Occupational Exposure to MMA Vapors in Medical Environments

The use of certain substances in today’s medical treatments exposes medical personnel to potentially hazardous levels of harmful materials. Ongoing research is studying these concerns in an effort to improve quality of care for patients and improve workplace safety for medical staff. When required real time monitoring systems are installed to protect medical staff from long-term exposure risks. Photoacoustic Spectroscopy (PAS) is a helpful tool for both the study and monitoring of potentially harmful gases that can be present in such environments. Two such examples are Methyl Methacrylate (MMA) and anesthesia gases.

Many orthopedic surgeons use acryl ester plastic cement when they are replacing joints (e.g., the hip, knee, etc.) with new artificial components. Due to the type of plastic-cement and the importance of sterile handling, the plastic-cement is produced during the operation by mixing the acrylate with the monomer Methyl Methacrylate (MMA). Work of this kind with the acryl ester often leads to the medical staff complaining of headaches, as well as soreness in eyes and noses. MMA is a volatile liquid and its fumes are known to irritate mucous membranes, such as those in the eyes and nose, even when the concentration is far below the permitted levels.

The Challenge of Measuring Exposure

In order to evaluate how much MMA personnel are exposed to, it is necessary to know both the average dose and the peak value of the MMA while they are working in the fumes. It is also necessary to evaluate the settings and efficiency of the ventilation system. Traditional methods of measuring MMA make it difficult to document the problem as it is not always possible to measure the peak levels or short term dosing levels of MMA during joint replacement operations. In addition to the MMA fumes, it is more than likely that the medical staff is also exposed to trace levels of anesthetic gases.

The Gas Measurement Solution

The Photoacoustic Multi-gas Monitor 1412 is well suited for these challenging measurements so that exposure can be understood and then brought to safe levels. The monitor can measure average, short-term, and peak exposure levels of MMA. Furthermore, it only requires a few hours of training before it can be operated by hospital staff. The instrument can be configured to measure Nitrous Oxide, Halothane, Enflurane, Isoflurane, 2-propanol, Carbon Dioxide and MMA. The filters used and the detection limits for these gases are shown in the table below. Halothane, Enflurane and Isoflurane are all measured using the same filter. As they are not all present at the same time, this does not cause a problem. As one filter is sensitive to a number of gases, sometimes you need to compensate the readings obtained. The monitor is able to do this automatically if the interfering gases are measured separately with other filters (Cross Compensation) Carbon Dioxide was measured in order to compensate for interference on the Nitrous Oxide measurement, and 2-propanol is measured to compensate for interference to the anesthetic gases.

Gas	Detection Limit (ppm)	Filter Number
Nitrous Oxide	0.03	UA0985
Halothane	0.02	UA0972
Isoflurane	0.009	UA0972
Carbon Dioxide	1.5	UA0982
MMA	0.02	UA0971
SF6	0.006	UA0988
Freon 134a	0.01	UA0970

The results presented here were obtained during a hip replacement operation at Martha Hanssens Hospital in Oslo. The measurements were made in the area around the surgeons face during 2 consecutive, traditional hip replacement operations (two portions of MMA-plastic were used; one for securing the ball on the femur and the second for securing the socket on the pelvis). The operating room was normally ventilated (the air being completely changed approximately 20 times every hour; no special laminar airflow system is installed). The patient, during both operations, was under spinal anesthetic, which does not require gaseous anesthesia thus simplifying measurements.

This product has not been cleared by the US FDA.

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