Human exposure to inorganic arsenic through agronomic food chains

摘要

Background: Arsenic is a class one non-threshold carcinogen whose main exposure to humans is dietary. Aims: To illustrate that rice grain is the dominant form of human exposure to inorganic arsenic, particularly the importance of arsenic speciation in arsenic assimilation by rice, dietary exposure and human metabolism. Methods: Inductively coupled plasma - mass spectrometry (ICP-MS), coupled with ion exchange chromatography, was used to characterize arsenic speciation in paddy soils, rice grain from a wide range of sources, rice products intended for human consumption and in urine from humans with known dietary exposure to rice. In this way arsenic in the human food-chain can be followed from soil to human excretion. Using this data it will be illustrated how different populations and sub-populations (based on special diets, structured by age or structured by ethnicity, etc.) leads to differing inorganic, and total organic, exposure patterns. The findings will be discussed in context of the cancer risk that arsenic in rice poses to humans. Conclusions: Inorganic arsenic exposure varies greatly depending on the geographical origin of rice, food processing and dietary consumption patterns. Cancer risks for the highest exposed populations are calculated to be in the order of 20 in 10,000 lifetime excess cancers for populations that consume 500 g of rice per day, the typical quantity ingested in the rice based diets of the poorest economies in SE Asia. Data also suggests that particular attention should be given to baby and toddler exposure to rice, as they have a high rice component to their diet, and high food consumption rates when expressed on a body weight basis.