Incident Discussion

2-mercaptoethanol

Incident Summary• Bottle of 2-Mercaptoethanol (Link to MSDS)

placed in Class II A2 biosafety cabinet in xx-xxx after researcher noticed bottle’s cap was cracked.– This chemical is highly odorous and is toxic.

• 0.12 ppm odor threshold.• 0.2 ppm exposure limit, 8 hr TWA.

• Student entered xx-xxx after bottle was moved to fume hood in nearby room.

• Student felt nauseous and lightheaded while working in xx-xxx and after returning to office.

• Student dialed 100 for assistance.• Cambridge Fire evacuated the building.• EHS responded, verified that the bottle was

now safe in the fume hood, and also noted a chemical odor in room with BSC.

• Student transported to Mount Auburn Hospital; after observation, was back working in the lab the next day.

Incident Summary

Incident Summary

• Proximate causes of the incident were:– Placing a cracked bottle of a highly odorous

compound in a biosafety cabinet where 70% of the exhaust is recirculated.

– Using an old bottle that had a deteriorated cap.

• Also interesting to note– After hours, but not working alone!– Inadequate disposal of contaminated solids?

Fume Hood ≠ ≠ BioSafety Cabinet!Fume Hood: 100% exhausted Type A2 BioSafety Cabinet:

30% exhausted, 70% recirculated

From a manufacturer’s website:“Airflow in a Type A2 cabinet is not suited for work with hazardous Airflow in a Type A2 cabinet is not suited for work with hazardous

vaporsvapors.”

Classes of Biosafety CabinetsCurrent NSF Classification

Previous NSF Classification Intake General Description

A1 Class II, Type A 75 FPM•70% air recirculated; 30% exhausted from common plenum to room•May have biologically contaminated positive pressure plenum

A2Class II, Type B3 or Class II,

Type A/B3100 FPM

•70% air recirculated; 30% exhausted when connected to building exhaust system – otherwise recirculates into room•Biologically contaminated plenum under negative pressure or surrounded by negative pressure

B1 Class II, Type B1 100 FPM

•40% air recirculated; 60% exhausted from cabinet through dedicated exhaust duct into facility exhaust system•Back area of cabinet provides 100% exhaust•All biologically contaminated plenums are negative to the room or surrounded by negative pressure plenums

B2 Class II, Type B2 100 FPM

•0% air recirculated; 100% exhausted from cabinet•Exhaust air pulled through HEPA filter and dedicated exhaust duct into facility exhaust system•All ducts and plenums under negative pressure, and contaminated ducts are under negative pressure or surrounded by directly exhausted negative pressure ducts or plenums

• Perform work with hazardous chemicals in the fume hood, and biological work in the BioSafety Cabinet.

• Examine chemical bottles before using.• Don’t use old / out of date / expired chemicals.• Read the chemical’s MSDS.• Dispose of chemically contaminated solids

(gloves/paper towels etc) into closed top container (keep in fume hood if odorous).

• Possibility of less hazardous chemical?• Don’t work alone.

Lessons Learned / Takeaways