COD
Contact Dermatitis • Original Article
Contact Dermatitis
Screening occupational contact allergy to bisphenol F epoxy resin Kristiina Aalto-Korte1 , Katri Suuronen1 , Outi Kuuliala1 , Maj-Len Henriks-Eckerman2 and Riitta Jolanki1 1 Occupational Medicine, Finnish Institute of Occupational Health (FIOH), 00250 Helsinki, Finland and 2 Chemistry Laboratory, Finnish Institute of
Occupational Health (FIOH), 20520 Turku, Finland doi:10.1111/cod.12223
Summary
Background. Epoxy resins based on diglycidyl ether of bisphenol F (DGEBF) are widely used as such in applications requiring chemical resistance, and also together with diglycidyl ether of bisphenol A resin (DGEBA-R). Concomitant patch test reactions to DGEBA-R and DGEBF resin (DGEBF-R) are common. Previous studies have yielded conflicting results on the frequency of independent DGEBF-R contact allergies. Objectives. To report the results of over 11 years of screening with DGEBF-R. Methods. An in-house test substance of DGEBF-R (Epikote® 862) was tested in the baseline patch test series, first at 1% and later at 0.25%. Test files were screened for allergic reactions to DGEBF-R and DGEBA-R, and the clinical records of positively reacting patients were analysed for occupation and exposure. Results. Among 1972 patients, 66 (3.3%) reacted to DGEBF-R and 96 (4.9%) to DGEBA-R. Independent DGEBF-R allergies were seen in 5 patients only, and independent DGEBA-R allergies in 35. Specific exposure to DGEBF-R was found in 26 patients. The main occupational fields were the aircraft industry, the electrical and sports equipment industry, boat building, painting/floor coating, tile setting, and pipe relining. Conclusions. Independent contact allergies to DGEBF-R were rare, and screening with it was not found to be useful. Key words: composites; cross-allergy; diglycidyl ether of bisphenol A (DGEBA); diglycidyl ether of bisphenol F (DGEBF); Epikote® 862; patch test.
Epoxy resins are among the most important causes of occupational allergic contact dermatitis. Approximately 75% of the epoxy resins currently used worldwide are derived from diglycidyl ether of bisphenol A (DGEBA; CAS no. 1675-54-3; Fig. 1) (1). Epoxy resins based on diglycidyl ether of bisphenol F (DGEBF; bisphenol F epoxy resin; CAS no. 28064-14-4; Fig. 1) are also quite commonly used. DGEBF occurs as three different structural isomers: p,p -DGEBF, o,p -DGEBF, and o,o -DGEBF. All isomers are potent sensitizers in animal tests (2), and are
Correspondence: Kristiina Aalto-Korte, Occupational Medicine, Finnish Institute of Occupational Health (FIOH), Topeliuksenkatu 41 a A, FI00250 Helsinki, Finland. Tel: +358-30-4741; Fax: +358-9-5875 449. E-mail: [email protected] Conflict of interests: The authors declare no conflict of interests. Accepted for publication 22 January 2014
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commonly present in epoxy products (3). There is strong cross-reactivity between p,p -DGEBF, o,p -DGEBF, and DGEBA (2), and concomitant patch test reactions to DGEBF resin (DGEBF-R) and DGEBA resin (DGEBA-R, CAS no. 25068-38-6) are common in clinical patients, owing to cross-allergy or concomitant exposure (4–6). Some DGEBF-R-positive patients may not react to DGEBAR (4, 6–11), but data on the importance of this independent DGEBF-R allergy are somewhat conflicting: Swedish researchers have reported these patients in relatively large numbers (4), but in Germany independent allergies have been rare (6). At the Finnish Institute of Occupational Health (FIOH), DGEBF-R was included in the baseline patch test series in 1999, to be screened in all patch tested patients. The objective of this study was to report the results of this screening and describe the exposure of patients reacting to DGEBF-R.
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Contact Dermatitis, 71, 138–144
SCREENING WITH BISPHENOL F EPOXY RESIN • AALTO-KORTE ET AL.
CH3
O H2C
CH
CH2 O
O
C
O
CH2
CH2 HC
CH3
Diglycidyl ether of bisphenol A (DGEBA)
O H2C
O CH
CH2 O
O
CH2 HC
CH2
p,p'-Diglycidyl ether of bisphenol F (p,p'-DGEBF) H2C
O O
HC O
CH2
O
CH2 HC
CH2
CH2
O
o,p'-DGEBF
CH O CH2 O CH2
o,o'-DGEBF
CH O CH2 H2C
O
HC
Fig. 1. Chemical structures of diglycidyl ether of bisphenol A (DGEBA), three isomers of diglycidyl ether of bisphenol F (DGEBF), and DGEBF polymer.
Materials and Methods We performed the patch tests with Finn Chambers® (Epitest Ltd Oy, Tuusula, Finland), according to the recommendations of the ICDRG. We read the tests two or three times: on D2, D3, and D4, on D2, D3, and D6, or on D2 and D5, depending on the day of application. We asked patients to tell us whether they had noticed new reactions after the final reading. All patch tested patients at the FIOH have a suspected occupational skin disease. They come from all parts of Finland. Many of them have been patch tested in a local hospital prior to investigations at the FIOH. An in-house DGEBF-R test substance was included in the baseline series in November 1999. The substance was
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Contact Dermatitis, 71, 138–144
H2C
H2C
O
HC
O
HC
CH2
CH2
CH2
O
O
O
n DGEBF resin
prepared from Epikote® 862 (Resolution Europe B.V., Hoogvliet Rt, The Netherlands), which, according to the analyses performed in the Department of Occupational and Environmental Dermatology in Malm¨o, contains 30–38% p,p -DGEBF, 33–36% o,p -DGEBF, 12–13% o,o -DGEBF, and approximately 1–2% DGEBA (3, 6). The concentration of this in-house DGEBF-R test substance was initially 1% (petrolatum; Period I), and in August 2005 it was lowered to 0.25% (pet.; Period II). We screened the test files from November 1999 to May 2011 for allergic reactions to DGEBA-R and DGEBF-R. We included all patients with an allergic reaction (+/++/+++) to either of the compounds. Patients with previously diagnosed DGEBA-R allergy were also included. The patients’ clinical records were analysed for
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occupation, symptoms, safety data sheets (SDSs), results of the chemical analyses of their own products, patch test reactions to their own products, and diagnosis. For chemical analyses, samples of patients’ own epoxy materials were dissolved in acetone. Acetone soluble epoxy compounds were determined by gas chromatography with mass spectrometry (MS) detection. Epikote® 828 containing 89% DGEBA was used as an external standard for both DGEBF and DGEBA, and also for other aromatic epoxy compounds identified from MS spectra. Aliphatic glycidyl compounds were quantified by the use of pure standards. The epoxy products containing DGEBF-R that are on the market in Finland were gathered from the Product Register of Chemicals, which is maintained by the Finnish Safety and Chemicals Agency. For a chemical that is on the market or in use in Finland and poses a risk to health or to the environment, a chemical notification must be submitted; this is filed in the Chemical Products Register used by the Finnish Poison Information Centre and various authorities. Information on DGEBF-based products was gathered from the register, updated on 7 November 2013, according to substance by CAS number, that is, DGEBF resins without DGEBA (28064-14-4, 39817-099, or 87110-76-7), and resins containing a mixture of DGEBA and DGEBF (40216-08-8 or 9003-36-5).
the respective time period. A total of 92% of the DGEBFR-allergic patients had contact allergy to DGEBA-R, and 64% of the DGEBA-R-allergic patients reacted to DGEBFR. It is noteworthy that the frequency of DGEBA-R allergy was somewhat higher during Period II than during Period I (5.9% versus 4.3%). Only 5 patients reacted to DGEBF-R without having a clear concomitant allergic reaction to DGEBA-R. Three of these did not react to DGEBA-R, and 2 had doubtful (?+) reactions to DGEBA-R. All of these 5 patients were tested with a special epoxy patch test series at the same time as the baseline series was applied. Even if the DGEBF-R test substance had been included in the epoxy series and not in the baseline series, we would still have identified the 5 patients. Four patients were diagnosed with occupational allergic contact dermatitis caused by DGEBF-R, and their clinical details are presented as case reports below. The fifth patient, with a ?+ reaction to DGEBA-R, had experienced skin symptoms from splashes of an unidentified epoxy product in his former flooring work over 10 years before the investigations at the FIOH. Because he was not exposed to epoxy products in his present work, he was diagnosed with occupational contact allergy to DGEBF-R (as opposed to occupational allergic contact dermatitis caused by DGEBF-R).
Results
Case reports of DGEBF-R-allergic patients without clear DGEBA-R allergy
During the whole study period of 11.5 years, a total of 1972 patients were patch tested with the baseline series. Sixty-six (3.3%) patients had allergic reactions to DGEBFR and 90 (4.6%) patients had allergic reactions to DGEBAR. In addition, 6 patients had previously diagnosed contact allergy to DGEBA-R, and were not retested with this allergen at the FIOH, which increased the total number of DGEBA-R-allergic patients to 96 (4.9%). Table 1 shows the patch test results for the two different concentrations of DGEBF-R, and relates them to the total number of DGEBA-R-allergic patients during
Patient 1 was a 47-year-old male entrepreneur in the manufacture of reinforced plastic (products such as wind turbine rotor blades and snowmobile hoods). In 1999, he developed dermatitis on his hands, wrists, and face. He had handled two-component epoxy paint, epoxy carbon fibre, and SP Ampreg® 20 resin (SP Systems Ltd, Cowes, Isle of Wight, UK). Inquiries to the manufacturer revealed that the resin part of SP Ampreg® 20 contained 46% DGEBA, and also DGEBF, alkyl glycidyl ether, and 1,6-hexanediol glycidyl ether, and that the hardener contained xylylene diamine. On patch testing in 2003, the patient had allergic
Table 1. Patch test results of screening with diglycidyl ether of bisphenol F resin (DGEBF-R) in the baseline series. During Period I, the test
concentration was 1% pet., and during Period II it was 0.25% pet. DGEBF results are related to the total number of diglycidy lether of bisphenol A resin (DGEBA-R)-allergic patients
Time period Period I: DGEBFR 1% Period II: DGEBFR 0.25% Whole study period: DGEBFR 1% or DGEBFR 0.25%
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No. of patients tested with the baseline series 1198 774 1972
No. (%) of allergic reactions to DGEBF-R
Total no. (%) of DGEBA-R-allergic patients during the same time period
No. (%) of patients with concomitant contact allergy to DGEBA-R and DGEBF-R
32 (2.7) 34 (4.4) 66 (3.3)
51 (4.3) 45 (5.9) 96 (4.9)
29 (91) 32 (94) 61 (92)
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SCREENING WITH BISPHENOL F EPOXY RESIN • AALTO-KORTE ET AL.
reactions to 1% DGEBF-R (+), xylylene diamine (++), and SP Ampreg® 20 resin (++). He did not react to to DGEBAR. He was diagnosed with occupational allergic dermatitis caused by DGEBF-R and xylylene diamine. Patient 2 was a 50-year-old assembler working in the production of composite parts for aero technical applications and measuring devices. He developed hand dermatitis in 2000, soon after he started the work. He handled various epoxy products for gluing, laminating, and casting, and also prepreg products. On patch testing in 2004, he reacted to 1% DGEBF-R (+), butanediol diglycidyl ether (++), N,N-diglycidyl-4-glycidyloxyaniline (TGPAP; +), and Araldite® LY 5052 epoxy resin (2%, ++; 1%, ++; Huntsman Advanced Materials, Everberg, Belgium). He did not react to DGEBA-R. According to chemical analysis at the FIOH, Araldite® LY 5052 contained 33% butanediol diglycidyl ether, 18% DGEBF, 0.2% DGEBA, and 0.2% phenyl glycidyl ether. TGPAP was not found in the products available for analysis, but the patient had handled prepreg products, which are known to often contain this compound (12). He was diagnosed as having occupational allergic contact dermatitis caused by butanediol diglycidyl ether and DGEBF-R, and occupational contact allergy to TGPAP. Patient 3 was a 50-year-old female composite worker employed in the production of ice hockey sticks. She had handled epoxy glues for 5 years without any skin symptoms. In 2007, she developed dermatitis, first on her eyelids, and later on other parts of her face and on her forearms. This happened soon after she had started to work on the production of mandrels, in which a new product, Hybtonite® Fusion G4 (Amroy Europe Oy, Lahti, Finland), had been introduced for trial. The symptoms resolved when she returned to her previous work, in which Hybtonite® RTM resin was used (Amroy Europe Oy). On patch testing in 2007, she reacted to 0.25% DGEBF (+), Hybtonite® RTM epoxy resin (1%, ++; 0.32%, +; 0.1%, +), Epopox® A28 epoxy resin (+; Amroy Europe Oy), and carbon fibre (+). She did not react to DGEBA-R. Her products were analysed at the FIOH: Hybtonite® Fusion G4 epoxy resin contained 37% DGEBF, 27% DGEBA, 0.04% phenyl glycidyl ether, and 3% cresyl glycidyl ether; Hybtonite® RTM contained 48% DGEBF, 33% DGEBA, and 0.04% phenyl glycidyl ether (the SDS declared only DGEBA resin 90–100%); Epopox® A28 contained 82% DGEBA and no DGEBF, and the carbon fibre contained 0.5% DGEBA. The weak reactions to the latter two products were possibly false allergic reactions. The patient stopped working with all epoxy products, and remained symptom-free. Her diagnosis was occupational allergic contact dermatitis caused by DGEBF-R.
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Contact Dermatitis, 71, 138–144
Patient 4 was a 43-year-old male impregnation worker employed in the manufacture of electrical machines. In 2007, he developed dermatitis on the hands and forearms. He handled XD® 4159 epoxy resin (Isovolta, Wiener Neudorf, Austria) for impregnation. On patch testing in 2008, he reacted to 1% DGEBF (+), DGEBA (?+), and XD® 4159 (1%, +; 0.32%, ?+). According to the SDS, the last of these contained an epoxy resin based on bisphenol A and bisphenol F. The patient was diagnosed with occupational allergic contact dermatitis caused by DGEBF-R. Patients with concomitant contact allergy to DGEBF and DGEBA resins
Table 2 shows 45 patients with concomitant occupational contact allergy to DGEBF-R and DGEBA-R for whom it was possible to assess the exposure to epoxy products in detail. Exposure to DGEBF-R was identified by CAS numbers 28064-14-4, 87110-76-7, 39817-09-9, 9003-36-5 and 40216-08-8 in the SDSs. In 3 cases, exposure was detected by analysing the worksite’s epoxy products for DGEBF. Eight of the DGEBF-R-allergic patients with concomitant allergy to DGEBA-R were not being and had not been exposed to any epoxy compounds at work. Some of them had handled epoxy products (specific composition not retrieved) at home, but, in most cases, the source of the sensitization remained unknown. In addition, 8 patients had been exposed to epoxy compounds in their work, but it was no longer possible to obtain detailed information on the exposure. Epoxy products containing DGEBF-R on the Finnish market
According to the chemical notifications filed in the Finnish Product Register of Chemicals, a total of 264 products containing DGEBF-R were on the market in Finland at the end of 2013: CAS no. 28064-14-4 (117 products), CAS no. 39817-09-9 (zero products), CAS no. 87110-76-7 (four products), CAS no. 40216-08-8 (29 products), and CAS no. 9003-36-5 (116 products). Only 27 (10.2%) of these did not contain DGEBA-R components with CAS no. 1675-54-3 (DGEBA), CAS no. 25068-38-6 (DGEBA-R), CAS no. 25085-99-8 (DGEBA-R), CAS no. 40216-08-8 (DGEBA/F-R), or CAS no. 9003-36-5 (DGEBA-R/DGEBFR). The purposes of the products are shown in Table 3.
Discussion Chemical products containing DGEBF resins are quite widely used, and may often be found in metal or concrete paints, lacquers and other coating agents, adhesives, glues, bonding agents, flooring products, composite
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Table 2. Patients with concomitant occupational contact allergy to diglycidyl ether of bisphenol F (DGEBF) resin and diglycidyl ether of
bisphenol A (DGEBA) resin, whose exposure to epoxy products could be assessed in detail: occupational fields or occupations, number of sensitized patients, number of patients with identified exposure to DGEBF products, and types of DGEBF-containing product in each occupational field No. of patients with DGEBF resin allergy
No. of patients with identified exposure to DGEBF-containing products
Aircraft industry Sewage pipe relining Manufacture of sports equipment
4 2 3
3 2 1
Boat building Manufacture of electrical machines Tile setting Painters/floor layers Electronics Manufacture of door frames
4 3 4 10 1 1
3 2 3 4 1 1
Lamination of tanks and pipes Foundry work Production of paints Manufacture of fibreglass Metalwork Dentist/dental nurse Laboratory nurse Laboratory in printing industry Maintenance of machines Total
1 1 2 2 1 2 2 1 1 45
1 1 – – – – – – – 22
Occupational field or occupation
materials, and injection resins used to repair concrete cracks. As far as we are aware, the screening of consecutive patients with DGEBF-R has only previously been reported from Malm¨o (4). In this Swedish study, of a total ¨ of 1299 patients tested with 1% DGEBF-R (Rutapox 0161; Bakelite, Duisburg, Germany), 22 (1.7%) reacted positively, and 13 had concomitant allergic reactions to DGEBA-R. Nine of the DGEBF-R-allergic patients did not react to DGEBA-R, and only one DGEBA-R-positive patient did not react to DGEBF-R. One of the DGEBFR-positive patients had handled composite material, which, according to the SDS, was impregnated with epoxy novolac resin (mainly DGEBF). In our study population, the prevalence of positive patch test reactions was almost double that in the above study. In Malm¨o, general dermatology patients were also tested, whereas at the FIOH, all patients were investigated for a possible occupational disease. In Malm¨o, the number of DGEBFR-positive patients exceeded the number of DGEBA-Rpositive patients (22 versus 14), but at the FIOH the opposite was true (66 versus 96). Consequently, at the FIOH, the proportion of patients with independent DGEBA-R allergy among all DGEBF-R-positive and DGEBA-R-positive cases was much larger (35% versus 4%), and the proportion of patients with DGEBF-R reactions was much smaller (5% versus 39%).
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Types of DGEBFcontaining product Adhesives, epoxy film Sealing product Hybtonite® RTM epoxy resin (same as Patient 3) Adhesive, filler, resin Resin Seaming materials Floor paints, filler Glue Two-component filler: 4.4% DGEBF and 0.04% DGEBA (13) Glue Resin – – – – – – – –
In Malm¨o, further screening with epoxy resin of the bisphenol F type (0.25% pet.) was performed in connection with a phenyl glycidyl ether study on 2227 patients, and detected 23 (1%) patients with contact allergy to DGEBA-R and 19 (0.9%) patients with contact allergy to bisphenol F-based epoxy resin (14). The number of independent allergies to bisphenol F-based resin and exposure data were not given, but the number of DGEBA-R reactions exceeded the number of DGEBF-R reactions. In a multicentre study, EPOX 2002, with 0.25% DGEBF-R, was tested in 87 patients with either previously diagnosed DGEBA-R allergy or with suspected contact allergy to epoxy compounds (6). In agreement with our results and the later results from Malm¨o, the number of DGEBA-R reactions exceeded the number of DGEBF-R reactions, and independent reactions to DGEBF-R were quite rare. In the United States, 41 DGEBA-R-allergic patients were tested with four different bisphenol F-based products, and all reacted to at least one of the products. The individual products gave positive results in 93–95% of the patients (5). At the FIOH, the test concentration of DGEBF-R was lowered in the middle of the study period. During Period I, when 1% was used, the frequency of positive reactions (2.7%) was lower than during Period II (4.4%), when a
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SCREENING WITH BISPHENOL F EPOXY RESIN • AALTO-KORTE ET AL.
Table 3. Products containing diglycidyl ether of bisphenol F resin
(DGEBF-R) on the market in Finland at the beginning of 2014 according to their purpose, and products that also contain diglycidyl ether of bisphenol A resin (DGEBA-R) according to chemical notifications filed with the Finnish Product Register of Chemicals at the beginning of 2014
Products by purpose Composite materials Paints and lacquers Epoxy resins Other coating agents Adhesives and glues Flooring products Bonding agents Injection resins for repairing concrete cracks Pigment dispersions Primers Filling agents Casting resins Laminating resins Others Total
Products with DGEBF-R but without DGEBA-R
Products with DGEBF-R and DGEBA-R
7 6 5 4 < 4∗ < 4∗ < 4∗ < 4∗
5 45 8 33 44 28 11 10
< 4∗ < 4∗ < 4∗ < 4∗ < 4∗ < 4∗ 27
9 9 7 6 6 16 237
∗ According to the principles of the register, numbers smaller than 4 are not published.
lower concentration of 0.25% was used. However, the number of DGEBA-R-allergic patients was also higher during Period II, explaining most of the difference. The same proportion of DGEBF-R-allergic patients had concomitant allergy to DGEBA-R (Table 1). The slightly higher proportion of DGEBF-R-positive patients among the DGEBA-R-positive patients (71% in Period II and 57% in Period I) might indicate some increase in exposure to DGEBF-R during Period II as compared with Period I. Analysis of exposure data for our DGEBF-allergic patients gives some support to this speculation: during Period I, 31% of patients were specifically exposed to DGEBF products, and during Period II the proportion was 50%. Despite the above-mentioned studies (4, 6), patients with reactions to DGEBF-R without reactions to DGEBA-R have been reported only rarely. Kanerva et al. described a worker in an electrical factory who had handled insulating tape that contained phenol novolac epoxy resin. The patient, who was investigated in 1980, reacted to the tape but not to DGEBA-R in the baseline series or to allergens in the plastic and glue series (7). The allergen was probably DGEBF-R, although it was not tested separately. Bruze et al. described 3 workers in an aircraft plant who reacted to epoxy novolac (mainly DGEBF-R) and an adhesive for composite bonding that contained epoxy novolac. Only 1 of the 3 patients reacted to DGEBA-R (8). In Australia, a worker in a plant manufacturing adhesives developed eyelid dermatitis and reacted to bisphenol F
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Contact Dermatitis, 71, 138–144
epoxy resin (Araldite® GY 281), but not to DGEBA-R (9). In Taiwan, five subway construction workers were patch tested, and 3 of them reacted to resins of the bisphenol F type, but only 1 reacted to DGEBA-R. They had used a product that contained 30–40% DGEBA-R and < 15% bisphenol F epoxy resin (10). A study of workers in a plant producing wind turbine rotor blades found 2 cases of independent allergy to DGEBF-R. In addition, 34 workers reacted to DGEBA-R, 24 of whom also reacted to DGEBFR. The products based on DGEBF were mainly used for the repair and finish of the blades, but the exposure of the individual workers was not described (11). Pont´en and Bruze also described a tiler who had handled a putty that contained DGEBF-R and DGEBA-R, and reacted to epoxy novolac resin on patch testing down to a concentration of 0.00016%. He also reacted to DGEBA-R (15). In the present study population, 26 workers who were allergic to the compound were specifically exposed to DGEBF-R products. Several patients worked in the aircraft industry, the electrical industry, boat building, painting/floor coating, tile setting, sewage pipe relining, and the sports equipment industry. Other types of industry included foundry work, the manufacture of door frames, the lamination of pipes and tanks, electronic work, and the manufacture of reinforced plastic and composite parts. The safety data sheets for the epoxy did not always declare the presence of bisphenol F epoxy resins, and we needed to analyse them. DGEBF-R-containing products usually also contain DGEBA-R, and co-exposure to DGEBA-R was identified in nearly all of the DGEBF-R-positive patients in Table 2. The only exception was a dentist who had handled dental composite resins based on epoxyacrylates (these products were not analysed for DGEBA-R or DGEBF-R). Geier et al. (6) did not recommend routine testing of DGEBF-R, even in a special series, because of the low number of independent reactions and the risk of patch test sensitization [three cases sensitized by a concentration of 1% were described by Pont´en and Bruze (4)]. We are not aware of any active sensitizations to DGEBF-R among our patients. We stopped screening our patients with DGEBF-R in the baseline series, because it did not help us to identify those with independent allergy any better than aimed testing. All of the patients with an independent allergy were clearly exposed to epoxy products, and were therefore tested with the specific epoxy series. However, we continue to perform aimed testing of DGEBF-R, because we want to determine the exact allergen whenever possible, and the diagnosis of occupational allergic contact dermatitis of 2 of our patients was based on the reaction to DGEBF-R only. In conclusion, concomitant allergy to DGEBF-R and DGEBA-R is common, owing to cross-allergy or
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simultaneous exposure, but independent contact allergies to DGEBF-R are rare, despite the high number of products with DGEBF on the market. Thus, screening with DGEBFR was not found to be useful. DGEBA-R allergy is usually more common than allergy to DGEBF-R. Independent reactions to DGEBF-R occur especially in workers handling composite products, but they are relatively rare. In some cases, the diagnosis of occupational allergic
contact dermatitis requires testing with DGEBF-R or with the patients’ own DGEBF-based products.
Acknowledgements The study was financially supported by the Finnish Work Environment Fund.
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Contact Dermatitis • Original Article
Contact Dermatitis
Screening occupational contact allergy to bisphenol F epoxy resin Kristiina Aalto-Korte1 , Katri Suuronen1 , Outi Kuuliala1 , Maj-Len Henriks-Eckerman2 and Riitta Jolanki1 1 Occupational Medicine, Finnish Institute of Occupational Health (FIOH), 00250 Helsinki, Finland and 2 Chemistry Laboratory, Finnish Institute of
Occupational Health (FIOH), 20520 Turku, Finland doi:10.1111/cod.12223
Summary
Background. Epoxy resins based on diglycidyl ether of bisphenol F (DGEBF) are widely used as such in applications requiring chemical resistance, and also together with diglycidyl ether of bisphenol A resin (DGEBA-R). Concomitant patch test reactions to DGEBA-R and DGEBF resin (DGEBF-R) are common. Previous studies have yielded conflicting results on the frequency of independent DGEBF-R contact allergies. Objectives. To report the results of over 11 years of screening with DGEBF-R. Methods. An in-house test substance of DGEBF-R (Epikote® 862) was tested in the baseline patch test series, first at 1% and later at 0.25%. Test files were screened for allergic reactions to DGEBF-R and DGEBA-R, and the clinical records of positively reacting patients were analysed for occupation and exposure. Results. Among 1972 patients, 66 (3.3%) reacted to DGEBF-R and 96 (4.9%) to DGEBA-R. Independent DGEBF-R allergies were seen in 5 patients only, and independent DGEBA-R allergies in 35. Specific exposure to DGEBF-R was found in 26 patients. The main occupational fields were the aircraft industry, the electrical and sports equipment industry, boat building, painting/floor coating, tile setting, and pipe relining. Conclusions. Independent contact allergies to DGEBF-R were rare, and screening with it was not found to be useful. Key words: composites; cross-allergy; diglycidyl ether of bisphenol A (DGEBA); diglycidyl ether of bisphenol F (DGEBF); Epikote® 862; patch test.
Epoxy resins are among the most important causes of occupational allergic contact dermatitis. Approximately 75% of the epoxy resins currently used worldwide are derived from diglycidyl ether of bisphenol A (DGEBA; CAS no. 1675-54-3; Fig. 1) (1). Epoxy resins based on diglycidyl ether of bisphenol F (DGEBF; bisphenol F epoxy resin; CAS no. 28064-14-4; Fig. 1) are also quite commonly used. DGEBF occurs as three different structural isomers: p,p -DGEBF, o,p -DGEBF, and o,o -DGEBF. All isomers are potent sensitizers in animal tests (2), and are
Correspondence: Kristiina Aalto-Korte, Occupational Medicine, Finnish Institute of Occupational Health (FIOH), Topeliuksenkatu 41 a A, FI00250 Helsinki, Finland. Tel: +358-30-4741; Fax: +358-9-5875 449. E-mail: [email protected] Conflict of interests: The authors declare no conflict of interests. Accepted for publication 22 January 2014
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commonly present in epoxy products (3). There is strong cross-reactivity between p,p -DGEBF, o,p -DGEBF, and DGEBA (2), and concomitant patch test reactions to DGEBF resin (DGEBF-R) and DGEBA resin (DGEBA-R, CAS no. 25068-38-6) are common in clinical patients, owing to cross-allergy or concomitant exposure (4–6). Some DGEBF-R-positive patients may not react to DGEBAR (4, 6–11), but data on the importance of this independent DGEBF-R allergy are somewhat conflicting: Swedish researchers have reported these patients in relatively large numbers (4), but in Germany independent allergies have been rare (6). At the Finnish Institute of Occupational Health (FIOH), DGEBF-R was included in the baseline patch test series in 1999, to be screened in all patch tested patients. The objective of this study was to report the results of this screening and describe the exposure of patients reacting to DGEBF-R.
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SCREENING WITH BISPHENOL F EPOXY RESIN • AALTO-KORTE ET AL.
CH3
O H2C
CH
CH2 O
O
C
O
CH2
CH2 HC
CH3
Diglycidyl ether of bisphenol A (DGEBA)
O H2C
O CH
CH2 O
O
CH2 HC
CH2
p,p'-Diglycidyl ether of bisphenol F (p,p'-DGEBF) H2C
O O
HC O
CH2
O
CH2 HC
CH2
CH2
O
o,p'-DGEBF
CH O CH2 O CH2
o,o'-DGEBF
CH O CH2 H2C
O
HC
Fig. 1. Chemical structures of diglycidyl ether of bisphenol A (DGEBA), three isomers of diglycidyl ether of bisphenol F (DGEBF), and DGEBF polymer.
Materials and Methods We performed the patch tests with Finn Chambers® (Epitest Ltd Oy, Tuusula, Finland), according to the recommendations of the ICDRG. We read the tests two or three times: on D2, D3, and D4, on D2, D3, and D6, or on D2 and D5, depending on the day of application. We asked patients to tell us whether they had noticed new reactions after the final reading. All patch tested patients at the FIOH have a suspected occupational skin disease. They come from all parts of Finland. Many of them have been patch tested in a local hospital prior to investigations at the FIOH. An in-house DGEBF-R test substance was included in the baseline series in November 1999. The substance was
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Contact Dermatitis, 71, 138–144
H2C
H2C
O
HC
O
HC
CH2
CH2
CH2
O
O
O
n DGEBF resin
prepared from Epikote® 862 (Resolution Europe B.V., Hoogvliet Rt, The Netherlands), which, according to the analyses performed in the Department of Occupational and Environmental Dermatology in Malm¨o, contains 30–38% p,p -DGEBF, 33–36% o,p -DGEBF, 12–13% o,o -DGEBF, and approximately 1–2% DGEBA (3, 6). The concentration of this in-house DGEBF-R test substance was initially 1% (petrolatum; Period I), and in August 2005 it was lowered to 0.25% (pet.; Period II). We screened the test files from November 1999 to May 2011 for allergic reactions to DGEBA-R and DGEBF-R. We included all patients with an allergic reaction (+/++/+++) to either of the compounds. Patients with previously diagnosed DGEBA-R allergy were also included. The patients’ clinical records were analysed for
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occupation, symptoms, safety data sheets (SDSs), results of the chemical analyses of their own products, patch test reactions to their own products, and diagnosis. For chemical analyses, samples of patients’ own epoxy materials were dissolved in acetone. Acetone soluble epoxy compounds were determined by gas chromatography with mass spectrometry (MS) detection. Epikote® 828 containing 89% DGEBA was used as an external standard for both DGEBF and DGEBA, and also for other aromatic epoxy compounds identified from MS spectra. Aliphatic glycidyl compounds were quantified by the use of pure standards. The epoxy products containing DGEBF-R that are on the market in Finland were gathered from the Product Register of Chemicals, which is maintained by the Finnish Safety and Chemicals Agency. For a chemical that is on the market or in use in Finland and poses a risk to health or to the environment, a chemical notification must be submitted; this is filed in the Chemical Products Register used by the Finnish Poison Information Centre and various authorities. Information on DGEBF-based products was gathered from the register, updated on 7 November 2013, according to substance by CAS number, that is, DGEBF resins without DGEBA (28064-14-4, 39817-099, or 87110-76-7), and resins containing a mixture of DGEBA and DGEBF (40216-08-8 or 9003-36-5).
the respective time period. A total of 92% of the DGEBFR-allergic patients had contact allergy to DGEBA-R, and 64% of the DGEBA-R-allergic patients reacted to DGEBFR. It is noteworthy that the frequency of DGEBA-R allergy was somewhat higher during Period II than during Period I (5.9% versus 4.3%). Only 5 patients reacted to DGEBF-R without having a clear concomitant allergic reaction to DGEBA-R. Three of these did not react to DGEBA-R, and 2 had doubtful (?+) reactions to DGEBA-R. All of these 5 patients were tested with a special epoxy patch test series at the same time as the baseline series was applied. Even if the DGEBF-R test substance had been included in the epoxy series and not in the baseline series, we would still have identified the 5 patients. Four patients were diagnosed with occupational allergic contact dermatitis caused by DGEBF-R, and their clinical details are presented as case reports below. The fifth patient, with a ?+ reaction to DGEBA-R, had experienced skin symptoms from splashes of an unidentified epoxy product in his former flooring work over 10 years before the investigations at the FIOH. Because he was not exposed to epoxy products in his present work, he was diagnosed with occupational contact allergy to DGEBF-R (as opposed to occupational allergic contact dermatitis caused by DGEBF-R).
Results
Case reports of DGEBF-R-allergic patients without clear DGEBA-R allergy
During the whole study period of 11.5 years, a total of 1972 patients were patch tested with the baseline series. Sixty-six (3.3%) patients had allergic reactions to DGEBFR and 90 (4.6%) patients had allergic reactions to DGEBAR. In addition, 6 patients had previously diagnosed contact allergy to DGEBA-R, and were not retested with this allergen at the FIOH, which increased the total number of DGEBA-R-allergic patients to 96 (4.9%). Table 1 shows the patch test results for the two different concentrations of DGEBF-R, and relates them to the total number of DGEBA-R-allergic patients during
Patient 1 was a 47-year-old male entrepreneur in the manufacture of reinforced plastic (products such as wind turbine rotor blades and snowmobile hoods). In 1999, he developed dermatitis on his hands, wrists, and face. He had handled two-component epoxy paint, epoxy carbon fibre, and SP Ampreg® 20 resin (SP Systems Ltd, Cowes, Isle of Wight, UK). Inquiries to the manufacturer revealed that the resin part of SP Ampreg® 20 contained 46% DGEBA, and also DGEBF, alkyl glycidyl ether, and 1,6-hexanediol glycidyl ether, and that the hardener contained xylylene diamine. On patch testing in 2003, the patient had allergic
Table 1. Patch test results of screening with diglycidyl ether of bisphenol F resin (DGEBF-R) in the baseline series. During Period I, the test
concentration was 1% pet., and during Period II it was 0.25% pet. DGEBF results are related to the total number of diglycidy lether of bisphenol A resin (DGEBA-R)-allergic patients
Time period Period I: DGEBFR 1% Period II: DGEBFR 0.25% Whole study period: DGEBFR 1% or DGEBFR 0.25%
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No. of patients tested with the baseline series 1198 774 1972
No. (%) of allergic reactions to DGEBF-R
Total no. (%) of DGEBA-R-allergic patients during the same time period
No. (%) of patients with concomitant contact allergy to DGEBA-R and DGEBF-R
32 (2.7) 34 (4.4) 66 (3.3)
51 (4.3) 45 (5.9) 96 (4.9)
29 (91) 32 (94) 61 (92)
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reactions to 1% DGEBF-R (+), xylylene diamine (++), and SP Ampreg® 20 resin (++). He did not react to to DGEBAR. He was diagnosed with occupational allergic dermatitis caused by DGEBF-R and xylylene diamine. Patient 2 was a 50-year-old assembler working in the production of composite parts for aero technical applications and measuring devices. He developed hand dermatitis in 2000, soon after he started the work. He handled various epoxy products for gluing, laminating, and casting, and also prepreg products. On patch testing in 2004, he reacted to 1% DGEBF-R (+), butanediol diglycidyl ether (++), N,N-diglycidyl-4-glycidyloxyaniline (TGPAP; +), and Araldite® LY 5052 epoxy resin (2%, ++; 1%, ++; Huntsman Advanced Materials, Everberg, Belgium). He did not react to DGEBA-R. According to chemical analysis at the FIOH, Araldite® LY 5052 contained 33% butanediol diglycidyl ether, 18% DGEBF, 0.2% DGEBA, and 0.2% phenyl glycidyl ether. TGPAP was not found in the products available for analysis, but the patient had handled prepreg products, which are known to often contain this compound (12). He was diagnosed as having occupational allergic contact dermatitis caused by butanediol diglycidyl ether and DGEBF-R, and occupational contact allergy to TGPAP. Patient 3 was a 50-year-old female composite worker employed in the production of ice hockey sticks. She had handled epoxy glues for 5 years without any skin symptoms. In 2007, she developed dermatitis, first on her eyelids, and later on other parts of her face and on her forearms. This happened soon after she had started to work on the production of mandrels, in which a new product, Hybtonite® Fusion G4 (Amroy Europe Oy, Lahti, Finland), had been introduced for trial. The symptoms resolved when she returned to her previous work, in which Hybtonite® RTM resin was used (Amroy Europe Oy). On patch testing in 2007, she reacted to 0.25% DGEBF (+), Hybtonite® RTM epoxy resin (1%, ++; 0.32%, +; 0.1%, +), Epopox® A28 epoxy resin (+; Amroy Europe Oy), and carbon fibre (+). She did not react to DGEBA-R. Her products were analysed at the FIOH: Hybtonite® Fusion G4 epoxy resin contained 37% DGEBF, 27% DGEBA, 0.04% phenyl glycidyl ether, and 3% cresyl glycidyl ether; Hybtonite® RTM contained 48% DGEBF, 33% DGEBA, and 0.04% phenyl glycidyl ether (the SDS declared only DGEBA resin 90–100%); Epopox® A28 contained 82% DGEBA and no DGEBF, and the carbon fibre contained 0.5% DGEBA. The weak reactions to the latter two products were possibly false allergic reactions. The patient stopped working with all epoxy products, and remained symptom-free. Her diagnosis was occupational allergic contact dermatitis caused by DGEBF-R.
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Contact Dermatitis, 71, 138–144
Patient 4 was a 43-year-old male impregnation worker employed in the manufacture of electrical machines. In 2007, he developed dermatitis on the hands and forearms. He handled XD® 4159 epoxy resin (Isovolta, Wiener Neudorf, Austria) for impregnation. On patch testing in 2008, he reacted to 1% DGEBF (+), DGEBA (?+), and XD® 4159 (1%, +; 0.32%, ?+). According to the SDS, the last of these contained an epoxy resin based on bisphenol A and bisphenol F. The patient was diagnosed with occupational allergic contact dermatitis caused by DGEBF-R. Patients with concomitant contact allergy to DGEBF and DGEBA resins
Table 2 shows 45 patients with concomitant occupational contact allergy to DGEBF-R and DGEBA-R for whom it was possible to assess the exposure to epoxy products in detail. Exposure to DGEBF-R was identified by CAS numbers 28064-14-4, 87110-76-7, 39817-09-9, 9003-36-5 and 40216-08-8 in the SDSs. In 3 cases, exposure was detected by analysing the worksite’s epoxy products for DGEBF. Eight of the DGEBF-R-allergic patients with concomitant allergy to DGEBA-R were not being and had not been exposed to any epoxy compounds at work. Some of them had handled epoxy products (specific composition not retrieved) at home, but, in most cases, the source of the sensitization remained unknown. In addition, 8 patients had been exposed to epoxy compounds in their work, but it was no longer possible to obtain detailed information on the exposure. Epoxy products containing DGEBF-R on the Finnish market
According to the chemical notifications filed in the Finnish Product Register of Chemicals, a total of 264 products containing DGEBF-R were on the market in Finland at the end of 2013: CAS no. 28064-14-4 (117 products), CAS no. 39817-09-9 (zero products), CAS no. 87110-76-7 (four products), CAS no. 40216-08-8 (29 products), and CAS no. 9003-36-5 (116 products). Only 27 (10.2%) of these did not contain DGEBA-R components with CAS no. 1675-54-3 (DGEBA), CAS no. 25068-38-6 (DGEBA-R), CAS no. 25085-99-8 (DGEBA-R), CAS no. 40216-08-8 (DGEBA/F-R), or CAS no. 9003-36-5 (DGEBA-R/DGEBFR). The purposes of the products are shown in Table 3.
Discussion Chemical products containing DGEBF resins are quite widely used, and may often be found in metal or concrete paints, lacquers and other coating agents, adhesives, glues, bonding agents, flooring products, composite
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Table 2. Patients with concomitant occupational contact allergy to diglycidyl ether of bisphenol F (DGEBF) resin and diglycidyl ether of
bisphenol A (DGEBA) resin, whose exposure to epoxy products could be assessed in detail: occupational fields or occupations, number of sensitized patients, number of patients with identified exposure to DGEBF products, and types of DGEBF-containing product in each occupational field No. of patients with DGEBF resin allergy
No. of patients with identified exposure to DGEBF-containing products
Aircraft industry Sewage pipe relining Manufacture of sports equipment
4 2 3
3 2 1
Boat building Manufacture of electrical machines Tile setting Painters/floor layers Electronics Manufacture of door frames
4 3 4 10 1 1
3 2 3 4 1 1
Lamination of tanks and pipes Foundry work Production of paints Manufacture of fibreglass Metalwork Dentist/dental nurse Laboratory nurse Laboratory in printing industry Maintenance of machines Total
1 1 2 2 1 2 2 1 1 45
1 1 – – – – – – – 22
Occupational field or occupation
materials, and injection resins used to repair concrete cracks. As far as we are aware, the screening of consecutive patients with DGEBF-R has only previously been reported from Malm¨o (4). In this Swedish study, of a total ¨ of 1299 patients tested with 1% DGEBF-R (Rutapox 0161; Bakelite, Duisburg, Germany), 22 (1.7%) reacted positively, and 13 had concomitant allergic reactions to DGEBA-R. Nine of the DGEBF-R-allergic patients did not react to DGEBA-R, and only one DGEBA-R-positive patient did not react to DGEBF-R. One of the DGEBFR-positive patients had handled composite material, which, according to the SDS, was impregnated with epoxy novolac resin (mainly DGEBF). In our study population, the prevalence of positive patch test reactions was almost double that in the above study. In Malm¨o, general dermatology patients were also tested, whereas at the FIOH, all patients were investigated for a possible occupational disease. In Malm¨o, the number of DGEBFR-positive patients exceeded the number of DGEBA-Rpositive patients (22 versus 14), but at the FIOH the opposite was true (66 versus 96). Consequently, at the FIOH, the proportion of patients with independent DGEBA-R allergy among all DGEBF-R-positive and DGEBA-R-positive cases was much larger (35% versus 4%), and the proportion of patients with DGEBF-R reactions was much smaller (5% versus 39%).
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Types of DGEBFcontaining product Adhesives, epoxy film Sealing product Hybtonite® RTM epoxy resin (same as Patient 3) Adhesive, filler, resin Resin Seaming materials Floor paints, filler Glue Two-component filler: 4.4% DGEBF and 0.04% DGEBA (13) Glue Resin – – – – – – – –
In Malm¨o, further screening with epoxy resin of the bisphenol F type (0.25% pet.) was performed in connection with a phenyl glycidyl ether study on 2227 patients, and detected 23 (1%) patients with contact allergy to DGEBA-R and 19 (0.9%) patients with contact allergy to bisphenol F-based epoxy resin (14). The number of independent allergies to bisphenol F-based resin and exposure data were not given, but the number of DGEBA-R reactions exceeded the number of DGEBF-R reactions. In a multicentre study, EPOX 2002, with 0.25% DGEBF-R, was tested in 87 patients with either previously diagnosed DGEBA-R allergy or with suspected contact allergy to epoxy compounds (6). In agreement with our results and the later results from Malm¨o, the number of DGEBA-R reactions exceeded the number of DGEBF-R reactions, and independent reactions to DGEBF-R were quite rare. In the United States, 41 DGEBA-R-allergic patients were tested with four different bisphenol F-based products, and all reacted to at least one of the products. The individual products gave positive results in 93–95% of the patients (5). At the FIOH, the test concentration of DGEBF-R was lowered in the middle of the study period. During Period I, when 1% was used, the frequency of positive reactions (2.7%) was lower than during Period II (4.4%), when a
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Table 3. Products containing diglycidyl ether of bisphenol F resin
(DGEBF-R) on the market in Finland at the beginning of 2014 according to their purpose, and products that also contain diglycidyl ether of bisphenol A resin (DGEBA-R) according to chemical notifications filed with the Finnish Product Register of Chemicals at the beginning of 2014
Products by purpose Composite materials Paints and lacquers Epoxy resins Other coating agents Adhesives and glues Flooring products Bonding agents Injection resins for repairing concrete cracks Pigment dispersions Primers Filling agents Casting resins Laminating resins Others Total
Products with DGEBF-R but without DGEBA-R
Products with DGEBF-R and DGEBA-R
7 6 5 4 < 4∗ < 4∗ < 4∗ < 4∗
5 45 8 33 44 28 11 10
< 4∗ < 4∗ < 4∗ < 4∗ < 4∗ < 4∗ 27
9 9 7 6 6 16 237
∗ According to the principles of the register, numbers smaller than 4 are not published.
lower concentration of 0.25% was used. However, the number of DGEBA-R-allergic patients was also higher during Period II, explaining most of the difference. The same proportion of DGEBF-R-allergic patients had concomitant allergy to DGEBA-R (Table 1). The slightly higher proportion of DGEBF-R-positive patients among the DGEBA-R-positive patients (71% in Period II and 57% in Period I) might indicate some increase in exposure to DGEBF-R during Period II as compared with Period I. Analysis of exposure data for our DGEBF-allergic patients gives some support to this speculation: during Period I, 31% of patients were specifically exposed to DGEBF products, and during Period II the proportion was 50%. Despite the above-mentioned studies (4, 6), patients with reactions to DGEBF-R without reactions to DGEBA-R have been reported only rarely. Kanerva et al. described a worker in an electrical factory who had handled insulating tape that contained phenol novolac epoxy resin. The patient, who was investigated in 1980, reacted to the tape but not to DGEBA-R in the baseline series or to allergens in the plastic and glue series (7). The allergen was probably DGEBF-R, although it was not tested separately. Bruze et al. described 3 workers in an aircraft plant who reacted to epoxy novolac (mainly DGEBF-R) and an adhesive for composite bonding that contained epoxy novolac. Only 1 of the 3 patients reacted to DGEBA-R (8). In Australia, a worker in a plant manufacturing adhesives developed eyelid dermatitis and reacted to bisphenol F
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epoxy resin (Araldite® GY 281), but not to DGEBA-R (9). In Taiwan, five subway construction workers were patch tested, and 3 of them reacted to resins of the bisphenol F type, but only 1 reacted to DGEBA-R. They had used a product that contained 30–40% DGEBA-R and < 15% bisphenol F epoxy resin (10). A study of workers in a plant producing wind turbine rotor blades found 2 cases of independent allergy to DGEBF-R. In addition, 34 workers reacted to DGEBA-R, 24 of whom also reacted to DGEBFR. The products based on DGEBF were mainly used for the repair and finish of the blades, but the exposure of the individual workers was not described (11). Pont´en and Bruze also described a tiler who had handled a putty that contained DGEBF-R and DGEBA-R, and reacted to epoxy novolac resin on patch testing down to a concentration of 0.00016%. He also reacted to DGEBA-R (15). In the present study population, 26 workers who were allergic to the compound were specifically exposed to DGEBF-R products. Several patients worked in the aircraft industry, the electrical industry, boat building, painting/floor coating, tile setting, sewage pipe relining, and the sports equipment industry. Other types of industry included foundry work, the manufacture of door frames, the lamination of pipes and tanks, electronic work, and the manufacture of reinforced plastic and composite parts. The safety data sheets for the epoxy did not always declare the presence of bisphenol F epoxy resins, and we needed to analyse them. DGEBF-R-containing products usually also contain DGEBA-R, and co-exposure to DGEBA-R was identified in nearly all of the DGEBF-R-positive patients in Table 2. The only exception was a dentist who had handled dental composite resins based on epoxyacrylates (these products were not analysed for DGEBA-R or DGEBF-R). Geier et al. (6) did not recommend routine testing of DGEBF-R, even in a special series, because of the low number of independent reactions and the risk of patch test sensitization [three cases sensitized by a concentration of 1% were described by Pont´en and Bruze (4)]. We are not aware of any active sensitizations to DGEBF-R among our patients. We stopped screening our patients with DGEBF-R in the baseline series, because it did not help us to identify those with independent allergy any better than aimed testing. All of the patients with an independent allergy were clearly exposed to epoxy products, and were therefore tested with the specific epoxy series. However, we continue to perform aimed testing of DGEBF-R, because we want to determine the exact allergen whenever possible, and the diagnosis of occupational allergic contact dermatitis of 2 of our patients was based on the reaction to DGEBF-R only. In conclusion, concomitant allergy to DGEBF-R and DGEBA-R is common, owing to cross-allergy or
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simultaneous exposure, but independent contact allergies to DGEBF-R are rare, despite the high number of products with DGEBF on the market. Thus, screening with DGEBFR was not found to be useful. DGEBA-R allergy is usually more common than allergy to DGEBF-R. Independent reactions to DGEBF-R occur especially in workers handling composite products, but they are relatively rare. In some cases, the diagnosis of occupational allergic
contact dermatitis requires testing with DGEBF-R or with the patients’ own DGEBF-based products.
Acknowledgements The study was financially supported by the Finnish Work Environment Fund.
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