Determination of concentration and risk assessment of toxic metals in the settled dust from school yards of Mashhad metropolis.

The present study aims to measure the values of metal pollutants in the dust of schools in Mashhad metropolis, determine the source of metal pollution, evaluate the degree of pollution, assess the health risk (carcinogenicity/non-carcinogenicity) and evaluate the potential ecological risk. For this purpose, after measuring the concentration of metals using an inductively coupled plasma-mass spectrometer, from various indices including Geoaccumulation Index (I), Pollution Load Index (PLI), Contamination Factors (CF), Potential Ecological Risk Index (PERI), Enrichment Factor (EF), and Health Risk Indices such as Hazard Quotient (HQ), Hazard Index (HI), Carcinogenic Risk (CR) were used. The average concentrations of iron, arsenic, cadmium, chromium, copper, nickel, lead, vanadium and zinc (Fe, As, Cd, Cr, Cu, Ni, Pb, V and Zn) were 6361.50, 5.96, 0.59, 61.89, 37.13, 61.31, 28.93, 25.64 and 142.00 µg g, respectively. Based on CF, PLI and I indices, most of the findings for the studied elements were at the low pollution level. The results also showed that the most likely origin of the studied metals was anthropogenic sources. The results of PERI indices showed that potential ecological risk at only one of the collection sites. In contrast, a high ecological risk was obtained for Cd. Hazard Index values were below safe levels for all studied elements. CR levels for elements were also classified as negligible and acceptable or tolerable risk, although the highest CR value for Cr indicated possible harm to humans. The findings showed the need for more attention and continuous monitoring of the concentration of metals, especially chromium, to announce a possible warning and prevent their harmful effects. It should be noted that the present study is the first research with mentioned objectives in Mashhad city and also in Khorasan Razavi province.