By Brent Stephens on September 15, 2012
I dig through a lot of literature on air quality (indoors and outdoors), environmental exposures, health effects, as well as energy use, energy efficiency, energy policy, not to mention other scientific and engineering miscellanea. I will try to post links to papers that I find interesting to this blog on a semi-regular basis (shooting for monthly, but we’ll see).
So, for the month of September, I’ve come across the following interesting papers:
- Residential radon and lung cancer in a Danish cohort – A study of almost 60000 Danish people over ~20 years tracked lung cancer incidence and looked for associations between incidence and modeled radon concentrations in their homes (lots of uncertainty there). Found a slight increased risk for each 100 Bq/m3 (about 2.7 pCi/L), but confidence intervals were very wide, so no statistical significance (Environmental Research).
- Exposure to VOCs and lung function/heart rate variability in urban cyclists – A study of about 40 healthy Canadian cyclists biking for an hour on either high or low traffic roads was conducted. VOC samples were collected via SUMMA canisters and analyzed by GC-MS; lung function was measured using exhaled nitric oxide (which is a kind of tracer for lung function) and exhaled breath volume; and heart rate variability was measured at the last 5-minutes of each study period. 26 VOCs were identified, but propane, butane, ethane, isoprene, and benzene were those significantly associated with the various health outcomes (Environmental Research).
- Household mold and allergens and asthma symptoms – A study of about 1200 homes with 5-10 year old children in Connecticut collected spot samples of indoor airborne fungi (later analyzed via agar plate) and allergens in house dust (later sampled by enzyme-linked immunosorbent assay for dust mite, cat, dog, and cockroach allergens). The children kept a diary of asthma symptoms (e.g., times of wheeze, use of medication, etc.) for about a month. The study found significant associations between (a) fungi (Penicillium) and increased wheeze, cough, and asthma severity; (b) pet allergens (dog and cat, although cat at much lower concentrations) and increased cases of wheeze; and (c) cat and dust mite allergens and increased use of asthma medication (Environmental Research).
- Home dampness, children’s genetic polymorphisms, and asthma – A study about about 6000 school children in Taiwan surveyed parents (via questionnaire) about their children’s asthma and wheeze symptom frequency, as well as the presence of dampness, visible mold, and mildewy odors in their homes. The study also collected mouth swabs of the children, which were analyzed using realtime PCR to detect specific genetic polymorphisms previously known to be linked to asthma. Their analysis shows that children exposed to dampness and mildewy odors at home were more likely to be awakened at night with wheeze symptoms if they carried a specific genetic polymorphism (Environmental Research).
- Indoor air quality in day cares – A study of about 20 day care centers in Canada measured temperature, relative humidity, carbon dioxide, VOCs (via SUMMA canisters), and formaldehyde in conjunction with surveys of building characteristics and operation. From the measurements and surveys, the study concludes that CO2 concentrations were often quite high (a sign of inadequate ventilation) and that the presence of a mechanical ventilation system, as well as more play area per child (bigger spaces), were associated with lower CO2 levels. But the presence of a mechanical ventilation system alone wasn’t as good of a predictor of indoor VOC levels as CO2 levels, suggesting that it’s better to know more about the actual building’s mechanical system operation than the mere existence of a system. Fair enough (Environmental Research).
- Penetration of fine particles through rough cracks – A lab study setup a small facility with known crack geometries to simulate airflow through an idealized leak in a building’s exterior wall with different surface roughnesses. This general idealized penetration work has been performed before, and although idealized, this kind of work offers good insight into the material, leak, and flow characteristics that impact particle penetration through envelope cracks and gaps. This study added to these by looking not only at smooth surfaces, but by then installing sandpapers of different roughness characteristics. Their findings showed that the level of roughness didn’t much matter, but that the presence of any roughness at all (versus smooth surfaces) made more particles deposit, particularly those in the ultrafine range (Atmospheric Environment).
- Modeling impacts of US vehicle emissions standards on ozone and PM2.5 – A modeling study by ENVIRON International estimated the potential impacts of light-duty vehicle emissions standards in the U.S. on outdoor air quality, including concentrations of ozone and particulate matter (PM2.5) in the eastern U.S. through 2022. The study predicts that transitioning from “Tier 1” to “Tier 2” standards could reduce daily maximum 8-hour ozone concentrations 14% and maximum 24-hour PM2.5 by 9%. These “tiers” were part of the Clean Air Act Amendments of 1990. Tier 1 vehicles were phased in through the 1990s, and basically included six different emissions categories for vehicles based on weight. Tier 2 vehicles were phased in over the end of the 2000s and included different metrics. The whole tier system is somewhat complex, but here is an idea of what emissions are controlled under the various tiers. Basically, emissions of NOx, organics, CO, PM, and formaldehyde are controlled. Limiting NOx and organics (VOCs) help add to the reductions in ozone predicted by this study (NOx + VOC lead to ozone formation in complex photochemistry), and the PM restrictions directly result in the predicted lower PM2.5 concentrations (Atmospheric Environment).
- Review of toxicity of ambient particulate matter in terms of size, source, and chemical composition – A really good review of previous studies of ambient particulate matter and health effects, particularly looking at the relative impacts of different sizes, sources, and chemical composition of PM. Basically, there is some evidence out there now that traffic-related PM emissions show some degree of higher toxicity than other constituents (traffic-related constituents include file and ultrafine particles, some metals, and elemental carbon). But overall, this review describes the need for more work with stronger programs involving toxicology and epidemiology in conjunction with better estimates of size, source, and composition of PM (Atmospheric Environment).
- Building energy simulation: impact of surrounding buildings versus stand-alone buildings – A study used EnergyPlus to simulate ~20 residential buildings as if they were standing alone without any surrounding buildings (something we often do in energy modeling but something that is rare or nonexistent in actual urban environments) or if they were part of a network of other homes in a neighborhood. They simulated buildings in an extreme hot (Miami) and cold (Minneapolis) climate. They found that in both climates, energy used for cooling is greatly over-predicted in the single-building analysis versus the network-analysis (by up to ~60%!), primarily due to shading by other buildings that goes unaccounted for in the single-building analysis. In the cold months in the cold climate, single-building analysis actually under-predicted energy use versus the neighborhood analysis, probably again due to shading (i.e., solar gain helps reduce heating loads in a stand-alone building, lowering the estimate of energy req’d; solar gain is blocked in a network analysis (Building and Environment).
- Zero peak electric housing – This study used ESP-r to model the possibility of eliminating electrical power draws from a home during the hours of peak demand on the electric grid. It’s a really good concept and this study explores first the use of efficiency and energy-saving measures to reduce demand at peak hours, then looks at what kind of solar PV integration would be necessary to get to zero peak demand. They conclude that almost 50% could be met by architectural design, equipment efficiency, and occupant behavior measures. The rest could be met by a small PV and battery system (Building and Environment).
- Indoor air quality in commercial reference buildings – The good people at NIST published a study on a bunch of indoor air quality modeling (using CONTAM) for a series of commercial buildings that can be used as reference or “typical” commercial buildings. They modeled indoor CO2, VOCs from indoor sources, and indoor ozone and PM2.5 from outdoor sources. Provides a good reference for others to use in case studies (Building and Environment).
- Intake fraction for the indoor environment – This study used the metric “intake fraction,” which is a measure of what fraction of a pollutant emitted in a particular environment actually enters a human body (via inhalation, ingestion, or dermal exposure). Indoor sources have much higher intake fractions than outdoor sources because we spend so much time indoors and are in such close contact with indoor sources. So for every gram of a pollutant emitted indoors, more enters our bodies than a gram of the same pollutant emitted outdoors. This study advanced work on intake fractions to explore a suite of typical indoor-generated compounds (with different physical characteristics) released into the air, or from carpets, or from vinyl surfaces. This helps guide exposure assessment by showing the relative importance of types of indoor surfaces for different compounds in terms of exposure to adults and humans (Environmental Science and Technology).
Filed under: Literature round-up