Abstract
Occupational exposure of chloralkali workers to highly concentrated mercury (Hg) vapour has been linked to an increased risk of renal dysfunction and behavioural changes. It is generally believed that these workers are exposed to elemental Hg, which is used in abundance during the production process however, the lack in analytical techniques that would allow for identification of gaseous Hg species poses a challenge, which needs to be addressed in order to reach a consensus. Here, we present the results from simulated exposure studies, which provide sound evidence of higher adsorption rate of HgCl2 than Hg0 and its irreversible bonding on the surface of hair. We found that chloralkali workers were exposed to HgCl2, which accumulated in extremely high concentrations on the hair surface, more than 1,000 times higher than expected from unexposed subjects and was positively correlated with Hg levels in the finger- and toenails.
Highlights
Atmospheric mercury (Hg) is usually categorized according to its physical and chemical properties into elemental highly concentrated mercury (Hg) (Hg0), reactive gaseous or oxidized Hg (RGM) and particulate Hg (p-Hg)
We hypothesise that the observed high Hg concentrations in the hair of chloralkali workers are direct evidence of RGM adsorption on the hair surface caused by its rapid deposition within the plant environment rather than accumulation of Hg0 or dietary Hg species
The hair samples from the ICL group showed extremely high concentrations of total Hg (n = 23, median 177 μg g−1 from a range between 4.06 ± 0.10 μg g−1 and 9,341 ± 76 μg g−1, Fig. 1, Supplementary Table 1 and 2)
Summary
Atmospheric mercury (Hg) is usually categorized according to its physical and chemical properties into elemental Hg (Hg0), reactive gaseous or oxidized Hg (RGM) and particulate Hg (p-Hg). While previous studies showed that the concentration of the latter accounts only for up to 4% of total Hg emitted from the chloralkali roof vents under normal operation condition, it was suggested that its concentration can significantly increase during the invasive maintenance procedure[9,10]. Despite their generally low ambient air concentration, RGM species are of a particular concern due to their high water solubility 1.4 × 106 M atm−1 at 25 °C (0.11 M atm−1 at 25 °C of Hg0)[11] rapid deposition velocity (5–10 time greater than p-Hg)[12] and extremely high bioavailability for bacterial methylation. We hypothesise that the observed high Hg concentrations in the hair of chloralkali workers are direct evidence of RGM adsorption on the hair surface caused by its rapid deposition within the plant environment rather than accumulation of Hg0 or dietary Hg species
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