Health risk assessment of PM 2.5 and PM 2.5 -bound trace elements in Pretoria, South Africa.

Exposure to outdoor air pollutants poses a risk for both non-carcinogenic and carcinogenic respiratory disease outcomes. A standardized health risk assessment (US EPA) utilizes air quality data, body mass and breathing rates to determine potential risk. This health risk assessment study assesses the hazard quotient (HQ) for total PM 2.5 and trace elemental constituents (Br, Cl, K, Ni, S, Si, Ti and U) exposure in Pretoria, South Africa. The World Health Organization (WHO) air quality guideline (5 µg m -3 ) and the yearly South African National Ambient Air Quality Standard (NAAQS) (20 µg m -3 ) were the references dosages for total PM 2.5 . A total of 350 days was sampled in Pretoria, South Africa. The mean total PM 2.5 concentration during the 34-month study period was 23.2 µg m -3 (0.7-139 µg m -3 ). The HQ for total PM 2.5 was 1.17, 3.47 and 3.78 for adults, children and infants. Non-carcinogenic risks for trace elements K, Cl, S and Si were above 1 for adults. Seasonally, Si was the highest during autumn for adults (1.9) and during spring for S (5.5). The HQ values for K and Cl were highest during winter. The exposure to Ni posed a risk for cancer throughout the year and for As during winters.