Biological monitoring of occupational exposure to inorganic arsenic

Objectives-This study was undertaken to assess reliable biological indicato rs for monitoring the occupational exposure to inorganic arsenic (iAs), tak ing into account the possible confounding role of arsenicals present in foo d and of the element present in drinking water. Methods-51 Glass workers exposed to As trioxide were monitored by measuring dust in the breathing zone, with personal air samplers. Urine samples at t he end of work shift were analysed for biological monitoring. A control gro up of 39 subjects not exposed to As, and eight volunteers who drank water c ontaining about 45 mu g/l iAs for a week were also considered. Plasma mass spectrometry (ICP-MS) was used for the analysis of total As in air and urin e samples, whereas the urinary As species (trivalent, As-3; pentavalent, As -5; monomethyl arsonic acid, MMA; dimethyl arsinic acid, DMA; arsenobetaine , AsB) were measured by liquid chromatography coupled with plasma mass spec trometry (HPLC-MS) Results-Environmental concentrations of As in air varied widely (mean 84 mu g/m(3), SD 61, median 40) and also the sum of urinary iAs MMA and DMA, var ied among the groups of exposed subjects (mean 106 mu g/l, SD 84, median 65 ). AsB was the most excreted species (34% of total As) followed by DMA (28% ), MMA (26%), and As-3+As-5 (12%). In the volunteers who drank As in the wa ter the excretion of MMA and DMA increased (from a median of 0.5 to 5 mu g/ day for MMA and from 4 to 13 mu g/day for DMA). The best correlations betwe en As in air and its urinary species were found for total iAs and As-3+As-5 . Conclusions-To avoid the effect of As from sources other than occupation on urinary species of the element, in particular on DMA, it is proposed that urinary As-3+As-5 may an indicator for monitoring the exposure to iAs. For concentrations of 10 mu g/m(3) the current environmental Limit for iAs, the limit for urinary As-3+As-5 was calculated to be around 5 mu g/l, even if the wide variation of values needs critical evaluation and application of d ata. The choice of this indicator might be relevant also from a toxicologic al point of view. Trivalent arsenic is in fact the most active species and its measure in urine could be the best indicator of some critical effects o f the element, such as cancer.