Subjects will be excluded if any of the following are present: regular use of anti-inflammatory medication; presence of any inflammatory disease of the respiratory tract including moderate or worse COPD (FEV1 < 80% predicted and FEV1/FVC ratio < 0.7). Subjects with normal lung function who meet criteria for diagnosis of chronic bronchitis will be excluded. Subjects with stable medical conditions, excluding inflammatory lung disease, will be permitted to participate, providing anti-inflammatory therapies are not used regularly and providing there has been no change in their clinical status in the two months prior to beginning the study.