08]; p=0·012), stomach (1·03 [1·01-1·06]; p=0·017), colon and rectum (1·08 [1·05-1·11]; p<0·0001), larynx (1·06 [1·02-1·11]; p=0·0031), skin (1·06 [1·00-1·12]; p=0·033), breast (1·04 [1·01-1·06]; p=0·0074), prostate (1·03 [1·01-1·06]; p=0·019), and testis (1·10 [1·03-1·17]; p=0·0022). For all-cancers combined, the attributable deaths were 37 per 100 000 people during the study period.InterpretationLong-term exposure to wildfire-related PM2·5 can increase the risk of cancer mortality at various sites. The effect was greater for wildfire-related PM2·5 than for PM2·5 from other sources.FundingAustralian Research Council and National Health & Medical Research Council; China Scholarship Council.Copyright © 2022 Elsevier Ltd. All rights reserved.

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