Effects of Ceiling-Mounted HEPA-UV Air Filters on Airborne Bacteria Concentrations in an Indoor Therapy Pool Building

Abstract

The purpose of this study was to assess the effectiveness of a new generation of high-volume, ceiling-mounted high-efficiency particulate air (HEPA)-ultraviolet (UV) air filters (HUVAFs) for their ability to remove or inactivate bacterial aerosol. In an environmentally controlled full-scale laboratory chamber (87 m³), and an indoor therapy pool building, the mitigation ability of air filters was assessed by comparing concentrations of total bacteria, culturable bacteria, and airborne endotoxin with and without the air filters operating under otherwise similar conditions. Controlled chamber tests with pure cultures of aerosolized Mycobacterium parafortuitum cells showed that the HUVAF unit tested provided an equivalent air-exchange rate of 11 hr^?1. Using this equivalent air-exchange rate as a design basis, three HUVAFs were installed in an indoor therapy pool building for bioaerosol mitigation, and their effectiveness was studied over a 2-year period. The HUVAFs reduced concentrations of culturable bacteria by 69 and 80% during monitoring periods executed in respective years. The HUVAFs reduced concentrations of total bacteria by 12 and 76% during the same monitoring period, respectively. Airborne endotoxin concentrations were not affected by the HUVAF operation.     

Inorganic and Carbonaceous Components in Indoor/Outdoor Particulate Matter in Two Residential Houses in Oslo,Norway

Abstract

A detailed analysis of indoor/outdoor physicochemical aerosol properties has been performed. Aerosol measurements were taken at two dwellings, one in the city center and the other in the suburbs of the Oslo metropolitan area, during summer/fall and winter/spring periods of 2002–2003. In this paper, emphasis is placed on the chemical characteristics (water-soluble ions and carbonaceous components) of fine (PM_2.5) and coarse (PM_2.5–10) particles and their indoor/outdoor relationship. Results demonstrate that the carbonaceous species were dominant in all fractions of the PM₁₀ particles (cut off size: 0.09–11.31 μm) during all measurement periods, except winter 2003, when increased concentrations of water-soluble inorganic ions were predominant because of sea salt transport. The concentration of organic carbon was higher in the fine and coarse PM₁₀ fractions indoors, whereas elemental carbon was higher indoors only in the coarse fraction. In regards to the carbonaceous species, local traffic and secondary organic aerosol formation were, probably, the main sources outdoors, whereas indoors combustion activities such as preparation of food, burning of candles, and cigarette smoking were the main sources. In contrast, the concentrations of water-soluble inorganic ions were higher outdoors than indoors. The variability of water-soluble inorganic ion concentrations outdoors was related to changes in emissions from local anthropogenic sources, long-range transport of particles, sea salt emissions, and resuspension of roadside and soil dusts. In the indoor environment the infiltration of the outdoor air indoors was the major source of inorganic ions.     

室内空气污染分析及防治措施

简述了室内空气污染的种类和特点，多角度论述了室内空气污染的防治措施。     

室内空气污染的生物监测与生物防治

介绍了室内空气污染的来源及其危害,采用常见花木来监测室内的空气污染,并可用常见盆栽植物来防治室内的空气污染.     

The Transfer of Trichloroethyene (TCE) from a Shower to Indoor Air: Experimental Measurements and Their Implications

Experiments were performed to measure the transfer of trlchloroethylene (TCE), a volatile organic compound (VOC), from tap water In showers to Indoor air. In these experiments, the loss of TCE from tap water in the shower is based on the difference between Influent and effluent concentrations. We have developed and previously published a three-compartment model, which we use to simulate the 24-h concentration history of VOCs in the shower, bathroom, and remaining household volumes resulting from the use of contaminated tap water. An important input to this model is the transfer efficiency of the VOC from water to air. The experiments reveal that the transfer efficiency of TCE from shower water to air has an arithmetic mean value of 61 percent and an arithmetic standard deviation of 9 percent. Analysis of the results shows that there Is no statistically significant difference between the transfer efficiency measured with hot (37°C) or cold (22°C) shower water and that there Is no statistically significant change In transfer efficiency with time during a 20-mln shower. The implications for exposure assessment are considered.     

Air Levels and Mutagenicity of PM-10 in an Indoor Ice Arena

Abstract

Hazardous waste sites and industrial facilities contain area sources of fugitive emissions. Emission rate measurements or estimates are necessary for air pathway assessments for these sources. Emission rate data can be useful for the design of emission control and remediation strategies as well as for predictive modeling for population exposure assessments. This paper describes the use of a direct emission measurement approach – the enclosure approach using an emission isolation flux chamber – to measure emission rates of various volatile organic compounds (VOCs) from contaminated soil and water. A variety of flux chamber equipment designs and operating procedures have been employed by various researchers. This paper contains a review of the design and operational variables that affect the accuracy and precision of the method. Guidance is given as to the optimum flux chamber design and operating conditions for various types of emission sources. Also presented is a generic quality control program that gives the minimum number of duplicate, blank, background, and repeat samples that should be performed.     

Two Sensitive Tests for Carcinogens in the Air

Presently, the carcinogenicity of polluted air is determined by repeated skin painting or subcutaneous injection of crude organic extracts of atmospheric particulates in adult mice. In general such techniques are not ideal, inasmuch as large amounts of extracts are required to produce significant yields of local tumors, and these may take one to two years to develop. A photodynamic bioassay for poly cyclic atmospheric pollutants, based on the previous demonstration of a positive and significant association between high photodynamic activity and carcinogenicity in a large series of polycxjclics, has been developed in an attempt to provide a simple and rapid, but presumptive, indirect index of carcinogenicity attributable to polycyclic compounds. Photodynamic activity, measured with Paramecium caudatum, was found to vary widely between organic extracts, and even more widely between 6 eluted fractions thereof, from over 100 different sources in the U.S.A. Additionally, the carcinogenicity of organic extracts of atmospheric pollutants has been directly measured with newborn mice, based on the well-known enhanced response cf neonates to a variety of defined chemical carcinogens. Mice were injected subcutaneously with extracts at doses of 55 mg or less, fractionally administered in the first 21 days of life. A high incidence of pulmonary adenomas, and hepatomas, and a lower incidence of lymphomas developed over a period from 12 to 50 weeks. Current correlative evaluation with chemical and other data indicates the practical utility of both assays for carcinogenic air pollutants.     

Characterization of Air Quality Problems in Five Finnish Indoor Ice Arenas

ABSTRACT

The air quality in five Finnish ice arenas with different volumes, ventilation systems, and resurfacer power sources (propane, gasoline, electric) was monitored during a usual training evening and a standardized, simulated ice hockey game. The measurements included continuous recording of carbon monoxide (CO), nitric oxide (NO), and nitrogen dioxide (NO₂) concentrations, and sampling and analysis of volatile organic compounds (VOCs). Emissions from the ice resurfacers with combustion engines caused indoor air quality problems in all ice arenas. The highest 1-hour average CO and NO₂ concentrations ranged from 20 to 33 mg/m³ (17 to 29 ppm) and 270 to 7440 µg/m³ (0.14 to 3.96 ppm), respectively. The 3-hour total VOC concentrations ranged from 150 to 1200 µg/m³. The highest CO and VOC levels were measured in the arena in which a gasoline-fueled resurfacer was used. The highest NO₂ levels were measured in small ice arenas with propane-fueled ice resurfacers and insufficient ventilation.

In these arenas, the indoor NO₂ levels were about 100 times the levels measured in ambient outdoor air, and the highest 1-hour concentrations were about 20 times the national and World Health Organization (WHO) health-based air quality guidelines. The air quality was fully acceptable only in the arena with an electric resurfacer. The present study showed that the air quality problems of indoor ice arenas may vary with the fuel type of resurfacer and the volume and ventilation of arena building. It also confirmed that there are severe air quality problems in Finnish ice arenas similar to those previously described in North America.     

Toxicological Appraisal of Lead in Relation to the Tolerable Concentration in the Ambient Air

The issue to be considered is that of the significance of lead in the air, but not that alone, since lead in the food and beverages consumed by people generally must also be taken into account. The magnitude of one of these sources must, of necessity, be adjusted to that of the other.

After a consideration of certain general toxicological principles such as the limitations of the term “cumulative poison,” as applied to lead in the ambient atmosphere, the role of physiology is emphasized as the decisive element in the issue. Reliance must be based on the capacity of the human organism to deal effectively with lead absorbed at a low rate, by eliminating it from the body at an equivalent rate, thus promoting a steady state. Criteria for the ideal determination of the tolerable concentration of lead in the ambient air, are stated in physiological terms as follows: The tolerable concentration of the (inorganic) compounds of lead, singly or collectively, in the air breathed by human beings of all ages, sexes, and physical and functional types, can be defined ideally, as that resulting in a rate of absorption of lead into their bodies, which when augmented by that derived from all sources in the common environment other than air, can be eliminated regularly from the body, without permitting a significant degree of progressive accumulation therein, and without inducing or contributing to disease or to the impairment of any essential function of the human organism.

A summary of available evidence begins by stating the facts as to the intake and output of lead by various groups of persons in the general population. It proceeds to the results of detailed balance experiments on human subjects under controlled conditions, which indicate that there is indeed an approximate equilibrium between the intake of lead and the output of lead over prolonged periods of time, during which the absorption of lead is limited strictly to that which derives from the food and beverages and from the ambient air.

On this background, a review, of the principal contributions to the literature, mainly that of the decade just ending, with respect to the behavior of lead and its inorganic compounds, examined such matters as: (1) The body burden of lead in the general population of the United States. The conclusion is reached that the information obtained thus far by the analysis of the tissues of deceased persons is insufficient to prove the case for or against the accumulation of lead in the body with age. It appears that the balance experiments have yielded more reliable information thus far. (2) The disposition of airborne lead compounds in the human respiratory tract. Quantitative evidence concerning the fate of airborne particulate compounds of lead in the human respiratory tract is limited, largely, to measurements of the retention of the particles in the respiratory tract. Recent experiments have extended this information to apply to the manner of the distribution of the particles within the various parts of the respiratory tract, as determined by their size and the respiratory rate. It is not possible, on present information, to visualize the extent of the clearance of lead from the respiratory tract, and until the mechanisms involved in such clearance have been appraised under a variety of conditions, one cannot measure the absorption of lead from the ambient air in the respiratory tract. An experimental basis for bridging this gap in our knowledge has been advanced.

(3) Chemical evidence which is indicative of approaching or impending danger from the absorption of lead compounds. The value of determinations of lead in the blood and of coproporphyrin III and of delta-aminolevulinic acid in the urine, in relation to the absorption of lead under a variety of conditions of exposure to lead has been explored on the basis of the experience and the experimental work of many investigators. The conclusions arrived at may be summarized as follows: The difference between the current levels of the concentration of lead in the blood of persons in the general “normal” population, and of those which are found in individuals and groups of persons who are subjected to potentially dangerous exposure to and absorption of lead, is ample for the purposes of differentiation. The hematological responses to lead absorption by individuals and groups, including the more subtle chemical disturbances in the metabolism of hemoglobin, do not put in their appearance when the rate of absorption remains within the limits encountered in the so-called “normal” population. (4) Unusual susceptibility to the absorption of lead at low rates. It has been suggested that there are certain sensitive groups in the general population, especially young children, pregnant women, and persons with impaired renal function, who may be at considerable disadvantage. It seems unlikely that the history of lead poisoning and its sequelae, which tend to justify a degree of concern for the safety of these, and perhaps for other special groups in the general population, applies to the absorption of lead at the present common environmental level.     

Investigation of the Treatability of the Primary Indoor Volatile Organic Compounds on Activated Carbon Fiber Cloths at Typical Indoor Concentrations

Abstract

Volatile organic compounds (VOCs) are a major concern for indoor air pollution because of the impacts on human health. In recent years, interest has increased in the development and design of activated carbon filters for removing VOCs from indoor air. Although extensive information is available on sources, concentrations, and types of indoor VOCs, there is little or no information on the performance of indoor air adsorption systems for removing low concentrations of primary VOCs. Filter designs need to consider various factors such as empty bed contact time, humidity effects, competitive adsorption, and feed concentration variations, whereas adsorption capacities of the indoor VOCs at the indoor concentration levels are important parameters for filter design. A preliminary assessment of the feasibility of using adsorption filters to remove low concentrations of primary VOCs can be performed. This work relates the information (including VOC classes in indoor air, the typical indoor concentrations, and the adsorption isotherms) with the design of a particular adsorbent/adsorbates system. As groundwork for filter design and development, this study selects the primary VOCs in indoor air of residences, schools, and offices in different geographical areas (North America, Europe, and Asia) on the basis of occurrence, concentrations, and health effects. Activated carbon fiber cloths (ACFCs) are chosen as the adsorbents of interest. It is demonstrated that the isotherm of a VOC (e.g., toluene on the ACFC) at typical indoor concentrations—parts per billion by volume (ppbv) level—is different than the isotherm at parts per million by volume (ppmv) levels reported in the publications. The isotherms at the typical indoor concentrations for the selected primary VOCs are estimated using the Dubinin–Radushkevitch equation. The maximum specific throughput for an indoor VOC removal system to remove benzene is calculated as a worst-case scenario. It is shown that VOC adsorption capacity is an important indicator of a filter’s lifetime and needs to be studied at the appropriate concentration range. Future work requires better understanding of the realistic VOC concentrations and isotherms in indoor environments to efficiently utilize adsorbents.     

水中有机成分及其对饮用水质的影响

微量有机污染物和氯化消毒副产物对饮用水构成直接威胁,是饮用水中要重点控制的;天然大分子有机物对水质构成间接影响,导致胶体稳定性提高、增加药耗;藻类和代谢产物影响常规处理工艺效果,对水质产生不良影响。     

A Rating of the Major Air Pollutants and Their Sources by Effect

The available national annual air pollution emissions are based on mass. Different air pollutants have greatly different toxicities per unit mass, hence the emissions should be rated by effect, not by mass, so that more sensible priorities can be set in control research and regulation. Effect factors are derived from the health effect literature indirectly by using the national ambient air quality standards. The resulting analysis by effects shows transportation to be still the largest source as it is in the mass analysis while hydrocarbons become the largest pollutants by effect compared to carbon monoxide being the largest pollutant by mass.     

Prescribed Burns and Wildfires in Colorado: Impacts of Mitigation Measures on Indoor Air Particulate Matter

Abstract

Wildfires and prescribed burns are receiving increasing attention as sources of fine particulate matter (PM_2.5). The goal of this research project was to understand the impact of mitigation strategies for residences impacted by scheduled prescribed burns and wildfires. Pairs of residences were solicited to have PM_2.5 concentrations monitored inside and outside of their houses during four fires. The effect of using air cleaners on indoor PM_2.5 was investigated, as well as the effect of keeping windows closed. Appropriately sized air cleaners were provided to one of each pair of residences; occupants of all of the residences were asked to keep windows shut and minimize opening of exterior doors. Additionally, residents were asked to record all of the activities that may be a source of particulate matter, such as cooking and cleaning. Measurements were made during one prescribed burn and three wildfires during the 2002 fire season. Outdoor 24‐hr average PM_2.5 concentrations ranging from 6 to 38 µg/m³ were measured during the fires, compared with levels of 2–5 µg/m³ during background measurements when no fires were burning. During the fires, PM_2.5 was <3 µg/m³ inside all of the houses with air cleaners installed. This corresponds with a decrease of 63–88% in homes with the air cleaners operating when compared with homes without air cleaners. In the homes without the air cleaners, measured indoor concentrations were 58–100% of the concentrations measured outdoors.     

空气中PM_(10)浓度的BP神经网络预报研究

建立了某市PM10浓度预报的分段BP神经网络模型,经验证,所建立的BP预报模型,预测精度比较高,PM10日平均浓度误差大多在-0．010～0．010mg／m^3范围内,相对误差在-20％～20％,表明BP神经网络对PM10的浓度预报是一种有效的工具。     

Impact of Toll Removal on Air Particulate Concentration in Jacksonville,Florida

The concentration of total suspended particulate (TSP) matter was determined at commercial, residential, rural and industrial sites in metropolitan Jacksonville during the summers of 1989 and 1990. These data were compared to samples taken at the Mathews Bridge Toll Plaza in 1989 and at a similar location one year later, after removal of the toll facility. All samples were analyzed by reflectance analysis and the approximate elemental carbon content used to estimate the contribution of vehicular traffic at the roadway. The results indicate a significant improvement in air quality at the location of the previous toll facility, but did not show that a widespread improvement resulted from the removal of tolls in Jacksonville, Florida.     

Modeling of Indoor Air Treatment of Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans Using High-Efficiency Particulate Air-Carbon Filtration

Abstract

A high-efficiency particulate air (HEPA)-carbon filtration system was developed by the Access Business Group, LLC, to reduce the indoor levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). The HEPA filter removes the particle-bound PCDD/Fs, and the carbon filter removes the gaseous fraction. Because of the toxicity of PCDD/Fs, it is very difficult to handle them in the laboratory. In this study, mathematical modeling was performed to evaluate the performance of the HEPA-carbon filtration system for PCDD/Fs removal and to optimize its design and operation. The model was calibrated with experimental data conducted with toluene in a sealed room. Model simulations with four selected congeners demonstrated that it takes ～1 hr for the indoor air treatment system to reach the maximum removal efficiency and that the carbon air filter has a life time of 10⁷ yr for dioxin removal. Given a zero emission from the HEPA filter, the overall removal efficiency is 78.7% for 2,3,7,8-tetrachloro dibenzo-p-dioxins, 89.8% for octa-chlorodibenzodioxin, 78% for tetra-chlorodibenzofuran, and 89.8% for octachlorodibenzofuran. The larger the mass emission from the HEPA filter, the lower the overall removal efficiency, and the larger the ratio of the filter flow rate (Q_f) to the room flow rate (Q), the higher the overall removal efficiency. When the ratio of Q_f/Q is 15, an overall removal efficiency of 90% can be reached for all four of the selected compounds. The removal of the four selected compounds does not change as the relative humidity increases ≤90%.     

Modeling Inorganic Aerosols and Their Response to Changes in Precursor Concentration in Mexico City

Abstract

Based on data from the 1997 Investigación sobre Materia Particulada y Deterioro Atmosférico-Aerosol and Visibility Evaluation Research (IMADA-EVER) campaign and the inorganic aerosol model ISORROPIA, the response of inorganic aerosols to changes in precursor concentrations was calculated. The aerosol behavior is dominated by the abundance of ammonia and thus, changes in ammonia concentration are expected to have a small effect on particle concentrations. Changes in sulfate and nitrate are expected to lead to proportional reductions in inorganic fine particulate matter (PM_2.5). Comparing the predictions of ISORROPIA with the observations, the lowest bias and error are achieved when the aerosols are assumed to be in the efflorescence branch. Including crustal species reduces the bias and error for nitrate but does not improve overall model performance. The estimated response of inorganic PM_2.5 to changes in precursor concentrations is affected by the inclusion of crustal species in some cases, although average responses are comparable with and without crustal species. Observed concentrations of particle chloride suggest that gas phase concentrations of hydrogen chloride may not be negligible, and future measurement campaigns should include observations to test this hypothesis. Our ability to model aerosol behavior in Mexico City and, thus, design control strategies, is constrained primarily by a lack of observations of gas phase precursors. Future campaigns should focus in particular on better understanding the temporal and spatial distribution of ammonia concentrations. In addition, gas phase observations of nitric acid are needed, and a measure of particle water content will allow stable versus metastable aerosol behavior to be distinguished.     

The distribution of chlorpyrifos following a crack and crevice type application in the US EPA Indoor Air Quality Research House

A study was conducted in the US EPA Indoor Air Quality (IAQ) Research House to determine the spatial and temporal distribution of chlorpyrifos following a professional crack and crevice application in the kitchen. Following the application, measurements were made in the kitchen, den and master bedroom over 21 days. Airborne concentrations were collected using both polyurethane foam (PUF) and the OSHA versatile sampler composed of XAD and PUF media located in tandem. Measured airborne concentrations were similar for the two samplers and were higher in the three rooms following the application. The highest measured concentrations were reached during the initial 24-h following application; concentrations subsequently declined over the 21-day study period to levels slightly above background. Spatial and temporal distributions onto surfaces were measured using 10-cm² rayon deposition coupons located on the floor. Sections were cut from existing carpet to determine the total extractable residues. Chlorpyrifos was measured from all matrixes in the kitchen, den and bedroom and the data shows the transport of airborne residues from the point of application to remote locations in the house. The findings are compared and discussed relative to another study conducted in which total release aerosols containing chlorpyrifos were activated in the IAQ research house and the resulting distributions evaluated. For both studies dose estimates were constructed for the exposure pathways using the Stochastic Human Exposure and Dose Estimation Model for pesticides.The United States Environmental Protection Agency has been mandated to examine children's exposure to environmental pollutants such as pesticides. This research specifically reduces uncertainties associated with estimating children's potential exposures to residentially applied pesticides and provides inputs to further evaluate and validate residential exposure models which might be used to reduce exposures and perform risk assessments.     

The Effects of Infiltration and Insulation on the Source Strengths and Indoor Air Pollution from Combustion Space Heating Appliances

Many energy conservation strategies for residences involve reducing house air exchange rates. Reducing the air exchange rate of a house can cause an increase in pollutant levels if there is an indoor pollution source and if the indoor pollutant source strength remains constant. However, if the indoor pollutant source strength can also be reduced, then it is possible to maintain or even improve indoor air quality. Increasing the insulation level of a house is a means of achieving energy conservation goals and, in addition, can reduce the need for space heating and thereby reduce the pollutant source strengths of combustion space heaters such as unvented kerosene space heaters, unvented gas space heaters, and wood stoves. In this paper, the indoor air quality trade-off between reduced infiltration and increased insulation in residences is investigated for combustion space heaters. Two similar residences were used for the experiment. One residence was used as a control and the other residence had infiltration and insulation levels modified. An unvented propane space heater was used as the source in this study. A model was developed to describe the dependence of both indoor air pollution levels and the appliance source strengths on house air exchange rates and house insulation levels. Model parameters were estimated by applying regression techniques to the data. Results show that indoor air pollution levels in houses with indoor combustion space heating pollution sources can be held constant (or lowered) by reducing the thermal conductance by an amount proportional to (or greater than) the reduction of the air exchange rate.