Asthma and chemical bronchitis in vanadium plant workers.

BACKGROUND: Whether vanadium induces bronchial hyperresponsiveness and asthma in previously normal subjects is unresolved: the two reported series addressing this question both have shortcomings.
OBJECTIVE: To determine the cause of cough and breathlessness in vanadium plant workers after variable periods of exposure.
DESIGN: Case series of employees presenting with persistent symptoms over a 24-month study period. PATIENTS AND METHODS: Forty of an estimated 1,440 patients were investigated by 1) blood count and serum IgE, 2) intracutaneous allergen skin tests, 3) spirometry, and 4) bronchoprovocation by histamine inhalation or exercise challenge. Exposure was assessed by measurement of 1) ambient V2O5, NH3 and SO2 over 7 days during the 24-month study period, 2) urine vanadium concentration at time of first presentation.
RESULTS: Twelve of 40 subjects had bronchial hyperreactivity (BHR), and these were compared to 12 age-matched companion subjects whose BHR was normal. In 10, BHR was diagnosed by histamine inhalation (PC20 0.25-1.82 mg/ml, nl > 8.0 mg/ml), and in six of these the abnormality was severe (PC20 < 0.5 mg/ml). A further two had BHR by exercise challenge (FEV1, 600 ml/30% and 770 ml/18% pre/post exercise). After removal from exposure, 9 of the 12 subjects returned for follow-up 5 to 23 months later. BHR was worse in one, still present although less severe in five, and was no longer found in one subject. Baseline spirometry measurements were normal in seven subjects and only mildly impaired in the remaining five of the 12 subjects with BHR.
CONCLUSION: This study provides strong supporting evidence that inhaled V2O5 induces BHR and asthma in subjects previously free of lung disease; the abnormality may persist for up to 23 months following exposure; routine spirometry will not detect affected subjects.