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Subchronic Toluene Exposure alters Retinal Function in Long Evans Rats: Experimental Evidence Supporting Observations from Studies of Exposed Humans.
Citation:
BOYES, W. K., L. DEGN, M. S. BERCEGEAY, J. MWANZA, C. Pinckney, T. E. SAMSAM, A. M. GELLER, AND P. J. BUSHNELL. Subchronic Toluene Exposure alters Retinal Function in Long Evans Rats: Experimental Evidence Supporting Observations from Studies of Exposed Humans. Presented at Joint meeting of 20th International Conference on Epidemiology in Occupational Health & 10th International Symposium on Neurobehavioral Methods and Effects in Environmental and Occupational Health, San Jose, COSTA RICA, June 09 - 13, 2008.
Impact/Purpose:
We have examined retinal function by recording electroretinograms (ERG) from three sets of rats exposed repeatedly to toluene.
Description:
Studies of humans chronically exposed to volatile organic solvents commonly report impaired visual functions, including low contrast sensitivity and reduced color discrimination. These reports have been controversial, however, in part due to a lack of confirmation from controlled laboratory experiments. We have examined retinal function by recording electroretinograms (ERG) from three sets of rats exposed repeatedly to toluene. The first study examined rats following exposure to 0, 10, 100 or 1000 ppm toluene by inhalation (6 hr/d, 5 d/wk) for 13 weeks. Four to five weeks after completion of exposure, rats were anesthetized, evaluated with an ophthalmoscope, and electroretinograms (ERG) were recorded. Several sets of ERGs were obtained, including a dark-adapted intensity series over a 5-log range of flash luminance values. In the ERG dark-adapted intensity series, B-wave amplitudes were significantly reduced at high stimulus luminance values in rats previously exposed to 1000 ppm toluene. A second set of rats, exposed concurrently with the first set, was tested approximately one year after the termination of exposure to toluene. Again, dark-adapted ERG B-wave amplitudes were reduced at high stimulus luminance values in rats previously exposed to 1000 ppm toluene. A third set ofrats was exposed to the same concentrations of toluene for only 4 weeks. As observed previously, the ERG B-wave amplitudes in rats exposed to 1000 ppm toluene for 4 weeks were reduced in comparison to other groups. These three data sets provide experimental evidence that repeated exposure to toluene may lead to subtle persistent changes in visual function, and support observations of visual deficits in exposed human populations.