Impact of an urban city-wide Bradford Clean Air Plan on health service use and nitrogen dioxide 24 months after implementation: An interrupted time series analysis

There is limited evidence of the health impact of Low Emission Zones (also known as Clean Air Zones, CAZ). This study examines the impact of the Bradford Clean Air Plan (CAP), including a CAZ, on health and nitrogen dioxide (NO2) in the first two years of implementation using an interrupted time series design. Primary care and emergency department visits for respiratory and cardiovascular illness in Bradford were recorded between January 2018 to September 2023 with diabetic footcare and head injury visits as controls. A total of 157,623 primary care, and 37,865 emergency department visits for respiratory and cardiovascular conditions were recorded. At the start of implementation respiratory primary care visits decreased by 25% (RR=0.75; 95%CI: 0.68 to 0.82) and cardiovascular visits by 24% (RR=0.76; 95%CI: 0.64 to 0.92) compared to a pre-COVID-19 baseline (January 2018-February 2020). Post-implementation monthly respiratory and cardiovascular visits declined by 598 (95%CI: -614 to -583) and 134 (95%CI: -137 to -131), respectively, with continued downward trends (both: RR=0.99; 95% CI: 0.99 to 0.99). Diabetic foot-care decreased (RR=0.69; 95%CI: 0.60-0.80) but showed upward trends post-implementation (RR=1.01; 95%CI: 1.00-1.01). Emergency department visits showed minimal changes across all outcomes. NO₂ concentration decreased by 11.5 μg/m³ (95%CI: -23.2 to 0.2) and continued to decrease by 0.2μg/m³ (95%CI: -0.4 to -0.1) post-implementation. Policies which restrict the movement of polluting vehicles have the potential to reduce air pollution and improve health, although evaluating their impact is challenging. Studying the longer-term impact of these initiatives is warranted.