Prevalence and sources of occupational contact sensitization to acrylates in Italy

Acrylates and Methacrylates Sensitization in Patients with Orthopedic and Dental Prostheses: Asymptomatic Pre-Implant and Symptomatic Post-Implant Testing

Acrylates and methacrylates are widely used in dental and orthopedic prostheses, false nails, adhesives, glues, and paints, and are strong sensitizers. The aim of our study was to assess the prevalence of acrylate sensitization in patients before the application of dental or orthopedic prostheses or after the application in case of potentially related contact dermatitis. Methods: The subjects were tested according to haptens reported in safety data sheets, including methyl methacrylate (MMA) 5%, methyl acrylate (MA) 1%, ethyl methacrylate (EMA) 2%, ethyl acrylate (EA) 1%, butylacrylate 0.1%, 2 hydroxyethyl methacrylate (HEMA) 5%, ethylene glycol dimethacrylate 2% (EGDMA), tetraethylene glycol dimethacrylate 2% (TEGDMA), and dimethyl amino ethyl methacrylate 0.2% (DAEMA). Multivariable logistic regression was used to study the factors associated with (meth)acrylate sensitization. Results: Six hundred sixty-five patients (75.4% of the total sample) without contact dermatitis before the placement of any dental or orthopedic prosthesis and 217 patients (24.6% of the total sample) with contact dermatitis potentially due to already placed prostheses were involved. In total, 37 cases of patch test positivity to at least 1 acrylate (4.2%) were found. In the pre-implant population, previous dermatitis and respiratory allergy were associated with increased sensitization to acrylates in multivariable regression analysis (odds ratio [OR] 2.38, 95% confidence interval [CI] 1.05-5.39; OR 2.96, 95% CI 1.32-6.64, respectively). The prevalence of sensitization was 3.5% for EGDMA, 2.7% for EA, 1.5% for 2-HEMA, 1.4% for both MA and MMA, 1.28% for DAEMA, and 0.8% for EMA. No statistically significant difference was found in the prevalence of sensitization between the pre- and post-implant groups. Discussion: Our study found a similar profile of sensitization in pre-implant and post-implant patients, suggesting the need to better study the specificity and sensitivity of patch tests to (meth)acrylate and to define relevance considering a detailed history of exposure.

Final Report on Ethyl Methacrylate

Ethyl Methacrylate is the ester of ethyl alcohol and methacrylic acid used as the major structural monomer of artificial fingernail formulations that are cross-linked with one or more multifunctional methacrylates. Ethyl methacrylate monomer is polymerized rapidly and very little free monomer is available even during filing of the fingernails. The oral LD50 for rats ranged from 12.7 to 18.14 g/kg, with lesions in the respiratory system and hemoglobinuria observed in treated animals. Ocular, nasal, and respiratory tract irritation was observed in acute inhalation tests using rats. Very little toxicity was seen in subchronic studies using rabbits. Ethyl Methacrylate caused irritation and vehicle dependent sensitization in animals, but no photosensitization. Evidence of embryotoxic and teratogenic effects were observed in pregnant rats after intraperitoneal injection of Ethyl Methacrylate at a range of concentrations. Both positive and negative mutagenicity test data were found. Clinical testing showed little evidence of irritation, although case studies report allergic contact dermatitis as a result of exposure to Ethyl Methacrylate and related methacrylates with application of artificial fingernails. Occupational contact dermatitis from acrylates and methacrylates are also reported, with some evidence for cross-reactivity between the two chemical classes. Based on the sensitizing potential of this ingredient the CIR Expert Panel recommended that fingernail enhancement formulations with Ethyl Methacrylate be applied only by trained individuals and that the ingredient not be used in products intended for retail sale (currently, these products are believed to be sold only for application by a trained individual). Because of the low likelihood of significant exposure if such formulations are applied properly, the Expert Panel concluded that the ingredient is safe as used, with the caveat that skin contact should be avoided.

Assessment of the skin sensitising potency of the lower alkyl methacrylate esters

There is continued interest in, and imperatives for, the classification of contact allergens according to their relative skin sensitising potency. However, achieving that end can prove problematic, not least when there is an apparent lack of concordance between experimental assessments of potency and the prevalence allergic contact dermatitis as judged by clinical experience. For the purpose of exploring this issue, and illustrating the important considerations that are required to reach sound judgements about potency categorisation, the lower alkyl methacrylate esters (LAM) have been employed here as a case study. Although the sensitising potential of methyl methacrylate (MMA) has been reviewed previously, there is available new information that is relevant for assessment of skin sensitising potency. Moreover, for the purposes of this article, analyses have been extended to include also other LAM for which relevant data are available: ethyl methacrylate (EMA), n-butyl methacrylate (nBMA), isobutyl methacrylate (iBMA), and 2-ethylhexyl methacrylate (EHMA). In addressing the skin sensitising activity of these chemicals and in drawing conclusions regarding relative potency, a number of sources of information has been considered, including estimates of potency derived from local lymph node assay (LLNA) data, the results of guinea pig assays, and data derived from in silico methods and from recently developed in vitro approaches. Moreover, clinical experience of skin sensitisation of humans by LAM has also been evaluated. The conclusion drawn is that MMA and other LAM are contact allergens, but that none of these chemicals has any more than weak skin sensitising potency. We have also explored here the possible bases for this modest sensitising activity. Finally, the nature of exposure to LAM has been reviewed briefly and on the basis of that information, together with an understanding of skin sensitising potency, a risk assessment has been prepared.

Methacrylate and acrylate allergy in dental personnel

BACKGROUND

Methacrylates are important allergens in dentistry.

OBJECTIVE

The study aimed to analyse patch test reactivity to 36 acrylic monomers in dental personnel in relation to exposure.

METHODS

We reviewed the test files at the Finnish Institute of Occupational Health from 1994 to 2006 for allergic reactions to acrylic monomers in dental personnel and analysed the clinical records of the sensitized patients.

RESULTS

32 patients had allergic reactions to acrylic monomers: 15 dental nurses, 9 dentists, and 8 dental technicians. The dentists and dental nurses were most commonly exposed to 2-hydroxyethyl methacrylate (2-HEMA), triethyleneglycol dimethacrylate (TREGDMA), and 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]propane (bis-GMA). 8 dentists and 12 dental nurses were allergic to 2-HEMA. The remaining dentist was positive to bis-GMA and other epoxy acrylates. The remaining 3 dental nurses reacted to diethyleneglycol diacrylate (DEGDA) or triethyleneglycol diacrylate (TREGDA), but not to monofunctional and multifunctional methacrylates. Our dental technicians were mainly exposed and sensitized to methyl methacrylate (MMA) and ethyleneglycol dimethacrylate (EGDMA). 1 technician reacted only to 2-HEMA, and another to ethyl methacrylate (EMA) and ethyl acrylate (EA).

CONCLUSIONS

2-HEMA was the most important allergen in dentists and dental nurses, and MMA and EGDMA in dental technicians. Reactions to bis-GMA, DEGDA, TREGDA, EMA and EA were relevant in some patients.

Skin sensitization potency of methyl methacrylate in the local lymph node assay: comparisons with guinea-pig data and human experience

There is compelling evidence that contact allergens differ substantially (by 4 or 5 orders of magnitude) with respect to their inherent skin-sensitizing potency. Relative potency can now be measured effectively using the mouse local lymph node assay (LLNA) and such data form the basis of risk assessment and risk management strategies. Such determinations also facilitate distinctions being drawn between the prevalence of skin sensitization to a particular contact allergen and inherent potency. The distinction is important because chemicals that are implicated as common causes of contact allergy are not necessarily potent sensitizers. One example is provided by nickel that is undoubtedly a common cause of allergic contact dermatitis, but is a comparatively weak sensitizer in predictive tests. In an attempt to explore other examples of contact allergens where there may exist a discrepancy between prevalence and potency, we describe here analyses conducted with methyl methacrylate (MMA). Results of LLNA studies have been interpreted in the context of historical clinical data on occupational allergic contact dermatitis associated with exposure to MMA.

Amended final report on the safety assessment of ethyl methacrylate

Ethyl Methacrylate is a methacrylate ester used as a chemical additive in artificial fingernail enhancement products. These products may be applied by trained professionals or be provided directly to consumers with instructions for use. Ethyl Methacrylate readily polymerizes and rapidly reacts with multifunction methacrylates to form a highly cross-linked polymer. The oral LD(50) of Ethyl Methacrylate for rats ranged from 12.7 to 18.14 g/kg. In acute studies with rats, hemoglobinuria and respiratory tract lesions were observed. Animal studies indicate that Ethyl Methacrylate is a skin irritant and sensitizer. In some cases the results were dependent on the vehicle. Evidence of embryotoxicity and teratogenicity were observed in rats injected intraperitoneally with 0.1223 to 0.4076 ml/kg Ethyl Methacrylate. Positive evidence of mutagenicity was observed in the L5178Y mouse lymphoma cell assay, but not in two Ames tests. Case reports cite examples of individuals suffering allergic contact dermatitis from exposure to Ethyl Methacrylate and related methacrylates, and some degree of cross-reactivity appears to exist between widely used acrylates and methacrylates. Information from several clinical registries of sensitization reactions to various agents reported that Ethyl Methacrylate is a sensitizer, but not a potent one. Because Ethyl Methacrylate monomer is short-lived in the normal course of using artificial fingernail-enhancement products, the primary hazard is expected to be inadvertant skin contact. In order to avoid sensitization, it is necessary to avoid skin contact. It is recommended that fingernail-enhancement products containing Ethyl Methacrylate include directions to avoid skin contact because of the sensitizing potential. Based on the available data on the formulation of nail products containing this ingredient, it is concluded that Ethyl Methacrylate is safe as used, when application is accompanied by directions for use as above.

Toxicological profile of diethyl phthalate: a vehicle for fragrance and cosmetic ingredients

Diethyl phthalate (DEP; CAS No. 84-66-2) has many industrial uses, as a solvent and vehicle for fragrance and cosmetic ingredients and subsequent skin contact. This review focuses on its safety in use as a solvent and vehicle for fragrance and cosmetic ingredients. Available data are reviewed for acute toxicity, eye irritation, dermal irritation, dermal sensitization, phototoxicity, photoallergenicity, percutaneous absorption, kinetics, metabolism, subchronic toxicity, teratogenicity, reproductive toxicity, estrogenic potential, genetic toxicity, chronic toxicity, carcinogenicity, in vitro toxicity, ecotoxicity, environmental fate and potential human exposure. No toxicological endpoints of concern have been identified. Comparison of estimated exposure (0.73 mg/kg/day) from dermal applications of fragrances and cosmetic products with other accepted industrial (5 mg/m(3) in air) and consumer exposures (350 mg/l in water; 0.75 mg/kg/day oral exposure) indicates no significant toxic liability for the use of DEP in fragrances and cosmetic products.

Allergic contact dermatitis to plastic banknotes

Allergic contact dermatitis to ultraviolet (UV) cured acrylates occurs predominantly in occupationally exposed workers. Two men presented with dermatitis coinciding with the location of banknotes in their pockets. Patch testing confirmed allergic contact dermatitis to multiple acrylates and Australian plastic banknotes. This is the first report of contact allergy to acrylates present in Australian plastic banknotes.

Cross-reactivity patterns of contact-sensitizing methacrylates

Methacrylates are well-known contact sensitizers with increasing frequency of contact leading to occupational skin disease. Here, we developed an animal model to facilitate studies on the sensitizing capacities and cross-reactivity patterns between four clinically most important allergens: methacrylate (MMA), 2-hydroxyethyl methacrylate (2-HEMA), 2-hydroxypropyl methacrylate (2-HPMA) and ethyleneglycol dimethacrylate (EGDMA). Inbred guinea pigs were immunized by ic injections of 300 microliters of 1.0 M methacrylate solutions in Freund's complete adjuvant into both flanks, both ears, and the neck. After 14 days open skin tests were performed with 50% MMA, 2-HEMA, or 2-HPMA or 10% EGDMA solutions in 40% DMSO in ethanol. Cross-reactivities were investigated 14 days later by skin testing with all four methacrylates. Using this newly developed protocol, strongly positive skin tests for methacrylates could be induced in almost all guinea pigs (MMA 26/26, 2-HEMA 16/18, 2-HPMA 15/16 and EGDMA 11/11). Whereas EGDMA induced only weak or infrequent cross-reactivities, 2-HEMA sensitization led to strong cross-reactions to all other methacrylates. Both MMA and 2-HPMA induced strong cross-reactivity to EGDMA but only weak to moderate reactivities to the other methacrylates. The absence of strong cross-reactions with monomethacrylates in EGDMA (dimethacrylate)-sensitized animals may be explained by the predominance of highly EGDMA-specific T-cells in these animals. In contrast, sensitization with MMA, 2-HEMA, and 2-HPMA would lead to recruitment of T-cells cross-reactive to the other monomethacrylates, according to their molecular similarities. The strong skin hypersensitivities observed for EGDMA in these latter groups are ascribed to enzymatic degradation into monomethacrylate compounds, notably 2-HEMA, at a rate sufficient to elicit cognate effector T-cells. The results of this study offer new insights in the development of methacrylate hypersensitivities and common cross-sensitization patterns in clinical practice.

10 years of patch testing with the (meth)acrylate series

Statistics on 10 years of patch testing with 30 (meth)acrylates were compiled. Altogether 275 patients were patch tested and 48 patients (17.5%) had an allergic reaction to at least 1 (meth)acrylate. The (meth)acrylates most often provoking an allergic patch test reaction were 2-hydroxyethyl acrylate (2-HEA; 12.1%), 2-hydroxypropyl methacrylate (2-HPMA; 12.0%) and 2-hydroxyethyl methacrylate (2-HEMA; 11.4%). No allergic reactions were caused by 2-ethylhexyl acrylate (2-EHA), 2,2-bis[4-(methacryloxy)phenyl]propane (BIS-MA), trimethylolpropane triacrylate (TMPTA), oligotriacrylate 480 (OTA 480), N,N-methylenebisacrylamide (MBAA), or ethyl cyanoacrylate (ECA). The frequency of allergic patch test reactions presented cannot be considered as a "ranking" list of the most sensitizing (meth)acrylate compounds. In order to be able to judge the sensitization capacity of various (meth)acrylate compounds in humans, it would be necessary to have detailed information on the exposure history of the patients studied, including the purity of the (meth)acrylate compounds. Currently, this is not possible because (meth)acrylate-containing products regularly contain undeclared (meth)acrylate compounds.

Self-reported occupational dermatological reactions among Danish dentists

The aims of the study were to investigate the causes and prevalences of occupational dermatological reactions among Danish dentists. Questionnaires and telephone interviews with Danish dentists revealed that 37.8% reported skin reactions. In 27.2% of the cases the reactions were related to occupation, occurring with a point prevalence of 9.6%, and with a 1-yr period prevalence of 21.4%. The main causes were hand washing/soaps, latex gloves and (di)methacrylate-containing materials occurring at point prevalences of 7.1%, 1.3% and 1.7%, respectively. In addition, several other causes were reported, each occurring at relatively low frequency. Diagnosed allergic latex eczema was reported by 0.6%, but the frequency might be more than 2%, estimated on basis of reported symptoms. Allergic eczema caused by (di)methacrylate-containing materials was diagnosed among 0.7%, but estimated by the description of symptoms to be nearly 2%. The results urge for developing safer materials for dental use.

Occupational allergic contact dermatitis due to acrylates in Lodz

Among 1619 patients suspected of occupational contact dermatitis examined during the years 1990-1994, sensitivity to acrylates was diagnosed in 9 persons (4 dental technicians, 4 dentists, 1 textile printer). Ethyleneglycol dimethacrylate (5 positive patch tests), methyl methacrylate (4), 2-hydroxyethyl methacrylate (4) and triethyleneglycol dimethacrylate (4) were the most common sensitizers. Comparison of patch test results in dental technicians and dentists indicated that dentists were sensitive to a greater number of (meth)acrylate (acrylate and methacrylate) allergens and also to certain other allergens (metals and rubber additives). Dental technicians were sensitive almost exclusively to methacrylates, while the textile printer only to acrylates.

Evaluation of patch test results with denture material series

791 patients, among them 59 dental technicians and 732 other patients, were tested with the denture material series (DMS) recommended by the German Contact Dermatitis Research Group (DKG) in the hospitals of the Information Network of Departments of Dermatology (IVDK) between January 1990 and July 1993. Most frequently, positive reactions occurred to cadmium chloride in both groups. However, there was no evidence at all for relevance of these reactions. Benzoyl peroxide (BPO) ranked 2nd in patch test positivity. Although not statistically significant, reactions were more frequent in dental technicians, who might be exposed to BPO the in working environment. Methyl methacrylate (MMA) and triethylene glycol dimethacrylate (TEGDMA) were common sensitizers in dental technicians but not in other patients. This finding, too, has its explanation in the working process of manufacturing dental prostheses.