Passive smoking, air pollution, and acute respiratory symptoms in a diary study of student nurses

A cohort of approximately 100 student nurses in Los Angeles was recruited for a diary study of the acute effects of air pollution. Smoking histories and presence of asthma and other allergies were determined by questionnaire. Diaries were completed daily and collected weekly for as long as 3 yr. Air pollution was measured at a monitoring location within 2.5 miles of the school. Incidence and duration of a symptom were modeled separately. Pack-years of cigarettes were predictive of the number of episodes of coughing (p < 0.0001) and of bringing up phlegm (p < 0.0001). Current smoking, rather than cumulative smoking, was a better predictor of the duration of a phlegm episode (p < 0.0001). Controlling for personal smoking, a smoking roommate increased the risk of an episode of phlegm (odds ratio [OR] = 1.41, p < 0.001), but not of cough. Excluding asthmatics (who may be medicated), increased the odds ratio for passive smoking to 1.76 (p < 0.0001). In logistic regression models controlling for temperature and serial correlation between days, an increase in 1 SD in carbon monoxide exposure (6.5 ppm) was associated with increased risk of headache (OR = 1.09, p < 0.001), photochemical oxidants (7.4 pphm) were associated with increased risk of chest discomfort (OR = 1.17, p < 0.001) and eye irritation (OR = 1.20, p < 0.001), and nitrogen dioxide (9.1 pphm) was associated with increased risk of phlegm (OR = 1.08 p < 0.01), sore throats (OR = 1.26, p < 0.001), and eye irritation (OR = 1.16, p < 0.001). SO₂ was not significantly associated with any symptom. We conclude that passive smoking and short-term exposure to NO₂ and photochemical oxidants increase the incidence rates of respiratory illness.