Exposure-response relationship between ambient air PM10 pollution and health: a threshold effect model

Objective To explore whether there are inflection points and the number of the points for the exposure-response relationship between ambient air particulate matter less than 10 μm in aerodynamic diameter (PM₁₀) and health and to provide references for relevant policy-making.Methods PM₁₀ data for cities in the year of 2012 and 2014 were obtained from China Statistical Yearbook and Environmental Bulletins of cities and radar chart was adopted to describe the distribution of PM₁₀ level across provinces in China in 2011 and 2013.Based on the dataset of China Health and Retirement Longitudinal Study (2011 and 2013),we used threshold effect model to explore the exposure-response relationships between PM₁₀ levels across cities and 3 indicators including self-rated health,illness experience during past one month,and history of required hospitalization during past one year.Results Radar chart analysis indicated that the distribution of PM₁₀ across 27 provinces were similar between the two years and the pollution level in central China and north China was higher than that in southeast coastal regions.The threshold effect model analyses revealed two inflection points (threshold values) in the exposure-response curves between PM₁₀ level and the 3 indicators;every 1 μg/m³ increase in PM₁₀ was associated with the decreases of 0.092% (P<0.01),0.041% (P>0.05),and 0.01% (P>0.05) in the possibility of reporting good self-rated health when the PM₁₀ level being<96,between 96 and 199,and >199 μg/m³;every 1 μg/m³ increase in PM₁₀ was related to the 0.131% increase (P<0.05),0.070% decrease (P>0.05),and 0.023% increase (P<0.05) in the possibility of having illness during past one month when the PM₁₀ level being<52,between 52 and 60,and >60 μg/m³;and every 1μg/m³ increase in PM₁₀ was associated with the 0.061% increase (P>0.05),0.110% decrease (P<0.05),and 0.019% increase (P>0.05) in the probability of required hospitalization during past one year when the PM₁₀ level being<45,between 45 and 56,and >56 μg/m³,respectively.Conclusion There are inflection points in the exposure-response curves between PM₁₀ level and health outcomes and different impacts of various PM₁₀ pollution levels on health should be concerned when making relevant policies by governmental agencies to conduct reasonable health resources allocation.