Vision Concerns at Plant Lead NIOSH to Identify Link With 2 Chemicals, Suggest Safeguards

Contact: Fred Blosser (202) 401-3749
January 6, 2003

As the result of an investigation that teamed researchers from the National Institute for Occupational Safety and Health (NIOSH) with management and employees at a label printing plant, two chemicals in a widely used category of compounds were associated for the first time with a risk for job-related visual disturbances. The findings led to practical recommendations for reducing exposures to the chemicals DMIPA and DMAE and protecting employees’ vision.

NIOSH, a part of the U.S. Centers for Disease Control and Prevention (CDC), describes the study in a technical article in the January 2003 issue of the British journal Occupational and Environmental Medicine.

“Employers and employees frequently turn to NIOSH for help in solving complex health and safety concerns,” said NIOSH Director John Howard, M.D. “As in this case, finding the answer often involves a combination of technical expertise, practical experience on the shop floor, vigorous scientific sleuthing, and close collaboration with our partners.”

The company requested NIOSH’s assistance when several employees in the printing production area reported intermittent blurred vision. Although the employees’ vision typically improved within several hours after leaving work, the blurring posed a safety hazard while the workers were on the job operating machinery, and while they were driving home. The condition occurred intermittently and unpredictably, and was beginning to happen more frequently. One employee had been examined by an ophthalmologist who found a “film over his eyes.”

NIOSH’s subsequent investigation determined that the condition was linked with exposure to dimethylisopropylamine, or DMIPA, a component of an additive used to thin ink. NIOSH also found an association with dimethylaminoethanol, or DMAE, a component of water-based inks. Both compounds are tertiary amines, a type of chemical widely found in solvents, chemical intermediates, catalysts, preservatives, drugs, and herbicides. The number of employees reporting blurred vision, the number with film or opacities on the cornea, and the severity of the opacity increased with corresponding exposure to the compounds. Neither compound previously had been reported to cause visual disturbances in humans.

With the participation of management and employees, NIOSH identified the association through intensive legwork on several fronts – measuring exposure levels, assessing the plant ventilation system, administering eye examinations and questionnaires, and using rigorous statistical analysis to assess the likelihood that a given exposure was associated with symptoms of visual change.

It was impossible in the statistical analysis to distinguish the role of one compound from that of the other, but DMIPA was the more likely suspected cause for a number of reasons, although both compounds would be expected to produce the same effects, given their close chemical similarity.

As a result of the study:

• The company began diluting the DMIPA used in the printing process. Visual symptoms immediately ceased.
• Further recommendations were made to reduce exposures cost-effectively by first controlling specific sources of tertiary amines associated with the printing machines, and then repositioning the plant’s outdoor air intakes and exhaust discharge locations.
• Findings were generated that may help employers and employees at other sites anticipate, identify, and solve previously unsuspected problems.
• NIOSH tested a new analytical method for detecting amines, and found that it provided a more reliable tool for detecting amines than the existing method. NIOSH incorporated the new method in its widely used Manual of Analytical Methods, available on the NIOSH web site.

In addition to publishing the results in OEM, NIOSH has shared them directly with industry groups and others, so that the information can be used for material safety data sheet (MSDS) updating, and can be disseminated more widely to manufacturers, employers, and employees. In the last available national data collected by NIOSH in the 1980s, 35,000 workers were estimated to be exposed to DMAE, and 20,000 were estimated to be exposed to DMIPA. It is likely that the number of workers currently exposed is much higher, because solvent-based inks increasingly have been replaced in the past 20 years by water-based inks containing amines.

For further information on NIOSH research and recommendations for preventing work-related illnesses and injuries, call toll-free 1-800-35-NIOSH or visit NIOSH on the Web .