Spatial distribution and air-soil exchange of short and medium chain chlorinated paraffins in Lahore, Pakistan

This study provides the first systematic data on the distribution of short- (SCCPs) and medium chlorinated paraffins (MCCPs) in the atmosphere and surface soils of Lahore, Pakistan. The spatial distribution of SCCPs and MCCPs in air (n = 12) and soil (n = 15) was investigated from industrial, residential, commercial, conventional e-waste burning and background areas of Lahore. The concentrations ranged from below the limit of detection (3. Higher CPs contaminated soil and air were observed in industrial and commercial areas likely due to the use of CPs as flame retardants/plasticizers in products and metalworking. Total organic carbon (TOC), SCCPs and MCCPs in soil were not correlated with each other however, a significant association between SCCPs and MCCPs was observed in air samples. Among all the samples of soil and air C_10, Cl_7-8 and C_14,16Cl_7-8 were the predominant congeners for SCCPs and MCCPs, respectively. The comprehensive investigation of soil-air exchange for SCCPs and MCCPs revealed approximately 67 % of fugacity fractions (ffs) above 0.7, indicating net volatilization for most of the congeners. This study also revealed a notably high emission flux for SCCPs and MCCPs compared to their deposition flux, indicating that soil acted as a major source of CPs. Additionally, the emission flux for SCCPs was higher than for MCCPs, owing to their greater volatility and transport potential. A preliminary risk assessment suggested limited risks (Risk quotient <0.02) to the soil community while, the adult and toddler community had daily intakes of 5.7 and 7.2 ng/kg/day of CPs, respectively via different pathways highlighting the hotspots with high risk areas.