Effect of energy renovation and occupants' activities on airborne particle concentrations in Swedish rental apartments.

Exposure to airborne particles causes detrimental health effects, hence their assessment in indoor environments, where people spend most of the time, is important. The influence of energy renovation and occupants' activities on airborne particle concentrations was assessed in seven occupied Swedish residences. Ultrafine particle (UFP, <100 nm) number concentrations, PM2.5 (<2.5 µm) and black carbon (BC, <900 nm) mass concentrations were simultaneously measured inside and outside before, after renovation, and during follow-up. The average indoor UFP number concentrations increased from 6200 (±4070) cm-3 before renovation to 12,700 (±6040) cm-3 during the follow up, as the number of indoor activities doubled. Indoor UFP number concentrations depended mainly on frequency and type of occupants' activities in studied residences (e.g., cooking, candle burning). The average indoor PM2.5 concentration decreased from 8.6 (±5.8) µg m-3 before renovation to 2.5 (±1.3) µg m-3 during follow up, as the activities that generated PM2.5 decreased, and infiltration of outdoor particles could have been decreased due to renovation measures. However, the indication of infiltration decrease during the follow up, assessed on the basis of indoor to outdoor ratios during non-activity times (with no influence of occupants' activities), was not observed after the renovation and should be treated with caution. In this study indoor PM2.5 and BC were influenced by activities and outdoor concentrations. Reduction of exposure to indoor UFP, might be obtained by optimization of kitchen exhaust flows. An improved design of supply air inlets in mechanical exhaust ventilation systems may reduce PM2.5 infiltration. Occupants' logbook records, needed for identification of sources contributing to particle exposure, proved useful but not always accurate compared to technical measurements of activities and UFP concentrations. Development of simple and reliable activity detection systems is needed to complement logbooks and allow accurate assessment of source contribution to particle exposure in homes and associated health effects.

Healthy Indoor Environments: The Need for a Holistic Approach.

Indoor environments have a large impact on health and well-being, so it is important to understand what makes them healthy and sustainable. There is substantial knowledge on individual factors and their effects, though understanding how factors interact and what role occupants play in these interactions (both causative and receptive) is lacking. We aimed to: (i) explore interactions between factors and potential risks if these are not considered from holistic perspective; and (ii) identify components needed to advance research on indoor environments. The paper is based on collaboration between researchers from disciplines covering technical, behavioural, and medical perspectives. Outcomes were identified through literature reviews, discussions and workshops with invited experts and representatives from various stakeholder groups. Four themes emerged and were discussed with an emphasis on occupant health: (a) the bio-psycho-social aspects of health; (b) interaction between occupants, buildings and indoor environment; (c) climate change and its impact on indoor environment quality, thermal comfort and health; and (d) energy efficiency measures and indoor environment. To advance the relevant research, the indoor environment must be considered a dynamic and complex system with multiple interactions. This calls for a transdisciplinary and holistic approach and effective collaboration with various stakeholders.