Because signs and symptoms of toluene intoxication typically depend on the intensity, duration, and frequency of exposure, assessment of a patient with suspected toluene exposure begins with defining the route or routes of exposure and determining if the exposure was acute or chronic and at what concentrations the exposure occurred. The temporal relationship of symptom onset to possible exposure should be explored. In addition, the following information might be helpful: history of chronic illness; chronic use of medications (e.g., aspirin); social history; tobacco use and exposure to tobacco smoke; alcohol or illicit drug use; occupational history; recent hobbies and household remodeling projects, particularly painting and furniture refinishing; and use of consumer products such as nail polish, adhesives, aerosols, and solvent-based cleaners. Because many products containing toluene are mixtures, attempts should be made to ascertain the total composition. Proximity of residence to landfills and industrial facilities and the source of drinking water might provide clues to environmental exposures. (See Case Studies in Environmental Medicine: Taking an Exposure History.)

Clinical evaluation of a patient with acute exposure should focus on the organ systems most often affected by toluene: neuropsychiatric, renal, cardiovascular, and respiratory. In the case of chronic abusers, the hepatic system should also be evaluated. Possible volatile-solvent abuse and concomitant use of alcohol or other drugs of abuse should be considered when chemically induced CNS depression is present.

Acute Exposure

• Symptoms are unlikely to occur after exposure to airborne concentrations below the odor threshold.

Substantial nonoccupational, acute exposures to toluene are most frequently the result of intentional inhalation of glue, paint, or solvent vapors. High-concentration exposures can also occur in hobbyists and do-it-yourself workers in confined spaces. Short-term exposure to high concentrations of toluene (e.g., 600 ppm) can produce fatigue, dizziness, headaches, loss of coordination, nausea, and stupor; 10,000 ppm can cause death from respiratory failure.

Acute exposure results in CNS depression with headache, dizziness, lightheadedness, and euphoria, and can lead to cardiopulmonary collapse, coma, and death. In addition to CNS depression, acute ingestion can cause nausea, vomiting, possible hematemesis, and burning of the oropharynx and epigastrium. Aspiration can lead to hoarseness, coughing, and chemical pneumonitis.

If a large ingestion of toluene is suspected or if respiratory distress develops after acute inhalation exposure, hospital admission, chest radiography, spirometry, determination of arterial blood gases, and monitoring of vital signs are recommended. Acutely exposed patients who are asymptomatic and have a negative chest radiograph do not require further hospital observation.

Dermal exposure usually only causes skin irritation. When contact with the solvent is unusually extensive and prolonged, some systemic absorption can occur. Ocular exposure to liquid toluene can cause corneal burns.

Chronic Exposure

• Chronic solvent abuse is associated with various neurobehavioral and neuropsychologic effects.

Repeated high-dose exposures associated with solvent abuse can result in progressive memory loss, fatigue, poor concentration, irritability, persistent headaches, and signs and symptoms of cerebellar dysfunction. Although these effects generally are reversible if exposure ceases, some patients remain substantially impaired. Muscular weakness has been noted in patients who develop renal-tubular acidosis.

In general, if toluene exposure is suspected, baseline studies should include the following:

• electrolytes with blood urea nitrogen and creatinine;
• complete blood count and smear;
• electrocardiogram with rhythm monitoring;
• liver enzymes;
• urinalysis;
• creatine kinase;
• neuropsychologic assessment (a referral for detailed neuropsychologic evaluation is indicated only if the patient's abnormal mental status or behavioral changes persist after exposure ceases); and
• chest radiograph, if symptomatic.

Baseline tests should be repeated in 3 to 6 months to detect delayed hepatic or renal abnormalities or both. A neuropsychologic follow-up evaluation should also be carried out at this time. Patients with substantial chronic exposures should have annual reassessments.

The patient in this case study should be hospitalized and connected to a cardiac and fetal monitor, with a pulse oximeter in place; vital signs should be monitored at short interval periods. An obstetrical and environmental medical consult should also be part of this patient's initial clinical assessment and followup.

• Toluene can be measured in blood, but the level has little clinical relevance.

Because excretion of toluene and its metabolites is rapid (essentially complete within 12 to 24 hours), biologic samples for analysis must be obtained soon after exposure. A venous blood sample taken within 1 day after exposure can be used to confirm toluene exposure (normal for unexposed populations is 0.1 milligrams/deciliter [mg/dL]); however, the toluene level obtained will not correlate well to the degree of exposure or to symptoms. Analysis of exhaled air for toluene is experimental only.

• Urinary hippuric acid levels should be interpreted with caution.

Hippuric acid, a metabolite of toluene, can also result from the metabolism of other chemicals, including common food additives, and is typically found in significant amounts in the urine from unexposed persons. Hippuric acid levels of >2.5 grams per gram (g/g) creatinine suggest toluene exposure.