Health Risk Assessment of Metals and Metalloids in PM_2.5 of Lanzhou

Objective To explore the air pollution of metals and metalloids in PM_2.5 of Lanzhou and their health impact.

Methods A total of 168 air samples were collected in Chengguan and Xigu Districts of Lanzhou in 2015. The inhalation exposure and risk assessments of Sb, Al, As, Pb, Cd, Cr, Se, Hg, Mn and Ni in ambient PM_2.5were carried out by the Heath Risk Assessment Model of US EPA.

Results The annual average concentrations of PM_2.5 in Chengguan and Xigu Districts were 0.088 mg/m³ and 0.075 mg/m³ respectively, which were 2.6 and 2 times higher than the limit for grade two standard, ruled in the Ambient Air Quality Standards(GB 3095-2012). The concentrations of ten metals and metalloids in PM_2.5were in sequence, Al > Pb > Mn > As > Cd > Sb > Ni > Cr > Se > Hg in Chengguan District and Al > Pb > Mn > As > Sb > Cr > Ni > Cd > Se > Hg in Xigu District. The concentrations of As and Cr were higher than the standard limits. The respiratory pathway exposures of such elements assessed by annual excess risk were 3.45×10^-12~2.81×10^-7, which were below the acceptable risk level of population (10^-6). The excess risks of 10 elements in Chengguan District were in sequence, As > Cr > Cd > Al > Ni > Mn > Pb > Hg > Sb > Se, and in Xigu District were Cr > As > Cd > Al > Ni > Pb > Mn > Sb > Hg > Se. The health risks of population were in the orders, adult males > adult females > children.

Conclusion Cr and As in ambient air at two monitoring sites showed the most dangerous elements to human health, especially for adult male.