Imaging Studies

Electromyogram (EMG) and nerve conduction study (NCS) abnormalities have been demonstrated in individuals and groups exposed to VOCs. Evidence of a mixed sensory/motor neuropathy has been found in many of these patients, while some studies have even demonstrated dose-response data correlating exposure dose to physiological abnormalities (36).

Table 23.4. Levels of exposure believed to be acceptable for workers.

Compound

Measured in:

Compounds and levels believed safe

Acetone

Urine

Acetone, formic acid: 100 mg/L

Benzene

Urine

Total phenol: 50 mg/g at end of shift

Benzene

Expired air

Benzene: preshift 0.08 ppm; at end

of shift 0.12 ppm

Carbon disulfide

Urine

2-TTCA (2-thiothiazolidine

4-carboxylic acid): 5 mg/g

Ethylene oxide

Urine, blood, expired air

None

N-hexane

Urine

2,5-hexanediol: 5 mg/g at end of shift

Hydrogen sulfide

Urine, blood, expired air

None

Methane

Urine, blood, expired air

None

Methyl mercaptan

Urine, blood, expired air

None

Methanol

Urine

Formic acid: 80 mg/g at start

of work week;

Methanol: 15 mg/g at end of shift

Methyl-«-butyl ketone

Urine, blood, expired air

None

Methylene chloride

Urine, blood, expired air

None

Organochlorine

Urine, blood, expired air

None

Organophosphates

Urine, blood, expired air

None

Perchlorethylene (PER)

Blood

PER: 1 mg/L

Perchlorethylene

Expired air

PER: 10 ppm before last shift

of week

Styrene

Urine

End of shift: mandelic acid (MA):

800 mg/g, phenylglyoxylic acid

(PGA): 240 mg/g

Before shift: MA 300 mg/g, or PGA

100 mg/g

Styrene

Blood

Styrene: at start of shift 0.02 mg/L;

end of shift 0.55 mg/L

Toluene

Urine, blood, expired air

Hippuric acid in urine, toluene in

blood and expired air: none

1,1,1-Trichlorethane

Urine

Trichloroacetic acid (TCA) at end

(methyl chloroform)

of workweek: 10 mg/L

Total trichloroethanol at end of

shift and at end of workweek:

30 mg/L

1,1,1-Trichlorethane

Blood

Total trichloroethanol: 1 mg/L

(methyl chloroform)

1,1,1-Trichlorethane

Expired air

Methyl chloroform prior to last

(methyl chloroform)

shift of workweek: 40 ppm

Trichloroethylene (TCE)

Urine

TCE or TCA: 100 mg/g at end

of workweek

TCA plus TCE: 300 mg/g at end

of workweek

Trichloroethylene

Blood

TCE: 4 mg/L at end of workweek

Vinyl chloride

Urine, blood, expired air

None

Xylene

Urine

Methylhippuric acid: 1.5 g/g at end

of shift

Source: Data from American Conference of Governmental Industrial Hygienists (39).

Source: Data from American Conference of Governmental Industrial Hygienists (39).

A study performed on industrial workers in Scandinavia assessed 87 patients with diagnoses of chronic solvent intoxication after occupational exposure. Sixty-two percent had abnormal EMG/NCS results on the first evaluation and 74% on the second evaluation 3 to 9 years later. Fibrillations were noted in 54% on initial examination and 61% on reexamination. The same authors found a high percentage of slow motor and sensory conduction velocities and/or prolonged motor distal latencies in car painters versus none in nonexposed controls (38).

Computed tomography (CT) scan, MRI, positron emission tomography (PET), and single photon emission computed tomography (SPECT) have been utilized to evaluate the mechanism and extent of VOC neurotoxicity in specific cases but have shown no consistent or unique pattern of pathological change. Cerebral, cerebellar, and olivopontocerebellar atrophy are commonly reported, with most frequent abnormalities noted in the temporal lobes and frontal lobes, with associated changes in the basal ganglia and the thalamus (38).

Electroencephalographic abnormalities also have been demonstrated in many populations exposed to organic solvents. In one study, acute effects of exposure to less than 400 ppm of xylene were assessed in healthy volunteers. Such exposure increased the dominant alpha frequency and percentage during the early phase of exposure and counteracted the effect of exercise. These effects were deemed minor and not deleterious. This (or any other) study did not address the more germane issue of longer-term exposure (38).

In acute intoxication cases, the most important presentations include lethargy and depressed sensorium, while coma is relatively uncommon. Other systems (gastrointestinal, skin, respiratory) are often affected and present with easy-to-interpret changes (pneumonitis, skin erythema, vomiting) (38).

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