USEPA recently released the long-awaited final version of its vapor intrusion risk assessment and mitigation guidance. Vapor intrusion is the intrusion of volatile chemicals into an overlying building from contaminated soil, soil gas and/or groundwater. Two separate guidance documents were released on June 11 to address chlorinated volatile organic compounds (VOCs) generally, and petroleum-related compounds (e.g. benzene, toluene, etc.). While emphasizing the importance of using multiple lines of evidence to assess vapor intrusion risks, the guidance documents rely extensively on the use of non-site-specific (generic), and conservative vapor intrusion screening levels (VISLs) calculated using a Vapor Intrusion Screening Level Calculator. The guidance barely mentions the Johnson-Ettinger vapor intrusion model, a powerful chemical transport model endorsed by USEPA for almost 20 years and widely used in many states (especially California) to develop site-specific estimates of vapor intrusion health risks. The guidance recommends the use of models primarily for assessing risks to future development, rather than existing buildings. The guidance places new emphasis on: 1) the need to use special risk assessment techniques to address carcinogenic chemicals that are considered to act via a mutagenic mode of action, and 2) addressing short-term or acute indoor air exposures caused by vapor intrusion. However, the guidance offers few details as to the methods that should be used to evaluate acute exposures. The guidance also clarifies that occupational exposure levels (e.g. PELs or TLVs) are not to be used for evaluating vapor intrusion health risks. At this point many states have already developed their own vapor intrusion risk assessment guidance so it will be interesting to see to what extent states adopt the new guidance. The two new guidance documents may be downloaded at the following link: http://www.epa.gov/oswer/vaporintrusion/guidance.html#PVIGuideFinal.
USEPA has released an updated version of the Regional Screening Levels (RSLs). The USEPA RSLs are the most widely used and cited health-risk based screening levels for chemicals in soil in the United States. They are also an important source of risk-based benchmarks for current or potential drinking water sources for which no drinking water standard (Maximum Contaminant Level or MCL) exists. To a lesser extent they are also sometimes used as a source of health-risk based chemical limits in ambient (outdoor) air and indoor air. Normally the RSLs are updated twice a year in May and November. However, in some instances USEPA will update the RSLs if important changes to the RSLs are required in the interim. This latest update was necessary because the soil ingestion pathway was omitted for 17 chemicals. It is important to always use the latest version of the RSLs when using the RSLs to perform a screening evaluation of health risks at contaminated sites. Note also that the California Department of Toxic Substances Control (DTSC) has recently adopted the RSLs as the preferred risk screening benchmark for soil instead of the California Human Health Screening Levels (CHHSLs), except in a few cases (e.g. lead). The corrected RSLs can be found at this link: http://www.epa.gov/region9/superfund/prg/
Please see our News page for additional risk assessment developments and tips.
Bisphenol A (BPA) was officially listed under Proposition 65 as a reproductive toxicant effective May 11, 2015. BPA was listed on the basis of female reproductive toxicity. BPA is used to manufacture numerous plastics, coatings and resins often used in consumer products. Coatings containing BPA have been used to coat food and beverage cans and line water pipes. When a chemical is listed under Prop 65 the manufacturer or distributor has one year to show compliance with Prop 65. For a reproductive toxicant such as BPA, compliance with Prop 65 entails either posting a warning sign or demonstrating through an exposure assessment (typically conducted by a toxicologist) that use of the product by the typical consumer will not exceed a “safe daily exposure level” (Maximum Allowable Dose Level [MADL]) established by the California Office of Environmental Health Hazard Assessment (OEHHA). In the case of BPA, OEHHA has not yet formally published an MADL, although an MADL of 290 µg/day has been proposed. However, now that BPA has been officially listed it is likely that the proposed MADL will be formally adopted soon..
It is especially important to carefully consider your analytical method reporting limits when investigating or remediating a Brownfield site (i.e., a contaminated site scheduled for redevelopment). Here’s why: Suppose your client (a developer) initially says they want to redevelop a contaminated site for commercial use (e.g. office buildings, a manufacturing facility or an industrial warehouse). Risk-based cleanup levels for commercial use are always higher (less stringent) than for residential use. You proceed with the investigation, selecting an analytical method that appropriately provides reporting limits just under the higher commercial use-based cleanup levels. However, after you collect and analyze your samples the developer changes their mind and now wants to develop the site for residential use. Unfortunately, the analytical method that previously provided reporting limits low enough to show compliance with the commercial use-based cleanup levels is not sensitive enough (reporting limits are not low enough) to show compliance with the lower residential-based cleanup levels. This means that even if a target analyte for the site shows as non-detect using the higher commercial use reporting limits it cannot be shown that it is safe for residential use and new samples will have to be collected and reanalyzed using a method that is more sensitive. Bottomline: if there is any possibility that the site in question may be redeveloped for residential use make sure your analytical method will provide reporting limits below residential use-cleanup levels. As an example, for volatile organic compounds (VOCs) in soil vapor, the standard EPA method 8260B may not be sensitive enough for some target analytes, and 8260B using Selected Ion Monitoring (SIM) mode for target analytes, or method TO-15 must be used instead.
USEPA has recently (June 2015) released an updated version of the human health ambient water quality criteria for surface waters. Required under Section 304(a) of the Clean Water Act, the criteria are typically applied to untreated, natural (ambient) surface waters such as lakes, rivers and streams. Ambient water quality criteria have been developed for both the protection of aquatic life and to protect human health based on potential drinking water and/or fish consumption. Although the criteria are USEPA recommendations, and do not constitute enforceable standards as issued, they may be adopted by the states as enforceable surface water quality standards. Unlike drinking water standards (Maximum Contaminant Levels) the ambient water quality criteria are developed without taking into consideration economic or technical feasibility issues. Updated human health criteria have been issued for 94 chemicals. Some important chemicals, including arsenic and hexavalent chromium, were not updated due to outstanding technical issues. The updated human health criteria reflect updated exposure parameters (e.g. drinking water consumption rate, fish consumption rate), updated toxicity criteria (i.e. the underlying toxicity data), and changes in USEPA risk assessment policy. Complete information regarding the updated criteria can be found at the following USEPA website: