Environment Health & Safety Department Header

Ethidium Bromide Fact Sheet

Ethidium bromide is commonly used as a nucleic acid stain in molecular biology laboratories for techniques such as agarose gel electrophoresis. It is not a regulated hazardous waste, however the mutagenic properties of the substance may present a hazard to persons or the environment if it is disposed of improperly. The following disposal procedures are recommended by UMSL EHS:

Electrophoresis Gels

Trace amounts of ethidium bromide in gels pose minimal hazard and can be disposed of in your laboratory trash. Solids with higher concentrations of ethidium bromide should be managed as hazardous waste and placed in clear bags for offsite thermal destruction. EHS recommends the following:

  • Less than 0.1% ethidium bromide: place in regular trash
  • Greater than 0.1% ethidium bromide: place in hazardous waste for disposal

Gloves, Equipment, and Debris

Gloves, test tubes, pipette tips, paper towels, etc. that are grossly contaminated with ethidium bromide should be placed in hazardous waste for thermal destruction. Consider bleach deactivation prior to disposal if items are significantly contaminated.

Ethidium Bromide Solutions

  • Aqueous solutions containing less than 10 mg/mL ethidium bromide can be drain disposed as is.
  • Aqueous solutions containing greater than 10 mg/mL ethidium bromide should be filtered or deactivated using one of the methods described below.
  • Solutions containing heavy metals, cyanides, sulfides, or other significant organics should be turned over to EHS for hazardous waste disposal.

Charcoal Filtration

Filtering the aqueous ethidium bromide solution through a bed of activated charcoal is a simple and effective method for removing ethidium bromide. The resulting filtrate may then be drain disposed.

S & S Extractor Funnel Kit

A commercial filter funnel kit that utilizes a packaged charcoal disk that is graduated for easily tracking the amount of aqueous solution calculated for a fixed quantity of ethidium bromide residue. This is particularly useful for labs that generate large amounts of solutions at a time.

  • Filter the ethidium bromide solution through the charcoal filter
  • Pour filtrate down the drain
  • Place charcoal filter in a sealed bag and place in hazardous waste for thermal destruction

Bio 101 "The Green Bag"

Another simple charcoal filtration method is the Green Bag (trademark), which allows rapid and trouble-free concnetration of ethidium bromide from large volumes of solutions into a small "tea" bag containing activated carbon which is then disposed of along with other solid hazardous wastes. One kit has the capacity to remove 500 mg of wthidium bromide solutions (10 mg EtBr per bag)

  • Place the GreenBag into the ethidium bromide solution
  • Allow to sit for the allotted time
  • Pour filtrate down the drain
  • Dispose of the GreenBag in hazardous waste for thermal destruction.

Chemical Neutralization

Solutions containing ethidium bromide can be deactivated, neutralized and drain disposed with copious amounts of water using one of the following approved methods. Deactivation can be confirmed using UV light to detect fluorescence.

Armour Method

This is the simplest method, but may be the least effective. One study found traces of mutagenic reaction mixtures using this method. (Lunn, G. and E. Sansone, Analytical Biochemistry, vol. 162, pp. 453-458, 1987.)

  • Combine equal parts ethidium bromide solution and household bleach
  • Stir CONSTANTLY for four hours OR let sit for 2-3 days
  • Adjust pH to 5-10 with sodium hydroxide or similar
  • Pour down drain with copious amounts of water

Lunn and Sansone Method

For each 100 mL of ethidium bromide solution:

  • Add 5% hypophosphorus acid
  • Add 12 mL of 0.5 M sodium nitrate solution
  • Stir briefly and let stand for 20 hours
  • Adjust pH to 5-10 with sodium hydroxide or similar
  • Pour down drain with copious amounts of water