Speciated arsenic in air: Measurement methodology and risk assessment considerations

Abstract

Accurate measurement of arsenic (As) in air is critical to providing a more robust understanding of arsenic exposures and associated human health risks. Although there is extensive information available on total arsenic in air, less is known on the relative contribution of each arsenic species. To address this data gap, the authors conducted an in-depth review of available information on speciated arsenic in air. The evaluation included the type of species measured and the relative abundance, as well as an analysis of the limitations of current analytical methods. Despite inherent differences in the procedures, most techniques effectively separated arsenic species in the air samples. Common analytical techniques such as inductively coupled plasma mass spectrometry (ICP-MS) and/or hydride generation (HG)- or quartz furnace (GF)-atomic absorption spectrometry (AAS) were used for arsenic measurement in the extracts, and provided some of the most sensitive detection limits. The current analysis demonstrated that, despite limited comparability among studies due to differences in seasonal factors, study duration, sample collection methods, and analytical methods, research conducted to date is adequate to show that arsenic in air is mainly in the inorganic form. Reported average concentrations of As(III) and As(V) ranged up to 7.4 and 10.4 ng/m⊃, respectively, with As(V) being more prevalent than As(III) in most studies. Concentrations of the organic methylated arsenic compounds are negligible (in the pg/m3 range). However, because of the variability in study methods and measurement methodology, the authors were unable to determine the variation in arsenic composition as a function of source or particulate matter (PM) fraction. In this work, the authors include the implications of arsenic speciation in air on potential exposure and risks. The authors conclude that it is important to synchronize sample collection, preparation, and analytical techniques in order to generate data more useful for arsenic inhalation risk assessment, and a more robust documentation of quality assurance/quality control (QA/QC) protocols is necessary to ensure accuracy, precision, representativeness, and comparability.

Implications:

The detailed review of the speciation techniques for arsenic in air samples presented in this study showed that (1) a variety of efficient methods (sampling, extraction, and analytical) developed across research studies were available for the determination of arsenic species in air; (2) arsenic species in the air were predominantly inorganic forms; and (3) the organic forms in air were largely below detection limits. Despite these general findings, more consistent methods must be developed to understand potential risks from arsenic in ambient air. Research needs to advance air arsenic risk assessment are identified.

Acknowledgments

This work was sponsored by the Electric Power Research Institute. The authors would like to thank Sagar Thakali and Gautham Jegadeesan for their assistance in performing background research; Jasmine Lai and Bethany Allen for their help in editing and preparing the manuscript; and Barbara Beck for providing her scientific input.