Executive Summary Ethidium Bromide: Table of Contents

Solubility: Moderately soluble in water (20 mg/ml) and ethylene glycol monomethyl ether (20 mg/ml); slightly soluble in chloroform and ethanol (Budavari, 1989; Green, 1990)

Stability: Stable under normal temperatures and pressures. Hazardous thermal decomposition may release toxic oxides of carbon and nitrogen, and corrosive hydrogen bromide gas (Anon., 1994b)

UV/Visible Spectral Data: Max. (in water): 210, 285, 316, 343, 506 nm (Budavari, 1989) (Anon., 1994a)

Technical Products and Impurities: Ethidium bromide is commercially available in both powder (95-96% pure) and aqueous solution forms. Sigma Chemical Company also provides molecular biology reagent grade aqueous solutions at concentrations of 10 mg/ml and 500 µg/ml and tablets at 100 mg per tablet (Anon, 1993).

EXPOSURE INFORMATION

Commercial Availability

Production and Producers: EB was reported by Watkins (1952) to be prepared from 3.8-dintro-6-phenyl phenanthridine with excess ethyl toluene-p-sulfonate followed by treatment with ammonium bromide. No producers of EB were reported in EPA's 1983 TSCAPP database (CIS, 1994). No listing of large, commercial scale production was found in any of the major chemical industry directories; but it is available from numerous chemical suppliers in research quantities-typically 1, 5, 10, 25, or 250 grams. Ethidium bromide is listed by numerous catalog suppliers, including Sigma Chemical Company; Aldrich Catalog/Handbook of Fine Chemicals; American Tokyo Kasei, Inc.; Atomergic Chemetals Corporation; Calbiochem; Mallinckrodt, Inc.; Lancaster Synthesis Ltd.; Eastman Kodak Company; Janssen Chimica; Fluka Chemical Corp.; J.T. Baker Inc.; Chem Service, Inc. (DIALOG, 1994)

EB is listed on the EPA TSCA Inventory (STN, 1994).

Use Pattern: EB is a widely used red cationic fluorescent dye and nucleic acid visualizing agent which binds to both RNA and DNA (Lunn & Sansone, 1987). As both a DNA-dependent intercalating agent and a DNA-independent protein inhibitor, it is useful as a simple and general indicator in many biochemical and biomedical laboratory procedures (Lai & Herr, 1992). There are many variations on EB's use in biochemical, molecular biology, enzymology and other types of laboratories described in the available literature. Numerous techniques employ EB, including gel and capillary electrophoresis, fluorometry, spectrophotometry, flow cytometry, polymerase chain reaction (PCR) amplification, etc. Some representative examples are summarized as follows:

as a molecular probe for staining nucleic acids in fluorescent microscopy studies of multidrug resistance (Neyfakh, 1988)

as a DNA probe for various studies including characterizing and quantifying DNA (Green, 1990).

as a derivatizing analytical reagent in clinical settings for continuous monitoring of levels of anticancer drugs in biological fluids, including blood, serum, and urine by measurement of dose-critical levels of DNA-binding (Miller & Hirschfeld, 1992).

EB has also been used as a drug or drug precursor, for example as a parasitotoxic, antiprotozoal drug for the treatment of Leishmaniasis, in combination therapeutic regimens using DNA reactive agents, and in the development of anionic and hydrophobic derivatives as trypanocides (Pavelic et al., 1985; Budavari, 1989; Anon., 1992). It was one of a number of phenanthridine trypanocides developed for use in cattle in the early 50's (Watkins, 1952). Studies have been conducted in animals to evaluate EB as a potential antitumorigenic chemotherapeutic agent (Kramer & Grunberg, 1973).

Human Exposure: Laboratory personnel are potentially exposed to EB during its use as a biological stain and laboratory reagent. Concern for contact with highly mutagenic EB in laboratory reagent solutions and spills has been expressed in several citations. In spite of routine and widespread use of EB in biochemical and biomedical laboratories, no validated methods of destruction have been established, according to Lunn and Samsone (1987). Safe handling of EB in laboratories to avoid human exposures to mutagenic solutions containing EB has been addressed by Lunn and Sansone (1987) and Quillardet and Hofnung (1988). Armour (1993) has concluded that EB should be handled as a carcinogen in terms of identifying methods of safe waste disposal.

The National Occupational Exposure Survey (NOES) conducted by NIOSH from 1980 to 1983 indicated that a total of 21 employees in 3 occupations employed in 7 facilities of 1 industry were potentially exposed to EB. The estimate of numbers of workers is based on a survey of U.S. companies and did not involve measurements of actual exposures (NOES, 1990; NLM/RTECS, 1994).

Environmental Occurrence: EB is not known to occur naturally. No information was found in the available literature on detection of EB in environmental media. Several spill clean-up and disposal methods have been recommended in the available literature for EB. They are based on careful removal to achieve elimination of mutagenicity of solutions by decontamination and degradation. Published methods include treatment with potassium permanganate/hydrochloric acid or hypophorous acid/sodium nitrite, adsorption on activated charcoal, and incineration at high temperatures (Quillardet & Hofnung, 1988).

Regulatory Status: No standards or guidelines have been set for occupational exposures to or environmental levels of EB. The American Conference of Governmental Industrial Hygienists (ACGIH) has not adopted a time-weighted average/threshold limit value (TLV/TWA) for this compound. EB is categorized as an acute hazard under SARA sections 311/312 (40 CFR 370.21) (Anon., 1994b).

Web page last updated on January 14, 2005

National Toxicology Program

Executive Summary Ethidium Bromide: Table of Contents