Health risk assessment of heavy metals in indoor dust from a university based on Monte Carlo simulation

To investigate the concentrations, source apportionments and probabilistic health risks of heavy metals in indoor dust, a total of 60 indoor dust samples were collected from a college in Anhui province, covering five functional zones, i.e. classrooms, libraries, laboratories, offices, and dormitories. The pollution assessment was carried out by geo-accumulation index method, improved Nemerow pollution index method and potential ecological risk index method. Then, the positive definite matrix factor decomposition model (PMF) and Monte Carlo simulation were used to quantitatively evaluate the risk of heavy metals from different sources to human health. The results showed that the mean concentrations of Pb, Zn, Cu, Cr, Mn, Ni, Cd and Hg were 131.78, 436.48, 113.60, 152.54, 511.69, 83.38, 0.84, 0.32 mg·kg−1, respectively. Except for Mn, all other heavy metals concentrations were greater than the soil background values of Anhui Province. The order of the geo-accumulation index for the eight heavy metals was Hg>Cd>Zn>Pb>Cu>Ni>Cr>Mn, with Hg and Cd in the dust indicating moderately to heavily polluted. The improved Nemerow pollution index illustrated that the comprehensive pollution degree of dust was moderate pollution to heavy pollution, and the overall pollution was moderate to heavy pollution. The potential ecological risk index showed that 65% of the samples were at high ecological risk levels, 6.7% of the samples were at extremely high ecological risk. Four sources (including indoor renovations, equipment usage, experimental activities and traffic emissions) were identified by combining the positive matrix factorization model and correlation analysis, with the contribution rate of 26.98%, 23.64%, 20.64% and 28.74%, respectively. The assessment of probabilistic health risks indicated that the non-carcinogenic risks for all populations were negligible, while the carcinogenic risk cannot be negligible. Based on the source-specific health risk assessment, equipment usage was estimated to be the most important anthropogenic sources of health risks for all populations and the higher carcinogenic risk of Cd should be monitored continuously.