Experience with a vocabulary test for workers previously and still exposed to styrene.

Objectives This study examined the possible influence of styrene exposure on the results of vocabulary tests because verbal ability is assumed to be relatively resistant to the toxic effects of organic solvents and short vocabulary tests are used as "hold tests" in many neurobehavioral epidemiologic studies. Methods To evaluate the chronic neurotoxic effects of styrene, a vocabulary test was administered to a group of still-exposed workers (N = 27) and an earlier exposed group of workers (N = 90). A self-administered questionnaire was filled out on life events, general health, educational level, and amount of education. The still-exposed group had a mean exposure duration of 4700 hours, and that for the formerly exposed group was 3610 hours. Results The vocabulary score of the still-exposed group was significantly lower [12.5 (SD 2.9, range 6-18)] than that of their former colleagues [14.3 (SD 3.4, range 8-22)], even though they originally belonged to the same group and had done the same tasks. The exposure duration explained a significant part of the vocabulary results, resulting in decreasing vocabulary scores even when the influence of years of education and age was taken into account. Even after correction for the possible influence of having been laid off or staying at work, there remained a negative influence on the vocabulary score for the duration of styrene exposure. Conclusions The use of short vocabulary tests as hold tests in cross-sectional studies of solvent-exposed workers may be limited as they seem to lack the essential toxicity-independent property.