Since toxicity and bioavailability depend on chemical form, conventional health risk assessment based strictly on the total element concentration is meaningless. Dr. Le has developed new techniques for chemical analysis of human urine to assess the health risk and occupational exposure to arsenic. Occupational exposure to arsenic often involves several toxic arsenic compounds, released through activities such as mining, smelting, glass making, and pesticide manufacturing. Dietary sources of arsenic, particularly from seafood, generally contain more complex non-toxic organoarsenic compounds such as arsenobetaine. While arsenobetaine is excreted rapidly in urine unchanged, other arsenic compounds are metabolized following ingestion.
Urinary excretion is the major pathway for the elimination of arsenic compounds from the body.
Because arsenic compounds ingested from both occupational and dietary sources contribute to urinary arsenic, it had been difficult to differentiate these two sources. Consequently, some earlier arsenic exposure assessments, based on the determination of the total arsenic concentration in urine, were misleading. Dr. Le developed several techniques that are capable of differentiating toxic from non-toxic arsenic compounds, and successfully applied these techniques to distinguish the sources of urinary arsenic, either occupational or dietary. Urine analysis using such techniques has contributed to some important findings on the metabolic fate of arsenic compounds in the human body and provided an important analytical strategy for studying exposure to many chemical species. Dr. Le's other studies on the speciation of arsenic in the environment show how arsenic species are transformed from one to another, leading to a better understanding of trace element cycling in the environment.