The Complexity Associated with Setting Non-cancer Indoor Air Remediation Goals for Trichloroethylene Based on Short-term Exposure at Groundwater Contamination Sites

by Pepper Hamilton LLP
Contact

Over the last few years, there has been increasing consideration of vapor intrusion in groundwater investigations, groundwater remedy selection, periodic reviews of the continued safety of already implemented groundwater remedies, environmental due diligence, and property and personal injury litigation. The frequency and complexity of vapor intrusion evaluations and re-evaluations is driven by new, more explicit, vapor intrusion guidance documents and regulations promulgated by the Environmental Protection Agency (EPA) and state regulators, voluntary industry standards (such as the ASTM International’s E1527-13, Standard Practice for Phase I Environmental Assessments (December 30, 2013) (ASTM VI Standard)), the EPA’s controversial adoption of a novel, much more stringent non-cancer toxicity factor for trichloroethylene (TCE) in 2011, and the concerns of local residents. This article focuses particularly on the problems that plumes of TCE (a common groundwater contaminant) present to regulators and potentially responsible parties (whether private companies or governmental responsible parties) attempting to address vapor intrusion, and suggests some prudent actions that the private sector might consider.

The EPA’s New TCE Cancer Potency Is Unlikely to Result in More Stringent Remediation

There is no federal indoor air standard for TCE. Screening levels and site-specific remediation goals for TCE in indoor air are calculated using the EPA’s default exposure assumptions and the 2011 cancer potency or non-cancer reference air concentration (RfC).

The potential acceptable residential indoor air remediation goals for TCE based on cancer effects range from the concentrations that correspond to the one-in-one million (10-6) lifetime risk to a one-in-ten thousand (10-4) lifetime risk (using the EPA’s standard 30-year lifetime and the EPA’s new (2011) cancer potency), i.e., from 0.43 µg/m3 to 43 µg/m3 (see EPA Region 3, 6, and 9 Superfund screening level calculations), a concentration range 2.8 times lower than the EPA’s 2009 interim recommended indoor air remediation goals (1.2 µg/m3 to 120 µg/m3). As a practical matter, the 2011 TCE cancer potency is unlikely to change indoor air remediation goals selected by regulators (compared to the 2009 guidance). Background levels of TCE in indoor air and the practical quantification limit for measuring TCE in air are generally around 1 µg/m3. In any case, remedies are selected based on a case-by-case weighing of the nine remedy selection factors (including cost effectiveness and practicality), not just risk. Indoor air concentrations below 1.2 µg/m3 are on the low end of the acceptable cancer risk range and, therefore, are unlikely to justify changing the remedy. At sites with indoor air remediation goals for TCE that have already been set, regulators are unlikely to seek to lower an existing cancer-based TCE indoor air remediation goal for the reasons cited above and because the EPA’s five-year assessment policy only requires a revision of an existing cleanup goal if the concentration is unsafe (i.e., greater than 43 µg/m3 – the 10-4 lifetime risk level). Therefore, the change in the TCE inhalation cancer potency is not likely to trigger additional remedial action, although more sites may be subject to investigation.

The EPA and States Are Interpreting Non-cancer Regulatory Risks in an Inconsistent and Confusing Manner

The EPA’s 2011 novel non-cancer air reference concentration of 2 µg/m3 is more likely to result in a more stringent TCE indoor air remediation goal, because this concentration is much more stringent than either of the 2009 recommended non-cancer remediation goals of 10 µg/m3 or 600 µg/m3. More importantly, the EPA’s new recommended non-cancer remediation goal is based on an elevated risk of heart birth defects from short-term exposure to TCE during pregnancy (albeit in one unconfirmed rat study). This focus on short-term exposure differs from the EPA’s historic use of a lifetime exposure of 30 years to calculate non-cancer risk. Neither EPA Headquarters, nor any authoritative scientific body (such as the National Academy of Sciences) has defined “short-term” in this context or provided guidance on how to monitor or calculate the measured indoor air concentration that should be compared to 2 µg/m3. In this vacuum, the governmental scientists at the EPA and state regulatory agencies seem to be adopting their own, inconsistent definitions of short-term exposure during pregnancy. For example, EPA Region 9 has required evacuation of Navy office buildings based on this interpretation of short-term exposure. EPA Region 10 and Alaska interpret short-term to trigger action only if the 21-day average exceeds 2 µg/m3. Massachusetts requires notification within two hours of obtaining knowledge that the indoor air concentration exceeds 2 µg/m3, but does not specify in its written guidance the time over which the average concentration must be measured. New Hampshire considers a 2 µg/m3 indoor air level safe for “short-term exposure to TCE during the first trimester of pregnancy,” but also provides no averaging time in its guidance.

Similarly, the Agency for Toxic Substance and Disease Registry (ATSDR) also adopted the EPA’s RfC as its minimum risk level for non-cancer effects, but applies it over an intermediate-duration (i.e., an advisory applicable to exposures greater than 15 days to 364 days). In December 2013, the ATSDR concluded at a specific site that in homes that “have had TCE indoor air levels greater than 21 µg/m3,” there is:

A potential for developmental effects if a women was exposed even for a fairly short period of time (i.e., under three weeks) to these levels when the fetal heart is developing during the first trimester of pregnancy. … Given the narrow time window for health effects on a developing fetus, ATSDR is concerned that unidentified or future exposures could pose an urgent public health hazard. (boldface added.)

At the Millsboro, Del. Superfund site, ATSDR compared calculated 24-hour-average concentrations of TCE in indoor air to be 2.6 µg/m3 to 4.8 µg/m3 with the EPA’s RfC non-cancer levels and stated that this comparison “suggests that there may be an increased likelihood of adverse fetal cardiac effects.” At a site in Dracut, Mass., ATSDR stated that women exposed in an office building to between 54-61 µg/m3, based on an eight-hour air sample, “may be at risk of having a child with heart problems due to TCE exposure, and may be at risk for developing autoimmune effects (decreased thymus weight) due to TCE exposure.” The Wisconsin Department of Health states that “breathing TCE entering homes … via the vapor intrusion pathway for a long time (a year or more), or during pregnancy, could harm people’s health if TCE levels exceeded 2 µg/m3” and “breathing air approaching or exceeding these levels of TCE should be avoided.” (boldface added.)

The Alliance for Risk Assessment (a collaborative effort of private-sector non-profit organizations) recommends that a range of indoor air concentrations of between 3 to 20 µg/m3 (a range with a factor of 7) be considered and recommends a remediation goal concentration of 9 µg/m3 averaged over 24 days (the period over which the heart is formed in the fetus) as a reasonable approach. So averaging times cited above range from 8 hours to 30 years and the response actions varied from a caution that the information needed to make a decision is not available, to issuance of evacuation orders.

The frequency that remedial action will be triggered varies greatly, depending upon the averaging time. For example, use of a 24-hour averaging time will trigger an indoor air remediation if the concentration on one day exceeds 2.0 µg/m3, even if 20 days out of a 21-day averaging period do not exceed this limit, or even if 10,949 days out of 30 years may have average concentrations below 2.0 µg/m3.

In summary, there is no definitive guidance on what constitutes a “short” period of exposure to TCE in indoor air or on how to measure compliance. More generally, unlike the process of selecting a remediation goal based on carcinogenic risk, there is not a long-established process for making flexible risk management decisions for non-cancer effects from short-term exposure.

Suggested Courses of Action

These unique circumstances require thoughtful and scientifically supportable responses where vapor intrusion is considered. Specifically:

  • private parties should urge the EPA to consider the scientific uncertainties, the short-term exposure policy issues, and the other unique aspects of non-cancer risks in setting indoor air action levels for TCE
  • potentially responsible parties should include in the administrative record at cleanup sites documentation of these issues
  • buyers and sellers should consider these complexities in their environmental due diligence of properties potentially impacted by TCE vapors
  • defendants in litigation should avoid potential misinterpretation of exposure to concentrations above 2.0 µg/m3 of TCE. The regulatory reference dose is not a level that is likely to cause harm to a population as a whole, no less cause an individual’s injury.

 

DISCLAIMER: Because of the generality of this update, the information provided herein may not be applicable in all situations and should not be acted upon without specific legal advice based on particular situations.

© Pepper Hamilton LLP | Attorney Advertising

Written by:

Pepper Hamilton LLP
Contact
more
less

Pepper Hamilton LLP on:

Readers' Choice 2017
Reporters on Deadline

"My best business intelligence, in one easy email…"

Your first step to building a free, personalized, morning email brief covering pertinent authors and topics on JD Supra:
Sign up using*

Already signed up? Log in here

*By using the service, you signify your acceptance of JD Supra's Privacy Policy.
Custom Email Digest
Privacy Policy (Updated: October 8, 2015):
hide

JD Supra provides users with access to its legal industry publishing services (the "Service") through its website (the "Website") as well as through other sources. Our policies with regard to data collection and use of personal information of users of the Service, regardless of the manner in which users access the Service, and visitors to the Website are set forth in this statement ("Policy"). By using the Service, you signify your acceptance of this Policy.

Information Collection and Use by JD Supra

JD Supra collects users' names, companies, titles, e-mail address and industry. JD Supra also tracks the pages that users visit, logs IP addresses and aggregates non-personally identifiable user data and browser type. This data is gathered using cookies and other technologies.

The information and data collected is used to authenticate users and to send notifications relating to the Service, including email alerts to which users have subscribed; to manage the Service and Website, to improve the Service and to customize the user's experience. This information is also provided to the authors of the content to give them insight into their readership and help them to improve their content, so that it is most useful for our users.

JD Supra does not sell, rent or otherwise provide your details to third parties, other than to the authors of the content on JD Supra.

If you prefer not to enable cookies, you may change your browser settings to disable cookies; however, please note that rejecting cookies while visiting the Website may result in certain parts of the Website not operating correctly or as efficiently as if cookies were allowed.

Email Choice/Opt-out

Users who opt in to receive emails may choose to no longer receive e-mail updates and newsletters by selecting the "opt-out of future email" option in the email they receive from JD Supra or in their JD Supra account management screen.

Security

JD Supra takes reasonable precautions to insure that user information is kept private. We restrict access to user information to those individuals who reasonably need access to perform their job functions, such as our third party email service, customer service personnel and technical staff. However, please note that no method of transmitting or storing data is completely secure and we cannot guarantee the security of user information. Unauthorized entry or use, hardware or software failure, and other factors may compromise the security of user information at any time.

If you have reason to believe that your interaction with us is no longer secure, you must immediately notify us of the problem by contacting us at info@jdsupra.com. In the unlikely event that we believe that the security of your user information in our possession or control may have been compromised, we may seek to notify you of that development and, if so, will endeavor to do so as promptly as practicable under the circumstances.

Sharing and Disclosure of Information JD Supra Collects

Except as otherwise described in this privacy statement, JD Supra will not disclose personal information to any third party unless we believe that disclosure is necessary to: (1) comply with applicable laws; (2) respond to governmental inquiries or requests; (3) comply with valid legal process; (4) protect the rights, privacy, safety or property of JD Supra, users of the Service, Website visitors or the public; (5) permit us to pursue available remedies or limit the damages that we may sustain; and (6) enforce our Terms & Conditions of Use.

In the event there is a change in the corporate structure of JD Supra such as, but not limited to, merger, consolidation, sale, liquidation or transfer of substantial assets, JD Supra may, in its sole discretion, transfer, sell or assign information collected on and through the Service to one or more affiliated or unaffiliated third parties.

Links to Other Websites

This Website and the Service may contain links to other websites. The operator of such other websites may collect information about you, including through cookies or other technologies. If you are using the Service through the Website and link to another site, you will leave the Website and this Policy will not apply to your use of and activity on those other sites. We encourage you to read the legal notices posted on those sites, including their privacy policies. We shall have no responsibility or liability for your visitation to, and the data collection and use practices of, such other sites. This Policy applies solely to the information collected in connection with your use of this Website and does not apply to any practices conducted offline or in connection with any other websites.

Changes in Our Privacy Policy

We reserve the right to change this Policy at any time. Please refer to the date at the top of this page to determine when this Policy was last revised. Any changes to our privacy policy will become effective upon posting of the revised policy on the Website. By continuing to use the Service or Website following such changes, you will be deemed to have agreed to such changes. If you do not agree with the terms of this Policy, as it may be amended from time to time, in whole or part, please do not continue using the Service or the Website.

Contacting JD Supra

If you have any questions about this privacy statement, the practices of this site, your dealings with this Web site, or if you would like to change any of the information you have provided to us, please contact us at: info@jdsupra.com.

- hide
*With LinkedIn, you don't need to create a separate login to manage your free JD Supra account, and we can make suggestions based on your needs and interests. We will not post anything on LinkedIn in your name. Or, sign up using your email address.