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Ethidium bromide (EtBr) is commonly used in molecular biology laboratories. While it is not regulated as hazardous waste, the mutagenic properties of this substance may present a hazard if it is poured down the drain untreated or placed in the trash.
Based on these considerations, the Office of Environmental Health and Safety (EH&S) recommends the following disposal procedures for ethidium bromide.
When purchasing Ethidium Bromide make sure that you purchase the smallest amount possible for your use. Stock quantities of unused Ethidium Bromide should be returned to the supplier if possible. You should also check with other investigators in your area to see if they could use the product. When all other means of distribution have been eliminated then you should call EH&S to pickup the unused product and add it to the RECY-Chem Program.
Trace amounts of ethidium bromide in gels should not pose a hazard. Higher concentrations, e.g., when the color of the gel is dark pink or red, should not be placed in laboratory trash. EH&S recommends the following:
All ethidium bromide solutions that are deactivated should be neutralized and poured down the drain with copious amounts of water. Deactivation may be confirmed using UV light to detect fluorescence. There are three recognized methods for deactivation:
This is the simplest method, but is somewhat controversial. One study found traces of mutagenic reaction mixtures using this method. (Lunn, G. and E. Sansone, Analytical Biochemistry, vol. 162, pp. 453-458, 1987)
For each 100 ml of ethidium bromide solution:
This method uses 0.5 M potassium permanganate and 2.5 M hydrochloric acid. Since chlorine gas may be released in significant concentration, EH&S does not recommend using this method.
Gloves, test tubes, paper towels, etc., that are grossly contaminated with ethidium bromide should be placed in biohazard bags and labeled for pickup and incineration by Prospective Health. Consider deactivating in bleach before disposal if the items are significantly contaminated.
If you have any questions about disposal of ethidium bromide or any other hazardous material, contact EH&S at 328-6166. Information for this web page was provided with permission from the Princeton University Environmental Health and Safety Office.