Ann. occup. Hyg., Vol. 49, No. 8, pp. 719–725, 2005 # 2005 British Occupational Hygiene Society Published by Oxford University Press doi:10.1093/annhyg/mei040 Exposure to Low Molecular Weight Isocyanates and Formaldehyde in Foundries Using Hot Box Core Binders ˚ 1 ˚ ¨ 1,2 ´ 1 HAKAN WESTBERG *, HAKAN LOFSTEDT , ANDERS SELDEN , Downloaded from https://academic.oup.com/annweh/article/49/8/719/127584 by guest on 24 September 2021 BENGT-GUNNAR LILJA3 and PETER NAYSTRO¨ M4 1Department of Occupational and Environmental Medicine, O¨ rebro University Hospital, SE-701 85 O¨ rebro, Sweden; 2Department of Public Health Sciences, Division of Occupational Medicine, Karolinska Institutet, SE-171 77 Stockholm, Sweden; 3TMV-Environmental Consultant, Box 506 SE-541 28 Sko¨vde, Sweden; 4Swedish Foundry Association, Box 2033 SE-550 02 Jo¨nko¨ping, Sweden Received 7 April 2005; in final form 5 July 2005; published online 26 August 2005 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 mgmÀ3, with corresponding ICA levels between <4 and 280 mgmÀ3. Calculated 8 h time weighted average air concentrations of MIC, based on short-term samples for each indi- vidual, varied between <4 and 31 mgmÀ3; for ICA the corresponding levels varied from <4to 190 mgmÀ3. The formaldehyde time weighted average concentration levels ranged from 14 to 1600 mgmÀ3, and the Swedish occupational exposure limit (600 mgmÀ3) 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 INTRODUCTION bisphenyl diisocyanate (MDI; Archibald and Smith, 1988). During the thermal degradation of this binder, Exposure to isocyanates in iron, aluminium and metal monoisocyanates and diisocyanates could be formed, foundries has historically been associated with the use such as phenyl isocyanate and MDI (Renman et al., of isocyanate based chemical binders for core pro- 1986). Lately this has become true also for carbamide duction, the most common known as the Cold Box containing binders like the Hot Box system, and here process, using core binders containing methylene the monoisocyanates methyl isocyanate (MIC; CAS no 624-83-9) and isocyanic acid (ICA; CAS no *Author to whom correspondence should be addressed. Tel: +46-19-6022493; fax: +46-19-120404; 75-13-8) are emitted at high levels. In addition, e-mail: [email protected] monoisocyanates have been determined in a large 719 720 H. Westberg et al. number of new exposure situations in foundries, 40 workers) and in the grey iron foundry 24 core- including the use of Hot Box core-binders in static makers. Exposure measurements covering the whole die-casting foundries (Lilja et al., 1999). shifts were performed for all included workers, To specifically determine low air concentrations mostly (>90%) as 4–5 short-term samples of MIC of monoisocyanates, new analytical methods for and ICA. Formaldehyde was determined with diffu- the determination of low molecular isocyanates sive samplers (GMD) as full-shift samples. like ICA and MIC have been developed (Karlsson, 1998b; Spanne, 1999). Sampling and analysis Isocyanates are a group of chemically very reactive Sampling of isocyanates was performed by liquid agents; di-, poly- and prepolymerized isocyanates are chemosorption using impinger bottles, containing used to form polyurethanes. The industrial use of 0.01 M dibutylamine (DBA) dissolved in toluene Downloaded from https://academic.oup.com/annweh/article/49/8/719/127584 by guest on 24 September 2021 polyurethanes has increased drastically during the (Tinnerberg et al., 1997; Karlsson et al., 1998b). last decades (IARC, 1999a,b) and the products To adsorb fine particulate aerosol normally passing cover a wide range of industrial applications. Adverse through the adsorbing liquid, the impinger bottles health effects have been studied almost exclusively were connected to a cellulose ester filter with a for diisocyanates, the main effects are respiratory pore size of 0.3 mm. After the sampling, the filter disorders and irritative effects on the mucous mem- was introduced into the impinger bottle. The sam- branes (Baur et al., 1994). Little, if any knowledge pling flow was 1 l minÀ1 and the sampling was per- exists on exposure to monoisocyanates (MIC and formed with personal high-flow sampling pumps with ICA) and adverse health effects in industrial settings flow-rates between 1 and 5 l minÀ1. We used SKC (NIWL, 2002). 224-PCXR-9, SKC 224-PCXR-3, GILIAN HFS-513 In this study the exposures to MIC and ICA in and -113, MSA FLOW-LITE 34RI sampling pumps, Swedish foundries using Hot Box binders are and the air flow was controlled with calibrated described. The study includes core-makers, die- rotameters. Sampling of formaldehyde was carried casters and other workers in the foundry area. In out with diffusive samplers GMD, based on a reaction parallel to the exposure investigation, a study of res- between aldehydes and dinitrophenylhydrazine piratory symptoms and lung function was conducted (Levin et al., 1988). (reported elsewhere), and formaldehyde was, there- The analysis of formaldehyde was performed with fore, included in the monitoring programme of poten- high performance liquid chromatography techniques, tially harmful agents. the corresponding analysis of monoisocyanates and diisocyanates with liquid chromatography mass MATERIAL AND METHODS spectrometry techniques (Karlsson et al., 1998a). The detection concentration level for formaldehyde dur- À3 Study design ing an 8 h sampling is 20 mgm , and for methyl isocyanate and ICA 4 mgmÀ3 for 15 min short- The exposures to MIC, ICA and formaldehyde term sampling. All analyses were performed by were investigated in all four Swedish foundries the laboratory at the Department of Occupational using Hot Box binders, three small brass and one and Environmental Medicine, O¨ rebro University large grey iron foundry. The binder in use at all found- Hospital. The laboratory is accredited by the Swedish ries was based on a carbamide–formaldehyde resin Board for Accreditation and Conformity Assessment (<1% formaldehyde) and a curing agent containing (SBACA). ammonium nitrate (10–15%), urea and sodium hydroxide or water. The brass foundries were produc- ing armatures for households, and the grey iron foun- Statistical methods dry spare parts for the automobile industry. During The air concentrations for the individual ICA, MIC core production, both manual and enclosed automatic and formaldehyde samples were determined and 8 h core machines were used, and during die-casting time-weighted averages calculated for the total num- manually operated as well as enclosed robots were ber of measurements, different jobs and foundries. used. In the brass foundries, the alloy in use contained The data included a number of measurements (n), 62% copper, 32% zinc and 1–2% lead, in addition to and due to approximate log normal distributions of smaller amounts of aluminium and tin. The corres- air concentrations, the parameters of the air concen- ponding grey iron alloy contained 94% iron, 3% car- tration distributions were presented as the geometric bon, 2% silicone, 0.7% manganese, 0.3% chromium, mean (GM), and the corresponding geometric and 0.1% copper. The grey iron foundry was large, standard deviation (GSD). However, depending on producing some 75 000 ton per year, in contrast to the the further use of air concentration data, the arith- smaller brass foundries producing between 500 and metic mean and standard deviation were also 1000 ton per year. In the brass foundries, all core- presented (Seixas et al., 1988). Concentration values makers, die-casters and fettlers were included (in total less than the detection limits were estimated by Chemical pollutants in foundries 721 100 MIC 90 80 70 60 ICA % 50 40 30 Downloaded from https://academic.oup.com/annweh/article/49/8/719/127584 by guest on 24 September 2021 20 10 0 –24 25–48 49– –24 25–48 49– µg/m3 Fig. 1. Distribution of total short-term samples of methyl isocyanate (MIC) and isocyanic acid (ICA) air concentrations (mgmÀ3). pffiffiffi multiplying the detection limit by 1= 2 (Hornung Table 1. Exposure measurements, short-term samples of and Reed, 1990). Univariate ANOVA with a post hoc methyl isocyanate (MIC) and isocyanic acid (ICA), different test by Tukey (SPSS 12.0) was applied for ICA and foundries and job titles MIC with the different foundries and job titles as the Chemical agent Air concentration (mgmÀ3) explaining variables.