Should MMA be classified as a respiratory sensitizer?

August 16, 2022

Contradictions on the classification of MMA

In October 2020, ECHA's Risk Assessment Committee (RAC) had agreed that MMA, methyl methacrylate should be classified as a Category 1 respiratory sensitizer. MMA is a substance used in paints, adhesives and coatings. It is already classified under CLP(Classification Labelling Packaging Regulation) as a skin irritant and skin sensitizer.

While the Anses(French Agency for Food, Environmental and Occupational Health Safety) supports the fact that consumers can be exposed to MMA via different routes (detergents, paints, and adhesives, etc.), and that a wide range of testing is missing. Industry, on the other hand, disagrees with the addition of MMA as a respiratory sensitizer.

On July 5-6, 2022, Cefic's Methacrylates Sector Group (MSG) shared a document at a meeting of the REACH and CLP Competent Authorities. In this document, Cefic states that the classification decision is "scientifically and legally unfounded". Cefic says it found that the evidence provided by the RAC used "unreliable" human data. Thus, according to Cefic, the workers who reported having developed respiratory sensitization were not necessarily in contact with MMA.

What is the impact of a "respiratory/skin sensitization" hazard classification?

All manufacturers, importers and downstream users must classify and label their hazardous substances or mixtures to ensure protection of human health and the environment.

There are different hazard classes:

  • Carcinogenicity
  • Mutagenicity
  • Reproductive toxicity 
  • Respiratory sensitizers

Within the European Union (EU), it is mandatory to establish a harmonized classification and labeling for all substances of concern (which fall into one of the above mentioned hazard classes). 

This harmonized classification (HCC) is listed inAnnex VI of the CLP Regulation. ECHA provides a database of the C&L inventory including the list of harmonized classifications

The hazard class "respiratory / skin sensitization" is divided into 2 categories:

  • Category 1 respiratory sensitizers and subcategories 1A and 1B 
  • Category 1 and sub-category 1A and 1B skin sensitizers 

If a product already classified as a sensitizer, contains a substance that is part of this hazard class, then the product must be labeled with the sensitizing substance

If a product is not already classified as a sensitizer, it must be stated on the label "contains (name of substance)" / "may produce an allergic reaction".  

Finally, it is mandatory to establish a SDS (Safety Data Sheet) for the product.

Properties of Methyl Methacrylate

IUPAC name 2-methylprop-2-enoate

Gross formula C5H8O2

Chemical formula :    


CAS number : 80-62-6

EC number : 201-297-1

Density 0.93g/mL

Molecular weight 100.12g/mol

Physical form crystalline powder or crystals

Hazard statements :

H225 - Highly flammable liquid and vapors

H335 - May cause respiratory tract irritation

H315 - Causes skin irritation

H317 - May cause skin allergy


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