Size-specific particulate air pollution and hospitalization for cardiovascular diseases: A case-crossover study in Shenzhen, China.

Despite contributing to the majority of ambient fine particles (PM 2.5), PM 1 (particulate matter [PM] with aerodynamic diameter ≤1 μm) remains poorly studied in terms of its acute effects on cardiovascular diseases (CVDs) in China. This study aims to evaluate the short-term associations of size-specific PMs (i.e., PM 1 , PM 2.5 , and PM 10) exposures with hospital admissions for CVDs in a southern Chinese metropolis. We collected 5,969 records of hospital admissions for CVDs and daily average concentrations of air pollutants and weather conditions in Shenzhen from January 1st 2015 to December 31st 2017. We adopted a time-stratified case-crossover design and conditional logistic regression models to assess short-term associations between size-specific PMs and CVD hospitalizations along different exposure days. During the study period, annual average concentrations of PM 1 , PM 2.5 , and PM 10 were 18.7, 27.8, and 45.4 μg/m3, respectively. Compared to PM 2.5 and PM 10 , PM 1 exhibited a generally stronger association with CVD hospitalizations. Hospital admissions for CVDs increased by 6.7% (95% confidence interval: 1.2–12.5%), 4.5% (0.4–8.7%), and 3.4% (0.5–6.3%), corresponding to per 10-μg/m3 rise in exposure to PM 1 , PM 2.5 , and PM 10 at lag 03 days. In our stratified analyses by CVD sub-causes, size-specific PMs showed consistent effects on hypertension but no evident association with ischemic heart disease (IHD) and stroke. Seasonal analysis revealed significantly larger PM-associated risks among IHD patients in cold months (October–March). Nevertheless, in warm months (April–September), the older group (aged 65+ years) was more prone to adverse effects of PM 1 exposure at lag 0 day. Short-term exposure to size-specific PMs, PM 1 in particular, may trigger incidences of CVD hospitalization. To effectively mitigate adverse effects of particulate pollution, evidence-based PM 1 standards should be developed as well in Chinese less-polluted megacities. [Display omitted] • PM 1 exhibited relatively stronger effects on CVDs than PM 2.5 and PM 10. • Detected impacts from size-specific PMs on hypertension but not IHD and stroke. • PM-associated effects on IHD were only identified in cold months. [ABSTRACT FROM AUTHOR]