A maintenance worker became ill after working indoors over the course of 3 days with a commercially available contact adhesive containing toluene and methyl ethyl ketone. Respiratory protection or local exhaust ventilation was not used. The worker subsequently suffered from numerous medical symptoms including tremors and elevated blood pressure. Magnetic resonance imaging documented the occurrence of encephalopathy. The worker has alleged that the cause of these effects was exposure to the vapors from the contact adhesive. The objective of this study was to characterize/estimate the level of the worker's exposure by obtaining air samples in an exposure chamber while performing similar activities under similar conditions. We found that the worker may have been exposed to approximately 159 ppm toluene and 58 ppm methyl ethyl ketone 8-hr time-weighted averages for 8 hr of adhesive application. The maximum 15-min average exposures were 233 ppm toluene and 85 ppm methyl ethyl ketone.

Electrets in condenser microphones are typically made from varieties of Teflon. This work evaluates different formulations and thicknesses of vapor deposited Parylene electrets as potential alternatives to Teflon. Parylene-coated condenser backplates used in this study were obtained from two different suppliers, as a third variable in addition to formulation and thickness. Long-term charge stability of the electrets was tested with a thermally stimulated discharge (TSD) method. Charge stability was also evaluated by building the charged backplates into condenser microphones and running them through environmental accelerated-life testing. Standard PTFE and FEP Teflon backplates were used as controls in these tests. The experiments showed clear differences in the long-term charge stability of the Parylene electrets due to thickness, formulation, and supplier. Several combinations of thickness, formulation, and supplier were found to perform comparably to traditional Teflon electrets and appear suitable for use in high-end condenser microphones.