Exposure to inorganic arsenic from fish and shellfish

Humans are exposed to arsenic (As) from many sources such as food, water, air and soil. Most foods contain both organic and inorganic forms of As and the inorganic compounds are generally considered to be more toxic. Although fish and shellfish are major contributors to dietary As among seafood consumers, over 90% of the As in seafood is generally organic rather than inorganic. Thus, it is important to know the relative levels of various As species in fish and shellfish when estimating risks from seafood consumption. Data were collected from published and unpublished literature on the concentrations of total, inorganic and organic As present in fish and shellfish. Distributions were skewed with median concentrations, in this instance, a better representation of central tendency than mean concentrations. The data were used to estimate total exposure to inorganic As from consumption of fish/shellfish for several exposure scenarios applicable to seafood-consuming populations, including subsistence groups. Data on fish and shellfish consumption patterns were derived from the 1989-1991 U.S. Department of Agriculture Continuing Survey of Food Intake by Individuals. Organic As in ocean and estuarine fish and shellfish is primarily present as arsenobetaine (AsB) with smaller amounts as arsenocholine (AsC) or other organic compounds. Less is known about the identity of the organic arsenic in freshwater fish. Data on the toxicokinetics of AsB and AsC demonstrate that the As in these compounds is apparently not bioavailable for interaction with other biological molecules.