In January 2001, the National Institute for Occupational Safety and Health (NIOSH) received a health hazard evaluation (HHE) request from Superior Label Systems, Inc., (SLS) Mason, Ohio, a large flexographic printing operation for consumer product labels. Employees in the line division were experiencing intermittent blurred vision, while those in the adjacent prime division had few vision complaints. Workers and management had been unable to associate these visual changes with any particular substance in use. NIOSH investigators conducted medical questionnaires, eye exams, and personal breathing-zone (PBZ) sampling for two amines used in the label printing process, dimethylisopropanolamine (DMIPA) and dimethylaminoethanol (DMAE). The mean time-weighted average (TWA) concentration of DMIPA was significantly higher in the line division than in the prime division (7.8 milligrams per cubic meter [mg/m3] vs. 1.9 mg/m3, p<0.01), as was the mean TWA concentration for total amines (10 mg/m3 vs. 5.1 mg/m3, p<0.01). Conversely, the mean TWA concentration of DMAE was significantly higher in the prime division than the line division (3.2 mg/m3 vs. 2.3 mg/m3, p<0.01). Exposures to these amines were associated with visual and ocular changes and NIOSH investigators notified SLS management that the pH adjuster, which contained DMIPA, may be responsible for workers' visual complaints. The SLS management promptly began diluting the pH adjuster, which contained DMIPA, and eventually replaced it with a product containing only DMAE. This appeared to result in a resolution of visual complaints among the workers. In August 2002, NIOSH investigators returned to SLS for additional air sampling for DMIPA and DMAE to determine how exposures had changed since eliminating the use of the pH adjuster. We also asked employees if they were having blurry vision at work. A total of 64 PBZ air samples were collected on 40 day- and evening-shift employees in the line and prime divisions over a two-day period. Trace concentrations of DMIPA (between 0.06 and 0.2 mg/m3) were measured on 16 PBZ samples

no DMIPA was detected on the remaining 48 samples. DMAE concentrations ranged from 0.02 to 4.5 mg/m3 in the line division and from 0.71 to 5.0 mg/m3 in the prime division. Overall, DMIPA concentrations in both the prime and line divisions sharply decreased between the initial and follow-up surveys, while DMAE concentrations remained relatively unchanged. The continued presence of DMAE was not unexpected since DMAE was still used in both areas. No blurry vision or other visual problems were reported by any interviewed workers. A health hazard related to the use of DMIPA and DMAE no longer exists at this facility. The continued use of DMAE, and the accompanying lower total amine concentrations, do not appear to be causing any visual problems among the workers. A recommendation was made to continue covering all open 5-gallon ink pails to reduce chemicals vaporizing into the work environment.