Air toxics and indoor air quality in Australia

State of knowledge report
Environment Australia, 2001
ISBN 0 6425 4739 4

Part C: Factsheets (continued)

Methylenebis(phenylisocyanate) (MDI)

Substance name: Methylenebis(phenylisocyanate) (MDI)
CASR number: 101-68-8
Molecular formula: C15H10N2 O2
Synonyms: Isocyanic acid, methylenedi-p-phenylene ester, mdi benzene, 1,1'-methylenebis(4-isocyanato)- (9ci), methylenebis (4-isocyanatobenzene), bis(p-isocyanatophenyl)methane, 1,1-methylenebis(4-isocyanatobenzene), bis(1,4-isocyanatophenyl)methane, methylenebis(p-phenylene isocyanate), methylenebis(4-phenylene isocyanate), bis(4-isocyanatophenyl)methane, p,p'-methylenebis(phenyl isocyanate), caradate 30, desmodur 44, 4,4'diisocyanatodiphenylmethane, 4,4'-diphenylmethane diisocyanate, diphenylmethane-4,4'-diisocyanate hylene, m50 isonate, 125m isonate, 125mf methylenebis(p-phenyl isocyanate), methylenebis(4-phenyl isocyanate), 4,4'-methylenebis(phenyl isocyanate), 4,4'-methylenediphenyldiisocyanate, methylenedi-p-phenylene diisocyanate, methylenedi-p-phenylene isocyanate, 4,4'-methylenediphenylene isocyanate, nocconate 300 nci-c50668, MDI

Physical and chemical properties

Insoluble brown liquid, yellow to white crystals or solid at normal temperatures.

Melting point: 37.2°C
Boiling point: 196°C
Vapour density: 8.6
Specific gravity: 1.197

MDI is a stable solid under normal conditions in the atmosphere, insoluble in water but soluble in solvents such as acetone, kerosene and benzene. It will react vigorously with alcohol, acid and some other compounds.

Common uses

MDI is used in the making of polyurethane foams and other synthetic components of furniture, machinery and electrical components for a variety of household and other electrical appliances. It is used to bond rubber to other synthetic fibres such as rayon and nylon. It is also used in specialised spray paints, surface coatings, manufactured resin and artificial gum. Some printers ink may contain the compound. It is used in metal foundries to bind materials in the low-temperature curing of metal components.

Sources of emissions

Point sources

MDI may be emitted to air, land or water from locations that produce polyurethane foam, adhesives, resins and plastic coatings, or where large volumes of polyurethane spray paint are used (eg vehicle manufacturing and repair workshops, vehicle body shops and specialised marine dockyards).

Diffuse sources, and point sources included in aggregated emissions data

Trace amounts may enter the natural environment from the wide variety of uses and applications. Minute quantities may be derived from the widely distributed consumer products that use polyurethane foam, adhesives and coatings.

Natural sources

There are no natural sources.

Mobile sources

There are no mobile sources.

Consumer products that may contain MDI

Products include polyurethane foam, surface coatings, sprays, paint, synthetic components of household furniture and a variety of electronic components and accessories contained polyurethane products.

Health effects

How might I be exposed to MDI?

People may be exposed to very low levels of MDI from direct contact with freshly manufactured or produced products that contain it. People working in or living near industries that produce or use it may be subject to low but persistent exposure to minute amounts of dust particles. Exposure is limited to areas where it is used or manufactured.

By what pathways might MDI enter my body?

MDI can be inhaled as minute dust particles or in the form of a fine spray mist. It may result in irritation when in contact with the skin or eyes.

Health guidelines

National Occupational Health and Safety Commission (NOHSC):

The substance is listed as a sensitiser. Under the National Model Regulations for the Control of Workplace Hazardous Substances, isocyanates require health surveillance.

What effect might MDI have on my health?

MDI is irritating to the eyes, respiratory system and skin. It may cause sensitisation by inhalation. This depends on how much MDI you have been exposed to, for how long, and your current state of health. In certain circumstances, even a brief exposure to very high levels of MDI can result in skin and other irritations and affect breathing capacity. Exposure can result in symptoms such as skin dermatitis and nose, throat, lung and eye irritations. If MDI is inhaled as a dust, it can cause shortness of breath, wheezing, coughing, chest tightness, headache and nausea.

Environmental effects

Environmental fate

MDI remains as a solid at normal temperatures and may gradually break down as result of contact with organic compounds in the soil or atmosphere. It produces carbon dioxide and other compounds of nitrogen, carbon, hydrogen and oxygen as result of slow gradual breakdown through contact with the atmosphere.

Environmental transport

MDI is a solid or, less commonly, a sticky liquid; it will gradually react with acid or basic compounds in the atmosphere or soil to form less complex compounds such as urea, amine and carbon dioxide. It will generally be transported in the atmosphere as dust particles or as a component of an aerosol, but that occurs only within or surrounding manufacturing or production plants where it is used.

Environmental guidelines

There are no national guidelines.

What effect might MDI have on the environment?

The effect of MDI on animals is similar to its effect on humans (ie lung damage), but only where the compound has been inhaled as dust particles or an aerosol.


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