Assessing contamination and risk profiles of per- and polyfluoroalkyl substances across various types of water in South Africa: trends over the past decade (2014–2024)

Abstract

This study investigates the occurrence, spatial distribution, and ecological and human health risks of per- and polyfluoroalkyl substances (PFAS) in South African water systems over the period 2014–2024. In the absence of direct drinking water data, ecological risk assessments and indirect human exposure evaluations via potential crop irrigation were conducted using PFAS concentrations measured in surface water and wastewater across four regional zones: north (Gauteng, Limpopo, Mpumalanga, Northwest), west (Northern Cape), east (KwaZulu-Natal, Free State), and south (Eastern and Western Cape). Among the compounds analysed, perfluorooctanoic acid (PFOA) was the most prevalent, with concentrations ranging from 315 ng/L in the Eastern Cape to 420 ng/L in the Vaal River (Gauteng), yielding ecological risk quotient (RQ) values of 3.15 and 4.05, respectively, both exceeding the RQ safety threshold of 1. Perfluoro butanoic acid (PFBA) and perfluoro hexanoic acid (PFHxA) also presented moderate ecological risks, with peak concentrations of 380 ng/L (west) and 267 ng/L (north), corresponding to RQ values of 1.10–1.78. The north zone, particularly sites like the Vaal River and Hartbeespoort Dam, exhibited the highest PFAS burden. A strong correlation (r = 0.95) between PFOA and PFHxA suggests common sources of contamination. Spatial variability was more pronounced for PFHxA (CV = 12.84 %) than for PFOA (CV = 9.92 %). Indirect human health risks from crop ingestion were negligible, with hazard quotient (HQ) values below 0.019 and incremental lifetime cancer risk (ILCR) estimates below 2.70 × 10⁻⁸. Despite minimal human health risks, the persistent ecological threats particularly in the north zone underscore the need for enhanced regulatory oversight, long-term monitoring, and targeted PFAS treatment strategies.