1. Abbey, D.E., Petersen, F., Mills, P.K. and Beeson, W.L. (1993) Long-term ambient concentrations of total suspended particulates, ozone and sulphur dioxide and respiratory symptoms in a nonsmoking population.Arch. Env. Health 48, 33–46.
2. Ayres, J. (1994) Asthma and the atmosphere.Br. Med. J. 309, 619–20.
3. Balmes, D.R., Fine, J.M. and Sheppard, D. (1987) Symptomatic bronchoconstriction after short-term inhalation of sulphur dioxide.Am. Rey. Respir. Dis. 136, 1117–21.
4. Bauer, M.A., Utell, M.J., Morrow, P.E., Speers, D.M. and Gibb, F.R. (1986) Inhalation of 0.30 ppm nitrogen dioxide potentiates exercise-induced bronchospasm in asthmatics.Am. Rev. Respir. Dis. 134, 1203–8.
5. Bethel, R.A., Epstein, J., Sheppard, D., Nadel, J.A. and Boushey, H.A. (1983) Sulphur dioxide-induced bronchoconstriction in freely breathing, exercising, asthmatic subjects.Am. Rev. Respir. Dis. 128, 987–90.