San Francisco Bay Regional Water Quality Control Board, Environmental Screening Level Revisions and Updates

In the last year the San Francisco Bay Regional Water Quality Control Board (SFRWQCB) made some updates to the Environmental Screening Levels (ESLs).  According to the SFRWQCB website, they make these revisions periodically to reflect changes in toxicity values, changes in the understanding of the fate and transport of contaminants, and other developments in environmental risk assessment.  These updated ESLs are to be used as ways to quickly recognize and evaluate potential environmental impact for soil, vapor, groundwater and indoor air. They make major updates every few years and minor revisions when needed so be sure to check for the most current ESLs on their website or use this link http://www.waterboards.ca.gov/sanfranciscobay/water_issues/programs/esl.shtml. It is important to note that the updates and revisions are separate.

The last update for the all four elements in the ESLs was in December 2013.  The following will be a summary of these updates. First we will talk about the ESLs Workbook Updates.  The ESLs Workbook is an excel spreadsheet which includes four parts: Summary Tables, Interactive Tool, Calculations Tables, and Input Parameters Tables.  Below is a graphic of how it should be used.  While most of the screening levels remain the same the structure and layout of the Workbook has been altered.  They decided to make it easier to read and access things quickly so the workbook was reorganized and now only contains four groups of tables.  In addition to the layout edits they have also made some changes with the screening levels.  Previously, for all ESLs the ceiling value used nuisance/odor and gross contamination concerns as one screening level however now they have separated these into their own categories because they are two very different environmental concerns.  The ceiling value, defined by businessdictionary.com, is the maximum allowable human exposure limit for an airborne or gaseous substance which is not to be exceeded even momentarily.  Another workbook update to help convenience and usage is; trichloroethene (TCE) indoor air response action levels and trigger levels for soil gas and groundwater are now identified on ESL Table T2-1 when TCE is selected.  The last update to the workbook section was that screening levels for TPH Stoddard solvent have now been added.  Stoddard solvent or “White spirit” is usually just considered an irritant. It has a fairly low toxicity by inhalation of the vapor, dermal and oral routes, however, prolonged exposure can be very hazardous to one’s health.

esls-pic

Figure of the tiered process for selecting screening levels from http://www.waterboards.ca.gov/sanfranciscobay/water_issues/programs/
ESL/ESL%20Users%20Guide_22Feb16.pdf

Next we will take a look at the updates for groundwater ESLs.  First, a new category now called Tapwater ESLs was created for dermal contact under the health-risk-based groundwater direct exposure Drinking Water ESLs.  Similarly, there was previously no screening levels available for shallow groundwater under vapor intrusion, it was all greater than 10 feet bgs.  Now the new default is shallow groundwater, 10 feet bgs or less).  The soil screening levels for protection of groundwater were put in place to address potential leaching of chemicals into the surface soils and consequent migration to groundwater, for this reason, looking at the first 10 feet bgs is important.  The next update made was for surface water quality standards for bioaccumulation and consumption of aquatic organisms.   This previously had its own table but was not taken into account by the interactive tool.  They are now automatically assessed for the Ecological Aquatic Habitat ESL and listed as Seafood Ingestion screening levels.

There has also been some more general updates, they are as follows.  First, outdated methodology has led to the removal of the urban terrestrial habitat soil ESL.  Next, the subslab/ soil gas ESLs now incorporates subslab soil gas to indoor air attenuation factors for residential and commercial buildings.  In addition, for the input table, toxicity values and exposure factors have been updated.  Lastly, CAS numbers have been added to all tables.  According to Cas.com, a CAS Registry Number is a numeric identifier that can contain up to 10 digits, divided by hyphens into three parts.  These unique numbers are used to designate only one substance and is linked to information about the specific chemical.

There have also been updates to the User’s Guide but we will not address those here, we will however, list the major revisions.  In May 2016 there were three major revisions made to the ESL Workbook and Summary Tables.  These will all be copied directly form the website and can be found at http://www.waterboards.ca.gov/sanfranciscobay/water_issues/programs/ESL/
Status%20Sheet_5-23-2016.pdf
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The first was a “correction to the non-cancer hazard formula for the “any land use, construction worker soil exposure scenario” (Table S-1). Revision 2 corrected the ingestion and dermal formulas while Revision 3 is now correcting the inhalation formula. This current revision makes several of the noncarcinogenic metals (e.g., barium, beryllium, nickel, and vanadium) the risk driver for the Tier 1 soil ESLs, as was the case originally” (waterboards.ca.gov).  In this section they had previously revised the ESLs for skin contact but this new revision will help protect workers from inhaling dangerous chemicals. This will be important for your site if people will be coming into contact with the soil.

The second revision made was “The Final Soil Risk Based Screening Levels (Table S-1) for lead are based on the input of central tendency soil ingestion rates into blood lead models. In revision 2 both the “commercial/industrial” and “any land use, construction worker” soil exposure scenarios were changed based on a soil ingestion rate of 100 mg/day. However the “commercial/industrial” ingestion rate of 50 mg/day should not have been changed and therefore was changed back to its original value” (waterboards.ca.gov). This was basically just correcting a mistake they had made during the last revision.

The third and final revision was the “Adoption of the oral reference dose (RfD) toxicity value for vanadium given in the RSL user’s guide, which is based on taking the IRIS (integrated risk information system) RfD for vanadium pentoxide and factoring out the molecular weight of the oxide ion. This lowers the noncancer risk based ESLs for direct exposure to groundwater and soil” (waterboards.ca.gov).

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