Chest
Volume 90, Issue 4, October 1986, Pages 494-499
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Clinical Investigations
Chronic Asthma Due to Toluene Diisocyanate

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Twelve subjects were studied with inhalation challenge testing to toluene diisocyanate (TDI) because of suspected TDI asthma based on a consistent clinical and occupational history. In seven cases, TDI asthma was documented by a positive inhalation challenge to low levels of TDI. Six of the seven TDI reactors had persistent respiratory symptoms and required daily treatment even though they had been removed from isocyanate exposure for intervals as long as 12 years (mean 4.5 years). These six TDI reactors had either dual (four cases) or late bronchospasm (two cases) to less than 20 ppb TDI, and all had a positive methacholine or cold air challenge prior to study. The one TDI reactor with a negative methacholine challenge had a positive (immediate) bronchospastic response to a TDI challenge performed one week after removal from isocyanate exposure. Five workers had a negative TDI challenge, two of whom had persistent respiratory symptoms and positive methacholine challenges at the time of TDI inhalation testing. We conclude that respiratory symptoms may persist following long-term removal from occupational exposure to TDI and are associated with nonspecific bronchial hyperreactivity. The TDI sensitivity may also persist for a long time even in the absence of any additional occupational exposure. Long-term prospective studies of symptomatic isocyanate workers are needed to fully define the extent of this problem.

Section snippets

Patients

Patients were referred to the Occupational Health Clinic for evaluation of possible TDI asthma over a five-year period from 1980 to 1985. In only 12 workers was the clinical and occupational history consistent with a diagnosis of occupational asthma due to TDI. Approximately 20 other subjects were evaluated, and the history was not consistent with a diagnosis of occupational asthma. The 12 workers reported symptoms consistent with a diagnosis of TDI asthma including cough, shortness of breath,

RESULTS

In seven cases, TDI asthma was documented by a positive inhalation challenge to TDI (Table 1). Results of baseline pulmonary function tests were generally normal (FEV1 and FVC 80 percent predicted and FEV1/FVC 70 percent) or perhaps mildly decreased in the study population as follows: spirometric findings were normal in five of seven reactors and four of five nonreactors. One reactor had a FEV1 of 73 percent predicted (and FEV1/FVC of 33 percent); the second reactor had FEV1 of 69 percent and

DISCUSSION

In the present study, 12 workers with suspected TDI asthma were evaluated by bronchial challenge to TDI. Seven persons demonstrated sensitivity to low levels of TDI (reactors), confirming isocyanate sensitization. Six of these TDI reactors were challenged months to years after removal from their workplace exposure, demonstrating that isocyanate sensitization may persist for years in the absence of further occupational exposure. These six persons had chronic asthma symptoms and pulmonary

ACKNOWLEDGMENT

The authors thank Dr. Joan Gallagher for performing the RAST assays and Marilyn Clark and Mary Ann Brockman for secretarial assistance.

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This study was supported in part by NIEHS Center grant 5P30ES00159; GCRC grant MOL-RR-00068; NIHLB grant HL224I5; National Research Service Award Training grant HL06915–01; the National Heart, Lung and Blood Institute (Dr. Moller); and the Asthma and Allergy Foundation of America Fellowship Award (Dr. Moller).

Manuscript revision accepted April 8.

Reprint requests: Environmental Health Library, Mail Location 56, University of Cincinnati, Cincinnati 45267-0056

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