The effects of bushfire smoke exposure on oxidative stress and inflammatory biomarkers: a systematic review.

Abstract

Introduction: Bushfire smoke (BFS) is an escalating global health concern, with increasing bushfire frequency due to climate change. Exposure to BFS significantly impacts public health due to worsening respiratory and cardiovascular conditions, causing increased of hospitalizations and mortality. While BFS exposure is linked to morbidity of these conditions, the underlying biological mechanisms, particularly oxidative stress and inflammation, remain unclear.

Content: This systematic review (PROSPERO ID: CRD42024554409) synthesized evidence on oxidative stress and inflammatory biomarkers from BFS exposure. Comprehensive searches of PubMed, Embase, Web of Science, Scopus, and Cochrane Library were conducted. Fourteen studies met inclusion criteria, encompassing occupational and non-occupational populations. Risk of bias was assessed using NIH tools, and findings were synthesized narratively due to study heterogeneity. Commonly examined biomarkers included IL-8, IL-6, TNF-α, 8-isoprostane, malondialdehyde (MDA), and 8-hydroxy-2'-deoxyguanosine (8-OHdG).

Summary: IL-8 emerged as the most consistent inflammatory biomarker, with a pooled random-effects analysis of three firefighter studies showing an acute post-shift increase in blood IL-8 (mean difference 9.76 pg/mL, 95 % CI -8.26 to 27.79), though with substantial heterogeneity. Other inflammatory and oxidative stress biomarkers showed mixed or inconsistent associations with BFS exposure. Small sample sizes, heterogeneous exposure assessment, inconsistent exposure metrics, and unadjusted confounding limited generalizability.

Outlook: This review identifies IL-8 as the most consistent short-term biomarker of BFS exposure in occupational settings but highlights inconsistent evidence for other biomarkers. Future research should use standardized biomarker protocols, larger sample size, longitudinal designs, and include vulnerable populations to clarify biomarker responses to BFS and strengthen the evidence base for public health and occupational safety measures.