Health hazard evaluation report: HETA-99-0163-2771, Superior Drywall, Inc., Millsboro, Delaware.
The National Institute for Occupational Safety and Health (NIOSH) received a confidential Health Hazard Evaluation (HHE) request in March 1999, from employees of Superior Drywall, Millsboro, Delaware. The request named drywall hanging as a job of concern for possible exposure to vapors from drywall adhesive. On May 19-20, 1999, NIOSH investigators conducted a site visit at Superior Drywall operations. Environmental monitoring was conducted at different work sites for organic vapors evolving from drywall adhesive. The NIOSH physician interviewed drywall hangers and reviewed the Occupational Safety and Health Administration (OSHA) Log and Summary of Occupational Injuries and Illnesses (Form 200) for the years 1997 and 1998. Although the material safety data sheets (MSDS) for the drywall adhesive listed hexane, cyclohexane, and n-heptane specifically as its major components, thermal desorption tube samples (collected on the first day of the site visit) showed that in some areas other hexane isomers, toluene, and benzene vapors were present in the air in greater relative abundance than were cyclohexane or n-heptane individually. Quantitative analysis therefore was made only for "total hexanes," n-hexane, toluene, and benzene. There were no personal exposures to individual solvents above relevant occupational exposure criteria. The highest full-shift concentration, 37.7 parts per million (ppm) of n-hexane, was measured by an area sample in the hall bathroom: a small, enclosed area with poor ventilation. The lowest vapor concentrations both days were from personal breathing zone (PBZ) samples collected on drywall hangers. PBZ samples for combined exposure ranged from about 20-80% of the "mixture recommended exposure limit" (REL), 20-70% of the "mixture threshold limit value" (TLV), and 2-6% of the "mixture permissible exposure limit" (PEL). Therefore, during full-shift sampling there were no over exposures based on the potential combined effects of toxicologically similar compounds. All PBZ concentrations for n-hexane, toluene, benzene, and "total hexanes" were at least one order of magnitude below their respective PEL, and none exceeded their REL or TLV. One short-term sample collected in the box used to store expended adhesive tubes demonstrated that solvent vapors continue to off-gas from the used tubes. This may contribute a small amount to the ambient levels, in addition to what comes from the adhesive applied during drywall installation. To minimize potential exposures, emptied tubes should be removed from the work area and stored outside until they can be disposed. Drywall hangers should continue to work with windows and doors open when possible, to facilitate general ventilation. Based on the conditions witnessed during this evaluation, it is unlikely for hangers to be over exposed during normal work activities. If solvent exposures continue to be a concern of the workers, it may be beneficial to switch from a volatile, organic solvent-based adhesive to a water-based adhesive. Superior should develop a hazard communication program dealing with any hazardous chemicals used by their employees. There was no evidence that workers were experiencing adverse health effects secondary to solvent exposure on the job.