Effects of Food Production, Consumption and Trade on Agricultural Ammonia Emission and PM2.5 Pollution in China and Worldwide

Fine particulate matter (PM2.5) pollution threatens human lives and wellbeing worldwide. Agricultural ammonia (NH3) is a key precursor of PM2.5. In order to examine how the food consumption, production and trade in different countries affect global air quality, here we used the MASAGE NH3 emission inventory to drive the GEOS-Chem global chemical transport model to estimate the impacts of food production and consumption in China and eight other major food-importing and food-exporting countries or regions (Argentina, Brazil, Canada, European Union, India, Japan, Russia, United States) to their own and other countries PM2.5 pollution. We first constructed an NH3 emission scenario in 2014 by scaling up a year-2006 food-by-food NH3 emission inventory (MASAGE) according to temporal trends of food consumption and production, thus obtaining an estimation for the amount of food-derived NH3 in 2014 and finding that the China and global annual agricultural NH3 emissions decreases by 3.7% from 7.59 Tg N to 7.30 Tg N and increases by 8.0% from 33.4 Tg N to 36.1 Tg N respectively during 20062014. We then used the GEOS-Chem chemical transport model with the scaled MASAGE and performed sensitivity experiments by deducting NH3 emission related to different food items that are consumed domestically vs. exported. We found that domestic food production to feed domestic consumption in China and other countries contribute significantly (1030% for China and 540% for other countries) to regional PM2.5 pollution, among which ~40% is driven by the meat and feed crop production and consumption. We also found that food import from one country to another is generally not a major contributor to PM2.5 pollution in the exporting country (e.g., <1% of the total PM2.5 in the trading partners of the aforementioned countries). Our study highlights the significance of food consumption and production in shaping PM2.5 pollution worldwide, and it is important to incorporate sustainable food production, consumption and trading strategies to safeguard the health of citizens and also global food security.