1. Smog and soot in the Middle East: Severe air pollution spikes during annual Hajj pilgrimage in Saudi Arabia Isobel Simpson University of California, Irvine Irvine, California, USA isimpson@uci.edu Tao Wang Hong Kong Polytechnic University Hong Kong, China cetwang@polyu.edu.hk Haider Khwaja University at Albany Albany, New York, USA haider.khwaja@health.ny.gov Azhar Siddique King Abdulaziz University Jeddah, Kingdom of Saudi Arabia amohammad@kau.edu.sa Photo by Fadi El Binni, Al Jazeera English via Wikimedia Commons

2. Hajj: The Holy Pilgrimage of Islam World’s largest religious pilgrimage 3.0-4.0 million pilgrims during 2012 Hajj Worsens pre-existing air pollution in Mecca For more on this study: I. J. Simpson et al., Environ. Sci. Technol., 48, 8529-8539, 2014 Photo by Aiman Titi via Wikimedia Commons Photo by Magnus Manske via Wikimedia Commons

3. Sharply elevated air pollution Highest pollution levels in tunnels during Hajj Exceedances of benzene, carbon monoxide Concern for police, volunteers who work in tunnels For more on this study: I. J. Simpson et al., Environ. Sci. Technol., 48, 8529-8539, 2014 Photo by Dr. Jahan Zeb Photo by Dr. Azhar Siddique Photo by Arisdp via Wikimedia Commons

4. Major air pollution sources For more on this study: I. J. Simpson et al., Environ. Sci. Technol., 48, 8529-8539, 2014 Vehicle exhaust Gasoline evaporation Liquefied petroleum gas Air conditioners Photo by Dr. Azhar Siddique

5. Recommendations Air pollution in Saudi Arabia is severe but understudied Expand air quality monitoring Reduce emissions and exposure Contact: Isobel Simpson - isimpson@uci.edu; Call or text: 204-583-4880 Photo by King Elliot via Wikimedia Commons Photo by Dr. Azhar Siddique