Dermal uptake of arsenic through human skin depends strongly on its speciation

The most common routes of arsenic exposure are ingestion and inhalation, whereas dermal uptake has been considered as a minor uptake route based on uptake experiments with arsenate. Here the kinetics of arsenite, dimethylarsinic acid (DMA(V)) and arsenosugar penetration through full thick human skin (from one volunteer) was determined using a Franz Cell design and compared to that of arsenate. The accumulation in the epidermis and dermis was performed by using laser ablation ICP-MS as a bioimaging method, and the biotransformation reactions through the uptake experiment were monitored by hyphenated elemental mass spectrometry. The penetration and accumulation of arsenic is strongly dependent on its speciation. While arsenosugars penetrated through the unbroken skin at a similar rate as arsenate, arsenite and DMA(V) were taken up percutaneously at a rate which was more than a factor of 29 and 59 higher than that of arsenate. The dermal uptake route of arsenic has been underestimated in risk assessments where exposure to arsenite or DMA(V) would occur. The accumulation potential of arsenosugars and DMA(V) was however minimal, whereas arsenate and arsenite accumulated in the epidermis and in the dermis. No significant species transformations were observed.