Toluene exposure below 50 ppm and cognitive function: a follow-up study with four repeated measurements in rotogravure printing plants.

OBJECTIVE

There are findings of cross-sectional studies on slight cognitive effects due to toluene exposure below 50 ppm. The critical points of the earlier studies will be scrutinised by a follow-up study with four examinations in 5 years.

METHODS

Employees from 14 magazine rotary printing plants were classified into groups of "high" (printing area) vs "low" (end-processing) and "short" vs "long" exposure. The sample size of 333 in examination 1 decreased to 216 in examination 4. A repeated-measurement design could be applied for 192 persons. Current exposure was measured by personal air sampling (n=2,521). Data for past exposure (lifetime weighted average exposure, LWAE) were based on job exposure matrices. High-exposure and low-exposure groups were characterised by 26 ppm vs 3 ppm (current exposure) and 45 ppm vs 9 ppm (LWAE). For long-exposure and short-exposure groups 21 vs 6 years were ascertained. Attention (symbol digit substitution, switching attention, simple reaction), memory (digit span forward and backwards, immediate and delayed reproduction of pictures), and psychomotor functions (steadiness, line tracing, aiming, tapping, peg board) were measured as dependent variables.

RESULTS

Separate stepwise regressions for examinations 1 to 4, which included the co-variables age, level of education, carbohydrate-deficient transferrin as an alcohol marker, and trait anxiety as personality characteristic, did not exhibit remarkable exposure impacts on the performance variables. Repeated-measures analyses of covariance, which included all examination periods, also did not exhibit significant impacts of LWAE or current exposure on the functions measured. Age and education were the dominant factors for the variability of the data. Additionally, carbohydrate-deficient transferrin and trait anxiety showed sporadic impacts on the test results.

CONCLUSION

Evidence for psychological performance effects due to long-term toluene exposure below 50 ppm could not be proved.