Abstract
BACKGROUND AND AIM: The frequency and severity of wildfires have been sharply increasing due to climate change and largely contribute to ambient particulate matter (PM) pollution. We conducted a systematic literature review on the short-term relationships between wildfire-related PM and a variety of respiratory endpoints and compared the effects of wildfire-related PM and non-wildfire PM. METHOD: A comprehensive online search for the literature published from January 2000 to August 2022 was conducted for databases of PubMed, Web of Sciences, Scopus, and EMBASE. We applied search terms related to wildfire smoke and respiratory health outcomes, such as lung conditions, asthma, and wheeze. RESULTS: In total, 3,397 articles were retrieved, and 37 articles were included in this review. The majority of studies focused on associations of wildfire-related PM less than 2.5 µm or 10 µm with hospital admissions, emergency department visits/ambulance dispatches, or mortality, with a time-series or case-crossover study design. Studies were concentrated in the continent of the United States and Australia. Asthma/wheeze was the most studied specific respiratory outcome. Positive associations of wildfire PM with various respiratory outcomes were observed in most studies, with few studies showing non-significant or mixed associations. Some age groups (e.g., children or elders aged 65 years) and females were more vulnerable to wildfire smoke impacts. Most studies concluded that wildfire-specific PM was associated with higher risks of adverse respiratory outcomes than non-wildfire PM or stronger associations of PM pollution were observed during the wildfire period or on smoke days related to wildfires. CONCLUSIONS: To our knowledge, this is the first systematic review to summarize the comparison between the short-term respiratory health effects of wildfire vs. non-wildfire PM. Further investigations are needed to better understand the mechanisms of adverse respiratory effects of wildfire-specific PM pollution.