One-year occupational exposure to a cold environment alters lung function

Numerous observations have shown that breathing cold air causes bronchospasm and increases respiratory tract secretions in asthmatic patients and normal individuals. However, few studies have been conducted on the respiratory effects of protracted daily exposures to a cold environment. In this 1-yr study, the authors examined individuals who spent 6 hr a day in cold stores (+3 degrees C to + 10 degrees C) and spent approximately 25% of that time at +3 degrees C. The protocol included a questionnaire about clinical symptoms, with measurements of baseline pulmonary function and airway responses to carbachol and to nasal inhalation of cold air (-5 degrees C). Eleven subjects were examined prior to their first occupational exposure to cold, and again following 6 mo and 12 mo of work in the cold environment. Compared with a control group of 6 subjects engaged at the same time but who did not work in cold stores, 6 of 11 individuals who worked 12 mo in a cold environment experienced increased symptoms of rhinitis, sore throat, and cough. Physiological measurements at 6 mo and 12 mo showed a progressive decrease in forced expiratory volume in 1 sec and a progressive increase in the baseline value of central airway resistance. Forced expiratory flow measured between 25% and 75% of vital capacity had decreased at 6 mo, but showed no further change at 12 mo. A progressive enhancement of bronchial reactivity to carbachol was noted at 6 mo and again at 12 mo, but airway response to nasal breathing of cold air did not vary. The authors concluded that 1 yr of daily exposure to a cold occupational environment elicits a modest--but significant--airflow limitation, accompanied by bronchial hyperresponsiveness, with the effects beginning within 6 mo of exposure.