Emission of isothiazolinones from water-based paints

The isothiazolinone preservatives methylisothiazolinone (MI), methylchloroisothiazolinone (MCI), and benzisothiazolinone (BIT) are used in a wide variety of products including paint and cosmetics, and they are known to cause allergic contact dermatitis. Among painters they are one of the most common causes of contact dermatitis. Furthermore, they are all volatile, and severe reactions caused by emissions of especially MI from paint have been reported recently. In this study the concentrations of MI, BIT, and MCI in water-based paint were analyzed by LC-MS-MS, and the emissions from the paints were measured in climate chambers and in an apartment. Nineteen paints were analyzed for the content of MI, MCI, and BIT. All 19 paints contained MI, 16 contained BIT, and 4 contained MCI. In the chamber experiment emission of MI peaked within hours of application but then continued at a slow rate for more than 42 days. MCI was emitted more slowly and peaked after several days. BIT emissions were all around the limit of detection. In the apartment we were able to detect emission of MI several days after application. Long lasting evaporation and thus chronic exposure give credibility to the clinical observations that MI can be an important cause of airborne contact dermatitis among painters and consumers.