The Experts below are selected from a list of 171933 Experts worldwide ranked by ideXlab platform
Paige E Tolbert - One of the best experts on this subject based on the ideXlab platform.
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implications of different approaches for characterizing ambient air Pollutant concentrations within the urban airshed for time series studies and health benefits analyses
Environmental Health, 2011Co-Authors: Matthew J Strickland, Lyndsey A Darrow, Mitchel Klein, Dana W Flanders, James A Mulholland, Andrea Winquist, Paige E TolbertAbstract:Background: In time-series studies of the health effects of urban air Pollutants, decisions must be made about how to characterize Pollutant levels within the airshed. Methods: Emergency department visits for pediatric asthma exacerbations were collected from Atlanta hospitals. Concentrations of carbon monoxide, nitrogen dioxide, ozone, sulfur dioxide, particulate matter less than 10 microns in diameter (PM10), particulate matter less than 2.5 microns in diameter (PM2.5), and the PM2.5 components elemental carbon, organic carbon, and sulfate were obtained from networks of ambient air quality monitors. For each Pollutant we created three different daily metrics. For one metric we used the measurements from a centrally-located monitor; for the second we averaged measurements across the network of monitors; and for the third we estimated the population-weighted average concentration using an isotropic spatial model. Rate ratios for each of the metrics were estimated from time-series models. Results: For Pollutants with relatively homogeneous spatial distributions we observed only small differences in the rate ratio across the three metrics. Conversely, for spatially heterogeneous Pollutants we observed larger differences in the rate ratios. For a given Pollutant, the strength of evidence for an association (i.e., chi-square statistics) tended to be similar across metrics. Conclusions: Given that the chi-square statistics were similar across the metrics, the differences in the rate ratios for the spatially heterogeneous Pollutants may seem like a relatively small issue. However, these differences are important for health benefits analyses, where results from epidemiological studies on the health effects of Pollutants (per unit change in concentration) are used to predict the health impacts of a reduction in Pollutant concentrations. We discuss the relative merits of the different metrics as they pertain to time-series studies and health benefits analyses.
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ambient air Pollutant measurement error characterization and impacts in a time series epidemiologic study in atlanta
Environmental Science & Technology, 2010Co-Authors: Gretchen T Goldman, Matthew J Strickland, Mitchel Klein, Lance A Waller, James A Mulholland, Paige E Tolbert, Armistead G Russell, Abhishek K Srivastava, Eric S EdgertonAbstract:In time-series studies of ambient air pollution and health in large urban areas, measurement errors associated with instrument precision and spatial variability vary widely across Pollutants. In this paper, we characterize these errors for selected air Pollutants and estimate their impacts on epidemiologic results from an ongoing study of air pollution and emergency department visits in Atlanta. Error was modeled for daily measures of 12 air Pollutants using collocated monitor data to characterize instrument precision and data from multiple study area monitors to estimate population-weighted spatial variance. Time-series simulations of instrument and spatial error were generated for each Pollutant, added to a reference Pollutant time-series, and used in a Poisson generalized linear model of air pollution and cardiovascular emergency department visits. Reductions in risk ratio due to instrument precision error were less than 6%. Error due to spatial variability resulted in average risk ratio reductions of ...
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short term associations between ambient air Pollutants and pediatric asthma emergency department visits
American Journal of Respiratory and Critical Care Medicine, 2010Co-Authors: Matthew J Strickland, Lyndsey A Darrow, Mitchel Klein, Dana W Flanders, Jeremy A Sarnat, Lance A Waller, Stefanie Ebelt Sarnat, James A Mulholland, Paige E TolbertAbstract:Rationale: Certain outdoor air Pollutants cause asthma exacerbations in children. To advance understanding of these relationships, further characterization of the dose–response and Pollutant lag effects are needed, as are investigations of Pollutant species beyond the commonly measured criteria Pollutants. Objectives: Investigate short-term associations between ambient air Pollutant concentrations and emergency department visits for pediatric asthma. Methods: Daily counts of emergency department visits for asthma or wheeze among children aged 5 to 17 years were collected from 41 Metropolitan Atlanta hospitals during 1993–2004 (n = 91,386 visits). Ambient concentrations of gaseous Pollutants and speciated particulate matter were available from stationary monitors during this time period. Rate ratios for the warm season (May to October) and cold season (November to April) were estimated using Poisson generalized linear models in the framework of a case-crossover analysis. Measurements and Main Results: Both ozone and primary Pollutants from traffic sources were associated with emergency department visits for asthma or wheeze; evidence for independent effects of ozone and primary Pollutants from traffic sources were observed in multiPollutant models. These associations tended to be of the highest magnitude for concentrations on the day of the emergency department visit and were present at relatively low ambient concentrations. Conclusions: Even at relatively low ambient concentrations, ozone and primary Pollutants from traffic sources independently contributed to the burden of emergency department visits for pediatric asthma.
Michelle L Bell - One of the best experts on this subject based on the ideXlab platform.
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protecting human health from air pollution shifting from a single Pollutant to a multiPollutant approach
Epidemiology, 2010Co-Authors: Francesca Dominici, Roger D Peng, Christopher D Barr, Michelle L BellAbstract:To date, the assessment of public health consequences of air pollution has largely focused on a single-Pollutant approach aimed at estimating the increased risk of adverse health outcomes associated with the exposure to a single air Pollutant, adjusted for the exposure to other air Pollutants. However, air masses always contain many Pollutants in differing amounts, depending on the types of emission sources and atmospheric conditions. Because humans are simultaneously exposed to a complex mixture of air Pollutants, many organizations have encouraged moving towards “a multi-Pollutant approach to air quality.” While there is general agreement that multi-Pollutant approaches are desirable, the challenges of implementing them are vast. In this commentary, we discuss a multi-Pollutant approach for controlling ambient air pollution that describes multi-Pollutant concepts for different aspects of air quality management and science: (1) scientific estimation of the health risk of multiple Pollutants; (2) setting of regulatory standards for multiple Pollutants; and (3) simultaneously implementing compliance with regulatory standards for multiple Pollutants.
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Protecting human health from air pollution: shifting from a single-Pollutant to a multiPollutant approach.
Epidemiology (Cambridge Mass.), 2010Co-Authors: Francesca Dominici, Roger D Peng, Christopher D Barr, Michelle L BellAbstract:To date, the assessment of public health consequences of air pollution has largely focused on a single-Pollutant approach aimed at estimating the increased risk of adverse health outcomes associated with the exposure to a single air Pollutant, adjusted for the exposure to other air Pollutants. However, air masses always contain many Pollutants in differing amounts, depending on the types of emission sources and atmospheric conditions. Because humans are simultaneously exposed to a complex mixture of air Pollutants, many organizations have encouraged moving towards "a multiPollutant approach to air quality." Although there is general agreement that multiPollutant approaches are desirable, the challenges of implementing them are vast.
Matthew J Strickland - One of the best experts on this subject based on the ideXlab platform.
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implications of different approaches for characterizing ambient air Pollutant concentrations within the urban airshed for time series studies and health benefits analyses
Environmental Health, 2011Co-Authors: Matthew J Strickland, Lyndsey A Darrow, Mitchel Klein, Dana W Flanders, James A Mulholland, Andrea Winquist, Paige E TolbertAbstract:Background: In time-series studies of the health effects of urban air Pollutants, decisions must be made about how to characterize Pollutant levels within the airshed. Methods: Emergency department visits for pediatric asthma exacerbations were collected from Atlanta hospitals. Concentrations of carbon monoxide, nitrogen dioxide, ozone, sulfur dioxide, particulate matter less than 10 microns in diameter (PM10), particulate matter less than 2.5 microns in diameter (PM2.5), and the PM2.5 components elemental carbon, organic carbon, and sulfate were obtained from networks of ambient air quality monitors. For each Pollutant we created three different daily metrics. For one metric we used the measurements from a centrally-located monitor; for the second we averaged measurements across the network of monitors; and for the third we estimated the population-weighted average concentration using an isotropic spatial model. Rate ratios for each of the metrics were estimated from time-series models. Results: For Pollutants with relatively homogeneous spatial distributions we observed only small differences in the rate ratio across the three metrics. Conversely, for spatially heterogeneous Pollutants we observed larger differences in the rate ratios. For a given Pollutant, the strength of evidence for an association (i.e., chi-square statistics) tended to be similar across metrics. Conclusions: Given that the chi-square statistics were similar across the metrics, the differences in the rate ratios for the spatially heterogeneous Pollutants may seem like a relatively small issue. However, these differences are important for health benefits analyses, where results from epidemiological studies on the health effects of Pollutants (per unit change in concentration) are used to predict the health impacts of a reduction in Pollutant concentrations. We discuss the relative merits of the different metrics as they pertain to time-series studies and health benefits analyses.
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ambient air Pollutant measurement error characterization and impacts in a time series epidemiologic study in atlanta
Environmental Science & Technology, 2010Co-Authors: Gretchen T Goldman, Matthew J Strickland, Mitchel Klein, Lance A Waller, James A Mulholland, Paige E Tolbert, Armistead G Russell, Abhishek K Srivastava, Eric S EdgertonAbstract:In time-series studies of ambient air pollution and health in large urban areas, measurement errors associated with instrument precision and spatial variability vary widely across Pollutants. In this paper, we characterize these errors for selected air Pollutants and estimate their impacts on epidemiologic results from an ongoing study of air pollution and emergency department visits in Atlanta. Error was modeled for daily measures of 12 air Pollutants using collocated monitor data to characterize instrument precision and data from multiple study area monitors to estimate population-weighted spatial variance. Time-series simulations of instrument and spatial error were generated for each Pollutant, added to a reference Pollutant time-series, and used in a Poisson generalized linear model of air pollution and cardiovascular emergency department visits. Reductions in risk ratio due to instrument precision error were less than 6%. Error due to spatial variability resulted in average risk ratio reductions of ...
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short term associations between ambient air Pollutants and pediatric asthma emergency department visits
American Journal of Respiratory and Critical Care Medicine, 2010Co-Authors: Matthew J Strickland, Lyndsey A Darrow, Mitchel Klein, Dana W Flanders, Jeremy A Sarnat, Lance A Waller, Stefanie Ebelt Sarnat, James A Mulholland, Paige E TolbertAbstract:Rationale: Certain outdoor air Pollutants cause asthma exacerbations in children. To advance understanding of these relationships, further characterization of the dose–response and Pollutant lag effects are needed, as are investigations of Pollutant species beyond the commonly measured criteria Pollutants. Objectives: Investigate short-term associations between ambient air Pollutant concentrations and emergency department visits for pediatric asthma. Methods: Daily counts of emergency department visits for asthma or wheeze among children aged 5 to 17 years were collected from 41 Metropolitan Atlanta hospitals during 1993–2004 (n = 91,386 visits). Ambient concentrations of gaseous Pollutants and speciated particulate matter were available from stationary monitors during this time period. Rate ratios for the warm season (May to October) and cold season (November to April) were estimated using Poisson generalized linear models in the framework of a case-crossover analysis. Measurements and Main Results: Both ozone and primary Pollutants from traffic sources were associated with emergency department visits for asthma or wheeze; evidence for independent effects of ozone and primary Pollutants from traffic sources were observed in multiPollutant models. These associations tended to be of the highest magnitude for concentrations on the day of the emergency department visit and were present at relatively low ambient concentrations. Conclusions: Even at relatively low ambient concentrations, ozone and primary Pollutants from traffic sources independently contributed to the burden of emergency department visits for pediatric asthma.
Masoud Kayhanian - One of the best experts on this subject based on the ideXlab platform.
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modeling of highway stormwater runoff
Science of The Total Environment, 2005Co-Authors: Masoud Kayhanian, Michael K StenstromAbstract:Highways are stormwater intensive landuses since they are impervious and have high Pollutant mass emissions from vehicular activity. Vehicle emissions include different Pollutants such as heavy metals, oil and grease, particulates from sources such as fuels, brake pad wear and tire wear, and litter. To understand the magnitude and nature of the stormwater emissions, a 3-year study was conducted to quantify stormwater Pollutant concentrations, mass emission rates, and the first flush of Pollutants. Eight highway sites were monitored over 3 years for a large suite of Pollutants. The monitoring protocol emphasized detecting the first flush and quantifying the event mean concentration. Grab and flow-weighted composite samples, rainfall, and runoff data were collected. A new runoff model with four parameters was developed that to describe the first flush of Pollutants for a variety of rainfall and runoff conditions. The model was applied to more than 40 events for 8 Pollutants, and the parameters were correlated to storm and site conditions, such as total runoff, antecedent dry days, and runoff coefficient. Improved definitions of first flush criteria are also presented.
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IMPACT OF ANNUAL AVERAGE DAILY TRAFFIC ON HIGHWAY RUNOFF Pollutant CONCENTRATIONS
Journal of Environmental Engineering, 2003Co-Authors: Masoud Kayhanian, Amardeep Singh, Claus Suverkropp, Steve BorroumAbstract:The objective of this study was to evaluate correlations between annual average daily traffic (AADT) and storm water runoff Pollutant concentrations generated from California Department of Transportation (Caltrans) highway sites. Analyses of data collected from the Caltrans Cyear (1997-01) highway runoff characterization program revealed that, in general, Pollutant concentrations from urban highways were higher than those found from non-urban highways. For a limited number of Pollutants, however, the concentrations from norrurban highways were found to be higher than the concentrations from urban highways. No direct linear correlation was found between highway runoff Pollutant event mean concentrations (EMCs) and AADT. However, through multiple regression analyses, it was shown that AADT has an influence on most highway runoff constituent concentrations, in conjunction with factors associated with watershed characteristics and Pollutant build-up and wash oft The other noticeable factors shown to influence the accumulation of Pollutants on highways were antecedent dry period, drainage area, maximum rain intensity, and land use.
Bin Cao - One of the best experts on this subject based on the ideXlab platform.
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influence of 3 chloroaniline on the biofilm lifestyle of comamonas testosteroni and its implications on bioaugmentation
Applied and Environmental Microbiology, 2016Co-Authors: Anee Mohanty, Wu Siang Chia, Bin CaoAbstract:ABSTRACT Bioaugmentation has been frequently proposed in wastewater and soil treatment to remove toxic aromatic compounds. The performance of bioaugmentation is affected by a number of biological and environmental factors, including the interaction between the target Pollutant and the augmented bacterial cells. In this study, using Comamonas testosteroni and 3-chloroaniline (3-CA) as the model organism and target Pollutant, we explored the influence of toxic aromatic Pollutants on the biofilm lifestyle of bacteria capable of degrading aromatic compounds toward a better understanding of cell-Pollutant interaction in bioaugmentation. Our results showed that the exposure to 3-CA greatly reduced the retention of C. testosteroni cells in packed-bed bioreactors (from 22% to 15% after three pore volumes), which could be attributed to the altered bacterial motility and cell surface hydrophobicity. To further understand the molecular mechanisms, we employed an integrated genomic and transcriptomic analysis to examine the influence of 3-CA on the expression of genes important to the biofilm lifestyle of C. testosteroni. We found that exposure to 3-CA reduced the intracellular c-di-GMP level by downregulating the expression of genes encoding c-di-GMP synthases and induced massive cell dispersal from the biofilms. Our findings provide novel environmental implications on bioaugmentation, particularly in biofilm reactors, for the treatment of wastewater containing recalcitrant industrial Pollutants. IMPORTANCE Bioaugmentation is a bioremediation approach that often has been described in the literature but has almost never been successfully applied in practice. Many biological and environmental factors influence the overall performance of bioaugmentation. Among these, the interaction between the target Pollutant and the augmented bacterial cells is one of the most important factors. In this study, we revealed the influence of toxic aromatic Pollutants on the biofilm lifestyle of bacteria capable of degrading aromatic compounds toward a better understanding of cell-Pollutant interaction in bioaugmentation. Our findings provide novel environmental implications on bioaugmentation for the treatment of wastewater containing recalcitrant industrial Pollutants; in particular, the exposure to toxic Pollutants may reduce the retention of augmented organisms in biofilm reactors by reducing the c-di-GMP level, and approaches to elevating or maintaining a high c-di-GMP level may be promising to establish and maintain sustainable bioaugmentation activity.
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Influence of 3-Chloroaniline on the Biofilm Lifestyle of Comamonas testosteroni and Its Implications on Bioaugmentation
Applied and environmental microbiology, 2016Co-Authors: Anee Mohanty, Wu Siang Chia, Bin CaoAbstract:Bioaugmentation has been frequently proposed in wastewater and soil treatment to remove toxic aromatic compounds. The performance of bioaugmentation is affected by a number of biological and environmental factors including the interaction between the target Pollutant and the augmented bacterial cells. In this study, using Comamonas testosteroni and 3-chloroaniline (3-CA) as the model organism and target Pollutant, we explored the influence of toxic aromatic Pollutant on the biofilm lifestyle of bacteria capable of degrading aromatic compounds toward a better understanding of cell-Pollutant interaction in bioaugmentation. Our results showed that the exposure to 3-CA greatly reduced the retention of C. testosteroni cells in packed-bed bioreactors (from 22% to 15% after three pore volumes), which could be attributed to the altered bacterial motility and cell surface hydrophobicity. To further understand the molecular mechanisms, we employed an integrated genomic and transcriptomic analysis to examine the influence of 3-CA on the expression of genes important to the biofilm lifestyle of C. testosteroni . We found that the exposure to 3-CA reduced the intracellular c-di-GMP level by downregulating the expression of genes encoding c-di-GMP synthases and induced massive cell dispersal from the biofilms. Our findings provide novel environmental implications on bioaugmentation, in particular, in biofilm reactors, for the treatment of wastewater containing recalcitrant industrial Pollutants. IMPORTANCE Bioaugmentation is a bioremediation approach that has been often described in literature but has been hardly to no successfully applied in practice. Many biological and environmental factors influence the overall performance of bioaugmentation. Among which, the interaction between the target Pollutant and the augmented bacterial cells is one of the most important factors. In this study, we revealed the influence of toxic aromatic Pollutant on the biofilm lifestyle of bacteria capable of degrading aromatic compounds toward a better understanding of cell-Pollutant interaction in bioaugmentation. Our findings provide novel environmental implications on bioaugmentation for the treatment of wastewater containing recalcitrant industrial Pollutants; in particular, the exposure to toxic Pollutants may reduce the retention of augmented organisms in biofilm reactors by reducing the c-di-GMP level and the approaches to elevating or maintaining a high c-di-GMP level may be promising to establish and maintain a sustainable bioaugmentation activity.
