Health hazard evaluation report: HETA-99-0065-2780, General Motors Corporation Allison Transmission Division, Indianapolis, Indiana.
On December 30, 1998, the National Institute for Occupational Safety and Health (NIOSH) received a request from employees of the General Motors Corporation, Allison Transmission Division, located in Indianapolis, Indiana, to conduct a health hazard evaluation (HHE). The request centered on isocyanate exposures arising from a polyurethane foam packaging operation. The packaging system used was an Instapak foam-in-bag packaging system, marketed under the trade name of Speedy Packer. Allison Transmission began packaging parts in polyurethane foam in 1988 using an Instapak foam-in-place system. An employee using the foam-in-place packaging system had to be removed from the job after two days due to respiratory symptoms described by the affected employee as "constricting of the throat and wheezing." A different person began using the system and worked without incident. In February 1999, the foam-in-place system was replaced with the foam-in-bag system currently used in the warehouse. In response to the request, NIOSH conducted a site visit in April 1999 to observe how the packaging system was used, learn about the occupational health programs in place for users of the packaging system, and obtain environmental measurements for 4,4'-diphenylmethane diisocyanate (MDI) and MDI oligomers. One person works directly with the foam-in-bag system and several employees work adjacent to the foaming area at distances of approximately 30 feet. Batches of parts are periodically delivered to the foaming area by a fork truck. The number of parts and the rate at which they are delivered vary considerably. Area and personal breathing zone (PBZ) samples were collected for MDI and MDI oligomers. Six area samples were collected over the full shift, and two PBZ samples were collected over 15-minute periods to measure peak exposures while the foamer was using the foam-in-bag system. Wipe samples also were obtained for MDI on surfaces in the foaming area. MDI was detected in 4 of 8 air samples at concentrations below applicable exposure criteria. Oligomeric MDI was not detected in any sample. The greatest concentrations, 1.1 and 2.3 micrograms of MDI per cubic meter of air (ug/m3), were measured in two short-term PBZ samples collected while the foamer used the foam-in-bag system. Other detectable MDI concentrations were measured near where the bags of foam are placed into boxes and in an area sample collected 10 feet from the foaming operation. The data from this survey indicate that MDI airborne exposures may occur in the foaming area during periodic peak episodes, and that the concentration decreases to non-detectable levels beyond the foaming area, at a distance greater than 10 feet from the source. Surface wipe tests, conducted immediately after the foam-in-bag system was used, did not identify measurable levels of MDI. No local exhaust ventilation was in place in the foaming area. The foamer wore shorts and a tee shirt throughout the shift. Chemical goggles and full -length Sol-Vex nitrile gloves (model 37-185) were worn while using the Speedy Packer. Respiratory protection was not used. General Motors has a written medical surveillance program for employees who work with isocyanates. This program recommends and provides guidelines for pre -placement and periodic medical evaluations of employees who work with isocyanates. Medical evaluations are to emphasize the respiratory system.