Environmental health risk assessment of potential emerging contaminants identified from water sources around Bloemfontein in the Free State province of South Africa

Abstract

Background: The existence of emerging contaminants namely pharmaceuticals, personal care products, steroids hormones and pesticides in water sources is largely unregulated by legislation and they do not have to be extremely tenacious to cause environmental health effects as their decay is counterbalanced by their incessant introduction. The accumulation and detection of levels of these emerging contaminants in water sources has reduced water quality that makes water risky for aquatic and human life. Their quantity is likely to upsurge in water sources as a result of the rise in population density, which is a serious concern to our communities. Exposure to emerging contaminants has been reported to lead to health implications such as endocrine disruption, immunotoxicity, neurological disorders, reductions in fertility, spontaneous abortions, birth defects, poisoning of genes, sexual organs annoyance, resistance of antibiotics and congenital disorders, even at low concentrations. Aim: The aim of this study was to assess the environmental and health risks of potential emerging contaminants identified from water sources around Bloemfontein in the Free State province of South Africa. Methodology: In order to identify and monitor the presence of emerging contaminants in water sources around Bloemfontein, samples (n=72) were collected randomly by using the grab sampling method from various water sources such as rivers (n=5), dams (n=5), treated drinking water (n=2), wastewater influent (n=3) and wastewater effluent (n=3) during the spring, summer, autumn and winter seasons. The solid phase extraction cartridges were used for extraction of samples. The analysis was performed on a high performance liquid chromatography linked to a hybrid triple quadrupole ion trap mass spectrometer. Environmental risk assessment of individual compounds were estimated by a risk quotient (RQ) method, while risk quotient mixture (RQmix) and toxic unit sum (TUsum) methods were adopted to assess mixture risks of targeted emerging contaminants. The human health risk assessment method was adopted to estimate the carcinogenic and non-carcinogenic risks of selected pesticides. Moreover, multivariate statistical methods such as the Pearson coefficient correlation, the principal component analysis, and the hierarchical cluster analysis were used to trace the sources of pollution in water sources around Bloemfontein. Results: The results of qualitative screening revealed the occurrence of various classes of emerging contaminants such as stimulants, non-steroidal anti-inflammatory drugs, Illicit drugs, lipid regulators, antiepileptics, antibiotics, antidepresents, antidiabetics, betablockers, antivirals, diuretics, herbicides, fungicides and insecticides in rivers, dams, treated drinking water, wastewater influents and effluents around Bloemfontein. From these groups of emerging contaminants, herbicides and stimulants were the most commonly detected contaminants. The quantitative analysis of targeted compounds such as acetaminophen, carbamazepine, ibuprofen, triclosan, atrazine, metolachlor, simazine, terbuthylazine, 17- alpha-ethinyl-estradiol, estradiol, progesterone and testosterone showed the mean concentrations of 17-alpha-ethinyl-estradiol to be the highest in all water sources in all seasons. Generally, the autumn season recorded the highest mean concentrations of emerging contaminants in all selected water sources except in treated drinking water. The results of the environmental risk assessment indicated that the majority of targeted compounds have the possibility to contribute to high risks. The risks of simazine, ibuprofen, 17-alpha-ethinyl-estradiol, atrazine and carbamazepine were most remarkable on all aquatic species in all water sources. Moreover, both RQmix and TUsum proved that the mixture of the targeted compounds is likely to contribute to high environmental risks. In addition, the non-carcinogenic risks of all selected herbicides in all water sources showed RQ values below one for the entire population, signifying that the population is safe. Atrazine is the only contaminant that showed high carcinogenic risk to the adult group in river water during the summer season. Multivariate statistical analysis pinpointed wastewater effluent discharge, illegal dumping, domestic sewage overflow, stormwater runoff and agricultural runoff as the possible sources of emerging contaminants in water sources around Bloemfontein. Conclusion: Assessing the environmental health risks of emerging contaminants in water sources around Bloemfontein for the first time brings to an end the dearth of data on emerging contaminant pollution and its associated risk in the region. The project has shed light that water sources around Bloemfontein are vulnerable to pollution by emerging contaminants as a result of anthropogenic activities and their occurrence is likely to cause high ecological and human health risks. The outcomes of this study may be relevant for the prioritisation of hazardous substances in addressing suitable monitoring campaigns and any necessary countermeasures to be adopted for water sustainability, environmental and human health protection. This work may also facilitate the management of existing and future sources of emerging contaminant pollution in water sources around Bloemfontein.