Background and purpose: Today use of unleaded gasoline is increasing in the world which contain abundant amount of aromatic organic carcinogenic compounds. This study aimed at monitoring the temporal and spatial concentration of benzene and toluene as volatile organic compounds in ambient air in Yazd, Iran.

Materials and methods: This research, was carried out in different hours of the morning and evening in early fall, 2015. Sampling and measurement of benzene - toluene was done according to 1501 NIOSH guidelines using active sampling and GC-FID. GIS software was used for zoning.

Results: The mean concentrations of benzene and toluene in early and late morning-evening hours were 23 and 48.9 μg/m³, 25 and 58 μg/m³, respectively. These values indicates an increase in emissions in last hours of the morning. Also, toluene to benzene ratio (T/B) was 1.3 to 2.1 and 1.2 to 3, showing that benzene and toluene emissions were caused by traffic.

Conclusion: The central and southern parts of Yazd were found to be more polluted then northern areas. Also, spatial variations of pollutant concentrations were high, but the temporal trend was low. The correlation between benzene and toluene values in early hours of morning and evening confirmed the temporal and spatial trend. According to T/B ratio, the main cause of benzene and toluene emissions were street traffics and gasoline stations.