Occupational allergic contact dermatitis in a company manufacturing boards coated with isocyanate lacquer

Abstract

Over a short period of time, there was an outbreak of work-related skin lesions among workers at a company producing flooring laminate boards, after the introduction of a water-repellent lacquer based on diphenylmethane-4,4'-diisocyanate (MDI). In 5 workers, patch testing was performed with a standard series, an isocyanate series and work-environmental products when indicated. 3 of the workers were tested with the lacquer, and contact allergy was found with concurrent reactions to 4,4'-diaminodiphenylmethane (MDA). 1 of the 3 workers also showed a simultaneous reaction to MDI, whereas 1 showed a positive reaction to dicyclohexylmethane-4,4'-diisocyanate (HMDI). Of the 2 individuals not tested with the lacquer, 1 reacted to both MDI and MDA, whereas the other reacted to a soap used at work. In 3 of 4 cases, the isocyanate reactions appeared after D3. Occupational contact with isocyanates should not exclusively be focused upon respiratory hazards, as this report shows that skin contamination probably increases the risk of developing contact allergy to isocyanates and isocyanate-related substances. When aiming at diagnosing contact allergy to isocyanates, it is desirable to perform a late reading, as positive reactions appear late. MDA appears to be a good marker for isocyanate hypersensitivity.

Biological monitoring of exposure to 1,5–naphthalene diisocyanate and 4,4’-methylenediphenyl diisocyanate

“…Both our results and a previous study by Kääriä et al (2001) indicate a poor correlation between airborne exposure to MDI and urinary biomarker levels. This observation could be due to significant dermal uptake of MDA originating from exposure to MDI or MDI-related substances (Brunmark et al 1995, Frick et al 2003. Also, occupationally unexposed subjects have been shown to have significant U-MDA levels, indicating nonoccupational background exposure (Sennbro et al 2005).…”

Occupational allergic and irritant contact dermatitis in workers exposed to polyurethane foam

“…However, 7 individuals reacted to MDA, despite of lack of confirmed presence of this chemical in occupational setting. In other studies, sensitization to MDA, was frequently found together with contact allergy to MDI and MDA was considered as an indicator of MDI contact sensitization [2][3][4]19,24,25]. Simultaneous reactions to MDI and MDA were attributed to their cross-reactivity related to the similar structure [26], although according to some authors, these two chemicals could have been both primary sensitizers [3].…”

“…In other studies, sensitization to MDA, was frequently found together with contact allergy to MDI and MDA was considered as an indicator of MDI contact sensitization [2][3][4]19,24,25]. Simultaneous reactions to MDI and MDA were attributed to their cross-reactivity related to the similar structure [26], although according to some authors, these two chemicals could have been both primary sensitizers [3]. In some reports, as in our study, individuals exposed to MDI did not react to this compound in patch testing, whereas positive reactions were observed to MDA, regardless of the presence or absence of MDA in occupational setting [2,3].…”

“…Simultaneous reactions to MDI and MDA were attributed to their cross-reactivity related to the similar structure [26], although according to some authors, these two chemicals could have been both primary sensitizers [3]. In some reports, as in our study, individuals exposed to MDI did not react to this compound in patch testing, whereas positive reactions were observed to MDA, regardless of the presence or absence of MDA in occupational setting [2,3]. Such results had been explained by the fact that MDA could be formed from MDI by hydrolysis, i.e., a reaction with water on, or in, moist skin, especially in warm working conditions provoking sweating, as was the case in the examined workplace [2,3,13,19,27].…”

“…Isocyanates, the basic materials for the synthesis of PU, are aromatic, aliphatic or cycloaliphatic chemicals with a low molecular weight and a highly reactive -N=C=O group [2]. Polyols, multifunctional alcohols, are polyesters or polyethers with multiple hydroxyl groups [1,3]. Among additional substances, essential in manufacturing of PU products, there are also catalysts such as diaminodiphenylmethane (MDA), triethylenediamine, triethylamine and cobalt, nickel, copper and lead salts [1].…”