Vanadium is a naturally occurring metal that is present in all soils across Pennsylvania. Unfortunately, the Pennsylvania Department of Environmental Protection (PADEP) recently lowered Vanadium’s residential Statewide Health Standard (SHS) in soils to 15 mg/kg. This concentration is 2 to 6 times less than typical background concentrations in our area. This same standard also carries over to Pennsylvania’s Management of Fill Policy, resulting in virtually any soil being unusable as clean fill if it is analyzed for Vanadium. What does this mean for you?
Consider a school yard, or a park, or your own back yard. There is no known contamination. But if you analyze a sample of the soil for metals on the EPA’s Target Analyte List (TAL), you will almost assuredly find Vanadium at levels that exceed PADEP’s Residential SHS. What do you do? Cap the entire property with asphalt to prevent direct contact?
These questions have plagued landowners and environmental professionals when conducting due diligence, when using the Act 2 voluntary cleanup program, or when moving soil from one property to another in Pennsylvania. While PADEP is working towards an updated approach for evaluating Vanadium in the next year or two, what does this mean for sites seeking relief in the interim?
Risk Assessment – The Best Option
When it comes to residential property use in Pennsylvania (including school yards, parks, etc.), a Human Health Risk Assessment is the best method to address Vanadium in soils. While the PADEP’s SHS for Vanadium is based on conservative assumptions, a site-specific Risk Assessment provides an evaluation of actual risk factors, the realistic potential for human exposure to those risks, and the health effects of such an exposure. The use of actual site-specific data provides a realistic evaluation of acceptable health effects and can result in much higher allowable concentrations of Vanadium in soils.
Navigating A Tiered Approach
It should be noted that conducting a HHRA for Vanadium in Pennsylvania can be a bit tricky.
- In the absence of approved Vanadium oral toxicity values, the USEPA recommends an approach for evaluating Vanadium based on surrogate Vanadium Pentoxide values.
- However, the PADEP currently requires that a more stringent oral toxicity value be applied.
The result is that risk calculations can predict unacceptable noncancer health effects in the majority of PADEP assessments, even when site concentrations are within naturally occurring background levels.
Therefore, it is important to understand the deviation in approaches, as detailed below, in order to adequately evaluate Vanadium in a Risk Assessment that will result in an approved relief of liability for Act 2 Sites under the Site-Specific Standard (SSS).
For noncancer effects, oral toxicity values are expressed as reference doses (RfDs) for exposure through ingestion and dermal contact. The premise of noncancer toxicity values is that there is an exposure level below which adverse health effects are not expected to occur, even in sensitive populations. An RfD is inversely proportional to the toxic potency of a contaminant; the higher the RfD, the less toxic the contaminant.
The following summarizes the USEPA and PADEP-recommended tiered approach for selecting sources for toxicity values:
- Tier 1 – USEPA’s Integrated Risk Information System (IRIS)
- Tier 2 – USEPA’s Provisional Peer Review Toxicity Values (PPRTVs)
- Tier 3 – Other toxicity values including California EPA (CalEPA) values, Agency for Toxic Substances and Disease Registry (ATSDR) Minimal Risk Levels (MRLs), and toxicity values developed by various State agencies.
Vanadium may be present in a variety of oxidation states, which differ in their toxicities. As such, the USEPA-recommended RfD for Vanadium is derived from the only available Tier 1 oral RfD for Vanadium Pentoxide. The USEPA recommends factoring out the molecular weight of the oxide ion in order to develop a more conservative elemental Vanadium RfD. Note that this approach and revised RfD is used in developing the USEPA Residential Soil RSL for Vanadium, which is the PADEP-recommended source for screening contaminants as part of the HHRA Site Characterization. As this approach is not promulgated by PADEP and there is no Tier 1 value currently available for elemental Vanadium, a more stringent Tier 2 oral RfD is required to be used in Act 2 HHRAs.
Similar to the Tier 1 RfD, which is based on Vanadium Pentoxide, the Tier 2 RfD is based on sodium metavanadate, rather than elemental Vanadium. Although the oxidative states are the same for both of these compounds (+5), the uncertainty factor applied to the Tier 2 value is far greater than that applied to the Tier I value (3,000 vs. 100, respectively). As a result of the applied uncertainty factors and not intrinsic toxicity, the Tier 2 value is significantly more conservative and therefore results in significantly higher noncancer health estimates in HHRAs.
Removing the Burden on Clients
Sites seeking relief of liability for Vanadium through the Act 2 SSS should be aware that the PADEP promulgated Tier 2 RfD will likely result in unacceptable noncancer health effects in the majority of assessments, even when site concentrations are within naturally occurring background levels. The USEPA IRIS review of the oral assessment of Vanadium and compounds is anticipated to be through external peer review in the second quarter of 2022.
Until a more applicable toxicity value is approved for the evaluation of Vanadium in Pennsylvania, project teams should discuss seeking relief of liability for Vanadium with PADEP project officers and risk assessors in the planning phase of Act 2 Sites. As Brickhouse has discussed at length with PADEP, a weight of evidence approach can be used in HHRAs where noncancer health effects are evaluated with both the Tier 1 and Tier 2 toxicity values. The conservatism and uncertainty associated with the Tier 2 results can then be quantitatively discussed in the Uncertainty Analysis and Risk Summary for a more realistic understanding of the impacts to current and future human health receptors due to oral exposure to Vanadium.
In doing so, Brickhouse has removed the burden on clients to unnecessarily clean up naturally occurring background levels of Vanadium or leave Vanadium off their list of contaminants being sought for cleanup liability, saving them both time and money in the process.