The modifying effect of the building envelope on population exposure to PM2.5 from outdoor sources.

UNLABELLED: A number of studies have estimated population exposure to PM2.5 by examining modeled or measured outdoor PM2.5 levels. However, few have taken into account the mediating effects of building characteristics on the ingress of PM2.5 from outdoor sources and its impact on population exposure in the indoor domestic environment. This study describes how building simulation can be used to determine the indoor concentration of outdoor-sourced pollution for different housing typologies and how the results can be mapped using building stock models and Geographical Information Systems software to demonstrate the modifying effect of dwellings on occupant exposure to PM2.5 across London. Building archetypes broadly representative of those in the Greater London Authority were simulated for pollution infiltration using EnergyPlus. In addition, the influence of occupant behavior on indoor levels of PM2.5 from outdoor sources was examined using a temperature-dependent window-opening scenario. Results demonstrate a range of I/O ratios of PM2.5 , with detached and semi-detached dwellings most vulnerable to high levels of infiltration. When the results are mapped, central London shows lower I/O ratios of PM2.5 compared with outer London, an apparent inversion of exposure most likely caused by the prevalence of flats rather than detached or semi-detached properties. PRACTICAL IMPLICATIONS: Population exposure to air pollution is typically evaluated using the outdoor concentration of pollutants and does not account for the fact that people in London spend over 80% of their time indoors. In this article, building simulation is used to model the infiltration of outdoor PM2.5 into the domestic indoor environment for dwellings in a London building stock model, and the results mapped. The results show the variation in relative vulnerability of dwellings to pollution infiltration, as well as an estimated absolute indoor concentration across the Greater London Authority (GLA) scaled by local outdoor levels. The practical application of this work is a better understanding of the modifying effect of the building geometry and envelope design on pollution exposure, and how the London building stock may alter exposure. The results will be used to inform population exposure to PM2.5 in future environmental epidemiological studies.

Reproduction and development of laboratory and wild house dust mites (Acari: Pyroglyphidae) and their relationship to the natural dust ecosystem.

Life histories of "wild" house dust mites, Dermatophagoides pteronyssinus (Trouessart) (Acari: Pyroglyphidae), were compared with laboratory cultures by using a diet consisting of skin and dust or a laboratory diet consisting of dried liver and yeast. Under constant conditions of 25 degrees C and 75% RH, fecundity and rate of reproduction were higher in laboratory cultures on both diets compared with wild mites. There were also trends for a shorter prereproductive period and more rapid egg development of laboratory mites compared with wild mites. Overall, there was little effect of diet on either strain of mites at 75% RH. At low RH (64%), fecundity was significantly lower (for both strains on both diets), and there were also trends for longer prereproductive period, reduced rate of reproduction, reduced adult survival, prolonged egg and juvenile development, or a combination compared with 75% RH. Additionally egg and juvenile mortality were significantly higher on the liver and yeast diet. Overall, the skin and dust diet favored both strains of mites at 64% RH. On the liver and yeast diet at 64% RH, wild mite adults performed significantly better than laboratory mites, and egg mortality was lower. These results suggest that laboratory mites have stronger reproduction and development than wild mites, except when under environmental stress and that diet is a significant factor, particularly in suboptimal conditions. This could have important implications for predictive models of house dust mite populations in their natural habitat. Ideally, such models should be developed using data from wild dust mite populations reared on a natural diet.