Large organic aerosols in a human exposure chamber : applications in occupational dermatology and lung medicine

Abstract

Exposure to large organic aerosol particles may cause respiratory and skin reactions. The use of human exposure chambers offers possibilities for experimental exposure challenges carried out with patients, in research and for investigations of the effects of exposure on the skin and in the respiratory tract. The present aim was to study the performance of modern human whole-body exposure chambers during generation of large organic particles, and to develop and test new measuring techniques for use in exposure studies of the respiratory tract or on the skin.

The work reported in the present thesis was based primarily on studies in a whole-body human exposure chamber located at Karolinska University Hospital in Solna, Stockholm, Sweden. This chamber was specially constructed for challenges with aerosols. Dynamically controlled, the chamber is easy to operate. Since human exposure chamber set-ups and designs may vary and yield different performance and dust characteristics, the performance of another human chamber was also evaluated.

Performance as a measure of temporal and spatial variability of the aerosol concentration, and aerodynamic particle size, was evaluated for these two chambers based on different airand dust-mixing principles. Temporal and spatial variability close to the breathing zone during exposure was typically <10% in the chamber at Karolinska University Hospital. In a larger section around a human, only slightly higher spatial variation was found. The variability between exposure sessions was also low (<10%). Only limited influence of relative humidity on chamber performance for the evaluated aerosols was observed.

Similar performance characteristics with pinewood dust were obtained in both chambers. The particle size distribution curves differed slightly, but some were comparable to those found in occupational environments. Performance as measured with a heated mannequin was almost the same as with humans, indicating that a mannequin can be used in preparatory tests. The temporal variation during an exposure session varied considerably if a neutralizer device for removing static charges in the dust was not connected; here over 20 30% variation was not unusual. A neutralizer greatly decreased this variation to values near 10% as measured in one of the chambers. The same outcome was also found for spatial variation, which was high (over 20%) with no neutralizer.

Exposure to wood dust within the woodworking industry causes various respiratory disorders. A study of bronchoalveolar lavage (BAL) fluid from eleven healthy individuals exposed to pinewood dust in one of the chambers revealed an accumulation of eosinophils and T-lymphocytes in the lungs after exposure.

Skin exposure to aerosols of allergens and irritants may cause dermatitis. There are few methods for assessing skin exposure to such particles. A vacuuming sampler for removing particles from the skin was constructed and was tested in one of the chambers. This sampler was compared with two other skin and surface sampling techniques, one based on interception (a patch sampler - adhesive tape on an optical cover glass) and one using a tape stripping procedure. All three methods measure the mass of dust on skin. Healthy subjects were exposed to dust of wheat flour and cornstarch. Samples were taken from forearms and shoulders and analysed using optical microscopy. Small differences in the results were obtained. Agreement between the vacuuming sampler and the tape stripping technique was good. The three techniques are applicable for assessing skin exposure to particles and for dose/effect studies. The vacuuming technique allows for dust sampling from large areas of skin.