Ethidium bromide is a nucleic acid stain. It fluoresces under ultraviolet light, especially when bound to double-stranded DNA. It is also a strong mutagen and a possible carcinogen, so must be managed correctly.
Ethidium bromide is available as a powder, a concentrated solution (10 mg/ml) and as a dilute solution. Any ethidium bromide solutions if concentrations greater than 10 ug/ml (>10 ppm) must be treated or collected as hazardous waste.
EH&S recommends GreenBags for "treating" dilute (around 10 ug/L) solutions of ethidium bromide. Over fifty UW laboratories treat their ethidium bromide waste. The treated water can be disposed of in the sink. The tea bags, which contain activated carbon, absorb the ethidium bromide so tightly that it is safe to put them in the trash.
We give a starter kit of three tea bags to each laboratory. Call 206.616.5835 or email firstname.lastname@example.org to request them. You can buy more new GreenBags from VWR via eProcurement. The product number is 100371-168, and a pack of 25 teabags costs about $90.
EH&S is required by law to keep track of all hazardous waste treatment on campus. Please contact EH&S at email@example.com to let us know you are treating your waste. keep track of what you treat using the Chemical Treatment Log. EH&S will email you each January for the total amount you treat each calendar year.
Concentrated solutions (10 mg/ml) of ethidium bromide must be handled as hazardous waste. They will quickly saturate the treatment tea bags.
Items contaminated with concentrated ethidium bromide are managed as hazardous waste. Pipet tips contaminated with dilute ethidium bromide are dried and placed into a lab glass bin. Other items contaminated with dilute ethidium bromide may be double-bagged, labeled "non-hazardous", and placed in the trash. Please double-bag to exposure to ethidium bromide of waste handlers.
Gels that contain ethidium bromide may be doubled-bagged, labeled "non-hazardous" and placed in the trash if they contain less than 0.1% ethidium bromide. If the gel is pink or red, the ethidium concentration is higher than 0.1%. In this case, the gel is handled as hazardous waste.
Ethidium bromide spills
Clean spills of ethidium bromide carefully with soap and water. Collect the soap, water and ethidium bromide mixture onto absorbent material. If concentrated or powdered ethidium bromide was spilled, place it in a sturdy screw top container and dispose of as hazardous waste. All other materials may go in the trash after you double bag it and label it "non-hazardous".
Other nucleic acid dyes and stains are also mutagens and possible carcinogens. They should be treated like ethidium bromide with the methods above. SYBR Safe in particular might be less mutagenic than ethidium bromide, but should be treated like ethidium bromide before disposal.
GelRed and GelGreen at concentrations less than 750 mg/L may be disposed of in the sink if they have been neutralized with sodium bicarbonate first. GelRed and GelGreen have pH values between 4.0 and 5.3, and only wastes with a pH between 5.5 and 12 may be disposed of down the sink.