Hydrogeotoxicity assessment in aquifer systems of Malaga province (S Spain): a preliminary approach to evaluate the potential risk of groundwater consumption for human health

The increasingly water quality impairment due to anthropogenic pressures and environmental factors is one of the major public concerns and its control and management remain still challenging. Groundwater is highly vulnerable to human-induced pollution effects and, therefore, appropriate monitoring programs and representative groundwater quality stations are crucial to control pollutant levels for evaluating the qualitative status of aquifer systems as recommended by the EU Water Framework Directive. In Málaga province, 33 groundwater bodies hosted in two main river catchments (mostly Guadalhorce river draining to the Mediterranean Sea) partial or totally supply almost 1.5 million of inhabitants. Thus, the principal natural and induced factors such as the wide diversity of geological exposures -including those containing high solubility minerals-, the relatively high extension of cultivated areas, as well as the very often insufficient treatment of waste waters in urban and rural settlements, are demonstrated to endanger the groundwater quality in aquifers across the Málaga province. In this study, the regional assessment of toxicity levels in groundwater (understood as a potential risk for the human health), have been performed focused on selected inorganic (SO4-2, Cl-, Fand trace metals) and organic pollutants (N-compounds and plaguicides). To that, the statistical treatment of public water quality databases has been performed and single hydrogeotoxicity indices has been applied to evaluate the exposure levels for drinkable groundwater, according to national water regulations and international recommendations The groups of selected chemicals were categorized by means of the resulting toxicity levels (extremely toxic, highly toxic, moderately toxic and little toxic), but also based on the adverse effects potentially caused over the functional groups of human body (i.e. genotoxic, neurotoxic, hormonal disruptor, etc.). A hydrogeotoxicity (HGT) threshold equal to 1 was set up, according to precedent studies conducted in Spain, from which groundwater from aquifers are potentially considered toxic for human health in case of prolonged consumption. The first results obtained in this work suggest that HGT values for the evaluation of individual chemicals range between 0 (for total sum of plaguicides) and 2.1 (for SO4-2). Accordingly, 12% of total aquifer systems studied show HGT values >1 for inorganic and organic-derived pollutant such as iron, manganese, nitrate, sulphate and glyphosate, which reflects deficient qualitative status and significant groundwater quality impairment in the main cultivated areas of the province. The evaluation of groundwater toxicity must be included in the groundwater quality control programs performed by health authorities from the quantification of the susceptibility to health risk for citizens. Additionally, this type of human health-oriented hydrogeological research should be linked to epidemiological studies in medical centres to predict potential mid/long-term consequences of polluted groundwater intake in the human population.