Fine particulate matter (PM2.5) in a compost facility: heavy metal contaminations and health risk assessment, Tehran, Iran.

The aim of this study was to evaluate the concentration of PM2.5 particles, potential sources, and determination of health risk assessment of heavy metals in various parts of composting facilities of Tehran's Kahrizak. A total of 60 PM2.5 particle samples were collected every 3 days from January to March 2016. To analyze the heavy metals, inductively coupled plasma atomic emission spectroscopy (ICP-AES) was applied. SEM-EDX analysis indicated that metals of Al, Si, Mg, Na, Au, S, Ca, K, and Co were dominant in the structure of particles. The concentration of PM2.5 was found to be the highest in the final processing site (c), followed by primary processing site (a) and the aerated site (b). The mean concentrations of Al and Fe in all sampling sites of a, b, and c were 7.46 ± 2.73, 1.48 ± 0.59, 24.30 ± 8.23 μg/m3 and 4.97 ± 2.83, 1.33 ± 0.48, 16.48 ± 7.36, respectively. The enrichment factor order of the trace elements was as follows: Cd > As > Pb > Zn > Cu > V > Cr > Ni > Mn > Fe > Al, with the highest EF value exceeding 10,000 for Cd at the a site. For all sampling sites in composting facilities, the cancer risk was more than > 1 × 10-4 as posed by the total of five carcinogenic metals (Pb, Cr, As, Ni, and Cd), indicating that risk factors were not negligible.