oa Roads to Makkah: Ambient Air Quality and Personal Exposure Assessment During Ritual of Hajj

Hajj, an annual pilgrimage of Islam, draws millions of pilgrims from more than 200 countries for religious rituals in Mecca, Saudi Arabia. The Mecca population during Hajj grows equal to a mega city and traffic activities in Mecca remain busiest during Hajj. Traffic emissions are the principal local source of air pollutants. Air quality in Mecca and surrounding holy sites was investigated during the 2012 (1433 H) and 2013 (1434 H) Hajj. This is the first detailed study to elucidate the exposure to air pollutants among pilgrims. It is also the very first VOCs emission study in the region (GCC) which assesses VOCs including Alkanes, Alkenes, Alkynes, Aromatics, Alkyl Nitrates, cycloalkanes/alkenes, sulfur species, and halocarbons in air sample. Spatial and temporal variations in total suspended particulate (TSP), PM10, PM7, PM2.5, PM1, ozone (O3), and black carbon (BC) levels along the route were also recorded using portable monitors. Strongly elevated levels of carbon monoxide and volatile organic compounds (VOCs) were measured. The most pilgrim routes had on average exceeded the World Health Organization (WHO) recommended threshold for PM10 and PM2.5 during Hajj, especially in the tunnels of Mecca, and are a concern for human health. High volume of traffic, construction work, re-suspension of particles, and geographical conditions (arid regions) are identified as major causes of health significant pollutants. The pilgrim's longer trip duration lead to their highest whole trip exposure to air pollutants, which indicate that they are subject to higher health risk. Better understanding of air pollution exposure and their determinants in the environments will contribute to the development of more appropriate exposure reductive strategies and have significant public health meanings.