Methanol

by Posted on

2023-02-24

Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH (often abbreviated MeOH). It is the simplest alcohol, and is a light, volatile, colourless, flammable liquid with a distinctive odour very similar to, but slightly sweeter than, ethanol (drinking alcohol). At room temperature, it is a polar liquid, and is used as an antifreeze, solvent, fuel, and as a denaturant for ethanol. Because of its toxic properties, methanol is frequently used as a denaturant additive for ethanol manufactured for industrial uses — this addition of methanol exempts industrial ethanol from liquor excise taxation. Methanol is often called wood alcohol because it was once produced chiefly as a by-product of the destructive distillation of wood. Methanol is produced naturally in the anaerobic metabolism of many varieties of bacteria, and is ubiquitous in the environment. As a result, there is a small fraction of methanol vapour in the atmosphere. Over the course of several days, atmospheric methanol is oxidised with the help of sunlight to carbon dioxide and water. [1]

Uses [2]

Methanol is used in many ways. On its own, applications include:

  • Transportation Fuel – Methanol is the most basic alcohol. It is easy to transport, readily available, and has a high octane rating that allows for superior vehicle performance compared to gasoline.
  • Wastewater Denitrification – Methanol is also used by municipal and private wastewater treatment facilities to aid in the removal of nitrogen from effluent streams. As wastewater is collected in a treatment facility, it contains high levels of ammonia. Through a bacterial degradation process this ammonia is converted into nitrate. If discharged into the environment, the nutrient rich nitrate in sewage effluent can have a devastating effect on water ecosystems. Methanol, which quickly biodegrades, is a cost-effective way to help revitalise waterways tainted by the effects of nitrates.
  • Fuel Cell Hydrogen Carrier – Methanol is used as a key component in the development of different types of fuel cells. From large-scale fuel cells to power vehicles or provide back-up power to remote equipment, to portable fuel cells for electronics and personal use, methanol is an ideal hydrogen carrier.
  • Biodiesel Transesterification – In the process of making biodiesel fuel, methanol is used as a key component in a process called transesterification. Methanol is used to convert the triglycerides in different types of oils into usable biodiesel fuel. The transesterification process reacts methanol with the triglyceride oils contained in vegetable oils, animal fats, or recycled greases, forming fatty acid alkyl esters (biodiesel) and the by-product glycerin.
  • Electricity Generation – Different companies are also exploring the use of methanol to drive turbines to create electricity.

Methanol is also used as a key component of hundreds of chemicals including formaldehyde, acetic acid and olefins –which are all basic chemical building blocks for a number of common products. An example of some types of materials that are made from methanol include:

  • Plastics
  • Synthetic fibres
  • Paints
  • Resins
  • Magnetic film
  • Safety glass laminate
  • Adhesives
  • Solvents
  • Carpeting
  • Insulation
  • Refrigerants
  • Windshield washer fluid
  • Particle board
  • Pigments and dyes

Sources & Routes of Exposure [3]

Exposure to methanol can occur in many ways. Occupational exposure to methanol can commonly occur through inhalation and dermal contact. Individuals may be exposed to methanol in the ambient air from its evaporation during solvent uses or from automobile exhaust, through the consumption of various foods, and through dermal contact with various consumer products such as paint thinners and strippers, adhesives, cleaners, and inks. Natural emission sources of methanol include volcanic gases, vegetation, microbes, and insects; methanol is also formed during biological decomposition of biological wastes, sewage, and sludge.

Health Effects

Acute Effects [4]

Methanol may be acutely toxic following inhalation, oral or percutaneous exposure. Acute toxicity from methanol manifests as CNS depression, followed by a latent period of varying duration from 8-36 hours and occasionally up to 48 hours. Subsequently, metabolic acidosis develops, superimposed with headache, nausea and features of ocular toxicity. Ocular toxicity may range from photophobia and misty or blurred vision to markedly reduced visual acuity and complete blindness; ingestion of as little as 4-10 mL methanol in adults may cause permanent damage. Coma and death may occur after substantial exposures. The minimal lethal dose following ingestion is considered to be in the range of 300-1000 mg kg-1. Severe intoxication, if survived, may cause permanent damage to the CNS, manifest as a Parkinsonian-like condition and permanent blindness.

Chronic Effects [3]

Chronic inhalation or oral exposure to methanol may result in headache, dizziness, giddiness, insomnia, nausea, gastric disturbances, conjunctivitis, visual disturbances (blurred vision), and blindness in humans. EPA has not established a Reference Concentration (RfC) for methanol. The Reference Dose (RfD) for methanol is 0.5 milligrams per kilogram body weight per day (mg/kg/d) based on increased liver enzymes (SAP and SGPT) and decreased brain weight in rats.

Reproductive/Developmental Effects

No information is available on the reproductive or developmental effects of methanol in humans. Developmental effects have been observed in the offspring of rats and mice exposed to methanol by inhalation. These included skeletal, cardiovascular, urinary system, and central nervous system (CNS) malformations in rats and increased resorptions and skeletal and CNS malformations in mice.

Cancer Risk

No information is available on the carcinogenic effects of methanol in humans or animals. EPA has not classified methanol with respect to carcinogenicity.

Safety [5]

First Aid Measures

  • Eye Contact: Check for and remove any contact lenses. Immediately flush eyes with running water for at least 15 minutes, keeping eyelids open. Cold water may be used. Get medical attention.
  • Skin Contact: In case of contact, immediately flush skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes. Cover the irritated skin with an emollient. Cold water may be used. Wash clothing before reuse. Thoroughly clean shoes before reuse. Get medical attention immediately.
  • Serious Skin Contact: Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream. Seek immediate medical attention.
  • Inhalation: If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical attention immediately.
  • Serious Inhalation: Evacuate the victim to a safe area as soon as possible. Loosen tight clothing such as a collar, tie, belt or waistband. If breathing is difficult, administer oxygen. If the victim is not breathing, perform mouth-to-mouth resuscitation. WARNING: It may be hazardous to the person providing aid to give mouth-to-mouth resuscitation when the inhaled material is toxic, infectious or corrosive. Seek immediate medical attention.
  • Ingestion: If swallowed, do not induce vomiting unless directed to do so by medical personnel. Never give anything by mouth to an unconscious person. Loosen tight clothing such as a collar, tie, belt or waistband. Get medical attention immediately.

Fire & Explosion

  • Fire Hazards: Highly flammable in presence of open flames and sparks, of heat. Non-flammable in presence of shocks. When Methanol is heated to decomposition, it emits acrid smoke and irritating fumes.
  • Explosion Hazards: Explosive in presence of open flames and sparks, of heat. Methanol is explosive in the form of vapour when exposed to heat or flame and may travel considerable distance to source of ignition and flash back. In addition, explosive mixtures are formed with air due to its low flash point. It is also explosive when mixed with choroform + sodium methoxide and diethyl zinc. It boils violently and explodes.
  • Fire Fighting Media and Instructions: Flammable liquid, soluble or dispersed in water. SMALL FIRE: Use DRY chemical powder. LARGE FIRE: Use alcohol foam, water spray or fog.

Engineering Controls & Personal Protection

  • Engineering Controls: Provide exhaust ventilation or other engineering controls to keep the airborne concentrations of vapours below their respective threshold limit value. Ensure that eyewash stations and safety showers are proximal to the work-station location.
  • Personal Protection to be used when handling methanol include: Splash goggles, lab coat, vapour respirator (be sure to use an approved/certified respirator or equivalent) and gloves.
  • Personal Protection in Case of a Large Spill: Splash goggles, full suit, vapour respirator, boots and gloves. A self contained breathing apparatus should be used to avoid inhalation of the product. Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling this product.

Regulation [5,6,7]

Exposure Limits

United States:

TWA: 200 from OSHA (PEL) [United States]

TWA: 200 STEL: 250 (ppm) from ACGIH (TLV) [United States] [1999] STEL: 250 from NIOSH [United States]

TWA: 200 STEL: 250 (ppm) from NIOSH SKIN

Australia:

TWA: 262 milligrams of methanol per cubic metre of air.

STEL: 328 milligrams of methanol per cubic metre of air.

Canada:

TWA: 200

STEL: 250 (ppm) [Canada]

European Union:

TWA: 200 PPM 8 hour(s).

TWA: 260 MG/M3 8 hour(s).

References

http://en.wikipedia.org/wiki/Methanol

http://www.methanol.org/Methanol-Basics/Methanol-Applications.aspx

http://www.epa.gov/ttn/atw/hlthef/methanol.html

http://www.hpa.org.uk/webc/HPAwebFile/HPAweb_C/1194947357226

http://www.sciencelab.com/msds.php?msdsId=9927227

http://www.npi.gov.au/substances/methanol/health.html

http://www.kpc.com.kw/InformationCentre/DataSheets/ProductsCrude%20Safety%20Data%20Sheets%20SDS/Methanol.pdf