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Reevaluation of 1999 Health-Based Environmental Screening Levels (HBESLs) for Chemical Warfare Agents
This report evaluates whether new information and updated scientific models require that changes be made to previously published health-based environmental soil screening levels (HBESLs) and associated environmental fate/breakdown information for chemical warfare agents (USACHPPM 1999). Specifically, the present evaluation describes and compares changes that have been made since 1999 to U.S. Environmental Protection Agency (EPA) risk assessment models, EPA exposure assumptions, as well as to specific chemical warfare agent parameters (e.g., toxicity values). Comparison was made between screening value estimates recalculated with current assumptions and earlier health-based environmental screening levels presented in 1999. The chemical warfare agents evaluated include the G-series and VX nerve agents and the vesicants sulfur mustard (agent HD) and Lewisite (agent L). In addition, key degradation products of these agents were also evaluated. Study findings indicate that the combined effect of updates and/or changes to EPA risk models, EPA default exposure parameters, and certain chemical warfare agent toxicity criteria does not result in significant alteration to the USACHPPM (1999) health-based environmental screening level estimates for the G-series and VX nerve agents or the vesicant agents HD and L. Given that EPA's final position on separate Tier 1 screening levels for indoor and outdoor worker screening assessments has not yet been released as of May 2007, the study authors find that the 1999 screening level estimates (see Table ES.1) are still appropriate and protective for screening residential as well as nonresidential sites. As such, risk management decisions made on the basis of USACHPPM (1999) recommendations do not require reconsideration. While the 1999 HBESL values are appropriate for continued use as general screening criteria, the updated '2007' estimates (presented below) that follow the new EPA protocols currently under development are also protective. When EPA finalizes and documents a position on the matter of indoor and outdoor worker screening assessments, site-specific risk assessments should make use of modified models and criteria. Screening values such as those presented in this report may be used to assess soil or other porous media to determine whether chemical warfare agent contamination is present as part of initial site investigations (whether due to intentional or accidental releases) and to determine whether weather/decontamination has adequately mitigated the presence of agent residual to below levels of concern. However, despite the availability of scientifically supported health-based criteria, there are significant resources needs that should be considered during sample planning. In particular, few analytical laboratories are likely to be able to meet these screening levels. Analyses will take time and usually have limited confidence at these concentrations. Therefore, and particularly for the more volatile agents, soil/destructive samples of porous media should be limited and instead enhanced with headspace monitoring and presence-absence wipe sampling
Developing Health-Based Pre-Planning Clearance Goals for Airport Remediation Following a Chemical Terrorist Attack: Decision Criteria for Multipathway Exposure Routes
In the event of a chemical terrorist attack on a transportation hub, post-event remediation and restoration activities necessary to attain unrestricted facility re-use and re-entry could require hours to multiple days. While timeframes are dependent on numerous variables, a primary controlling factor is the level of pre-planning and decision-making completed prior to chemical release. What follows is the second of a two-part analysis identifying key considerations, critical information and decision criteria to facilitate post-attack and post-decontamination consequence management activities. Decision criteria analysis presented here provides first-time, open-literature documentation of multi-pathway, health-based remediation exposure guidelines for selected toxic industrial compounds, chemical warfare agents, and agent degradation products for pre-planning application in anticipation of a chemical terrorist attack. Guideline values are provided for inhalation and direct ocular vapor exposure routes as well as percutaneous vapor, surface contact, and ingestion. Target populations include various employees as well as transit passengers. This work has been performed as a national case study conducted in partnership with the Los Angeles International Airport and The Bradley International Terminal. All recommended guidelines have been selected for consistency with airport scenario release parameters of a one-time, short-duration, finite airborne release from a single source followed by compound-specific decontamination
Developing Health-Based Pre-Planning Clearance Goals for Airport Remediation Following Chemical Terrorist Attack: Introduction and Key Assessment Considerations
In the event of a chemical terrorist attack on a transportation hub, post-event remediation and restoration activities necessary to attain unrestricted facility reuse and re-entry could require hours to multiple days. While restoration timeframes are dependent on numerous variables, a primary controlling factor is the level of pre-planning and decision-making completed prior to chemical terrorist release. What follows is the first of a two-part analysis identifying key considerations, critical information, and decision criteria to facilitate post-attack and post-decontamination consequence management activities. A conceptual site model and human health-based exposure guidelines are developed and reported as an aid to site-specific pre-planning in the current absence of U.S. state or Federal values designated as compound-specific remediation or re-entry concentrations, and to safely expedite facility recovery to full operational status. Chemicals of concern include chemical warfare nerve and vesicant agents and the toxic industrial compounds phosgene, hydrogen cyanide, and cyanogen chloride. This work has been performed as a national case study conducted in partnership with the Los Angeles International Airport and The Bradley International Terminal. All recommended guidelines have been selected for consistency with airport scenario release parameters of a one-time, short-duration, finite airborne release from a single source followed by compound-specific decontamination