Development of an arsenic speciation method for drinking water and its application to human health and risk assessment

• Main Author: Flores del Pino, Lisveth V
• Format: Dissertation
• Language: English
• Subjects: engineering, environmental; health sciences, public health; health sciences, toxicology

Chemical speciation is essential in order to understand the toxic and carcinogenic nature of elemental contaminants found in environmental and biological systems. For example, the measurement of total arsenic content does not indicate the levels of the individual species. Analytical data on the individual species of an element present in a sample provides useful information for studying its toxicity, bioavailability, metabolism, or transport. The risk assessment of the human health associated with the ingestion of such elements via drinking water and food should therefore be based on analytical data of the individual species.
The aim of the research described in this thesis was to develop a simple, rapid, sensitive, accurate, and inexpensive on-site speciation method of the most toxic dissolved arsenic species: As (III), As (V), monomethylarsonic acid (MMA) and dimethylarsenic acid (DMA). Development criteria included ease of use under field conditions, applicable at levels of concern for drinking water, and analytical performance. The approach is based on selective retention of arsenic species on specific ion-exchange chromatography cartridges followed by selective elution and quantification using graphite furnace atomic absorption spectroscopy. Water samples can be delivered to a set of three cartridges using either syringes or peristaltic pumps.
Species distribution is stable at this point, and the cartridges can be transported to the laboratory for elution and quantitative analysis. These results suggest that this method can be used for analysis of the four primary arsenic species of concern in drinking water supplies. The method developed was used to evaluate the stability of arsenic species in groundwater sample over time. It was tested at different temperatures, pH and dissolved oxygen concentrations. To estimate potential health risks of inorganic arsenic the analysis of the sources of inorganic arsenic is critical. Our analysis found that food is the greatest source of inorganic arsenic intake, especially when the arsenic concentration in drinking water is low.