ObjectiveMany interventions to reduce allergen levels in the home are recommended to asthma and allergy patients. One that is readily available and can be highly effective is the use of high performing filters in forced air ventilation systems.MethodsWe conducted a modeling analysis of the effectiveness of filter-based interventions in the home to reduce airborne asthma and allergy triggers. This work used “each pass removal efficiency” applied to health-relevant size fractions of particles to assess filter performance. We assessed effectiveness for key allergy and asthma triggers based on applicable particle sizes for cat allergen, indoor and outdoor sources of particles <2.5 µm in diameter (PM2.5), and airborne influenza and rhinovirus.ResultsOur analysis finds that higher performing filters can have significant impacts on indoor particle pollutant levels. Filters with removal efficiencies of >70% for cat dander particles, fine particulate matter (PM2.5) and respiratory virus can lower concentrations of those asthma triggers and allergens in indoor air of the home by >50%. Very high removal efficiency filters, such as those rated a 16 on the nationally recognized Minimum Efficiency Removal Value (MERV) rating system, tend to be only marginally more effective than MERV12 or 13 rated filters.ConclusionsThe results of this analysis indicate that use of a MERV12 or higher performing air filter in home ventilation systems can effectively reduce indoor levels of these common asthma and allergy triggers. These reductions in airborne allergens in turn may help reduce allergy and asthma symptoms, especially if employed in conjunction with other environmental management measures recommended for allergy and asthma patients.

Background: Reducing exposure to environmental agents indoors shown to increase asthma symptoms or lead to asthma exacerbations is an important component of a strategy to manage asthma for individuals. Numerous investigations have demonstrated that portable air cleaning devices can reduce concentrations of asthma triggers in indoor air; however, their benefits for breathing problems have not always been reproducible. The potential exposure benefits of whole house high efficiency in-duct air cleaners for sensitive subpopulations have yet to be evaluated.

Health risks of fine particle air pollution (PM 2.5 ) are an important public health concern that has the potential to be mitigated in part by interventions such as air cleaning devices that reduce personal exposure to ambient PM 2.5 . To characterize exposure to ambient PM 2.5 indoors as a function of residential air cleaners, a multi-zone indoor air quality model was used to integrate spatially resolved data on housing, meteorology, and ambient PM 2.5 , with performance testing of residential air cleaners to estimate short-term and annual average PM 2.5 of outdoor origin inside residences of three metropolitan areas. The associated public health impacts of reduced ambient PM 2.5 exposure were estimated using a standard health impact assessment methodology. Estimated indoor levels of ambient PM 2.5 varied substantially among ventilation and air cleaning configurations. The median 24-h average indooroutdoor ratio of ambient PM 2.5 was 0.57 for homes with natural ventilation, 0.35 for homes with central air conditioning (AC) with conventional filtration, and 0.1 for homes with central AC with high efficiency in-duct air cleaner. Median modeled 24-h average indoor concentrations of PM 2.5 of outdoor origin for those three configurations were 8.4, 5.3, and 1.5 mg/m 3 , respectively. The potential public health benefits of reduced exposure to ambient PM 2.5 afforded by air cleaning systems were substantial. If the entire population of single-family homes with central AC in the modeling domain converted from conventional filtration to high-efficiency in-duct air cleaning, the change in ambient PM 2.5 exposure is estimated to result in an annual reduction of 700 premature deaths, 940 hospital and emergency room visits, and 130,000 asthma attacks in these metropolitan areas. In addition to controlling emissions from sources, high-efficiency whole-house air cleaner are expected to reduce exposure to particles of outdoor origin and are projected to be an effective means of managing public health impacts of ambient particle pollution.

Humans are continuously exposed to low levels of ionizing radiation. Known sources include radon, soil, cosmic rays, medical treatment, food, and building products such as gypsum board and concrete. Little information exists about radiation emissions and associated doses from natural stone finish materials such as granite countertops in homes. To address this knowledge gap, gross radioactivity, g ray activity, and dose rate were determined for slabs of granite marketed for use as countertops. Annual effective radiation doses were estimated from measured dose rates and human activity patterns while accounting for the geometry of granite countertops in a model kitchen. Gross radioactivity, g activity, and dose rate varied significantly among and within slabs of granite with ranges for median levels at the slab surface of ND to 3000 cpm, ND to 98,000 cpm, and ND to 1.5EÀ4 mSv/h, respectively. The maximum activity concentrations of the 40 K, 232 Th, and 226 Ra series were 2715, 231, and 450 Bq/kg, respectively. The estimated annual radiation dose from spending 4 h/day in a hypothetical kitchen ranged from 0.005 to 0.18 mSv/a depending on the type of granite. In summary, our results show that the types of granite characterized in this study contain varying levels of radioactive isotopes and that their observed emissions are consistent with those reported in the scientific literature. We also conclude from our analyses that these emissions are likely to be a minor source of external radiation dose when used as countertop material within the home and present a negligible risk to human health.

Radon gas ( 222 Rn) is a natural constituent of the environment and a risk factor for lung cancer that we are exposed to as a result of radioactive decay of radium ( 226 Ra) in stone and soil. Granite countertops, in particular, have received recent media attention regarding their potential to emit radon. Radon flux was measured on 39 full slabs of granite from 27 different varieties to evaluate the potential for exposure and examine determinants of radon flux. Flux was measured at up to six pre-selected locations on each slab and also at areas identified as potentially enriched after a full-slab scan using a Geiger-Muller detector. Predicted indoor radon concentrations were estimated from the measured radon flux using the CONTAM indoor air quality model. Whole-slab average emissions ranged from less than limit of detection to 79.4 Bq/m 2 /h (median 3.9 Bq/m 2 /h), similar to the range reported in the literature for convenience samples of small granite pieces. Modeled indoor radon concentrations were less than the average outdoor radon concentration (14.8 Bq/m 3 ; 0.4 pCi/l) and average indoor radon concentrations (48 Bq/m 3 ; 1.3 pCi/l) found in the United States. Significant within-slab variability was observed for stones on the higher end of whole slab radon emissions, underscoring the limitations of drawing conclusions from discrete samples.