Determination of Acute Exposure Guideline Levels in a Dispersion Model

Stage, Steven A.

doi:10.1080/10473289.2004.10470885

Cited by 18 publications

(16 citation statements)

References 4 publications

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“…In groundwater flows, the interaction of flow with the grain matrix or lenses of varied porosity may result in the spread of a toxic contaminant plume, with acute effects on human health [1]. In wetland systems, many arthropods and macrophytes rely on water currents for the passive dispersal of larval stages and seeds [2,3].…”

Section: Introductionmentioning

confidence: 99%

Prediction of near-field shear dispersion in an emergent canopy with heterogeneous morphology

Lightbody

Nepf

2006

Environ Fluid Mech

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The evaluation of longitudinal dispersion in aquatic canopies is necessary to predict the behavior of dissolved species and suspended particles in marsh and wetland systems. Here we consider the influence of canopy morphology on longitudinal dispersion, focusing on transport before constituents have mixed over depth. Velocity and longitudinal dispersion were measured in a model canopy with vertically varying canopy density. The vertical variation in canopy morphology generates vertical variation in the mean velocity profile, which in turn creates mean-shear dispersion. We develop and verify a model that predicts the mean-shear dispersion in the near field from morphological characteristics of the canopy, such as stem diameter and frontal area. Close to the source, longitudinal dispersion is dominated by velocity heterogeneity at the scale of individual stems. However, within a distance of approximately 1 m, the shear dispersion associated with velocity heterogeneity over depth increases and eclipses this smaller-scale process.

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Section: Introductionmentioning

confidence: 99%

Prediction of near-field shear dispersion in an emergent canopy with heterogeneous morphology

Lightbody

Nepf

2006

Environ Fluid Mech

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“…Many have argued that the way toxic load is defined in Eq. (1) is unfounded and have proposed alternatives [5][6][7], including consideration of additional timescales such as the uptake time constant of a chemical for a given response [7], or the functional form of the recovery process [6]. However, formulating such toxic load models would create an even greater demand for chemical-specific toxicological data.…”

Section: Discussionmentioning

confidence: 99%

“…Recent studies have modeled the transport and dispersion of chemical compounds both outdoors and indoors under various release scenarios [1][2][3][4]. Model predictions of outdoor and indoor concentrations vary with time, but there is no consensus on how to relate time-varying air concentrations to health effects [5][6][7][8]. Moreover, exposure guidelines and limits are typically established assuming exposure to a constant concentration.…”

Section: Introductionmentioning

confidence: 99%

Computing Toxic Load for Shelter-in-Place Analysis Using Joint Urban 2003

Chan¹,

Sohn²

2012

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Toxic load is a metric used to quantify acute effects from inhalation exposures. The toxic load to individuals depends on the fluctuations of chemical concentrations because the exposureresponse relationship is often nonlinear. To study the effects of concentration fluctuations on toxic load, we analyzed concentration data from the Joint Urban 2003 series of city-scale tracer gas studies. We summarized the outdoor concentrations measured by fast-response gas analyzers and computed outdoor toxic load. We then analyzed the amount of tracer gas that entered a 16-story office building and compared indoor and outdoor toxic loads. We show that the time aggregation used to compute toxic load is a source of uncertainty in hazard assessments.However, in comparison to other uncertainties and variability inherent in hazard assessments involving buildings, the choice of time averaging interval plays a minor role, especially when toxic load is used to compute other aggregated metrics such as the effectiveness of sheltering indoors. In the absence of compound-specific information to dictate a time average, we propose following Acute Exposure Guideline Levels (AEGLs) and using timescales on the order of minutes for computing indoor toxic load.

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“…(11,pp.31-32) Atmospheric dispersion modelers have widely adopted this NAC philosophy concerning the utility of AEGLs for consequence management involving large-scale chemical exposures. For example, modelers currently claim that AEGL-exceedance-zone maps can "be interpreted quickly by emergency managers in terms of expected toxic consequences" (14) and "aid in determining health risks, recommending emergency actions (such as sheltering, evacuation, relocation, and reentry), and deploying emergency personnel." (15) Clearly, such claims are valid only if exposure scenarios addressed are simple enough and only if resources available for response and recovery are large enough to obviate any need to make tradeoffs or priorities.…”

Section: Current Chemical Exposure Guidelines Cannot Support Triage Dmentioning

confidence: 99%

Risk Analysis for Environmental Health Triage

Bogen¹

2005

Risk Analysis

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The Homeland Security Act mandates the development of a national, risk‐based system to support planning for, response to, and recovery from emergency situations involving large‐scale toxic exposures. To prepare for and manage consequences effectively, planners and responders need not only to identify zones of potentially elevated individual risk but also to predict expected casualties. Emergency response support systems now define “consequences” by mapping areas in which toxic chemical concentrations do or may exceed Acute Exposure Guideline Levels (AEGLs) or similar guidelines. However, because AEGLs do not estimate expected risks, current unqualified claims that such maps support consequence management are misleading. Intentionally protective, AEGLs incorporate various safety/uncertainty factors depending on the scope and quality of chemical‐specific toxicity data. Some of these factors are irrelevant, and others need to be modified, whenever resource constraints or exposure‐scenario complexities require responders to make critical trade‐off (triage) decisions in order to minimize expected casualties. AEGL‐exceedance zones cannot consistently be aggregated, compared, or used to calculate expected casualties and so may seriously misguide emergency response triage decisions. Methods and tools well established and readily available to support environmental health protection are not yet developed for chemically‐related environmental health triage. Effective triage decisions involving chemical risks require a new assessment approach that focuses on best estimates of likely casualties, rather than on upper plausible bounds of individual risk. If risk‐based consequence management is to become a reality, federal agencies tasked with supporting emergency response must actively coordinate to foster new methods that can support effective environmental health triage.

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Determination of Acute Exposure Guideline Levels in a Dispersion Model

Cited by 18 publications

References 4 publications

Prediction of near-field shear dispersion in an emergent canopy with heterogeneous morphology

Prediction of near-field shear dispersion in an emergent canopy with heterogeneous morphology

Computing Toxic Load for Shelter-in-Place Analysis Using Joint Urban 2003

Risk Analysis for Environmental Health Triage

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