[show abstract][hide abstract] ABSTRACT: Human exposure to particles depends on particle loss mechanisms such as deposition and filtration. Fine and ultrafine particles (FP and UFP) were measured continuously over 7 consecutive days during summer and winter inside 74 homes in Edmonton, Canada. Daily average air exchange rates were also measured. FP were also measured outside each home and both FP and UFP were measured at a central monitoring station. A censoring algorithm was developed to identify indoor-generated concentrations, with the remainder representing particles infiltrating from outdoors. The resulting infiltration factors were employed to determine the continuously changing background of outdoor particles infiltrating the homes. Background-corrected indoor concentrations were then used to determine rates of removal of FP and UFP following peaks due to indoor sources. About 300 FP peaks and 400 UFP peaks had measurable decay rates lasting from 30 minutes to 10 hours. Median (Interquartile range (IQR)) decay rates for UFP were 1.26 (0.82 to 1.83) h-1; for FP 1.08 (0.62 to 1.75) h-1. These total decay rates included, on average, about a 25% contribution from air exchange, suggesting that deposition and filtration accounted for the major portion of particle loss mechanisms in these homes. Models presented here identify and quantify effects of several factors on total decay rates, such as home age, use of central furnace fans and kitchen and bathroom exhaust fans, use of air cleaners, use of air conditioners, and indoor-outdoor temperature differences. These findings will help identify ways to reduce exposure and risk.
[show abstract][hide abstract] ABSTRACT: Several exposure studies of indoor air contaminants have used passive sampling devices (PSDs) to determine VOC levels. An existing passive method to determine airborne naphthalene at low levels offers reproducible but low recoveries, considered unacceptable for producing quantitative results. Given the need to determine airborne naphthalene quantitatively with high sensitivity and high quality, optimization of the passive sampling
method was undertaken. Seven solvent combinations were evaluated to determine the extraction efficiency, toluene being the most promising. Detailed assessments of toluene extracts allowed optimization of chromatographic performance and characterization of the new method. Passive sampling was then conducted as part of an indoor air exposure study in up to 6 locations within residences including the living room, garage, basement, bathroom, main bedroom and kitchen for both 7-day and 24-hr integrated samples. Results indicate summer naphthalene concentrations were highest in the garage, followed by the basement and then living room.
12th International Conference on Indoor Air Quality and Climate; 06/2011
[show abstract][hide abstract] ABSTRACT: Indoor air concentrations of formaldehyde, acetaldehyde and acrolein were measured in Halifax, Nova Scotia and Edmonton, Alberta. Seven consecutive 24-hr measurements were made in 50 non-smoking homes in winter and summer in each city. In addition, data on relative humidity, temperature, air exchange rates, housing characteristics and occupants’ activities were collected. Determinants of indoor levels for formaldehyde and acetaldehyde were examined using linear mixed-effects regression models. The housing characteristics and occupants’ activities investigated in this study explained between 26% and 50% of the variability in pollutant concentrations, with air exchange rates, year of construction, indoor temperature and indoor relative humidity being important predictors for both formaldehyde and acetaldehyde.
12th International Conference on Indoor Air Quality and Climate; 06/2011
[show abstract][hide abstract] ABSTRACT: There is a growing body of evidence demonstrating that coarse particles (PM10–2.5) have detrimental impacts upon health, especially for respiratory effects. There are limited data available for indoor residential exposures. Some data exist regarding the composition of this PM size fraction with emphasis on crustal elements and biological components. This study includes data from 146 homes sampled in Regina, Saskatchewan (SK) where 5-day integrated concurrent monitoring of indoor and outdoor coarse particles was conducted during the winter and summer of 2007. The coarse particle filters were subsequently analysed for endotoxin content to determine the contribution of this compound. Winter indoor geometric mean concentrations of coarse particles exceeded outdoor concentrations (3.73 μg m−3 vs 2.49 μg m−3; paired t-test p < 0.0001); however the reverse was found in summer (4.34 μg m−3 vs 8.82 μg m−3; paired t-test p < 0.0001). Linear regression indicated that winter predictors of indoor coarse particles were outdoor coarse particles, ventilation and presence of at least two or more occupants. During the summer, increased use of central air conditioning was associated with reduced coarse particles, while smoking and the presence of two or more occupants resulted in increased coarse particles. Endotoxin concentrations (EU μg−1) were lower indoors than outdoors in both seasons. Spatial variability of ambient coarse particles was assessed to determine the suitability of using a single monitoring station within a city to estimate exposure. The coefficients of variation between homes sampled simultaneously and the central monitoring station were calculated (median COV in summer = 15% and winter = 24%) and showed significant variability by week, especially during the summer months, suggesting a single site may be insufficient for characterizing exposure. Future studies should consider daily measurements per home to understand shorter term exposures and day to day variability of these pollutants.Highlights► Winter indoor concentrations of coarse PM exceeded outdoor concentrations. ► Endotoxin concentrations were lower indoors than outdoors in both seasons. ► Spatial variability of ambient coarse PM is higher in summer than winter.
[show abstract][hide abstract] ABSTRACT: Indoor concentrations of air pollutants (benzene, toluene, formaldehyde, acetaldehyde, acrolein, nitrogen dioxide, particulate matter, elemental carbon and ozone) were measured in residences in Regina, Saskatchewan, Canada. Data were collected in 106 homes in winter and 111 homes in summer of 2007, with 71 homes participating in both seasons. In addition, data for relative humidity, temperature, air exchange rates, housing characteristics and occupants' activities during sampling were collected. Multiple linear regression analysis was used to construct season-specific models for the air pollutants. Where smoking was a major contributor to indoor concentrations, separate models were constructed for all homes and for those homes with no cigarette smoke exposure. The housing characteristics and occupants' activities investigated in this study explained between 11% and 53% of the variability in indoor air pollutant concentrations, with ventilation, age of home and attached garage being important predictors for many pollutants.
International Journal of Environmental Research and Public Health 08/2010; 7(8):3080-99. · 2.00 Impact Factor
[show abstract][hide abstract] ABSTRACT: Concentrations of 26 volatile organic compounds (VOCs) were measured continuously for 7 days during winter in 96 homes in Quebec City, Canada. Characteristics of the houses and activities of the occupants were documented through detailed questionnaires filled out by one adult per household. VOCs were sampled using passive monitors and analyzed by gas chromatography-mass selective detector (GC-MSD). Results indicate contributions to indoor levels of some VOCs from combustion sources and recent renovation activities. Negative associations were seen between certain VOCs and the presence of carpets and furniture. In general, higher VOCs concentrations were found in newer houses. No association was found between individual VOCs and air change rate. Results suggest that multiple indoor sources contribute to occupants' exposure to VOCs during winter in Quebec City homes.
Indoor and Built Environment 01/2008; 17(2):128-137.
[show abstract][hide abstract] ABSTRACT: Concentrations of nitrogen dioxide and formaldehyde were determined in a study of 96 homes in Quebec City, Canada, between January and April 2005. In addition, relative humidity, temperature, and air change rates were measured in homes, and housing characteristics were documented through a questionnaire to occupants. Half of the homes had ventilation rates below 7.5 L/s person. Nitrogen dioxide (NO2) and formaldehyde concentrations ranged from 3.3 to 29.1 microg/m3 (geometric mean 8.3 microg/m3) and from 9.6 to 90.0 microg/m3 (geometric mean of 29.5 microg/m3), respectively. The housing characteristics documented in the study explained approximately half of the variance of NO2 and formaldehyde. NO2 concentrations in homes were positively correlated with air change rates (indicating a significant contribution of outdoor sources to indoor levels) and were significantly elevated in homes equipped with gas stoves and, to a lesser extent, in homes with gas heating systems. Formaldehyde concentrations were negatively correlated with air change rates and were significantly elevated in homes heated by electrical systems, in those with new wooden or melamine furniture purchased in the previous 12 months, and in those where painting or varnishing had been done in the sampled room in the previous 12 months. Results did not indicate any significant contribution of indoor combustion sources, including wood-burning appliances, to indoor levels of formaldehyde. These results suggest that formaldehyde concentrations in Quebec City homes are caused primarily by off-gassing, and that increasing air change rates in homes could reduce exposure to this compound. More generally, our findings confirm the influence of housing characteristics on indoor concentrations of NO2 and formaldehyde.
Environmental Research 10/2006; 102(1):1-8. · 3.24 Impact Factor