Brief exposure to high concentrations and prolonged inhalation of lower concentrations are problematic. Exposure levels leading to death vary from 1,600 to 60,000 ppm, depending on the duration of exposure (as a comparison exposure levels of 70 to 400 ppm of carbon monoxide cover the same spectrum of illness/death).
“A TLV–TWA of 1 ppm (3.89 mg/m3) is recommended for occupational exposure to methyl bromide”-ACGIH 8 hour time weighted average. Immediately Dangerous To Life or Health Concentration by NIOSH: “The revised IDLH for methyl bromide is 250 ppm based on acute inhalation toxicity data in humans [Clarke et al. 1945]. This may be a conservative value due to the lack of relevant acute toxicity data for workers exposed to concentrations above 220 ppm. [Note: NIOSH recommends as part of its carcinogen policy that the “most protective” respirators be worn for methyl bromide at any detectable concentration.]” Detectable concentration by Drager Tube is 0.5 ppm.
Respiratory, kidney, and neurological effects are of the greatest concern. Scientists have investigated whether bromomethane exposure was linked to the death of four New Zealand port workers who died of neuro-degenerative motor neurone disease between 2002 and 2004 and found no connection.
“Cases of severe methyl bromide poisoning in humans, some of them fatal, were frequently reported. For example, von Oettingen recorded 47 fatal and 174 nonfatal cases of methyl bromide intoxication between 1899 and 1952…Severe poisoning with some fatalities resulted from soil disinfection by injection of methyl bromide into greenhouse soil.”-ACGIH
Treatment of wood packaging requires a concentration of up to 16,000 ppm. An Australian Customs officer died of methyl bromide poisioning while inspecting a shipping container that was fumigated in the United States. Canada Border Services Officers avoided the same fate because a Mexican container of granite was fumigated with 98% methyl bromide and 2% chloropicrin fumigant, the chloropicrin has a tear-gas effect.
NIOSH considers methyl bromide to be a potential occupational carcinogen as defined by the OSHA carcinogen policy [29 CFR 1990]. “methyl bromide showed a significant dose-response relationship with prostate cancer risk” -www.aghealth.org
Excessive exposure[edit source | editbeta]
Expression of toxicity following exposure may involve a latent period of several hours, followed by signs such as nausea, abdominal pain, weakness, confusion, pulmonary edema, and seizures. Individuals who survive the acute phase often require a prolonged convalescence. Persistent neurological deficits such as asthenia, cognitive impairment, optical atrophy, and paresthesia are frequently present after moderate to severe poisoning. Blood or urine concentrations of inorganic bromide, a bromomethane metabolite, are useful to confirm a diagnosis of poisoning in hospitalized patients or to assist in the forensic investigation of a case of fatal overdosage.