Global air pollution exposure and hepatocellular carcinoma: a systematic review and meta-analysis of epidemiological studies

Air pollution poses a significant public health threat worldwide, contributing to adverse health outcomes and reduced life expectancy. Recent research has highlighted a growing interest in understanding the association between air pollution and cancer. This meta-analysis aims to comprehensively evaluate the association between prolonged exposure to air pollution and the risk of HCC. We searched PubMed, Scopus, and Embase databases. Eligible studies were selected based on predetermined inclusion criteria, and data were extracted independently by reviewers. Quality assessment was conducted using established tools, and statistical analysis was performed to calculate pooled hazard ratios (HRs), odds ratios (ORs) and risk ratios (RRs) with 95% confidence intervals (CI) using Review manager version 5.4.1. The search yielded 21 studies comprising a total of 90,319,213 participants. Meta-analysis revealed statistically significant association between NO2 and PM2.5 exposure and HCC incidence with a pooled HR (HR: 1.14, 95% CI: 1.03–1.27, P value = 0.01) and (HR: 1.11, 95% CI: 1.02–1.20, P value = 0.01), respectively. Also, a statistically significant association between NO2 and PM2.5 exposure and HCC mortality revealed with a pooled HR (HR: 1.07, 95% CI: 1.03–1.12, P value = 0.002) and (HR: 1.17, 95% CI: 1.10–1.25, P value = 0.00001), respectively. PM10 and NOx did not show a significant association according to our review. This meta-analysis provides evidence of a potential link between air pollution and HCC risk, particularly with PM2.5 and NO2 exposure. However, further research is needed to elucidate the underlying mechanisms and establish causality. Addressing air pollution through collaborative efforts and environmental regulations may help mitigate the risk of HCC and other types of cancer.