Table 1: Sampling sites characteristics.

Sampling Site Location Characteristics
Al-Haram 21° 25′ 19.2″ N,
39° 49′ 33.6″ E
Heavy constructions around the site and heavy traffic all the year
Arafat About 20 km from Central Makkah Heavy traffic of trucks and buses only in Hajj seasons
Muzdalifah 21° 24' 33” N
39° 54' 11” E
Heavy traffic of trucks and buses only in Hajj seasons
Aziziyah 32° 31′ 48″ N
13° 0′ 36″ E
Residential area with medium traffic load except in Hajj seasons
Al Nuzhah About 5 km from Al-Haram Residential and commercial area with medium to high traffic load presenting local activities
Al Awali 21° 19' 29” N
39° 53' 24” E
Reference area with low traffic and commercial activities

Samples were collected for one year (representing all seasons) and were distributed as follows: 9 weeks round-1 (Spring), 10 weeks round-2 (Summer), 8 weeks round-3 (Autumn), and 10 weeks round-4 (Winter). Hajj 2016-2017 took place during round-2 (10-15 September 2016).