Health effects of low emission and congestion charging zones: a systematic review

Low emission zones (LEZs) and congestion charging zones (CCZs) have been implemented in several cities globally. We systematically reviewed the evidence on the effects of these air pollution and congestion reduction schemes on a range of physical health outcomes. We searched MEDLINE, Embase, Web of Science, IDEAS, Greenfile, and Transport Research International Documentation databases from database inception to Jan 4, 2023. We included studies that evaluated the effect of implementation of a LEZ or CCZ on air pollution-related health outcomes (cardiovascular and respiratory diseases, birth outcomes, dementia, lung cancer, diabetes, and all-cause) or road traffic injuries (RTIs) using longitudinal study designs and empirical health data. Two authors independently assessed papers for inclusion. Results were narratively synthesised and visualised using harvest plots. Risk of bias was assessed using the Graphic Appraisal Tool for Epidemiological studies. The protocol was registered with PROSPERO (CRD42022311453). Of 2279 studies screened, 16 were included, of which eight assessed LEZs and eight assessed CCZs. Several LEZ studies identified positive effects on air pollution-related outcomes, with reductions in some cardiovascular disease subcategories found in five of six studies investigating this outcome, although results for other health outcomes were less consistent. Six of seven studies on the London CCZ reported reductions in total or car RTIs, although one study reported an increase in cyclist and motorcyclist injuries and one reported an increase in serious or fatal injuries. Current evidence suggests LEZs can reduce air pollution-related health outcomes, with the most consistent effect on cardiovascular disease. Evidence on CCZs is mainly limited to London but suggests that they reduce overall RTIs. Ongoing evaluation of these interventions is necessary to understand longer term health effects.