Indoor/outdoor relationships of particulate matter in domestic homes with roadside, urban and rural locations

Particulate matter was measured inside and outside seven homes within Birmingham, UK, and two homes in rural locations during a 12 month period. Two of the urban homes were on the 10th and 13th floor of a multi-storey block of flats in the city centre; others were at ground level. Direct reading TEOM instruments provided near real-time data for PM10, PM2.5 and PM1 mass concentrations. Particulate chemical composition was determined by the analysis of PTFE filters positioned in the bypass flow line of the TEOM, and QMA filters in modified Andersen cascade impactors. TEOM data were used in conjunction with information gained from activity diaries completed by occupants to identify the sources of episodic elevated particle concentrations within the home. Whilst the results indicated an important background contribution to indoor particulate matter from penetration of outdoor particles, indoor sources such as cooking, smoking, cleaning and general activity contributed substantially to indoor concentrations of PM10 and were the dominant source of episodic peaks in PM10. Cooking and smoking were determined to be major indoor sources of PM2.5 and PM1, whilst cleaning and general activity had little influence on concentrations within this size range. Chemical analysis of the particles collected was used to identify those particles with mainly indoor sources, such as organic carbon from cooking and those with outdoor sources, such as lead and sulphate. Sulphate proved a useful marker for demonstrating the greater ingress and/or indoor air lifetime of fine particles from outside the home (I/O ratio 0.8 for PM1.1) compared to coarse particles (I/O ratio 0.6 for PM10). I/O ratios for components such as zinc and elemental carbon were more site-specific.