Recently, a collaborative effort between Professor Ouchunquan's team from the School of Public Health at Southern Medical University and Researcher Zhou Maigeng's team from the Chinese Center for Disease Control and Prevention has shed light on the appropriate definition and health hazards of haze days. The findings were published in the Journal of Hazardous Materials. Haze is a specific weather phenomenon characterized by a significant amount of suspended particles in the air, with diameters typically less than a few micrometers, resulting in reduced atmospheric visibility to a certain extent and widespread air haziness. It is generally defined as weather conditions where both horizontal visibility and relative humidity are below certain threshold values. Haze, widely recognized as a severe form of air pollution due to its observable low visibility characteristics, serves as a common indicator for assessing air quality and is an integral component of air pollution warning systems, carrying significant public health implications. However, there is currently limited research evidence regarding the health hazards of haze days, along with inconsistencies in defining haze days, limited geographical representation, and weak representativeness in existing studies.
This study, based on mortality data from 190 cities nationwide, employed a two-stage research approach combining Poisson regression with distributed lag non-linear models and multivariate random-effects meta-analysis to explore the optimal definition of haze days from a public health perspective. It was found that defining haze days as those with daily average visibility below 10 km is appropriate, with no significant threshold for relative humidity.
Based on the optimal definition, it was discovered that haze days significantly increase the risk of non-accidental total mortality by 2.53%, as well as mortality risks from various causes, particularly with a 3.80% increase in lung cancer mortality. Even after adjusting for various individual air pollutants, the effect of haze days remained significant, indicating its ability to reflect the collective harm from multiple pollutants. Subgroup analysis revealed that the elderly population is more vulnerable to the effects of haze days and requires focused protection, with the severity of haze day hazards increasing with the intensity of haze and humidity. The southern regions experience slightly higher hazards from haze days compared to the northern regions.
This nationwide study provides robust epidemiological evidence for the public health burden of air pollution and offers important scientific grounds for improving haze day reporting guidelines, developing accurate warning systems, and implementing effective public health interventions in China.
Link to the related paper: https://doi.org/10.1016/j.jhazmat.2024.133561
