Pollution characteristics and health risk assessment of potentially toxic elements in school playground soils: A case study of Lagos, Nigeria

Soil samples were collected in February 2014 from 25 school playgrounds in Lagos, Nigeria to assess the potential adverse effects of the exposure of children to potentially toxic element (PTE). In each of the playgrounds, about 500 g of bulked soil samples were collected, dried, sieved, acid digested, and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Results showed that soils studied were characteristically unpolluted as the average PTE concentration at each site did not exceed the soil guideline values. Considering the pollution assessment tools employed, some soil samples showed some form of anthropogenic input from PTE. Health risk assessment was employed to assess PTE exposure from ingestion, inhalation, and dermal contact. Result indicated that the highest risk is associated with ingestion followed by dermal contact and inhalation. For non-carcinogenic effects, exposure to school playground soils poses no threat to children as the overall value of hazard index is less than the safe level of 1. For carcinogenic effects, only Cr and Ni were considered and were below the threshold of 1 x 10(-6). This study has demonstrated that minimal risk arises from the investigated playgrounds and that regular monitoring is required to keep the PTE contents low in soils to avoid risk to human health.