Human health risk assessment of heavy metals in roadside dust near hydropower dams construction areas in Wangduephodrang District of Bhutan

Abstract

The concern over the heavy metal laden dust and its impact on human health has gained global importance over the decade. Exposure to roadside dust is associated with various acute and chronic health issues. Bhutan too is battling environmental health issues due to increasing anthropogenic and developmental activities such as hydropower dam construction. This study analyses the heavy metals concentrations in roadside dust near hydropower dam construction areas and assesses the noncancer and cancer risk of exposure to heavy metals laden dust through inhalation. This study was a cross sectional study. The roadside dust samples near hydropower dam construction in Wangduephodrang District were collected and analyzed for As, Pb, Cr, and Hg concentration by using ICP-OES. The socio demographic data and exposure factors were collected through interviews. The mean concentration of the heavy metals in the dust samples were Cd<Hg<As<Pb<Cr at <7.59x10-4±0.00, 4.7x10-4±6.7x10-4, 6.5x10-1±1.16, 5.16±5.90 and 15.71±5.58 mg/kg respectively. All the concentrations of the heavy metals in the dust were lower than the permissible range for safety. The noncancer risk assessment showed that the HQ was 3.66x10-07, 1.21x10-3, 2.67x10-6, 9.27x10-10, and 2.17x10-09 for As, Cr, Cd, Hg and Pb. The HI was 1.22x10-03±3.34x10-04, which indicates an acceptable risk at <1. The mean cancer risk of As, Cr, Cd and Pb was 1.09x10-09±4.50x10-10, 4.59x10-9±1.26x10-9, 6.88x10-10±1.89x10-10 and 4.59x10-12±1.26x10-12 respectively. The mean total cancer risk in the study area due to exposure to As, Cr, Cd and Pb was 6.92x10-9±1.90x10-9, and lower than the acceptable range of 1.0x10-6. There is no potential non-carcinogenic and carcinogenic risk due to exposure to the heavy metals laden dust through inhalation in the hydropower dam construction areas in Bhutan. However, it’s recommended that residents should use face masks for self-protection from roadside dust and prevention of other adverse health effects apart from exposure to heavy metals under the study. Further dust suppression methods need to be strengthened in the area.