Heavy metal(loid)s contamination, pollution quantification, and health risk assessment along with coal mines in the Hangu and Kurram Districts, Northwest Pakistan

Abstract Heavy metal(loid)s (HM) was considered hazardous contaminants owing to their toxicity, persistency, and bio-accumulative nature in the environment. The current study aimed to examine HM concentrations in coal, coal dust, and surrounding soil along with coal mines in the Hangu and Kurram Districts. Using an Atomic Absorption Spectrophotometer, samples of coal, coal dust, and soil were analyzed for HM concentrations. Coal, coal dust, and soil showed maximum mean concentrations of 62100, 52610, and 45300 mg/kg for iron (Fe) and a minimum of 1.14, 0.9, and 2.0 mg/kg for molybdenum (Mo), respectively. HM concentrations in coal dust and soil were evaluated for contamination factor (CF), ecological risk index (ERi), potential ecological risk index (PERI), and human risk assessment. CF indicated very high contamination (CF > 6) in coal dust 6.05 and soil 5.2 of the Hangu District for cadmium (Cd). The ERi data showed that most HM in coal dust and soil of studied districts exhibited low ecological risk (ERi < 40), except for Cd. Moreover, the coal dust and soil of Hangu District showed considerable ecological risk (190 < PERI < 380), while the coal dust of Kurram District exhibited moderate ecological risk (95 < PERI < 190). Among human exposure pathways, ingestion was the primary exposure route compared to other routes (inhalation and dermal). The non-carcinogenic risk, i.e., hazard quotient (HQ), was observed in the order of; ingestion > dermal > inhalation in humans. The hazard index (HI) values were found to be higher in children (HI > 1) than in adults via coal dust and soil and could cause chronic health problems. Cancer risk (CR) values were noted within the US EPA threshold. Therefore, the current study recommends regular monitoring of HM in the area to control the health hazard to residents in the future.