Aerosol characterization in real life and a methodology for human exposure studies in controlled chamber settings

Abstract: Airborne particles are everywhere around us, and have always been. Particles generated by human activities has increased drastically since industrialization, and several epidemiological studies have shown that inhaled particles can cause adverse health effects. The concern about health effects have during the last decade shifted towards fine and ultrafine particles, not least due to the emerging field of nanotechnology. Of special interest are the particles to which we are exposed indoors – in the industrialized part of the world we spend around 90% of our time indoors (at home and at workplaces/schools). Particles generated in these environments often cause intense peaks in concentration, and are often consequences of our own activities. Especially combustion/thermal processes (such as welding, frying, burning candles etc.) cause peaks in number concentration, often more than an order of magnitude higher than ambient concentrations. We have conducted time-resolved particle measurements in several homes which confirm this. From these measurements, we have been able to show just how much occupants' activities affect the indoor concentration of ultrafine particles compared to outdoor concentrations. We have also estimated e.g. total integrated daily exposure. Exposure and emission measurements have also been conducted at a carbon nanotube producing facility, and a method for counting particles containing carbon nanotubes has been suggested and validated. Why certain particles are more dangerous than others is often investigated in animal exposure studies, where exposure levels are unrealistically high. For several reasons, the results of such studies are not simple to translate to the human system. To increase our understanding of which particle properties can cause effects in humans, a methodology for conducting human exposure studies have been developed and validated. In a controlled chamber we have exposed human test subjects to normal concentrations of common particle types; candle smoke, particles from terpene–ozone reactions and welding fume. Together with medical expertise, we have been looking for effects of these exposures. By using non-invasive tests (e.g. urine and blood samples and ECG) biochemical markers of exposure, and changes in heart rate variability (HRV) have been studied. A significant increase in the high frequency domain of the HRV during exopsure for candle smoke was found.