Air pollution and kidney cancer risk: a systematic review and meta-analysis

Although several risk factors of kidney cancer have already been well-addressed, many remain underappreciated, such as chronic exposure to air pollution. This systematic review and meta-analysis aims to assess the association between air pollutant exposure and the risk of kidney cancer.

With an exhaustive search equation including keywords related to air pollution and kidney cancer on EMBASE, PubMed, Web of science, Cochrane Library and CINAHL database, we identified all relevant articles published before March 23rd, 2023 (Prospero registration number: CRD42020187956). Using random-effects meta-analysis, we present pooled hazard ratios (with their respective 95% confidence interval) associated with a 10 µg/m³ increase in each pollutant level. Heterogeneity was quantified by the I₂ statistic. Risks of methodological and publication bias were also both assessed using appropriate tools.

Of the 1919 records identified, our review included 19 articles (13 cohort, 5 registry-based and 1 case-control studies), of which 9 were suitable for the meta-analysis. We found a significantly increased risk of kidney cancer incidence for a 10 μg/m³ elevation of both particulate matter of less than 10 µm (PM₁₀) (HR = 1.29 [1.10; 1.51], I² = 0%, p = 0.002) and nitrogen dioxide (NO₂) (HR = 1.10 [1.03; 1.18], I² = 20%, p = 0.004). Secondary analyses also suggest an increased risk of kidney cancer-related morbidity-mortality associated with PM₁₀ exposure.

Overall, our findings suggest a potential association between exposure to increased levels of PM₁₀ and NO₂ and the risk of kidney cancer. These results should nonetheless be interpreted with caution due to the limited number of included studies and their significant risk of methodological bias.