Congener specific distribution and health risk assessment of polychlorinated biphenyls in urban soils

Abstract

Polychlorinated biphenyls (PCBs) were primarily used in transformers and capacitors, lubricants, flame retardants, plasticizers, paint, carbonless papers, etc. These are capable of long-range atmospheric transport and have been designated as persistent organic pollutants by the Stockholm Convention. Due to their characteristic properties, PCBs are found worldwide in all environmental matrices (including human) and biota. Soils are usually considered to be the source as well as sink for environmental pollutants, with cumulative effects of long-range atmospheric transport and local sources. Around the world, comparatively higher concentrations of PCBs have been reported in urban soils than suburban or rural soils. Higher amount of PCBs in urban soils may cause toxicological health risks to urban residents through ingestion, inhalation and skin contact. This paper presents the PCB distribution in soils from Delhi, India, and exposure risk estimates for human health through soil ingestion. The concentration of ΣPCBs ranged between 1.08-100.67 ng g<sup>–1</sup> (mean 21.16 ng g<sup>–1</sup>±5.24 ng g<sup>–1</sup>), which was much lower than the Canadian soil quality guideline value of 1.3 mg/kg or 1300 ng g<sup>–1</sup>. Human health risk estimates through the soil ingestion pathway were made in terms of lifetime average daily dose (LADD), incremental lifetime cancer risks and non-carcinogenic hazard quotient (HQ). The LADD for Delhi adults and children was 3.02x10<sup>–8</sup> mg kg<sup>–1</sup> d<sup>–1</sup> and 1.57x10<sup>–7</sup> mg kg<sup>–1</sup> d<sup>–1</sup>, respectively, which corresponds to toxic equivalent quotients (TEQ) intake of 0.105 pg TEQ kg<sup>–1</sup> d<sup>–1</sup> (0.735 pg TEQ kg<sup>–1</sup> week<sup>–1</sup>) and 0.543 pg TEQ kg<sup>–1</sup> d<sup>–1</sup> (3.801 pg TEQ kg<sup>–1</sup> week<sup>–1</sup>), respectively. The estimated LADD for Delhi residents was lower than the acceptable intake values recommended by the World Health Organization (1 pg TEQ kg<sup>–1</sup> d<sup>–1</sup>), the European Commission (14 pg TEQ kg<sup>–1</sup>;1 week<sup>–1</sup>) and by the Japanese government (4 pg TEQ kg<sup>–1</sup> d<sup>–1</sup>). The probability of cancer risk ranges from 6.04x10<sup>–8</sup> (ΣPCBs) to 1.57x10<sup>–5</sup> (ΣTEQ) and 3.13x10–7 (ΣPCBs) to 8.15x10–5 (ΣTEQ) for adults and children, respectively, and was within acceptable ranges of 10<sup>–6</sup> to 10<sup>–4</sup>. The non-carcinogenic risk in terms of health HQ was 0.105 and 0.330 for adults and children, respectively, which was lower than the acceptable limit of 1. The study found lower concentrations of PCBs than guideline values and low health risk estimates through the soil ingestion pathway within acceptable levels, indicating a minimum risk for Delhi residents.