What happened? An organic arsenic compound (synthesized in-house) was obtained by an investigator in small, sealed ampoules. In a fume hood the ampoules were opened by their researcher and water was added to hydrolyze the compound to make stock solutions of the corresponding unstable acid – a suspected highly toxic and possibly carcinogenic metabolite of inorganic arsenic metabolism in mammals. While still in the fume hood, serial dilutions were made of the stock solution. The serial dilutions were moved to a biological safety cabinet (BSC) where cells were dosed with the dilutions and placed in a 37oC incubator for 24 hours. Initially a class IIA BSC was used (i.e., recirculates HEPA-filtered air back into the room) and later a class IIB BSC was used (discharges HEPA-filtered air to the bldg. exhaust). Following the incubation, the cell culture plates were moved back into the BSC, the liquid media was poured off into a waste container and the cells were analyzed.
A chemical odor and nasal irritation were reported by the researcher during cell dosing when the class IIA BSC was used and when the cell culture plates were moved to the incubator. A stronger chemical odor and nasal irritation were reported by the researcher when the incubator was opened and the cells were moved back into the BSC. The researcher also reported various persistent health effects and expressed concern about the odor and health effects to the principal investigator.
The researcher subsequently demonstrated experimentally the volatility of the organic arsenic compound and metabolite by sampling and analyzing the air space above one ampoule's contents (i.e., head space analysis) and the stock metabolite solution. As a result, the organic arsenic metabolite cell culture work was moved to a chemical fume hood and tried in sealed flasks. Ultimately, the metabolite research was discontinued after continued health concerns.
Why did it happen? The volatility of a potentially very hazardous chemical was not considered by an investigator and their researcher used it outside of an exhausted enclosure.
How can a similar occurrence be avoided? A fume hood, or other exhausted enclosure, must be used for operations which may result in the release of appreciable amounts of hazardous or odorous chemicals (Laboratory Chemical Safety Manual, section 1.8.4.6). Vapor pressure (VP) and boiling point (BP) are two indicators of a chemical's volatility or ability to become airborne. Chemicals with high vapor pressures and low boiling points have a greater ability to become airborne where than can be inhaled, and are inherently more risky than chemicals with low vapor pressures and high boiling points because exposures are more likely. Be aware that vapor pressure increases with temperature and chemicals become more volatile (airborne) with higher operating temperatures (as was the case in this incident with the 37oC incubation). The typical units of vapor pressure are millimeters of mercury (mmHg) at a specified temperature, typically 20oC (if no temperature is listed you assume 20oC). The boiling point is typically listed in oC or oF.
If VP and/or BP are not available, as was the case in this incident, a chemical should be assumed volatile unless proven otherwise and used in an exhausted enclosure like a fume hood or IIB BSC. When VP and/or PB are not available, volatility can be assessed by headspace analysis, as done here, and sometimes by a thorough review of the literature (It was later learned that another researcher also demonstrated the high volatility of the metabolite in culture media).
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