Estimates from 2017 assumed that 2,500 workers were potentially exposed to MOCA (methylene-bis-[2-chloroaniline]) across the EU. Since the authorisation duties for the substance under the REACH regulation have changed, it can be assumed that uses have even further decreased (applications show < 100 workers). MOCA exposure happens mainly through skin absorption of the substance. The substance has a harmonised classification as Carc. 1B (substances presumed to have a carcinogenic potential for humans based largely on animal evidence) according to the CLP Regulation.
The likely human target of carcinogenicity is the urothelium of the bladder causing bladder cancer.
Where risks occur
The main sector where exposure occurs is in the formulation and manufacturing of high-performance polyurethane products, e.g. hot cast polyurethane products, high-performance polyurethanes specifically for heavy-duty rollers, tensioner pads and spring blocks and for custom-made rollers. Tasks with high risk of MOCA exposure include weighing MOCA pellets, melting MOCA, dispensing molten MOCA and mixing molten MOCA with pre-polymer. In the Asia-Pacific region, it is also used as a curing agent in roofing and wood sealing.
More about the substance
Although pure MOCA is colourless crystalline solid, the most commonly used forms (industry grade) are tan-coloured pellets or flakes. It has a faint amine odour, very low solubility in water, and may explode when heated.
Hazards that may occur
Because of its handling, MOCA is taken up through both the skin and respiratory tract. Skin absorption is possible due to MOCA’s lipophilicity, relatively small molecular size, and presence of reactive amine groups. The highest concentrations are measured in the liver. Most of the absorbed substance is excreted within a few days in the urine and feces.
Acute high and accidental exposures may lead to irritation and a burning sensation to the skin and eyes, nausea, and gastrointestinal and renal effects. The EU also set a ‘skin notation’ for MOCA indicating that dermal exposure can contribute significantly to the total exposure.
Chronic exposure to MOCA might cause bladder cancer. The latency period between the exposure and the MOCA-related bladder cancer occurrence is on average 11.5 years and can be as long as 45 years.
What you can do
Substitution should be considered in applications where feasible. If alternatives are not available or MOCA may occur as by-product, perform regular exposure assessment so it is known when actions should be taken.
Strict conditions should exist for the use of MOCA in polyurethane manufacturing. In particular, good general housekeeping is also required throughout the sites and workers should take responsibility of their own work area and clean floors etc. The access to areas where MOCA is used is to be restricted to authorized personnel and safety signs are to be in place to remind workers what PPE they must wear. MOCA is to be stored in separate warehouses that are only accessible to authorized personnel. The use of PPE (Personal protective equipment) is to be made mandatory within the semi-industrial and machine casting.
Workers need to be aware of the effects of exposure and should be trained regularly on the control measures necessary for working safely with MOCA to prevent exposure. They should be encouraged to report early symptoms such as burning sensation to the skin and eyes. Involving an occupational physician is therefore recommended.
Biomonitoring is currently the best method to estimate the total exposure to MOCA in occupational settings. If biomonitoring is being performed, sampling should be carried out post-shift at the end of the working week.
Biomonitoring should also be complemented with air monitoring and, when appropriate, measurements of skin and surface contamination, to control the exposure sources.
Ensure that workers have adequate personal protective equipment, such as protective suits, gloves, footwear, headgear, direct vent googles and respirators, if necessary.
References: RAC, IARC, ATSDR, AGS, NIOSH, COM
