Proceedings of the Public Security S&T Summer Symposium 2009

CRTI 04-0018RD

Development of Standards for Decontamination of Buildings and Structures Affected by Chemical or Biological Terrorism

Project Lead: Environment Canada

Federal Partners: Public Health Agency of Canada, DRDC Suffield

Industry Partner: SAIC Canada

Other Partners: United States Environmental Protection Agency; University of Ottawa - Centre for Research on Environmental Microbiology; University of Leeds; Russian Research Institute of Hygiene, Toxicology, and Occupational Pathology

Objectives

The goal of this project is to develop clean-up standards for the decontamination of buildings after a chemical or biological attack. This work will use data generated from exposure experiments and focus on the development of a generic approach to decontamination and determination of specific guidelines for ascertaining “How clean is clean?” To this end, standards for agents that represent a real or potential risk for use in chemical or biological terrorism will be developed using three methds. First, the project team will establish the relationship between magnitude of exposure and expected health effects. Next, by identifying individuals at risk of exposure and considering all routes of exposure (contact, inhalation, and ingestion), the team will assess the real and potential exposure risks. Finally, the team will characterize the risk to determine potential for toxicity (chemical) or infectivity (biological).

Relevance

Decontamination of facilities following acts of biological or chemical terrorism is designed to mitigate hazards to the extent that the facilities can be recommissioned, usually to their former use. However, no suitable standards exist for determining levels safe for reoccupancy. Pertinent laboratory data, mainly from animal exposure models, is used to establish clean-up standards and to help determine whether levels necessary for rehabitation are practically attainable; the likely cost of decontamination to acceptable levels, and whether the cost is justifiable; and, if rehabitable, whether use restrictions need to be in place based on expected inhabitants and any associated toxicological or pathogenic risks.

Recent Progress and Results

By combining laboratory results with values determined for safe concentrations in the air, for dermal contact, and for ingestion, it will be possible to determine safe concentrations on surfaces and set preliminary decontamination standards. The results of this study will then be used to develop a model that will determine “safe” surface concentrations of hazardous chemicals under various environmental conditions.

Environment Canada and SAIC Canada project personnel recently focused on the desorption of chemical agents of concern from building surfaces and in surrounding air at various temperatures. Project personnel generated experimental results from chemical studies involving four pesticides (lindane, carbofuran, diazinon, and malathion) and variables such as temperature and surface materials. When compared to theoretical maximum concentrations of their respective vapours in air, results showed that, at room temperature, experimental and theoretical headspace concentrations were similar for all compounds except carbofuran. The experimental data for carbofuran were up to 500 times greater than the expected maximum concentration in vapour phase, and while headspace concentrations at 40°C were 5 to 10 times higher than at 20°C for all other compounds, carbofuran, displayed similar results at 20°C and 40°C. Important material-dependent variations in vapour concentrations were also observed.

Initial costing modelling has been completed, providing a tool to estimate the value of resources needed to meet decontamination standards. Values derived from the costing model have been validated against actual clean-up costs from selected incidents. Cost scenarios were found to be conservative in nature and continue to be refined.

The University of Ottawa’s Centre for Research on Environmental Microbiology (CREM) and the Public Health Agency of Canada have performed experiments on the biological side, focusing on determining the effectiveness of decontamination methods and the use of surrogates for distinct threats. Work continues on those aspects of sampling that can have a large impact on assessing contamination of environmental surfaces, determining an effective means to decontaminate the surfaces, and confirming the levels of pathogen reductions achieved.

Mathematical methods for determining decontamination standards have been proposed by several partners. These continue to be evaluated and combined, maintaining the strengths of the different models. Toxicological studies recently completed at the Russian Research Institute of Hygiene, Toxicology, and Occupational Pathology (RIHTOP) were based on these proposed standards. A complex set of equations was developed at RIHTOP to predict levels of concern based on hazard and toxicity indices and the physicochemical properties of a substance. Animal testing (rats and mice) of respiratory, dermal, and combined-exposure toxicity of substances was performed for the validation of the prototype method for setting decontamination limits.

Standards will be published for use by first responders and other government personnel involved in decontamination and reclamation. The information from this research will also be used to allow estimation of clean-up costs to determine whether a facility should be decontaminated and restored or simply demolished and rebuilt.

Impact

The project’s interim report provided a solid foundation from which the laboratory experiments evolved. Clean-up standards will first be established for those chemical and biological agents most likely to be used in an intentional release. Once the experimental and modelling work has been developed into standards, a broad range of personnel, from first responders to top-level decision makers, will use the standards. Special emphasis will be placed on using standards and associated models for post-remediation clearance of facilities and for determination of potential usage of facilities following a contamination event. Consequently, standards will be made available in condensed format for use in emergency response scenarios but will include more detailed analysis, including risk models, for determination of post-remediation use or for comparing the cost of remediation with that of facility destruction.

Authors:

Konstantin Volchek, Environment Canada, Konstantin.Volchek@ec.gc.ca

David Cooper, SAIC Canada, david.cooper@saic.com

Sayed Sattar, Centre for Research on Environmental Microbiology, University of Ottawa, ssattar@uottawa.ca

TABLE OF CONTENTS