Assessment of soil metal exposure, associated health risks and indoor dust screening in early learning programmes in Gauteng Province, South Africa.
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Exposure to heavy metals is a global health concern, especially for children under the age of five. In South Africa, industrial and mining activities have contributed to environmental accumulation of metals. Early learning programmes (ELPs) or preschools are primary spaces for learning and play, making them critical for mitigating early life metal exposure. This study examined arsenic (As), cadmium (Cd) and lead (Pb) levels in soil and dust from selected ELPs in two metropolitan municipalities in Gauteng Province, South Africa, to assess potential exposure risks for children under five. As part of a nationally represented survey of early childhood outcomes, 70 ELPs were stratified into three fee bands (low, medium, high). Soil and dust samples were collected from outdoor play areas and indoor classrooms and analysed using inductively coupled plasma-optical emission spectroscopy (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS). Dust results were semi-quantitative (no surface area measured) and not used in risk calculations. Potential Pb exposure in children was evaluated using the US EPA Integrated Exposure Uptake Biokinetic (IEUBK) model to predict blood Pb levels. Geographic Information System (GIS) mapping identified spatial patterns and hotspots of metal concentrations relative to potential pollution sources. Soil Pb levels were below South African reference values; however, 9.0% of samples exceeded Canadian guidelines, while dust Pb was detected in all samples. Soil As was detected in 95% of samples, with higher concentrations in low-fee schools (p = 0.002); 10.7% exceeded Canadian guidelines. Cd concentrations were low across all sites. Estimated As exposures suggested minimal non-carcinogenic health risk to children through soil ingestion, while IEUBK modeling predicted a geometric mean blood Pb levels of 1.72 µg/dL (95% CI 0.69-4.31), with 6.6% exceeding the CDC blood lead reference value. Children exposed to As at school for approximately 2 years had a combined lifetime cancer risk of ~ 2.2 × 10⁻4, exceeding the USEPA's acceptable threshold. Hotspot and kernel density estimation analysis identified localised elevated soil As and Pb levels near areas of concentrated mining activity, indicating legacy industrial sources as likely contributors. Localised hotspots of Pb and As highlight the need for continued environmental monitoring and targeted interventions to ensure safe learning environments for young children, particularly given the carcinogenic risk associated with As exposure.