Methanol Basics http://www.epa.gov/orcdizux/07-meoh.htm EPA400-F-92-009 August 1994 Fact Sheet OMS-7 Methanol Basics What is Methanol? Methanol is the simplest alcohol, containing one carbon atom. It is a colorless, tasteless liquid with a very faint odor and is commonlyknown as "wood alcohol." H h H CHgOH Methanol is one ofa number offuels that could substitute for gasoline or diesel fuel in passenger cars, light trucks, and heavy-duty trucks and buses. Why Consider Methanol? Methanol's physicaland chemical characteristics result in several inherent advantages as an automotive fuel: LOW POLLUTION Emissionsfrom methanol cars are low in reactive hydrocarbons (which form smog) and in toxic compounds. Methanol-fueled trucks and buses emit almost no particulate matter (which cause smoke and odor, and can also be carcinogenic), and muchless nitrogen oxides than their diesel-fiieled counterparts. FUEL SUPPLY OPTIONS Methanol can be manufactured from a variety ofcarbon-based feedstocks such as natural gas, coal, and biomass(e.g., wood). Use ofmethanolwould diversify the country's fuel supply and reduce its dependence on imported petroleum. FIRE SAFETY Methanol is much less flammable than gasoline and results in less severe fires when it does ignite. HIGH PERFORMANCE Methanol is a high-octane fuel that offers excellent acceleration and vehicle power. ECONOMICALLY ATTRACTIVE Witheconomiesofscale, methanol could be produced, distributed, and sold to consumers at prices competitive with gasoline. 1 of2 4/26/012:39 PM Methanol Basics http://www.epa.gov/orcdizux/07-meoh.htm Current Methanol Uses Because of its outstanding performance and fire safety characteristics, methanol is the only fuel used in Indianapolis-type race cars. Following a series of methanol vehicle development and demonstration programs throughout the 1980's, a limited number of methanol passenger cars and buses are now commercially available. There are approximately 14,000 methanol passenger cars in use, mostly in Federal and private fleets, and about 400 methanol buses in daily operation, mostly in California. Methanol is used in a number ofconsumer products, including paint strippers, duplicator fluid, model airplane fuel, and dry gas. Most windshield washer fluids are 50 percent methanol. Is Methanol Poisonous? Yes. As with many other fuels, methanol can be highly toxic and should never be taken orally. A few teaspoons ofmethanol can cause blindness and a few tablespoons can be fatal, if the exposure is not treated. It should be noted that the human body can metabolize and eliminate low concentrations of methanol with no ill effects. (Methanol is present in many cooked vegetables, andthe artificial sweetener in diet soft drinksbreaks down into methanol during digestion.) Methanol becomes poisonous only when it overwhelms the body's capacity to remove it. Toxic effects do not occur until several hours after exposure. Effective antidotes to methanol poisoning are readily available and can be administered during this interim period. For More Information: The Office ofMobile Sources is the national center for research and policy on air pollution from highway and off-highway motor vehicles and equipment. You can write to us at theEPANational Vehicle and Fuel Emissions Laboratory, 2565 Plymouth Road, Ann Arbor, MI 48105. Our phone number is (734) 214-4333. 2 of2 4/26/01 2:39 PM Methano1 http://www.embbs.com/cr/alc/alc6.html J. Methanol Pharmacology: Methanol (methyl alcohol) is produced from the distillation ofwood and is a clear, colorless, volatile liquid with a weak odor that is somewhat sweeter than ethanol. Methanol is used in the industrial production of many synthetic organic compounds and is a constituent of many commercially available solvents. Products that are available in the home that contain methanol include: windshield wiperfluids and de-icers, antifreeze, glass cleaner, canned heat, paints, varnishes, paint thinners and removers. It can also be used in gasohol, which could present problemsas people try to siphon the gas by mouth and accidentally ingest some. Methanol is a natural fermentation product and its concentration may be up to 300 mg/L in wine, and even higher in other spirits. Methanol is well absorbed from the gastrointestinal tract mucosa as well as through the skin and lungs. Both inhalation and transdermal exposure can result in toxicity. The exact lethal dose for a human is not known. Doses as low as 25 cc of40% methanol have been reported as causing toxicity. In other cases doses up to 500 cc have occurred with no side effects. Most sources consider the minimal lethal dose to be around 100 cc (1 g/kg). Poisoning with methanol may be accidental or intentional. There have been epidemics of methanol toxicity in cases where illicit whiskey has been sold to large populations or when the less expensive methanol was substituted for ethanol in drinks. Once methanol is absorbed it is rapidly distributed in the body water with peak blood levels occurring in about 30 to 90 minutes after exposure. Ifethanol is not present 2-5% ofthe methanol is excreted unchanged by the kidneys and a small amount is eliminated by the lungs. At low blood levels the half-life ofmethanol is 2-3 hours. Once the blood levels rise above 300 mg/dl, the enzymes that metabolize methanol become saturated and the elimination half-life increases to 27 hours. When this happens a greater amount ofthe methanol is eliminated unchanged by the lungs and the kidneys. During therapy with ethanol the half-life ofmethanol becomes 30-52 hours. Methanol itselfmay cause inebriation but by itselfin almost completely non-toxic. The methanol is metabolized by alcohol dehydrogenase to formaldehyde and then to formic acid. Clinical findings correlate better with formic acid levels than with methanol levels. It is these two metabolites that cause toxicity with formic acid being more responsible. It is the formic acid that causesthe profound metabolic acidosis that is typical ofmethanol poisoning. The overall mortalityofmethanol poisoning is approximately 20% and among survivors the rate of permanent visual impairment is 20-25%). Clinical Presentation: The presentation within the first 1-2 hours may be similarto ethanol intoxication inthat the patient may have drowsiness, vertigo, and uninhibited behavior. There is typically a delay of the toxic symptoms anywhere from six-30 hours and longer if ethanol has been co-ingested. In casesof methanol ingestiona lack ofsymptoms early on does not meanthat the patient has not ingested a toxic amount ofmethanol. Aside from the symptoms ofintoxication patients may also present with gastrointestinal symptoms due to acute gastritis or pancreatitis. The gastritis may be severe and is occasionally hemorrhagic. Symptoms include anorexia, severe abdominal pain, vomiting, diarrhea, increased transaminases or increased amylase. Early visual disturbances are the classic findings that are associated with methanol intoxication and include decreased vision or blurred vision. Patients may complain ofa 'snowstorm' in front ofthe eyes or photophobia. The pupils may be fixed and dilated with the funduscopic exam revealing retinal edema with hyperemiaofthe optic disc. In severe cases there may be papilledema and engorged retinal vessels. Other complications ofsevere methanol intoxication include coma, seizures, blindness, oliguric renal failure, cardiac failure, and pulmonary edema. Death may be rapid or may occur several hours after coma. lof4 4/26/01 3:00 PM Methanol http://www.embbs.com/cr/alc/alc6.html Deathis associated with inspiratory apnea, terminal opisthotonos and convulsions. Diagnosis: Patients who present early intheircourse withknowledge that they accidentally or intentionally ingested methanol present little difficulty. Those that cannot or will not provide an complete history as to their possible ingestion areclearly more difficult. Thesymptoms andphysical signs are non-specific. Thepatient may havea faint odor of methanol on the breathbut this can easily be missed. Ocular findings arethe most specific physical findings andare important diagnostically. Theocular physical findings or complaints inaddition to a severe metabolic acidosis as well as a high osmolar gap canjustify a presumptive diagnosis ofmethanol poisoning. The literature does contain caseswhere severe methanol intoxication hasbeenpresent but no anion gap metabolic acidosis was found (Palmisano et al. 1987). Themajority ofpatients reviewed had high ethanol levels which appeared to limited the formation of formic acid. Thus, it is important to be aware that a patient who presents with methanol exposure may havedelayed clinical and laboratoryfindings even if there was a large ingestionofmethanol. Treatment: As with any poisoned patient the initial managementincludes close attention to adequate airway, ventilation, and perfusion. Ifthe patient is seen early, gastric lavage to remove any residual gastric methanol should be done. Ifthere is exposure to the skin, then decontamination should be done. Syrup ofipecac is not recommended as the mental status may rapidly deteriorate and there is a significant risk ofaspiration. Activated charcoal has not been proven to absorb ethanol to any extent and these studieshave been presumed to apply to methanol. Also, because alcoholstend to be consumed in large amounts and are rapidly absorbed there does not appear to be any benefit. Therefore, ifthere is no concern ofcoingestion with other toxic substances there is probably little indication for charcoal. Labs should