Analyzing Uncertainties in Estimating PM2.5- and O3-Related Human Health Outcomes in the Mainland China Due to Emission Scenarios, Concentration Response Functions, and Other Assumptions Open Access

Chen, Futu (2016)

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Background: Exposures to fine particulate matter (particulate matter with an aerodynamic diameter of less than or equal to 2.5 μm; PM2.5) as well as ground-level ozone (O3) are associated with a variety of adverse health effects. Ambient air pollutants are also anticipated to continuously affect large populations in China in the future. However, although several assumptions affect the estimation of potential future health outcomes, only a few studies have discussed the associated uncertainties.

Objectives: Our goal is to assess the sensitivity of PM2.5- and O3-related human health outcomes to emission scenarios and to concentration-response (C-R) functions, as well as population projections, when estimating health outcomes.

Methods: We used the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) to simulate PM2.5 and O3 concentrations and conducted base year simulations for the year 2008 and future simulations for 2050. We used three different emission inventories for the base year and four scenarios for 2050. We applied population-weighted concentrations to quantify the change in exposure at the individual level between the base year and the future and applied the C-R function to project the pollutant-related mortality and morbidity. An analysis of variance was used to quantify uncertainty and to apportion the uncertainty to different inputs.

Results: Our research results show a decrease in mortality and morbidity in 2050 due to an up to 80% decrease in population-weighted PM2.5 concentration in the cold season and an up to 20% decrease in population-weighted O3 concentration in the summer in 2050, compared to the base year. 5-37% increase in O3 in January in 2050 led to excess mortality and morbidity. We found that the major source of uncertainty (74%) came from present emissions when projecting PM2.5-related health outcomes in January. Future emission scenarios contributed up to 79% uncertainty in O3-related health outcome estimations in July.

Conclusion: Our results illustrate that the source and the magnitude of emissions have a great impact on premature mortality and morbidity calculations. Our results also highlight the importance of using an ensemble approach to assess future air pollution-related health outcomes.

Table of Contents

Section 1: Background 1

1.1 PM2.5 and O3 Exposure 1

1.2 Air Quality in China 2

1.3 Concentration-response (C-R) Function 4

1.4 Air Quality Modeling and Uncertainty 5

Section 2: Methods 8

2.1 PM2.5 and O3 Concentration Estimation 8

2.2 Study Population 10

2.3 PM2.5 and O3 Population-Weighted Concentration Estimation 11

2.4 C-R Function and Health Impact Estimation 12

2.5 Sensitivity Analysis 14

Section 3: Results 15

3.1 National Air quality Characteristics 15

3.2 Population-weighted concentrations 18

3.3 Health estimates 22

3.4 Uncertainty and sensitivity analysis 24

Section 4: Discussions 28

Section 5: Conclusions and Recommendations 31

References 32

Tables and Figures 40

Appendices 57

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