Frequently Asked Questions

FAQs may be added or updated based on project developments.
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Note: In this FAQ, we interchange use of ‘Incident Command’ and ‘Unified Command’ depending on the incident. Unified Command exists under incidents where organizations or agencies have their own jurisdictional responsibilities concerning the response. Functionally, a Unified Command is an integrated group of Incident Commanders coordinating a consensus-based response management team.
Last Updated: January 31, 2024

General Information

  • Q: Who is CTEH?

    CTEH empowers teams of experts to help governmental entities, companies, and communities prepare for, respond to, and recover from threats to their environment and people. Our certified specialists include PhD toxicologists, masters in public health, industrial hygienists, and safety professionals, as well as hazardous materials and registered environmental managers.

    Our scientists conduct environmental monitoring and sampling according to plans approved and directed by the incident commanders of each response, including federal, state, and local stakeholders and the responsible party. With every response, we follow approved monitoring and sampling plans. Samples are all sent to third-party, nationally accredited environmental laboratories and analyzed by approved methods, with results provided to the relevant governmental entities. Analytical results are directly compared to guidelines and health-protective levels developed by the United States Environmental Protection Agency (EPA), Occupational Safety and Health Administration (OSHA), National Institute for Occupational Safety and Health (NIOSH), Agency for Toxic Substances and Disease Registry (ATSDR), and other relevant agencies to determine if chemical concentrations pose a health risk to people or the environment.

  • Q: If CTEH is hired by the responsible party after incidents, are they truly impartial?

    In the United States, there is a legal obligation for the party (company or individual) responsible for an environmental incident to financially and operationally cover the costs of assessment, cleanup, remediation, and restoration following the event. Established in 2004, the National Incident Management System (NIMS) provides a consistent nationwide framework to allow cooperation of Federal, state, local, tribal, and private entities to respond to and recover from incidents of any size, complexity, cause, or location. NIMS calls for the creation of an Incident Command structure for any incident that is flexible and scalable as the scope of an incident grows or as the situation is handled. Often, the Incident Commander (IC) begins as the highest-ranking first responder to a crisis. As a response grows in complexity or scale, the IC role transitions to a representative from the responsible party who is advised by subject matter experts and agency representatives — this is known as Unified Command. No operational plans, including environmental assessment, cleanup, safety, etc. are executed without the signed approval of the IC and the appropriate section chiefs following discussions and feedback in the operational structure.

    CTEH’s results and methodologies do not depend upon who has hired CTEH. We report the health risks that are indicated by the data we collect. CTEH responds to chemical incidents that impact or threaten to impact human and environmental health. Our data have indicated health risks on nearly every chemical incident we have responded to over the past 25+ years. The question is whether the health risks extend beyond the work area to the surrounding communities, and our data indicate if there is a risk or not compared to the context of established health-protective standards and guidelines. If we detect chemicals in the community that exceed health-based action levels, that is reported to the client and the Incident Command. It is also notable that the data collected in the work areas and communities surrounding the cleanup are collected by CTEH employees whose safety is just as important to us as the safety of the workers and the residents of the surrounding communities. Our responsibility is to locate harmful chemicals, determine their concentrations, and collaborate with stakeholders to understand the implications for human health and the environment.

  • Q: Isn’t it the EPA’s job to monitor the air and water?

    State and federal agencies, including EPA, do not have the capabilities in-house to conduct air monitoring and sampling at the scale required for most incidents, so they hire contractors to help conduct air monitoring and sampling, just as the responsible party does. CTEH works side-by-side with EPA and their contractors to compare data collected in communities. The EPA has consistently approved CTEH’s data and its interpretations regarding human health, having vetted our methods and procedures through numerous events, confirming our adherence to scientifically proven practices and methods.

  • Q: How are air sampling and analysis plans developed by CTEH during emergency response efforts? For example, what thresholds of different chemicals of concern are typically relied upon?

    CTEH draws upon state-of-the-science resources to develop action levels in air sampling and analysis plans. Where government agencies supply action levels, we consider those levels in the analysis. For example, the EPA establishes Acute Exposure Guideline Levels (AEGLs) that may be used to protect communities in the event of emergency chemical releases. Similarly, OSHA and the American Conference of Governmental Industrial Hygienists (ACGIH) establish values to protect workers over their working lifetime. Those values may be used as the basis for action levels across work areas.

    Because of the extremely long cycles required to update Federal exposure standards — OSHA Permissible Exposure Limits require Congress to pass legislation to update values — CTEH supplements Federal levels with state and third-party agency action levels in development of our plans. CTEH toxicologists also frequently review exposure studies published in scientific, peer-reviewed journals and resources like ACGIH and the American Industrial Hygiene Association (AIHA) to inform our sampling strategies. Accordingly, our action levels in CTEH-developed sampling and analysis plans are often significantly more conservative than published standards for some chemicals based on some of these trusted sources of information. On site, a response to an action level exceedance may vary from simply moving upwind or crosswind from a source to requiring enhanced respiratory protection to calling a work stoppage for hazard assessment.

  • Q: Why do community air exposure limits differ from occupational exposure limits?

    Occupational exposure limits and community air exposure limits have differing assumptions of exposure duration, and frequency action levels across work and community areas cannot be compared against each other. For example, an occupational limit may be based on a daily exposure for eight hours per day for 40 hours per week across a working lifetime. A community level might be based on a short-term exposure like less than an hour just once in a lifetime, or consider continuous exposure at a very low level across a lifetime for other chemicals. In the case of community action levels, sufficiently protective values must be balanced against the inherent risk associated with actions such as evacuation. At the same time, action levels implemented across work areas must account for the potential for daily exposures over a working lifetime.

  • Q: Why can you smell a chemical-like odor but still not detect any chemicals on an instrument?

    For many chemicals, there is a difference between the limit of detection for an analytical instrument and the odor threshold, at which some individuals may be able to detect the scent of a chemical. There are often orders of magnitude differences for concentrations at which a chemical odor can be perceived versus when it becomes detectable or may cause health effects.

    Odor sensitivities are highly subjective, and odor thresholds vary significantly between individuals based on a variety of factors, including a person’s physical ability (sensitivity) and their observational biases. Factors like genetics, health, whether the person is a smoker, and length of time experiencing an odor all affect the perceived strength of a particular odor. While this is very subjective, sampling and monitoring technologies are objective options for detecting the presence or absence of a chemical of concern. These technologies are carefully assessed to ensure they meet the accuracy, precision, specificity, sensitivity, linearity, and reliability requirement to ensure consistent performance. While some individuals may experience psychosomatic effects from the presence of a strong odor (e.g., headache, nausea, etc.), there is a difference between that temporary, transient experience and the significant health impacts against which exposure guidelines and standards are protective.

  • Q: When does a company call CTEH?

    The majority of the CTEH team’s efforts each year are spent supporting our clients’ “normal” business operations. This includes the items included under the Readiness, Recovery, and Resilience aspects of CTEH’s service umbrella. Our subject matter experts apply their education and professional expertise to consult on:

    • Industrial hygiene & safety programs
    • Occupational and public health
    • Helping clients convert their lessons learned on responses into specific and actionable preparedness and future response plans
    • Executing and supporting drills and tabletop exercises
    • Safety and gap assessment audits
    • Equipment training and maintenance
    • Expert research in emergent chemical and hazard studies to continuously inform best practices
    • Writing and contributing to journal articles and participating in continuing education — both teaching and learning.

    The emergency response phase represents a small time period in which CTEH supports and consults for our clients, industries, and communities.

  • Q: How do we address the claim that CTEH never detects anything?

    We pride ourselves on accurately representing the facts on any response or project in which CTEH is involved. Our response team is dedicated to observing and capturing data so that the information may be summarized or visualized and provided to Incident Command or client stakeholders. This allows those involved in a response to make well-informed decisions for containment, cleanup, restoration, and health-protective actions for workers, the community, and the environment.

    CTEH field staff employ methodologies, equipment, and strategies that have been vetted and verified by numerous state and federal agencies, as well as by various private and public response and assessment entities. Although it is not feasible to capture and assess every fugitive emission in an emergency response scenario, our approach is scientifically-driven and designed to help safeguard workers, communities, and the environment.

Project-Specific Questions

  • Norfolk Southern East Palestine (2023)

    Q: What was CTEH’s role in the East Palestine, Ohio rail incident?

    A: CTEH was hired by Norfolk Southern to conduct airborne chemical screening in residents’ homes, surface water sampling, and worker and community outdoor air monitoring and sampling in East Palestine and the surrounding areas.

    Q: Why were some chemicals related to the derailment and fire not monitored for during the derailment and subsequent vent and burn of the vinyl chloride car? Why were action levels changed during monitoring for home assessments?

    A: When CTEH is mobilized for an incident, much of the first hours of the response is focused on communication with the responsible party or first responders in an effort to identify as many of the potential chemical and physical hazards as possible. In a derailment, monitoring and sampling priority is given to chemicals confirmed or suspected to be released, which is then prioritized according to risk to human health. Once arriving on site and confirming actual breached or leaking vessels, the sampling strategy dials in to a more specific chemical set. Initial evaluation also includes assessing chemicals that are produced through combustion, incomplete combustion, reactions with water or humidity, reactions with oxygen or metals, reactions with other chemicals, and even the weathering effects of solar radiation. Real-time monitoring technology with the level of specificity required to assess for individual chemicals is limited. 

    For many suites of chemicals, colorimetric tubes, tapes, and wipes are used, which may have lower sensitivity than electronic electrochemical monitoring solutions. Many of the chemicals of interest may be detected on real-time devices that are less specific but highly sensitive — they simply require the application of a correction factor to the value, which is then compared to an action level. On multichemical responses, CTEH often uses these technologies together: a detection on a less specific instrument requires a validation with a secondary instrument that is more specific to confirm which chemical is present in order to identify subsequent follow-up actions.

    CTEH relies on the experience of our technical subject matter experts, PhD toxicologists, in conjunction with reviewing published research data and advising from chemical manufacturers, state and federal agencies, and other response contractors. In complex multichemical situations and especially when fire is present, risk management decisions have to be made by the Unified Command based on combined data and experiences. Incomplete combustion of vinyl chloride yields negligible percentages of other hazardous chemicals such as phosgene, which was classified as being low risk given that it was extremely unlikely that anyone in the work area or community would be exposed to a concentration or a duration that would yield any negative health effects.

    Information and strategies are often fluid on a response. As new hazards emerge or are eliminated, the sampling and monitoring strategy adjusts to either incorporate or remove those items from the operational plan, which is continuously evaluated based on new data. For this incident in particular, the Agency for Toxic Substances and Disease Registry (ATSDR) was consulted in addition to EPA for screening value consultation for butyl acrylate. Incident Command agreed on an initial level that was conservative, 3,300 ppb — approximately 1/3 of the EPA Acute Exposure Guideline Level-1 (AEGL-1). The AEGL-1 is a guideline at which the airborne concentration of a substance may cause transient, reversible, and non-disabling discomfort, irritation, or other nonsensory effects in the general population. Not long after, ATSDR suggested lowering the screening level by a factor of 10 to 330 ppb to account for individuals living in their homes 24 hours per day, which was adopted and incorporated into the Unified Command plan, with input from local and regional health departments, health and environmental agencies from Ohio and Pennsylvania, EPA, and Norfolk Southern. Weeks later, once most home screenings were complete, ATSDR further adjusted their recommended screening value to 20 ppb, more than an order of magnitude lower than the original recommendation. The new value was intended to minimize odors and has no relation to any suspected or unknown health effects.

    Q: What chemicals did CTEH test for when conducting indoor air screening? Was vinyl chloride (VC) detected in homes? 

    A: CTEH conducted indoor air screening per the EPA-approved air screening plan for VOCs and vinyl chloride (VC), the primary health risk driver of the compounds released in the derailment, in the homes of residents who requested screening. VOCs, which can be commonly detected in household from a variety of different causes, including aerosol sprays, candles, and disinfectants, were detected in some homes; however, VC was not. Results were provided to the residents, and the data from homes collectively did not indicate short- or long-term risks to human health.

    As of February 2024, CTEH has not been contracted to conduct any additional indoor air monitoring.

    More information about VOCs can be found here: USEPA Indoor Air Quality Information.

    Q: Why didn’t CTEH test for dioxins?

    A: There was no scientific basis for sampling for dioxins in people’s homes following the train derailment and burn. Dioxins are ubiquitous in the environment, can be created by many combustion sources, and were not expected to be significant combustion products of the prescribed burn conducted on the VC cars involved in the derailment. CTEH and the EPA conducted air monitoring for phosgene and hydrochloric acid — two marker combustion products of VC during the prescribed burn — and found only a few detections of low concentrations of hydrochloric acid in the community outside the immediate burn area, and only within the initial 24 hours following the burn. For these reasons, dioxin testing was unwarranted and unlikely to provide results relevant to the derailment.

    Q: How many homes did CTEH perform indoor air screening for? How many were found to have high or potentially unhealthy levels of vinyl chloride?

    A: Over 630 homes and commercial spaces participated in voluntary indoor air screening. Vinyl chloride was not detected in any of the indoor air screenings.

    Q: Is CTEH continuing to perform indoor air screening for Norfolk Southern? If not, when did that end? 

    A: CTEH’s indoor air screening work concluded in April 2023. More information regarding the conclusion of indoor air screening can be found here: USEPA East Palestine Operational Updates (April 2023) and USEPA East Palestine Newsletter (May 2023)

    Q: As of February 2024, what is CTEH’s current involvement with the Norfolk Southern East Palestine train derailment?

    A: CTEH continues to work at the direction of Unified Command to support Norfolk Southern in the recovery efforts in East Palestine. Specifically, CTEH experts continue to provide air monitoring in work areas, industrial hygiene consulting, and surface water sampling.

  • International Terminals Company (ITC) Deer Park (2019)

    Q: What was CTEH’s role in the International Terminals Company (ITC) Deer Park, Texas incident?

    A: CTEH was initially called to action by the City of Deer Park in response to a fire at the International Terminals Company (ITC) Deer Park facility. CTEH was then contracted by ITC to perform air monitoring and sampling, which grew to include water and soil sampling in later stages of the response efforts. CTEH toxicologists and consultants interacted continuously with the Unified Command providing air monitoring and operational updates for work done in the facility, assessments at neighboring facilities, and in the industrial and residential communities in the general vicinity of ITC. 

    While CTEH was not part of Unified Command (UC) in the ITC event, we gave our scientific input on the action levels approved and implemented by UC during the response. Based on our experience, the 1 ppm action level for 1 minute for benzene across community areas was highly conservative. It was substantially below the USEPA AEGL levels used to protect communities from short-term exposure scenarios. The benefit of establishing such short-term action levels (1 minute) is the quick identification of zones that are actually involved in a chemical release, allowing UC to take early actions and inform responses such as shelters-in-place. 

    CTEH continued to provide consulting and monitoring services through the deconstruction of the tank farm and removal of all affected soils from the impact zone.

  • CSX/West Point (2012)

    Q: What was CTEH’s role in the West Point, Kentucky rail incident? 

    A: In the West Point, Kentucky incident, CTEH conducted community and worker air monitoring and sampling. An unfortunate accident occurred that resulted in response workers being injured while conducting hot work, a procedure that uses a torch to cut metal in the process of separating damaged rail cars. A proper risk assessment was not conducted by those responsible for the hot work, and spilled chemicals were ignited. CTEH does not authorize or conduct hot work, and we were not responsible for the accident.

  • BP Deepwater Horizon Oil Spill (2010)

    Q: What was CTEH’s role in the BP Deepwater Horizon oil spill incident?

    A: CTEH was hired as the prime air monitoring consultant for the Deepwater Horizon response, operating across the entire Gulf region. CTEH’s work for the response involved many disciplines including industrial hygiene, safety, and environmental science. 

    Following the Deepwater Horizon response, CTEH has since been retained to provide testimony relevant to our involvement and the risk to workers, as evidenced by the data collected.

    During the Deepwater Horizon response, CTEH identified numerous situations where air quality was negatively impacted by the spill and communicated those instances to the Unified Command (that included EPA, U.S. Coast Guard, the states of Texas, Louisiana, Mississippi, Alabama, and Florida, and with oversight from OSHA, NIOSH, numerous other state and local agencies, and BP), resulting in actions to further protect those potentially impacted by those conditions. The data collected by CTEH, through methods approved by the Unified Command, was used to ensure the protection of human health. CTEH collected accurate data based on Unified Command-approved methods and reported those data daily for the benefit of all stakeholders.

  • Knauf Plasterboard Tianjin defective Chinese drywall in Florida (2010)

    Q: What was CTEH’s involvement in Knauf Plasterboard Tianjin defective Chinese drywall in Florida?

    A: In the case of Chinese drywall in Florida, our testing found that there were significant levels of chemicals attributed to the Chinese drywall inside the wall spaces where electrical components were found to be corroded and failing. Our results outside the wall spaces, in the breathable air in the homes, found that though there were detectable nuisance odors attributable to the drywall, the levels were not high enough to cause health effects in humans. CTEH’s interpretation of the data and resulting potential for human health effects in the air that people can breathe, as opposed to the air inside the walls, was accurate, based on the toxicology of the chemicals at issue, and not contradictory to studies conducted by other agencies.

  • TVA Kingston Fossil Plant (2008)

    Q: What was CTEH’s involvement in the coal fly ash spill at the Tennessee Valley Authority’s Kingston Fossil Plant?

    A: In the emergency phase of the response, CTEH was responsible for the community air monitoring for fly ash dust conducted outside the facility. That data was confirmed as accurate and correct. Following the emergency phase, a number of other contractors were hired to conduct long-term air monitoring onsite, and CTEH’s involvement ended. CTEH was neither involved during the cleanup phase nor conducted any air monitoring or sampling related to worker health and safety at the site.

  • Murphy Oil – Hurricane Katrina (2005)

    Q: What was CTEH’s involvement in the Murphy Oil incident following Hurricane Katrina?

    A: Hurricane Katrina devastated the Chalmette, LA community. Floodwaters destroyed many homes and also carried with them crude oil from a Murphy Oil tank severely damaged by the flood that contaminated hundreds of homes in the Chalmette community. The area was completely evacuated, and the police and first responders did not allow any homeowners into the area for a considerable period of time. There were many hazards to people after Hurricane Katrina, including structural damage to homes, wildlife, and other physical hazards such as flood damage and mold, in addition to oil contamination inside and outside people’s homes that remained after the floodwaters receded. The homes in the impacted areas were destroyed and uninhabitable, and many homes had more than a foot of sediment inside brought in by flood waters. CTEH was hired to determine which homes were impacted by the oil, and a federal judge agreed with the CTEH/EPA/Louisiana Department of Environmental Quality (LDEQ) boundaries of Murphy Oil-impacted homes. 

    Q: What sampling methodology did CTEH use in the Murphy Oil incident following Hurricane Katrina?

    A: Under the approved LDEQ / EPA sampling plan, and with the physical presence of EPA during sampling events, CTEH collected composite samples from several locations at each home. In accordance with the approved work plan, composite samples are considered more representative of conditions in an area than a single point sample. Such samples are classified as composites when multiple points within a small area, or grid, have a small amount of material collected into the same sample container. A method like this might be used, for example, to take sample material from several locations in a home’s yard to be representative of the full yard area rather than a pinpoint sample location within the yard. Some soil samples were baked by the sun into a hard brick-like state and had to be broken up prior to compositing and splitting samples with EPA. It is best practice when analyzing for volatile organic compounds in soil and water samples that air in the sample container is minimized since volatiles can evaporate from the soil or water into the headspace, which may cause the sample to be biased low if volatiles were present. Breaking up these brick-like bits of soil then tapping containers to better pack the containers, reducing available headspace, is the best practice for soil samples of this type.

    The affected homes were identified by this sampling plan and then remediated. Confirmation samples were collected and sent to an approved laboratory for analysis. The results were below RECAP standards, and based on those findings, LDEQ/EPA issued a No Further Action (NFA) letter. The NFA letter indicated that following the cleanup of the impacted properties, there was no additional risk to residents because the data proved that the oil had been removed.

  • Tobacco Industry (1999)

    Q: Did CTEH founders testify that tobacco smoke is not harmful?

    A: CTEH has never testified that second-hand smoke, also known as environmental tobacco smoke, is not harmful. CTEH’s founders currently believe, and always have, that cigarette smoke causes cancer and many other adverse health effects. They have repeatedly testified as such in legal proceedings. In the late 1990’s, these toxicologists reviewed the emerging science on the health effects of environmental tobacco smoke, including studying the efficacy of separation of smoking sections from non-smoking sections on board airplanes and other locations. Their opinions were limited to evaluations of the studies that existed at the time and the findings of their own investigations. Because of the known effects of cigarette smoking to cause lung cancer and numerous health effects in people, after completing these initial investigations, these founding toxicologists made a conscious decision to not engage in further studies of environmental tobacco smoke. In fact, CTEH’s founders helped Arkansas companies develop policies to prohibit smoking indoors many years before smoking indoors was banned by the Arkansas legislature in the Arkansas Clean Indoor Air Act of 2006.