Biological monitoring and possible health effects in workers occupationally exposed to methyl methacrylate

Methyl methacrylate and respiratory sensitisation: a comprehensive review

Methyl methacrylate (MMA) is classified under GHS as a weak skin sensitiser and a skin and respiratory irritant. It has recently been proposed that MMA be classified as a respiratory sensitiser (a designation that in a regulatory context embraces both true respiratory allergens, as well as chemicals that cause asthma through non-immunological mechanisms). This proposal was based primarily upon the interpretation of human data. This review, and a detailed weight of evidence analysis, has led to another interpretation of these data. The conclusion drawn is that persuasive evidence consistent with the designation of MMA as a respiratory sensitiser is lacking. It is suggested that one reason for different interpretations of these data is that occupational asthma poses several challenges with respect to establishing causation. Among these is that it is difficult to distinguish between allergic asthma, non-allergic asthma, and work-related exacerbation of pre-existing asthma. Moreover, there is a lack of methods for the identification of true chemical respiratory allergens. The characterisation and causation of occupational asthma is consequently largely dependent upon interpretation of human data of various types. Recommendations are made that are designed to improve the utility and interpretation of human data for establishing causation in occupational asthma.

Investigation of the oxidative stress condition for occupational exposure to methyl methacrylate

The purpose of this study is the evaluation of possible toxicological effects on dental personnel, who are exposed to the production materials of prostheses during their entire working life. In this study, the level of methyl methacrylate (MMA) in ambient air was measured as an indicator of external exposure on the personnel. In order to evaluate the possible toxic effects of oxidative stress, which is thought to play an important role in the formation process of many diseases such as cancer, blood samples of volunteers were examined via the ultraviolet-spectroscopic determination of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase antioxidant enzyme activities, comparing occupationally MMA-exposed ( n = 69) and control ( n = 67) groups. In these groups, malondialdehyde (MDA) and glutathione levels were also determined by the same method. The results showed that SOD activity and MDA and glutathione levels were significantly higher in the exposed group when compared with the control group ( p < 0.001). A significant decrease was determined in the glutathione peroxidase activities of the exposed group ( p < 0.05). No significant difference in CAT activities between the groups has been found. When the results obtained in the study are considered, it is suggested that an adaptive response might be developed by dental technicians against low-level MMA exposure.

Hypothesis-based weight-of-evidence evaluation of methyl methacrylate olfactory effects in humans and derivation of an occupational exposure level

Over 40 years of scientific evidence indicates that methyl methacrylate (MMA) causes olfactory effects in rodents that are relevant to humans. More recent scientific studies have focused on understanding the apparent lack of species concordance between the rodent and human studies. Toxicokinetic studies and a physiologically based pharmacokinetic (PBPK) model describing inhalation dosimetry of MMA in the upper respiratory tract (URT) of rats and humans point to differences in nasal morphology and biochemistry that could explain and reconcile these differences as species-specific manifestations of a common toxicological process. We have applied the hypothesis-based weight-of-evidence (HBWoE) approach to evaluate the concordance of the available data and the hypothesis that the observed difference in sensitivity between rats and humans may be the expected result of physiological and biochemical differences. Our WoE analysis indicates that when the several lines of evidence (i.e., animal, human, mode-of-action, and toxicokinetics data) are integrated, they inform interpretation of one another and, overall, support use of the human data for derivation of an MMA occupational exposure level (OEL) of 50 ppm.

Inhalation study of polymethyl methacrylate following radiologist exposure during percutaneous vertebroplasty

OBJECTIVE

To assess the atmospheric concentrations of methyl methacrylate (MMA) vapors during percutaneous vertebroplasty for the interventional radiologist and the other operating room staff.

MATERIALS AND METHODS

During percutaneous vertebroplasty, a polymethyl methacrylate (PMMA) mixture (about 20 mL) was prepared with a mixing system in a normally ventilated room. Atmospheric concentrations of MMA vapors were measured by a gas absorbent badge for individual exposure (GABIE) passive sampler attached to the surgical gowns of the interventional radiologist and the other operating room staff over a period of 460 min. Active sampling was performed over 15 min with an individual pump placed near the breathing zone of the radiologist. MMA vapor concentrations were then measured using gas chromatography and activated charcoal tubes.

RESULTS

Mean MMA vapor concentrations measured by the GABIEs over the period of 460 min were 0.51 parts per million (ppm) for the radiologist and 0.22 ppm for the other operating room staff. The emission peaks measured by using charcoal tubes over 15 min were 3.7 ppm.

CONCLUSION

MMA vapor concentrations during percutaneous vertebroplasty were well below the recommended maximum exposure of 100 ppm over the course of an 8-h workday.

Proportionate cancer mortality in methyl methacrylate-exposed orthopedic surgeons compared to general surgeons

Methyl methacrylate (MMA), a volatile liquid used to make dentures, hearing aids, joint prostheses, and medical adhesives, has been associated with colorectal carcinomas in acrylic sheet manufacturing workers. A case-control proportionate cancer mortality investigation was conducted to determine cancer death differences in orthopedic surgeons performing total joint replacements (TJRs) (MMA-exposed cases) and general surgeons not performing TJRs (unexposed controls). The American Colleges of Orthopedic Surgeons and General Surgeons provided complete demographic information on 468 male orthopedic surgeons and 1,890 male general surgeons who died during 1991-2001. Decedent data was submitted to the National Death Index for matching with underlying causes of death on state death certificates. Proportionate differences in ages at death, deaths from cancer, and deaths from site-specific cancers were analyzed for statistically significant differences by unpaired, two-tailed t tests for continuous variables and by both proportionate cancer mortality ratios and Yates-corrected chi squares for categorical variables. Orthopedic surgeons died of cancer more often (χ (2) = 7.699, P = 0.006) and at younger (t = 5.53, P < 0.001) ages (mean = 69.4 years) than general surgeons (mean = 79.2 years). For site-specific cancers, orthopedic surgeons died of esophageal cancer (χ (2) = 4.372, P = 0.037) and myeloproliferative malignancies (χ (2) = 4.369, P = 0.037) more often than general surgeons. Orthopedic surgeons are chronically exposed to MMA and are proportionately more likely to die from cancer, especially esophageal and myeloproliferative cancers, than general surgeons. MMA-exposed healthcare workers may be at increased risks of untimely deaths from site-specific malignancies.

Methyl methacrylate and respiratory sensitization: a critical review

Methyl methacrylate (MMA) is a respiratory irritant and dermal sensitizer that has been associated with occupational asthma in a small number of case reports. Those reports have raised concern that it might be a respiratory sensitizer. To better understand that possibility, we reviewed the in silico, in chemico, in vitro, and in vivo toxicology literature, and also epidemiologic and occupational medicine reports related to the respiratory effects of MMA. Numerous in silico and in chemico studies indicate that MMA is unlikely to be a respiratory sensitizer. The few in vitro studies suggest that MMA has generally weak effects. In vivo studies have documented contact skin sensitization, nonspecific cytotoxicity, and weakly positive responses on local lymph node assay; guinea pig and mouse inhalation sensitization tests have not been performed. Cohort and cross-sectional worker studies reported irritation of eyes, nose, and upper respiratory tract associated with short-term peaks exposures, but little evidence for respiratory sensitization or asthma. Nineteen case reports described asthma, laryngitis, or hypersensitivity pneumonitis in MMA-exposed workers; however, exposures were either not well described or involved mixtures containing more reactive respiratory sensitizers and irritants. The weight of evidence, both experimental and observational, argues that MMA is not a respiratory sensitizer.

Identification of covalent binding sites of ethyl 2-cyanoacrylate, methyl methacrylate and 2-hydroxyethyl methacrylate in human hemoglobin using LC/MS/MS techniques

Acrylates are used in vast quantities, for instance in paints, adhesive glues, molding. They are potent contact allergens and known to cause respiratory hypersensitivity and asthma. Here we study ethyl 2-cyanoacrylate (ECA), methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA). There are only limited possibilities to measure the exposure to acrylates, especially for biological monitoring. The aim of the present study was to investigate the chemical structures of adducts formed after reaction of hemoglobin (Hb) with ECA, MMA, and HEMA. This information may be used to identify adducted Hb peptides for biological monitoring of exposure to acrylates. Hb-conjugates with ECA, MMA, and HEMA were synthesized in vitro. The conjugates were digested by trypsin and pronase E. Adducted peptides were characterized and analyzed by liquid chromatography and nano electro spray/hybrid quadrupole time-of-flight mass spectrometry (MS) as well as tandem quadrupole MS. The search for the adducted peptides was facilitated by visualizing the MS data by different computer programs. The results showed that ECA binds covalently to cysteines at the 104 position in the α and the position 112 in the β-chains in Hb. MMA and HEMA bound to all the cysteines in both chains, Cys(104) in the α-chain and Cys(93) and 112 in the β-chain. The full-length spectra of in un-digested Hb confirmed this binding pattern. There was no reaction with N-acetyl-L-lysine at physiological pH. The adducted peptides were possible to measure using LC/MS/MS in selected reaction monitoring mode. These peptides may be used for biological monitoring of exposure to ECA, MMA and HEMA.

Validation of urine density correction in cases of hippuric acid and un-metabolized toluene in urine of workers exposed to toluene

To investigate if it is appropriate to apply urine density correction when a urine sample is dense or dilute. Data on hippuric acid (HA-U), toluene (Tol-U), creatinine (CR) and specific gravity (SG) in end-of-shift urine samples and exposure to air-borne toluene were cited from previous publications. In practice, 837 cases were available, and they were classified into dense, intermediate and dilute groups taking 0.3 and 3.0 g/l of CR and 1.010 and 1.030 of SG as cut-off points. Lines of regression of HA-U and Tol-U (as observed, CR-corrected or SG-corrected) with air-borne toluene were calculated for each density groups, and correlation coefficients (CCs) were compared. The dense groups gave CCs similar to those of the intermediate groups. Dilute versus intermediate group comparison also gave promising results. These conclusions were however based primarily on the findings with observed values, because the numbers of cases in the dilute or dense group were limited when CR- or SG-correction was applied. Literature survey showed that urine density correction does not always improve the correlation between solvents in air and exposure makers in urine. It was concluded that no correction for urine density may be necessary in evaluating HA-U and Tol-U in dense (and probably also dilute) urine samples as markers of occupational toluene exposure. Just in case when correction for urine density is desired for any reason, SG-correction may be recommended.

Surgical applications of methyl methacrylate: a review of toxicity

Methyl methacrylate (MMA) is a monomer of acrylic resin widely used in a variety of medical, dental, and industrial applications. Its extensive use in surgery, particularly for arthroplasties, has often raised concerns regarding potential human toxicity for orthopaedic surgeons, surgical nurses, and other operating-room staff who are occupationally exposed to the compound. The main toxic effects of MMA exposure appear to involve the cardiovascular system. When exposed to MMA in the work environment, surgical staff have been reported to suffer from hypersensitivity, asthmatic reactions, local neurological symptoms, irritations and local dermatological reactions. The integrity of latex gloves may also be compromised following exposure to MMA during surgical procedures. At present, MMA is not thought to be carcinogenic to humans under normal conditions of use. Nevertheless, sound occupational hygiene practices should still be used to help reduce workplace exposure to MMA during orthopaedic and other medical procedures. Surgical staff should avoid direct contact with MMA mixtures wherever possible, and room ventilation and adequate airflow should also be optimized. In the present article, the authors review studies relating to MMA toxicity in surgical practice, updating in part a previous literature review and expanding on the toxicity of MMA within the surgical setting.

A cross-industry assessment of personal exposures to methyl methacrylate

This study investigated personal exposures to methyl methacrylate (MMA) monomer during monomer production and use within the chemical manufacturing industry. The aim was to include multiple companies and sites to provide information regarding differences and similarities among exposure subgroups within the industry during the time period of 1998-2000. To this end, personal exposure data for MMA monomer from three chemical corporations was combined into a single data set. The data was stratified by sample type (full shift or short term), job classification (monomer production, monomer use, maintenance, distribution, and laboratory operations), company, and facility. Only classifications with three samples or more were included in the final data set, yielding 376 samples for analysis (334 full-shift and 42 short-term samples). Results compare well with previously published data on MMA monomer exposures. Although there was significant variability in several exposure subgroups (particularly among companies and facilities), MMA monomer use in the manufacture of other products resulted in the highest exposure distributions, with lower exposures associated with monomer production, maintenance, and distribution operations. The usefulness of these findings is related to the provision of information for discussion of current needs in the industry regarding data sampling, exposure assessment, and standards development.

Assessment of methyl methacrylate vapor toxicity on the rat tracheal epithelium

Methyl methacrylate (MMA) is a monomer that is polymerized into resin by light and heat, producing a clear, resistant, durable and relatively inert plastic material. Because of these characteristics, MMA is largely used in Medicine as bone cement and in Dentistry, in dental braces and prostheses, thus generating continuous interest in its toxicity. Experimental and clinical studies have documented that monomers may cause a wide range of adverse health effects. The most important occupational exposure route of MMA is by inhalation. This study aims to evaluate the toxicity of MMA to the tracheal epithelium, according to the time of exposure. For this purpose, two experimental groups of rats were exposed to MMA by inhalation under poor ventilation: one group (n = 36) was exposed permanently, and the other (n = 36) was exposed during 8 hours per day, without water and food supply during the exposure period. A control group (n = 8) received normal air supply. Twelve animals of each study group were sacrificed after 5, 8 and 10 days of exposure together with two or four control animals. Twenty-nine (80.5%) of the rats continuously exposed to MMA developed inflammation on the tracheal epithelium, as well as 58.33% (n = 21) of those exposed 8 h/day and 87.5% (n = 7) of the control rats. No association was observed between the inflammatory process and MMA exposure; no significant alterations in the tracheal epithelium thickness were observed. Further studies on longer exposure times and analysis of other parameters will have to be conducted to exclude the possibility of tracheal damage by vapors of MMA.

The effects of methyl methacrylate on nasal cavity, lung, and antioxidant system (an experimental inhalation study)

Methyl methacrylate (MMA) is a monomer, commonly used in neurosurgery, orthopedic surgery, and in dental clinics. The adverse effects of this monomer are well described in the literature. This study was designed to evaluate the effects of MMA on nasal cavity, lung, and antioxidant status. For this purpose, two experimental groups of rats were exposed to MMA (at 1,000 ppm, 6 h/day, 5 days/week for 4 weeks) by inhalation under poor (group A, n = 12) and normal ventilation (group B, n = 11) conditions. A control group (group C, n = 10) received normal air. Degeneration of olfactory epithelium, bronchopneumonia, interstitial pneumonia, hemorrhage, atelectasis, edema, emphysema, and bronchial epithelial hyperplasia were observed in groups A and B. Emphysema was the most common lesion. Bronchopneumonia with abscesses was only observed in group A. Glutathione levels were significantly decreased and malondialdehyde levels were significantly increased in group A. No significant difference was observed in superoxide dismutase levels between the groups. The data presented indicate that before using MMA, adequate protection systems should be in place to prevent occupationally related MMA respiratory-tract injuries.