According to ECHA, there are no manufacturing sites in the EU. The organisation found that imports of the agent amounted to somewhere between 1kT and 10kT in 2010. Using information sourced from the IARC, ECHA said that from 1986 to 2002 production volumes were 450 tonnes/year to 4.5kT/year. From 2006, production dropped below that, perhaps to as little as 225 tonnes a year.
In the UK, for 2006 the estimated import figure was 200 tonnes, the HSE report concluded.
Safety and workplace exposure
According to the UK HSE, airborne exposure to MbOCA in the PU industry from 2005 to 2007 was very low and well below the workplace exposure limit of 0.005mg/m3.
People working with MbOCA absorb the chemical directly through the skin, according to ECHA guidance. However, the HSE also monitored MbOCA levels in the urine of people working with the chemical. This showed that 90% of those exposures were about half the biological monitoring guidance value of 15 µmol set by the HSE in UK and noted in the ECHA’s Annex XV dossier on the chemical.
However, because MbOCA is used in casting elastomers, skin exposure was more likely to happen during casting and mould trimming and a need for improving guidance on suitable glove materials was identified.
Work carried out by Chemtura Europe showed that the choice of glove material is important to reduce the risk of dermal exposure. Tests indicated that nitrile or butyl rubber gloves were more effective in delaying migration of MbOCA through the glove than the more commonly used natural rubber latex gloves found in workplaces.
US use of MbOCA
Ray Scott, vp at US-based specialty industrial chemicals company The Hanson Group, told Urethanes Technology International magazine, it was the US flexible foam industry that led to such widespread MbOCA use. Scott was part of a team from UOP that developed an alternative to MbOCA around three decades ago.
As ecological issues increasingly gained attention worldwide– coupled with the Anderson contamination, some US companies stopped using it and found replacements. From the 220kT or so used yearly back in the 1980s, Scott said users changing to alternatives reduced the MbOCA market’s size by roughly one third.
However, he also said the flexible foam industry dropped its use of MbOCA almost overnight during the 1980s and adopted alternatives such as HR polyols and Graft polyols. Generally they changed from TDI/PTMG to MDI/Hydroxyl and eliminated the need to use MbOCA.
According to Scott, MbOCA replacements include Cyanacure (developed by American Cyanamid) and Polacure (developed by Polaroid). Both were bought by Air Products, he said. Polacure is the base of their current product line Polamines.
Another MbOCA replace is Polycure and is still made and sold by PTM&W in Los Angeles, California. Other MbOCA replacements include PolyLink 4230 (The Hanson Group) and "probably the most effective replacement" is Ethacure 300 by Albemarl, added Scott.
Today, he said, the use of MbOCA isn’t much lower in the US than it was 40 years ago but it would be cause for concernif US legislators took heed of the EU and decided to initiate a ban on the chemical there too.
Given that, according to Scott, the chemical is “significantly lower in price today than during the 1980s,” those still using it will probably never stop,” he said.
US users of the chemical are fully supported by the US Polyurethane Manufacturers Association (PMA), an organisation that Scott said some believe built its reputation on the battle over MbOCA use. From 1973, the PMA campaigned vigorously against the US Occupational Health and Safety Organisation’s bid to classify the agent a carcinogen, and prevailed in many instances.
The PMA says that “If recommended material handling and use procedures are followed when working with MOCA, along with routine urinalysis being performed to monitor employee exposure, exposure to workers will be at a safe level, assuming that there is any measurable exposure at all.”
Classification of MbOCA as a carcinogen
It was in 2012 that the International Agency for Research on Cancer changed MOCA’s classification from probable human carcinogen to known human carcinogen – a decision the PMA’s Mike Kocak branded “arbitrary” in absence of further information since IARC’s prior listing for the chemical.
The PMA says “mechanistic evidence is not necessarily sufficient to determine carcinogenicity” and said studies of workers with MbOCA urine levels of more than 20 times the suggested safe limit indicate a lack of human carcinogenicity.
The organisation points to several studies that it says refute the idea that MOCA as a human carcinogen. Among these are a DuPont study, Fayerweather et al study and a further one by Dost, Straughan and Sorahan published in Occupational Medicine in June 2009.
Andrew Davies, lead application development field chemist at Dow Hyperlast, thinks the sunset on the use of MbOCA under REACH regulations “provides an opportunity for the industry to change the way it thinks about the material it uses and why.”
Davies believes it is “likely to be a difficult adaptation process for users to phase out MbOCA” but that the “versatility of urethane chemistry means suitable alternatives are available.”
He thinks material selection will depend on the application needs in terms of physical performance. “MDI-based technologies whether polyester or polyether have demonstrated that they are equal and if not better than those using TDI/MbOCA, in wear resistance requirements such as pipeline scrapers or mining screens.
“While MDI/PTMEG systems are significantly better than polyester TDI/amine cured elastomers and have been proven to outperform TDI/PTMEG in hot wet or humid environments.”
Many responses to the ECHA’s consultation for the identification of MbOCA as a SVHC (substance of very high concern) were supportive of the move however, French company COURBIS – which uses it as a PU hardener – told the regulator that “in some families of polyurethanes, there can be no substitute.”
