Annals of Occupational Hygiene Advance Access originally published online on August 26, 2005
Annals of Occupational Hygiene 2005 49(8):719-725; doi:10.1093/annhyg/mei040
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© 2005 British Occupational Hygiene Society Published by Oxford University Press
Original Article |
Exposure to Low Molecular Weight Isocyanates and Formaldehyde in Foundries Using Hot Box Core Binders
1 Department of Occupational and Environmental Medicine, Örebro University Hospital, SE-701 85 Örebro, Sweden; 2 Department of Public Health Sciences, Division of Occupational Medicine, Karolinska Institutet, SE-171 77 Stockholm, Sweden; 3 TMV-Environmental Consultant, Box 506 SE-541 28 Skövde, Sweden; 4 Swedish Foundry Association, Box 2033 SE-550 02 Jönköping, Sweden
* Author to whom correspondence should be addressed. Tel: +46-19-6022493; fax: +46-19-120404; e-mail: hakan.westberg{at}orebroll.se
Emissions from a chemical core binder system (Hot Box) based on a formaldehyde–carbamide resin have been investigated. The binder is used in some Swedish die-casting foundries. During core-making and casting, low molecular monoisocyanates, in particular methyl isocyanate (MIC) and isocyanic acid (ICA), were identified. Exposure to air concentrations of MIC, ICA and formaldehyde were subsequently determined in all Swedish foundries using the Hot Box binder, and involved three brass and one grey iron foundry. The survey was carried out in the winter period of 2001, and involved core-makers, casters and fettlers in the brass foundries, whereas only core-makers were included in the grey iron foundry. For each worker, four to five short-term samples of isocyanates (n = 298) and one 8 h sample of formaldehyde (n = 64) were collected during one shift for 15 die-casters, 39 core-makers and 10 other workers in the foundry. The air concentrations of the MIC short-term samples varied between <4 and 68 µg m–3, with corresponding ICA levels between <4 and 280 µg m–3. Calculated 8 h time weighted average air concentrations of MIC, based on short-term samples for each individual, varied between <4 and 31 µg m–3; for ICA the corresponding levels varied from <4 to 190 µg m–3. The formaldehyde time weighted average concentration levels ranged from 14 to 1600 µg m–3, and the Swedish occupational exposure limit (600 µg m–3) was exceeded only in 3% of the samples. In general, the core-makers were exposed to higher average formaldehyde levels compared to the casters, the latter being more exposed to monoisocyanates. During core-making and die-casting, low molecular monoisocyanates, in particular MIC and ICA, were identified. Compared to the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value-time weighted average (TLV-TWA) for MIC, the exposures were low. The lack of toxicological and human data for ICA and the relatively high air concentrations call for medical examination and preventive measures in production, ventilation and the use of personal safety equipment in the investigated foundries.
Keywords: casting • core-making • exposure • foundries • isocyanic acid • methyl isocyanate