Abstract:
The objectives of this cross-sectional study were to study the factors and create an
equation to predict the effect of toluene exposure to the nervous system among spraying migrant
workers in a toy manufacturing factory in Pathumthani province. A sample of 103 Cambodian
workers per group consisted of the exposed group working at painting department of the factory
and the control group were working in other departments in the same factory. Data were collected
using an interview form that was adapted from an Euroquest questionnaire (EQ) to evaluate
neurological symptoms, the Digit span forward and backward memory test using the Psychology
Experiment Building Language (PEBL) computer program to evaluate neuropsychological
impairment. Urine samples were also taken to evaluate toluene concentration in urine.
The results of the study showed that most workers of exposed group were male with
an average age of 28.7 years (SD = 5.5). Their educational attainment ranged from grade one to
six. Half of the workers drank alcohol; 11.6 percent of the sample reported to currently smoke.
The number of male and female workers of the control group were almost the same. Their
average age was 28.4 (SD = 6.2) years, their educational level was similar to the exposed group,
most of them did not drink alcohol and 5.8 percent currently smoked. Most of the workers in both
groups were never exposed to organic solvents during previous jobs they held. The average
working duration of the exposed group at the painting department was 1.7 years (SD = 0.8). Both
the exposed and control groups worked more than 12 hours overtime per week on average.
Personal protective masks and gloves were used only by the exposed group. Both groups reported to wash their hands before eating, drinking and after work, and shower after work regularly. The
concentration of toluene found in the urine samples of the 97 exposed workers and 103 control
workers was less than 10 µg / L. The result of the interview data found that most workers in both
groups reported to never, seldom or sometimes experience abnormal acute and chronic
neurological symptoms. The exposed group had at least 3 more abnormal symptom per domain
for all symptom domains than the control group. The average score from the Digit span forward
and backward memory test of the two groups were also different with a t-test score of -2.842
(0.756 , -0.137) and -3.221 (-0.736, -0.177) respectively. Factors that were related to nervous
system complaints were educational attainment level and sex; workers who graduated grade one
to six had more chronic symptoms of the psychosomatic symptom domain with OR (95% CI)
2.179 (1.066, 4.454) than workers who graduated grade seven to twelve, and male workers
reported more chronic symptoms of the sleep disturbance symptom domain than females with OR
(95% CI) 4.000 (1.029, 15.546). Current smokers were found to have neuropsychological affects
that were higher than non-smokers, with Digit span forward memory test scores with a regression
coefficient -0.537. Thus, the prediction equation for toluene exposure to the nervous system can
be derived. Equation 1 can be derived from the data collected via the interview forms, as follows:
Psychosomatic symptom domain y = 1.862 + 0.779Education level (grade one to six) .Equation 2 can be
derived same Equation 1, as follows: Sleep disturbance symptom domain y = 3.664 + 1.386sex
(male). Equation 3 can be derived from the Digit span tests, as follows: y = 4.000 -0.537Smoking history
(current smoker) . In conclusion, the data collected in this study can be used as a guideline to assess the
health of workers exposed to toluene in their workplace, in order to reduce the effect of this
exposure on the nervous system. Intervention-wise, the effects of toluene exposure can be
reduced highlighting the negative effects of smoking. Overall, the knowledge of workers about
the long term impacts of toluene exposure and working practices should be improved.