Objective Evidence for the protective effects of dietary antioxidants on respiratory health following exposure to smoke from landscape fires is scarce. This study assessed whether the long-term respiratory effects of fine particulate matter (PM2.5) from the 2014 Hazelwood coal mine fire were moderated by dietary antioxidants, 8.5 years later. Methods We conducted a cross-sectional analysis of data collected 8.5 years after the mine fire from 282 residents of Morwell (a highly exposed town adjacent to the mine) and 166 residents from the nearby unexposed town of Sale. Coal mine fire-related PM2.5 was the primary exposure and meeting recommended dietary intake for antioxidants including vitamins (A, E and C), minerals (zinc, magnesium and selenium) and omega-3 fatty acids assessed through the Australian Eating Survey (AES) was the moderator. Respiratory symptoms were the primary outcome. Analyses used logistic regression models, adjusting for potential confounders. Results Vitamins A and E, magnesium, and zinc attenuated the association between fire-related PM2.5 and prevalence of chronic cough; three of the four (except magnesium) attenuated the association between fire-related PM2.5 and chronic phlegm. Omega-3 fatty acids attenuated the association between PM2.5 and COPD. Conclusion Meeting recommended intakes of vitamins, A and E, magnesium and zinc may provide protection against the long-term adverse effects of exposure to particulate matter from other medium duration but extreme exposure events. Advocating incorporation of fruits and vegetables in daily diet could offer more than the conventional health benefits due to their high antioxidant content. Key words: landscape fires, respiratory health, PM2.5, dietary antioxidants, chronic cough, chronic phlegm

MJA holds investigator-initiated grants from Pfizer, Boehringer-Ingelheim, Sanofi and GSK for unrelated research. He has undertaken an unrelated consultancy for Sanofi and received a speakers fee from GSK. The remaining authors declare that they have no known competing financial interests or personal relationships that could have influenced the work reported in this paper.

This work was funded by the Victorian Department of Health. The paper presents the views of the authors and does not represent the views of the Department.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Monash University Human Research Ethics Committee approved this study as part of the Hazelwood Adult Survey & Health Record Linkage Study (Project ID: 25680; previously CF15/872 - 2015000389 and 6066)

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