Dermal uptake of arsenic has been underestimated up to now based on low permeability of arsenate. A new study finds that uptake of arsenic as arsenite or dimethylarsinic acid is a factor of 29 and 59 higher than that of arsenate.
Inorganic arsenic is a confirmed human carcinogen causing skin and bladder cancer. The most common route of exposure is via ingestion of contaminated drinking water (see: our News about contaminated drinking water
). Due to the reported low permeability of arsenate dermal absorption of arsenic has been considered to be a minor exposure route and has so far not been studied in greater detail. The new study:
Fig.: Franz diffusion chamber
Researchers from the University of Aberdeen now had a closer look on the effect of different arsenic species on their uptake through the human skin. They used human skin (obtained from cosmetic surgical intervention) in a so called Franz Cell for permeation studies. Different arsenic compounds, such as arsenate, arsenite, dimethylarsinic acid (DMA(V)) and a seaweed extract containing mainly arsenosugars were used as model substances.
Total arsenic in the skin was determined by ICP-MS after microwave-assisted digestion and its spatial distribution was determined by laser ablation coupled to ICP-MS detection. Arsenic speciation analysis was performed via HPLC coupled with ICP-MS or ESI-MS detection.
The observed penetration rates of the different arsenicals were more than one order of magnitude different. Arsenite and DMA(V) exhibit 29 or 59 times faster dermal penetration in comparison to arsenate and the arsenosugars, respectively. Interestingly, no significant species transformation were observed during uptake and permeation. Also the concentration of arsenic within the epidermis was about a factor of 10 higher for arsenate and arsenite than for the organic arsenic species.
The authors conclude that exposure of farmers resulting from standing in the contaminated water of paddy rice fields might have been grossly underestimated. Such dermal exposure could therefore be the reason for the Blackfoot disease observed in Taiwan. The original study
Sairoong Ouypornkochagorn, Jörg Feldmann
, Dermal Uptake of Arsenic through Human Skin Depends Strongly on Its Speciation
, Environ. Sci. Technol. 44 (2010) 3972–3978. doi: 10.1021/es903667y Related studies
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. doi: 10.1016/faat.1993.1043 Related Information EVISA brief summary: LC-ICP-MS: The most often used hyphenated system for speciation
analysis EVISA brief summary: ESI-MS: The tool for the identification of chemical species EVISA Link database: Toxicity of arsenic species PermeGear: FAQs about Franz cells
Related News EVISA News, February 23, 2009: Toenail clippings reveal arsenic exposure EVISA News, January 17, 2007: Human metabolism of arsenic is altered by fasting
last time modified: May 18, 2010