The diagnosis of acute benzene toxicity is primarily clinical, based on effects on neurological signs and symptoms and respiratory effects. However, laboratory testing is useful for monitoring the patient and evaluating complications. Routine laboratory studies for all exposed patients include CBC, glucose, and electrolyte determinations. Additional tests for patients who have substantial benzene exposure include ECG monitoring, urinalysis, determinations of BUN, creatinine, and liver function test. Chest radiography and pulse oximetry (or ABG measurements) are recommended for severe inhalation exposure or if pulmonary aspiration is suspected.
Blood levels of benzene or phenol, a metabolite of benzene, may be used to document exposure, although they are not useful clinically. The OSHA benzene standard mandates that urinary phenol-testing be performed on all workers exposed to benzene in an emergency situation (see Follow-up below). However, other factors that may contribute to a high phenol level must be evaluated, such as ingestion of benzoate preservatives, certain medications (e.g., Pepto-Bismol and Chloraseptic), and smoking. Other urinary metabolites of benzene can also be used to document exposure. The ACGIH biological exposure index for benzene is 25 ¦Ìg S-phenyl-N-acetyl cysteine (PhAC)/g creatinine, and muconic acid is also a sensitive marker of benzene.