Exposure to methyl methacrylate and its subjective symptoms among dental technicians, Tehran, Iran

Our plain-English summary of Exposure to methyl methacrylate and its subjective symptoms among dental technicians, Tehran, Iran, by F. Golbabaei, M. Mamdouh, K.N. Jelyani, et al (International Journal of Occupational Safety and Ergonomics, 2005).

The study

• Authors: F. Golbabaei, M. Mamdouh, K.N. Jelyani, S.J. Shahtaheri
• Journal: International Journal of Occupational Safety and Ergonomics
• Published: 2005;11(3):283-9
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Exposure to methyl methacrylate (MMA), total dust and health symptoms were investigated in 20 dental laboratories located in Tehran, Iran. Time-weighted average (TWA) of MMA and peak concentrations were determined, using XAD-2 tubes followed by GC-FID analysis. Total dusts were evaluated gravimetrically. Health symptoms were asked using a questionnaire. TWA for technicians with direct and indirect exposure to MMA were 327.28 +/- 79.42 and 282.9 +/- 41.84 mg/m3, respectively. Peak concentration of MMA for those technicians were 337.0 +/- 36.81 and 328.88 +/- 45.40 mg/m3, respectively. There were no significant differences between TWA of MMA and peak concentration in different weekly workdays; however, within-day variations were observed (P < .05). TWA of MMA and peak concentration correlation with the laboratory volume were 0.61-0.65. Dust exposure of technicians was 2.35 +/- 2.70 mg/m3. Cough and skin dryness were the common health symptoms. Smoking and asbestos exposure history were factors influencing cough prevalence (p < .05). It is concluded that the current Short-Term Exposure Limit (STEL) is not low enough to protect technicians against the adverse effects caused by MMA.

In plain English

This study measured methyl methacrylate (MMA), a liquid used to make acrylic dentures, in the air breathed by 51 technicians (45 men, 6 women) in 20 registered dental laboratories in Tehran, Iran. Dust was also sampled, and a questionnaire asked about breathing and skin symptoms, smoking, and past asbestos exposure. The article does not describe this asbestos exposure. The discussion reported average full-shift MMA levels of 327.28 mg/m3 for technicians who mixed and packed acrylic and 282.98 mg/m3 for others; other parts of the article print different values. Full-shift levels exceeded the 204.70 mg/m3 limit the authors cited; short-term peaks were below the 409.41 mg/m3 short-term limit. Larger laboratories had lower MMA levels. Skin dryness was the most common skin complaint. The authors called cough the most common breathing complaint, but their table lists asthma and phlegm more often. Cough was reported as significantly more common among smokers and among technicians with past asbestos exposure. The authors concluded that MMA did not seriously affect the respiratory system, that smoking and earlier asbestos exposure seemed responsible for cough, and that the current short-term limit is not low enough to protect technicians.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Cross-sectional workplace survey: personal air sampling for MMA and dust, plus a questionnaire on symptoms
• Who was studied: 51 dental technicians (6 female, 45 male) in 20 dental laboratories in Tehran, Iran, that were registered with the Iranian Dental Technicians Association and made removable acrylic dentures; study dates not given
• Exposure: Methyl methacrylate vapor (full-shift average and short-term peak during mixing) and total dust from finishing and polishing acrylic. Past asbestos exposure and smoking were recorded by questionnaire; asbestos fiber type and source were not described.
• Main results:
  • Technicians involved in mixing and packing (direct exposure) had the highest full-shift MMA exposure, reported in the discussion as 327.28 ± 81.64 mg/m3 (79.94 ± 19.94 ppm)
  • Other (indirectly exposed) technicians had a full-shift MMA exposure reported in the discussion as 282.98 ± 41.84 mg/m3 (69.12 ± 10.22 ppm)
  • Short-term MMA concentrations were below the short-term exposure limit of 409.41 mg/m3 (100 ppm), while full-shift averages exceeded the TLV-TWA of 204.70 mg/m3 (50 ppm)
  • Laboratory volume was inversely related to MMA full-shift concentration (r = –.65, P < .05) and to peak concentration (r = –.44, P < .05); larger laboratories had lower exposure
  • Personal dust exposure of technicians using grinding machines ranged from 0.126 to 9.601 mg/m3 (2.35 ± 2.70 mg/m3); the authors stated that environmental dust (0.431 ± 0.550 mg/m3) did not exceed guidelines for particles not otherwise classified
  • Skin dryness was the most common skin symptom, and the authors reported a relationship between skin dryness and MMA concentration (P = .03)
  • The text calls cough the most common respiratory symptom. Table 4 lists, for directly exposed technicians, cough 7 (18.42%), phlegm 9 (23.68%) and asthma 16 (42.11%). For indirectly exposed technicians it lists cough 2 (15.38%), phlegm 4 (30.77%) and asthma 5 (38.46%).
  • Cough prevalence differed significantly between smoker technicians (92.86%) and non-smokers (P < .05)
  • A significant difference in cough was also reported for technicians with an asbestos exposure background (41.86% of individuals) (P < .05)
• The authors' conclusion: The authors concluded that MMA exposure did not seriously affect the respiratory system and that smoking and prior asbestos exposure seemed responsible for respiratory symptoms, especially cough. They also concluded that the current short-term exposure limit is not low enough to protect technicians from MMA's adverse effects, and they recommended a lower TLV-STEL.

Topics

Medical terms in this study, explained in our Lexicon: Time-Weighted Average (TWA), Asbestos Exposure, Short-Term Exposure.

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