5.3 Toxicity of fumigants

In order that librarians and archivists may more accurately assess the relative hazards of fumigants which may be in use in their institution, the following general information is provided.

Ethylene Oxide

Ethylene oxide was developed in 1859. By the late 1920's it was in common use as a fumigant for grain, and by the 1950's was widely used in museums, libraries and archives. Ballard and Baer provide an excellent study of the history, use, effectiveness, and hazards of ethylene oxide.⁸

In 1984 the Occupational Safety and Health Administration (OSHA) released a new standard for exposure to ethylene oxide of 1 ppm. Based on animal and human data, OSHA has determined that exposure to EtO "presents a carcinogenic, mutagenic, genotoxic, reproductive, neurologic, and sensitization hazard."⁹ Safety requirements for use of the gas include methods of exposure control, personnel protective equipment, measurement of employee exposure, training in use of the gas, (often a licence is required),, medical surveillance, signs and labels, regulated areas, emergency proceedures and record keeping requirements. The presence of EtO cannot be detected by humans without the aid of monitoring devices until it reaches a concentration of 300 ppm, far in excess of the OSHA standard.¹⁰

Ethylene oxide is known by a variety of other names, including dimethyl oxide, Carboxide, 1,2-Epoxythane, Oxyfume, Pennagas and Oxirane. It is highly flammable, and is usually used in a 10% concentration with a carrier gas.

Methyl Bromide

Methyl bromide is most commonly used in the fumigation of insect infestations, particularly against hard shell insects such as beetles. It is not particularly effective as a fumigant for mold growth, but is occasionally used as one. It is a colorless, transparent, easily liquified gas. It is easily detected, having a strong, chloroform-like smell. It is highly toxic by ingestion, inhalation or absorption through the skin. The tolerance level established by OSHA is 5 ppm. Methyl bromide affects the central nervous system, respiratory system, skin and eyes. Acute effects usually occur 30 minutes to 6 hours after exposure and may include convulsions followed by death due to pulmonary and/or circulatory failure. Chronic effects are usually limited to the central nervous system and include muscular pains, visual, speech and sensory disturbances and mental confusion.

Methyl bromide should not be used for the fumigation of any protein based material, as it seriously damages the protein structure. Leather for example becomes black and brittle when exposed to methyl bromide fumes.

Methyl bromide is also known by the proprietory names Brom-O-Gas, Brozone, MeBr, Meth-O-Gas and Terr-O-Gas.

Sulfuryl Fluoride

Sulfuryl fluoride is most often used in the tropics for the fumigation of termites in building structures. It has very high penetration even without a vacuum. Like methyl bromide it is not known to be effective against mold, but is occasionally used for that purpose. It is an odorless, colorless tasteless gas, and is usually available only to licenced fumigators. The OSHA standard is 5 ppm. It has not been tested extensively, and its carcenogenic and reproductive effects are unknown. It may be ingested by inhalation or absorption through the skin. Acute effects include nausea, vomiting and abdominal pain. Chronic effects include defects in bone and teeth, and in animals lung and kidney damage have been found.

Sulfuryl fluoride is most often available under the trade name Vikane.

Thymol

Thymol is a white crystal with a distinctive aromatic odor and taste. It is derived from thyme oil and may be mixed with camphor in its crystaline form. It is moderately toxic by ingestion and inhalation. Studies indicate that exposure to thymol vapors can affect the central nervous system and the circulatory system. No precise level for minimum exposure has been established.

Thymol is sometimes used in its gaseous form (produced by heating the crystaline form to release thymol vapor) as a fumigant for small quantities of materials. In order to be safely handled following fumigation, materials must be aerated, preferably in a fume hood. This removes any residual protection against mold growth, but renders the materials safe for staff and patrons. Staff members working with items immediately after fumigation, or in the area of the fumigation chamber should wear respirators approved for organic chemicals. Goggles and heavy weight, vapor barrier gloves should be worn when removing items from a chamber.

Orthophenyl Phenol

Orthophenyl phenol is considered slightly less toxic than thymol. The Merk Index lists it as a "slightly toxic irritant" when inhaled. It is however moderately toxic by ingestion. In its crystaline form it is a white or cream color and is soluble in alcohol. Several sources recommend the substitution of OPP for thymol whenever the latter is recommended. Relatively little testing has been done regarding the toxicity of OPP, and no exposure level is available.

In tests conducted by Haines and Kohler, orthophenyl phenol was found to be a not very effective fumigant. Of the seven fungi tested, fumigation with orthophenyl phenol failed to completely halt mold growth even after 10 days of continuous exposure to the vapors under controlled conditions.¹¹