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Remediating Indoor and Outdoor Environments

EPA was designated as the lead federal agency for the remediation of areas contaminated by chemical, biological, and radiological agents. EPA's homeland security research is responsible for providing procedures and methods to contain and mitigate contamination and remediate or decontaminate indoor and outdoor environments following terrorist attacks.



EPA’s homeland security research on indoor and outdoor decontamination work is focused on protecting human health and the environment from the after effects of terrorist attacks involving chemical, biological, or radiological (CBR) weapons or agents.

EPA provides research and state-of-the-art science products to assist in:

  • detecting contamination and determining its extent
  • containing contamination to minimize exposure
  • decontaminating buildings and outdoor areas in a timely and cost-effective manner
  • disposing of contaminated materials

Many CBR agents that might be used in an attack have not been well studied. A variety of other agents or explosive materials might also be used, so researchers have begun prioritizing the most likely classes of materials (for example, pesticides, metals, bacterial toxins), in addition to the most likely CBR agents.

For each class of CBR agent or contaminant, the effectiveness of existing methodologies for detection and containment, site decontamination, and waste disposal is being assessed.

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Contaminant Fate and Transport Research

Contaminant fate and transport research examines how CBR agents or related contaminants behave in different environments and under different conditions, and how they move through or within structures or the environment.

Contaminants in air can spread rapidly, either as volatile compounds or as particulates that settle and become airborne repeatedly. Contaminants can be spread beyond the initial contamination zone on skin, clothing, shoes, and tools.

To make decontamination plans, responders and others need to be able to:

  • characterize the extent of contamination
  • determine the levels of contaminants
  • know how the contaminants might spread
  • know how long contaminants can stay on surfaces
  • determine if breakdown compounds pose a threat

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Remediating Indoor and Outdoor Environments

EPA investigates how to decontaminate a variety of outdoor surfaces and building materials, heating and cooling systems, electronic equipment, and indoor materials such as carpet, wood, and painted wallboard.

Whenever possible, non-destructive decontamination is the major goal. Terrorist attacks have been - and most likely will be - aimed at areas where many people live, work, and travel. The key challenge is how to clean up a populated area as effectively and inexpensively as possible, while protecting the workers and nearby residents from deleterious health effects.

Decontamination covers a broad range of activities, including investigating the best way to use water or other liquids, specialized coatings, foams, or fumigants to decontaminate surfaces.

Because large quantities of waste and contaminated residual materials can be generated during decontamination, EPA conducts research and development on waste treatment and disposal.

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Related Information

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Contaminant Fate and Transport

EPA investigates what happens to contaminants as they move through structures and outdoor environments. Research on how to limit exposure to chemical, biological, or radiological (CBR) agents requires a detailed understanding of how contaminants in air spread: do they spread rapidly as volatile compounds or do they spread as particulates that repeatedly settle and become airborne?

Contaminants can also be spread on skin, clothing, shoes, or tools to areas beyond the original contamination zone. Understanding contaminant behavior allows responders to plan for containing the agents.

In order to develop decontamination plans, decision-makers require information about contaminant fate and transport. Current research investigates how:

  • contaminants spread through air or move within a structure or the outdoor environment
  • agents spread on skin, clothing, shoes, and tools to areas beyond the contamination zone
  • environmental conditions affect contaminants
  • contaminants react or interact with surfaces and materials


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Indoor and Outdoor Decontamination

Much of EPA's indoor and outdoor decontamination research has focused on developing safe and successful decontamination approaches, often using pilot-scale studies, and evaluating whether a particular decontamination method adversely affects materials and equipment.

EPA has found that studies done in the laboratory using small samples of materials (coupons) are difficult to apply to large scale decontamination problems; likewise, decontamination systems designed to use in large spaces are difficult to adapt to small test chambers. Consequently, field scale tests that will examine the costs and complexities associated with various decontamination technologies are in the planning stages.

Studies have shown that there is no universal decontamination approach. The effectiveness of a decontamination technology (efficacy) largely depends on the contaminated material type. What works well on one surface type contaminated with one agent does not necessarily work on a different surface with the same agent. In addition, the concentration of the decontaminant, the contact time of the decontaminant with the material, and conditions such as temperature, sunlight, or relative humidity all affect decontaminant efficacy.

Material Demand and Compatibility

In order to decontaminate the interior of a building, the proper concentration of fumigant needs to be maintained over a certain period of time. Vaporized hydrogen peroxide and chlorine dioxide gas are fumigants that have been in use for many years, and have been used to decontaminate interior surfaces contaminated by anthrax, which is one of the biological agents of greatest homeland security concern.

EPA designs their material demand effort to determine how building materials affect the ability to maintain the target decontamination vapor concentration within a closed interior space. Interior building materials such as concrete, steel, wood, carpet, ceiling tiles, or painted wallboard can interact with a decontaminant through sorption, reducing the amount available for decontamination. The fumigant concentration can also be reduced as it decomposes the decontaminant.

EPA also investigates the compatibility of materials with fumigant technologies. After fumigation, the physical properties of building materials have been measured, any changes in the appearance of office equipment documented, and the integrity of electrical circuits and related devices examined.

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Persistence Studies

EPA investigates persistence, which is the length of time that CBR agents remain active on various types of surface materials or under certain environmental conditions, such as ultraviolet light or high relative humidity. CBR agents interact with materials such as tile, carpeting, wood, steel, or concrete, and, therefore, present unique decontamination challenges that are also being investigated.

Much EPA research on biological weapons has focused on the spores of Bacillus anthracis, the microorganism that causes anthrax. B. anthracis is resistant to harsh environmental conditions and can persist for decades, able to grow when conditions are suitable. EPA also uses anthrax spore surrogates, which are similar to anthrax spores, but not dangerous.

It is presumed that decontamination methods successful on this resistant spore will be similarly successful on less resistant organisms. Additional study is necessary to verify this assumption and design effective decontamination approaches.

Other microorganisms (such as H5N1, the virus which causes highly pathogenic avian influenza) and biotoxins (such as ricin) have been studied under different concentrations of decontaminants, and different conditions of relative humidity, temperature, and ultraviolet light to see what affects persistence.

EPA has also investigated the persistence of toxic industrial chemicals and chemical warfare agents on various types of building materials under conventional environmental conditions. Other studies have included the persistence of chemical warfare agents and microorganisms in the leachates from landfills.

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Decontamination Methods

The effectiveness of a decontaminant depends on the contaminated material type. What works well on one surface might not work on another surface.

Studies have shown that there is no universal decontamination approach. The effectiveness of a decontamination technology (efficacy) depends on the contaminated material type. What works well on one surface type does not necessarily work on a different type. In addition, the concentration of the decontaminant, the contact time of the decontaminant on the material, and conditions such as temperature, sunlight, or relative humidity all affect the efficacy.

EPA's indoor and outdoor decontamination research covers a broad range of activities, including investigating the best way to use water (liquid and steam) or other liquids, foams, fumigants, or specialized coatings (such as strippable coatings for materials contaminated with radionuclides) to decontaminate indoor materials and outdoor surfaces.

Research on rapid decontamination in the event of the detonation of a radiological dispersal device evaluates commercially available technologies that could be used on buildings, outdoor areas, and contaminated equipment.

As with other EPA decontamination studies, minimizing cost and time, minimizing surface damage and secondary waste, and reducing recontamination were considerations for selecting decontamination technologies. Proposed future work includes investigating additional strippable coatings, sequestration coatings (the radionuclide binds to the coating rather than the building material), chemical methods, commercial cleaning products, and mechanical methods such as street sweepers.

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Waste Treatment

EPA continues to update its Incident Waste Assessment and Tonnage Estimator (I-WASTE). This Web-based tool organizes large amounts of information related to managing waste after natural disasters or homeland security events.

The decision support tool is not intended to override regulatory or legal requirements, but to provide information on options for removing, transporting, and disposing of contaminated materials. A wide-area waste estimator that allows users to calculate disposal waste amounts involving multiple structures is included. Databases of facilities such as incinerators, recyclers, and hazardous waste landfills are included.

Large amounts of materials possibly contaminated with chemical and biological agents might need to be incinerated after a homeland security event. In some cases, agents might not be destroyed because some building materials inhibit the penetration of heat. Residual agents or bacterial spores might remain even after being exposed to high temperatures for what is assumed to be a sufficiently long time. EPA has conducted a variety of studies using thermal destruction systems - for example, a rotary kiln incinerator simulator - and computer modeling designed to predict how well an incinerator might destroy chemical or biological agents.

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