Arsenic exposure in the U.S. population is an important part of the NHANES program conducted by CDC because dietary exposure to arsenic can cause serious health effects. A major challenge in the arsenic exposure assessment is that arsenic exists as various species in nature, and the toxicity of these species varies widely. An accurate assessment of toxic exposure to arsenic must include both the quantity and the speciation of arsenic. SRM 2669 has been developed to meet this need and challenge.
In the NHANES studies seven arsenic species are measured in urine, which is considered the best proxy for recent (one- to two-day) arsenic exposure. Arsenic in drinking water, which is limited to 0.01 mg/L by the Environmental Protection Agency (EPA), is in the most toxic inorganic forms of arsenite (AsIII) and arsenate (AsV). Food intake is the greatest source of dietary exposure (about 25 to 50 µg per day); however arsenic in foods such as fish and shellfish is typically in organic forms such as arsenobetaine (AB), arsenocholine (AC), and arsenosugars that are essentially nontoxic. In addition to the species associated with dietary exposure (AsIII, AsV, AB, and AC), the seven arsenic species measured in NHANES also include the metabolites of inorganic arsenic: monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), and trimethylarsine oxide (TMAO).
With certified values for all seven species at key levels, SRM 2669 is the first reference material to contain primary arsenic species of dietary exposure and their metabolites in one material, which makes it most suited as a quality assurance material for arsenic exposure measurements. The reference material is the first to contain As(III) and As(V) species, the most toxic and most important for assessment of arsenic poisoning yet most difficult to stabilize. Because the matrix of the reference material is natural rather than processed (e.g., freeze dried), the product is better suited for the intended purpose of validating the accuracy of methods for urine analysis.