[On the problem of passive smoking (author's transl)].

There is no evidence to date that passive smoking leads in the long run to typical smokers' diseases or to an increased health risk in an average healthy person. There are no plausible reasons to justify the assumption that such disturbances develop in passive smokers in the short term. Exposure to tobacco smoke can, under unfavourable conditions, lead to temporary irritation and impair the feeling of well-being which some persons may experience as a considerable nuisance.

[Studies on the reappearing of a bacterial flora in drinking water after ozonization (author's transl)].

The use of ozone as a drinking water disinfectant is increasing. As opposed to the commonly used chlorine the disinfecting activity of ozone cannot be sustained in the water during the distribution process, and as a result recontamination and bacterial growth are not adequately under control. Information about the safety margins of this disinfecting procedure was obtained in experiments simulating the working conditions of a water plant including supply system.

The biological effect of asbestos and asbestos cement products.

The importance of the physical characteristics, rather than the chemical composition of fibres, in relation to their alveolar deposition and biological effects is stressed. For alveolar deposition in the aerodynamic properties--depending on the fibres diameter--are decisive, whereas in the interaction between macrophages and fibres, fibre length is the decisive factor for cytotoxicity. Probably fibre length could, inter alia, be responsible for a pathogenic effect around the lung tissue.

1975 Yant Memorial Lecture New aspects on dust and pneumoconiosis research.

This lecture deals with pneumoconiosis, in particular with fibrotic tissue reactions caused by SiO2 and asbestos dusts in the lungs. The term "fine dusts" is defined in connection with the setting up of MAC-values. The aerodynamical diameter of particle shaped and fibrifom dust is set forth.