[Why do we need controlled clinical studies?]

Controlled clinical studies represent an important tool for quantifying the effects of air pollutants. Examinations can be carried out with the aid of exposure chambers, or employing inhalation via a mask. To date, pulmonary function tests have been the major means of establishing the effects of pollutants. Studies performed to date have served to identify high-risk groups, to demonstrate dose-effect relationships, and to examine borderline values. It is probable that pulmonary function tests are not suitable for detecting the influence of some of the environmental pollutants. More recent clinical techniques, such as broncho-alveolar lavage, nasal lavage, the measurement of alveolar permeability with the aid of labelled aerosols, represent possibilities for investigating other pollutant-induced effects. We need clinical studies because, over and beyond the traditional methods of epidemiology and animal experiments, they can contribute important aspects of the estimation of the risks of environmental pollutants.