Assessing urban noise exposure and health inequalities: a multi-city study in Zhejiang Province, China

Urban environmental noise pollution is emerging as a critical challenge to public health and sustainable urban development. Using grid-based urban regional noise data collected in March-June 2023 across 11 prefecture-level cities in Zhejiang Province, this study systematically evaluates the spatiotemporal distribution of urban noise exposure, diurnal variations, estimated health burdens among high-risk populations, and the underlying associated factors. Results indicate that Ningbo reported the highest day-evening-night equivalent sound level (L_den) at 61.3 dB(A), while Quzhou recorded the lowest at 55.1 dB(A), with noise hotspots concentrated along the Hangzhou-Jiaxing-Huzhou to Ningbo-Shaoxing urban corridor. The evening rush hour was identified as the noisiest period (mean equivalent continuous sound level, LAeq = 56.4 dB(A)), whereas nighttime equivalent sound level (L_night) declined markedly to 45.0 dB(A), yielding a day-night difference exceeding 11 dB(A). Health impact assessments estimated that approximately 4.75 million residents were highly annoyed, 2.79 million were highly sleep disturbed, and approximately 2,026 cardiovascular deaths were attributable to noise exposure, with Ningbo and Hangzhou bearing the heaviest burdens. Correlation analysis further showed that per capita income, industrial land use, and road length were positively associated with noise levels, whereas per capita green space was negatively associated. Therefore, targeted mitigation is needed in high-noise areas and periods, prioritizing stricter nighttime control, optimization of industrial and transport layouts, and expansion of urban green space. Such measures may help reduce noise pollution and its adverse health effects, contributing to a better balance between environmental protection and social equity.