Association of air pollution and green space with all-cause general practitioner and emergency room visits: A cross-sectional study of young people and adults living in Belgium

BACKGROUND: Residing in areas with lower levels of air pollution and higher green space is beneficial to physical and mental health. We investigated associations of PM2.5, tree cover and grass cover with in-hours and out-of-hours GP visits and ER visits, for young people and adults. We estimated potential cost savings of GP visits attributable to high PM2.5. METHODS: We linked individual-level health insurance claims data of 315,123 young people (10-24 years) and 885,988 adults (25-64 years) with census tract-level PM2.5, tree cover and grass cover. Deploying negative binomial generalized linear mixed models, we estimated associations between quartile exposures and the three outcome measures. RESULTS: For in-hours and out-of-hours GP visits, among young people as well as adults, statistically significant pairwise differences between quartiles suggested increasing beneficial effects with lower PM2.5. The same outcomes were statistically significantly less frequent in quartiles with highest tree cover (>30.00%) compared to quartiles with lower tree cover, but otherwise pairwise differences were not statistically significant. These associations largely persisted in rural and urban areas. Among adults living in urban areas lower grass cover was associated with increased in-hours GP visits and ER visits. Assuming causality, reducing PM2.5 levels to the lowest quartile (4.91-7.49 μg/m³), among adults, 195,964 in-hours and 74,042 out-of-hours GP visits could be avoided annually. Among young people, 27,457 in-hours and 22,423 out-of-hours GP visits could be avoided annually. Nationally, this amounts to an annual potential cost saving of €43 million (€5.7 million in out-of-pocket payments and €37.2 million in compulsory health insurance). CONCLUSION: Higher ambient PM2.5 and lower tree cover show associations with higher non-urgent and urgent medical care utilization. These findings confirm the importance of reducing air pollution and fostering green zones, and that such policies may contribute positively to economic growth.