This study was to evaluate the associations between urinary S-Phenyl-mercapturic acid(S-PMA) as a new indicator of biological monitoring for low level of exposure to benzene and independent variables such as the air concentration of benzene in the breathing zone of workers, the years of work, and smoking. In this study the subjects were the total of 145 drawn from 53 workers who were occupationally exposed to benzene and 92 workers who were not.
The results were as follows:
1. In the workplace geometric mean concentration of benzene in the breathing zone of workers was 0.31 ppm(0.02 - 3.26 ppm) for the spraying workers and 0.25 ppm(0.02 - 3.95 ppm) for the printing workers.
2. The geometric mean of uninary S-PMA for non exposed group was 8.9 ㎍/g creatinine(0.6 - 72.3 ㎍/g creatinine), 80.3% (74 workers) of the total non-exposed workers indicated less than 20 ㎍/g creatinine of uninary S-PMA. The difference of uninary S-PMA by sex, age, smoking was not significant.
3. The geometric mean of urinary S-PMA for workers who were exposed to benzene was 37.2 ㎍/g creatinine, and was four times higher than that of workers who were not exposed. And 79.3% (42 workers) of the total exposed workers indicated more than 20 ㎍/g creatinine of urinary S-PMA.
4. Regarding the level of benzene in the air, urinary S-PMA was the highest level of 147.9 ㎍/g creatinine in the workers who were exposed to air concentration of 0.5 ppm of benzene and was higher as the level in the air was increased.
5. The correlation coefficient between log urinary S-PMA and log benzene concentration in the breathing zone was 0.80, and the following linear equation was found between urinary log S-PMA and log benzene concentration in the breathing zone :
log S-PMA(㎍/g creatinine) = 0.564 log benzene in air(ppm) + 0.192 (n=53, r=0.80, p=0.000)
In conclusion, the concentration of S-PMA in urine proved to be good parameter for biological monitoring benzene exposure at the workplace even at low level of benzene in air.
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