Biomonitoring California Protocol for Following up on Elevated Levels of Urinary Arsenic

Objectives: to develop and implement a follow-up protocol for Biomonitoring California study participants with elevated levels of urinary arsenic, particularly inorganic forms. Methods: We selected 20 μg/L as the level of concern for urinary inorganic arsenic; samples with total arsenic ≥20 μg/L were speciated. Participants with elevated inorganic arsenic were notified of their level and invited to participate in a telephone survey to help determine possible exposure sources. We illustrate the protocol in four Biomonitoring California studies, which collected samples from 2010–2013 in locations across the state. Results: 48 participants in the four studies had elevated urinary inorganic arsenic levels. Consumption of rice and rice-based products was the most commonly identified potential source of inorganic arsenic exposure. Conclusions: Of 48 participants with elevated inorganic arsenic, 27 would have been missed if we had used the previously published threshold of 50 µg/L total arsenic to identify urine samples for speciation. This protocol fills a gap in the clinical literature by providing a more health-protective approach to identify individuals with elevated urinary inorganic arsenic and help determine potentially significant exposure sources.