Nitrogen dioxide exposure from domestic gas cooking and airway response in asthmatic women
- aDepartment of Community, Occupational and Family Medicine, Faculty of Medicine, National University of Singapore, Lower Kent Ridge Road, Singapore, bRespiratory Medicine Department, National University Hospital, Singapore, cDepartment of Chemical Engineering, National University of Singapore
- Dr T P Ng
- Received 12 April 2000
- Revision requested 5 June 2000
- Revised 9 April 2001
- Accepted 25 April 2001
BACKGROUND Previous studies have not found a consistent association between exposure to domestic cooking using gas appliances and exacerbation of asthma. We investigated the immediate airflow response to acute exposure from single episodes of gas cooking, and peak airflow variability from continued exposure to repeated episodes of gas cooking in a group of non-smoking asthmatic women.
METHODS Sixteen adult non-smoking women with mild to severe persistent asthma were studied. The acute short term level of nitrogen dioxide (NO2) during gas cooking episodes and the mean exposure to NO2 from repeated gas cooking episodes were measured over a 2 week period, as well as proxy measures of frequency of cooking on each day and the length of time spent cooking each day. Their asthma status was monitored using peak expiratory flow rates (PEFR) before and after cooking, 2 week self-recorded serial readings of PEFR, respiratory symptom severity score, and use of rescue bronchodilators for acute asthma attacks.
RESULTS Cooking was significantly associated with an immediate mean fall in PEFR of 3.4% (p=0.015, paired t test). The acute short term NO2 level during cooking was significantly correlated with the fall in PEFR (r=–0.579; p=0.019). The frequency of cooking over a 2 week period was positively correlated with the mean exposure to NO2(r=0.529; p=0.042). Continued exposure to NO2 over a 2 week period was associated significantly with increased frequency of rescue bronchodilator usage for asthma attacks (r=0.597; p=0.031). However, it was negatively associated with PEFR variability (r=–0.512; p=0.051) and respiratory symptom severity score (r= –0.567; p=0.043), probably due to the masking effects of bronchodilator treatment.
CONCLUSIONS Acute short term exposure to NO2 from single episodes of gas cooking is associated with immediate airflow limitation. Continued exposure from repeated episodes of gas cooking in asthmatic women is associated with greater use of rescue bronchodilators.