Methods to monitor toluene exposure:
(1) blood levels
(2) breath analysis (toluene in parts per minute)
(3) urinalysis
Toluene is metabolized to:
(1) hippuric acid
(2) ortho-cresol
(3) meta-cresol
(4) para-cresol
The molecular weight of toluene is 92.14; the molecular weight of cresol is 108.14.
Hippuric acid is commonly monitored for industrial exposures, but may be affected by soft drinks, fruits and certain medications. Ortho-cresol is very low in persons not exposed to toluene and it is not affected by food intake or medications.
corrected urinary ortho-cresol concentration in mg ortho-cresol per g creatinine =
= (ortho-cresol in mg/dL) / (creatinine in g/dL)
If the values for the line shown in Figure 3, page 221 are analyzed then the following line is defined:
predicted expired air toluene in parts per million =
= (12.534 * (corrected urinary orthocresol levels)) – 617.645
A corrected urinary ortho-cresol levels below 50 mg per g creatinine is associated with very low toluene levels in the expired air.
