4,4’-Methylenebis(2-chloroaniline) is a synthetic chemical that occurs as tan coloured pellets or flakes. It has a faint amine odour, very low solubility in water and may explode when heated. It may also be referred to as MOCA, methylene-bis-ortho-chloro-aniline, bisamine, MBOCA, and MCA. There are numerous other synonyms and product names; see HSDB for more information.
MOCA has been classified by IARC as a Group 1 carcinogen, carcinogenic to humans. It was first classified as a Group 2A carcinogen, but was re-classified as Group 1 in 2008 based on strong genotoxic mechanistic evidence. MOCA's Group 1 classification was reaffirmed under a more recent IARC review of Group 1 carcinogens. In experimental animals, MOCA causes liver, bladder and lung cancer.
Additionally, when MOCA is inhaled or ingested it can cause cyanosis (blue coloration of lips, fingernails or skin) as well as confusion, dizziness, headache, nausea, abdominal pain, unconsciousness and convulsions. Chronic exposure can cause blood disorders such as methemoglobinemia.
stel = short term exposure limit (15 min. maximum)
TLV = Threshold Limit Value (8 hour maximum)
Canadian Environmental Guidelines
MOCA was not included in the Canadian environmental guidelines reviewed (8-11).[8-11]
DSL – high priority substance with intermediate potential for exposure
DSL = Domestic Substances List
MOCA was no included in other Canadian government chemical listings reviewed[13,14]
MOCA is primarily used as a curing agent for polyurethane elastomers and for epoxy resins.
In Canada, MOCA is primarily used as a curing agent for polyurethane prepolymers for specialized castable polyurethane products such as industrial tires and rollers, shock absorption pads, conveyor belting, sport boots, roller skate wheels, cameras, computers, electrical components and wear-resistant industrial products.
MOCA has been used in research laboratories as a model compound for studying carcinogens.[2,4]
Canadian Production and Trade
Polyurethane products and epoxy resins are used and manufactured in Canada;[15,16] therefore MOCA is also likely to be used in conjunction with these processes in Canada.
MOCA was not being produced in Canada in 2000. In the same year, Canada imported 100 to 1000 tonnes of MOCA.
No export/import data on MOCA was included in the TradeMap database.
The most important route of occupational exposure to MOCA is dermal absorption, followed by inhalation and ingestion.
The main occupations exposed include workers involved in the manufacture of MOCA and in polyurethane and epoxy production where MOCA is used as a curing agent.[2,4] MOCA has been detected on a number of workplace surfaces in MOCA and polyurethane production plants, suggesting potential dermal exposure for workers.[4,7] In a polyurethane factory, MOCA was detected in the air in areas where it was melted and used, indicating that chemical mixers and moulders would have the highest inhalation exposure to MOCA.
CAREX Canada is reviewing whether it is feasible to prepare exposure estimates for Canadian workers exposed to MOCA. This will likely depend on availability of exposure data.
MOCA is not a naturally-occurring chemical, so any found in the environment is from industrial releases or spills.[7,18] Sources of environmental exposure include dermal exposure to contaminated soil and ingestion of root vegetables grown in contaminated soil.
Once released, MOCA will strongly adsorb to organic matter in soil or in sediment. Because of its low solubility in water, contamination of groundwater and surface water is unlikely.[4,7]
After an accidental release of MOCA by a chemical manufacturing plant in Adrian, Michigan in the US in 1979, up to several milligrams per kilogram of MOCA was found in soil in the nearby community. MOCA was also detected in the urine of children but not adults living in the affected area. Dermal contact with contaminated soil during play and barefoot activities was the most significant source of exposure.
Para-occupational exposures may occur for family members of workers exposed to MOCA.
Although trace amounts of unreacted MOCA may be present in some plastic products, because of MOCA’s high molecular weight and low volatility, exposure in consumers is expected to be very low.
No household products are listed as containing MOCA in the Household Products Database from the United States.
A search of the environmental NPRI databases yielded the following results on current potential for exposure to MOCA in Canada: