Annals of Occupational Hygiene Advance Access published online on September 26, 2009
Annals of Occupational Hygiene, doi:10.1093/annhyg/mep067
Dermal and Inhalation Exposure to Methylene Bisphenyl Isocyanate (MDI) in Iron Foundry Workers
1 Occupational Medicine, Department of Public Health and Clinical Medicine, Umeå University, SE-901 87 Umeå, Sweden
2 Department of Occupational and Environmental Medicine, Örebro University Hospital, SE-701 85 Örebro, Sweden
3 Department of Natural Sciences, Örebro University, SE-701 82 Örebro, Sweden
4 IVL Swedish Environmental Research Institute Ltd, SE-100 31 Stockholm, Sweden
5 Department of Occupational and Environmental Medicine, University Hospital of Umeå, SE-901 85 Umeå, Sweden
6 Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
* Author to whom correspondence should be addressed. Tel: +46-90-785-24-52; fax: +46-90-785-24-56; e-mail: ingrid.liljelind{at}envmed.umu.se
Diisocyanates are a group of chemically reactive agents, which are used in the production of coatings, adhesives, polyurethane foams, and parts for the automotive industry and as curing agents for cores in the foundry industry. Dermal and inhalation exposure to methylene bisphenyl isocyanate (MDI) is associated with respiratory sensitization and occupational asthma. However, limited research has been performed on the quantitative evaluation of dermal and inhalation exposure to MDI in occupationally exposed workers. The objective of this research was to quantify dermal and inhalation exposure levels in iron foundry workers. Workers involved in mechanized moulding and mechanized production of cores were monitored: 12 core makers, 2 core-sand preparers, and 5 core installers. Personal breathing-zone levels of MDI were measured using impregnated filter sampling. Dermal exposure to MDI was measured using a tape-strip technique. Three or five consecutive tape-strip samples were collected from five exposed skin areas (right and left forefingers, left and right wrists, and forehead). The average personal air concentration was 0.55 µg m–3, 50-fold lower than the Swedish occupational exposure limit of 30 µg m–3. The core makers had an average exposure of 0.77 µg m–3, which was not significantly different from core installers’ and core-sand preparers’ average exposure of 0.16 µg m–3 (P = 0.059). Three core makers had a 10-fold higher inhalation exposure than the other core makers. The core makers’ mean dermal exposure at different skin sites varied from 0.13 to 0.34 µg while the two other groups’ exposure ranged from 0.006 to 0.062 µg. No significant difference was observed in the MDI levels between the skin sites in a pairwise comparison, except for left forefinger compared to left and right wrist (P < 0.05). In addition, quantifiable but decreasing levels of MDI were observed in the consecutive tape strip per site indicating MDI penetration into the skin. This study indicates that exposure to MDI can be quantified on workers’ skin even if air levels are close to unquantifiable. Thus, the potential for uncured MDI to deposit on and penetrate into the skin is demonstrated. Therefore, dermal exposure along with inhalation exposure to MDI should be measured in the occupational settings where MDI is present in order to shed light on their roles in the development of occupational isocyanate asthma.
dermal • diisocyanate • exposure • foundry workers • inhalation • methylene bisphenyl isocyanate (MDI)
Received March 26, 2009; in final form August 20, 2009