Canada Finds MMA Does Not Meet Criteria for Classification as a Respiratory Tract Sensitizer

In a ruling issued on March 22, 2001, Health Canada found that methyl methacrylate (MMA) does not meet the criteria for classification as a respiratory tract sensitizer.

Health Canada's criteria are contained in the Controlled Products Regulations or CPR. The sensitization criteria are in section 56 (and interpreted in the Health Canada "Reference Manual for the WHMIS Requirements of the Hazardous Product Act and Controlled Products Regulations").

In making judgments about sensitization, CPR section 56 calls for consideration of various factors, including the number of cases reported in relation to the size of the exposed population and the extent of exposure. The recent MMA ruling makes the following comment: "For example, a high-production-volume chemical, used in large quantities in many workplaces would not warrant classification if only a few cases of sensitization had been reported over a period of several years."

The MMA decision briefly reviews four reports of respiratory tract sensitization following exposure to MMA. None of these reports definitively linked MMA as the causative agent. All of them involved exposure for long periods, ranging from "several years" to 27 years before onset of symptoms.

Health Canada concludes that the CPR criteria are not met: "As only a very few cases have been reported in the literature with this widely used chemical, MMA would not fall within the CPR criteria for respiratory tract sensitization."

Health Canada adds the cautionary note that MMA's potential to induce respiratory tract sensitization may be reevaluated if there are new cases reported in the literature.

The full text of the ruling can be found on Health Canada's website at the following address: http://www.hc-sc.gc.ca/hecs-sesc/whmis/pdfs/substance_specific_issues1.pdf

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