Abstract
Total arsenic (As) in environmental (water, soil, sediment) and biological (scalp hair, urine) samples collected from naturally As-rich areas in Argentina (San Juan and La Pampa) was determined by inductively coupled plasma mass spectrometry (ICP-MS) in collision cell mode. Arsenic levels in surface (11-133 μg/1 As) and groundwater (3-1326 μg/1 As) typically exceeded the World Health Organisation (WHO) guideline value of 10 μg/1 As for potable waters, the Argentinean national drinking water standard of 50 μg/1 As and in some cases the Food and Agriculture Organisation (FAO) of the United Nations irrigational water limit of 100 μg/1 As. A naturally low arsenic region, namely Rio Negro, was sampled to provide comparative data for the As-rich areas in Argentina. The development of a method for the in situ collection, preservation and separation of the arsenic species; arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MAV) and dimethylarsinic acid (DMAV) in natural waters was undertaken utilising solid phase extraction (SPE) cartridges. The assessment of arsenic species by SPE revealed the presence of the organoarsenicals MAV and DMAV up to 79 μg/1 (33% of the total arsenic) in San Juan (Encon) groundwater, which are not typically observed in literature data for corresponding water types. The major arsenic species in natural waters were the more toxic AsIII and AsV species. Surface soils and river sediments (dried and sieved) from San Juan and La Pampa Provinces had levels of 5-35 mg/kg As (dry weight, d.w.) and 6-32 mg/kg As (d.w.), respectively; comparative to reported world-wide values ranging from 0.4 to 70 mg/kg As (d.w.). The predominant arsenic species in Argentinean soils was AsV, with no detectable methylated forms. Sequential fractionation of soils and sediments confirmed the extractable forms of arsenic to be in the order: residual > exchangeable > bound to Fe and Mn oxides > bound to organic matter and sulphides. The assessment of washed human scalp hair and urine as potential biomarkers for arsenic exposure showed high arsenic levels in participants from San Juan and La Pampa (As-rich areas). Arsenic speciation of washed scalp hair revealed the presence of AsIII and AsV, whereas urinary arsenic species were principally organoarsenicals (DMAV > MAV > arsenobetaine, AB). The metabolic biotransformation of arsenic in exposed individuals (based on washed scalp hair and urine data) indicates a possible reduction in arsenic toxicity. This research highlights the potential sources of natural and anthropogenic arsenic in the Argentinean environment and the likely toxicological effects on the exposed population.