Distribution of select per- and polyfluoroalkyl substances at a chemical manufacturing plant.

Per- and polyfluoroalkyl substances (PFAS) are used in various industrial products; however, they pose serious health risks. In this study, soil, soil gas, and groundwater samples were collected at a PFAS manufacturing facility in New Jersey, USA, to determine the presence and distribution of PFASs from the soil surface to groundwater and at various distances from the presumed source. Fluorotelomer alcohols (FTOHs) were detected in soil (< 0.26-36.15 ng/g) and soil gas (160-12,000 E µg/m3), while perfluorinated carboxylic acids (PFCAs) were found in soil (4.3-810 ng/g), soil gas (<0.10-180 µg/m3), and groundwater (37-49 µg/L). FTOH and PFCA concentrations decreased as the distance from the presumed source increased, suggesting that PFCAs are likely to migrate in groundwater, whereas FTOHs primarily move in the vapor phase. The presence of PFAS in the groundwater, soil, and soil gas samples indicate its potential for vapor intrusion; thus, some PFAS may contribute to indoor air inhalation exposure. To the best of our knowledge, this is the first report on the quantification of volatile PFAS in soil gas at a PFAS manufacturing facility.

An alternative generic groundwater-to-indoor air attenuation factor for application in commercial, industrial, and other nonresidential settings.

The default groundwater-to-indoor air attenuation factor (AF) of 10-3 (0.001) to assess the vapor intrusion (VI) pathway and generate VI screening levels for groundwater was developed by the United States Environmental Protection Agency (EPA) based on chlorinated volatile organic compound (VOC) indoor air and groundwater data collected in residential buildings and compiled in EPA's 2012 VI database. In their VI guidance published in 2015, EPA recognized that this default AF may be overly conservative for nonresidential buildings. In 2015, the Department of Defense (DoD) began developing a first-of-its-kind VI database to assess AFs at commercial and industrial buildings at DoD installations and support the development of alternative generic AF values. This database was expanded in 2019 to include 76 buildings at 22 DoD installations across the United States and is comparable in size to the EPA VI database. The DoD database includes chlorinated VOC data from groundwater and indoor air samples collected from multiple sampling zones within these buildings. Empirical groundwater-to-indoor air AFs were calculated using similar screening methods employed by EPA, including a source strength screen, to filter out potential background source contributions unrelated to VI. Analysis of indoor air-groundwater data pairs found that there is more attenuation occurring from groundwater to indoor air in DoD commercial and industrial buildings relative to residential buildings and that the DoD buildings' AFs are one to four orders of magnitude lower than EPA's residential-based default of 10-3. The results support the use of a generic groundwater AF of 10-4 (0.0001) to support VI assessment and develop groundwater screening levels specific to large commercial and industrial buildings as an alternative to the residential default AF.Implications: The use of groundwater-to-indoor air attenuation factors (AFs) is a key component of vapor intrusion (VI) pathway assessments and VI screening-level development for groundwater. Currently, the United States Environmental Protection Agency (EPA) and many state regulatory agencies use a default groundwater AF of 10-3 (0.001) based on chlorinated volatile organic compound (VOC) data collected in residential buildings. VI assessment data collected at Department of Defense (DoD) installations indicate that there is significantly more groundwater-to-indoor air attenuation occurring at DoD commercial and industrial buildings. For that reason, the default AF of 10-3 results in groundwater screening levels that are overestimating VI-related risks in these types of building. The DoD data support the use of a generic groundwater AF of 10-4 (0.0001) for conducting VI assessment and developing groundwater screening levels at large commercial and industrial buildings.

Neutral Per- and Polyfluoroalkyl Substances, Butyl Carbitol, and Organic Corrosion Inhibitors in Aqueous Film-Forming Foams: Implications for Vapor Intrusion and the Environment.

Per- and polyfluoroalkyl substances (PFAS), butyl carbitol, and corrosion inhibitors are components of aqueous film-forming foams (AFFFs). Volatile (neutral) fluorotelomerization (FT)- and electrochemical fluorination (ECF)-based PFAS, butyl carbitol, and organic corrosion inhibitors were quantified in 39 military specification (MilSpec), non-MilSpec, and alcohol resistant-AFFF concentrates (undiluted) from 1974 to 2010. Fluorotelomer alcohols were found only in FT-based AFFFs and N-methyl- and N-ethyl-perfluoroalkyl sulfonamides, and sulfonamido ethanols were found only in ECF-based AFFFs. Neutral PFAS and benzotriazole, 4-methylbenzotriazole, and 5-methybenzotriazole occurred at mg/L levels in the AFFFs, while butyl carbitol occurred at g/L levels. Neutral PFAS concentrations in indoor air due to vapor intrusion of a nearby undiluted AFFF release are estimated to be anywhere from 2 to >10 orders of magnitude higher than documented background indoor air concentrations. Estimated butyl carbitol and organic corrosion inhibitor concentrations were lower than and comparable to indoor concentrations recently measured, respectively. The wide range of neutral PFAS concentrations and Henry's law constants indicate that field, soil-gas measurements are needed to validate the estimations. Co-discharged butyl carbitol likely contributes to oxygen depletion in AFFF-impacted aquifers and may hinder the natural PFAS aerobic biotransformation. Organic corrosion inhibitors in AFFFs indicate that these are another source of corrosion inhibitors in the environment.

An alternative generic subslab soil gas-to-indoor air attenuation factor for application in commercial, industrial, and other nonresidential settings.

The default subslab soil gas (SSSG)-to-indoor air attenuation factor (AF) of 0.03 to assess the vapor intrusion (VI) pathway and generate VI screening levels for SSSG was developed by the United States Environmental Protection Agency (EPA) based on chlorinated volatile organic compound (VOC) indoor air and SSSG data collected in residential buildings and compiled in EPA's 2012 VI database. In their VI guidance published in 2015, EPA recognized that this default AF may be overly conservative for nonresidential buildings. In 2015, the Department of Defense (DoD) began developing a first-of-its-kind VI database to assess AFs at commercial and industrial buildings at DoD installations and support the development of alternative generic AF values. This database was expanded in 2019 to include 76 buildings at 22 DoD installations across the United States and is comparable in size to EPA's VI database. The DoD database includes chlorinated VOC data from SSSG and indoor air samples collected from multiple sampling zones within these buildings. Empirical SSSG-to-indoor air AFs were calculated using the same screening methods employed by EPA to filter out potential background source contributions unrelated to VI, including a source strength screen. Analysis of indoor air-SSSG data pairs found that there is substantially more attenuation occurring from SSSG to indoor air in DoD commercial and industrial buildings relative to residential buildings, and that the DoD buildings' AFs are one to three orders of magnitude lower than EPA's residential-based default of 0.03. The results support the use of a generic SSSG-to-indoor air AF of 10-3 (0.001) to support VI assessment and develop SSSG screening levels at large commercial and industrial buildings as an alternative to the residential default AF.Implications: The use of subslab soil gas (SSSG)-to-indoor air attenuation factors (AFs) is a key component of vapor intrusion (VI) pathway assessments and VI screening level development for SSSG. Currently, the United States Environmental Protection Agency (EPA) and many state regulatory agencies use a default AF of 0.03 based on chlorinated volatile organic compound (VOC) data collected in residential buildings. VI assessment data collected at Department of Defense (DoD) installations indicate that there is significantly more SSSG-to-indoor air attenuation occurring at DoD commercial and industrial buildings. For that reason, the default AF of 0.03 results in SSSG screening levels that are overestimating VI-related risks in these types of building. The DoD data support the use of a generic SSSG-to-indoor air AF of 10-3 (0.001) for conducting VI assessment and developing SSSG screening levels at large commercial and industrial buildings as an alternative to the residential default AF.

Key Design Elements of Building Pressure Cycling for Evaluating Vapor Intrusion-A Literature Review.

Building pressure cycling (BPC) is becoming an increasingly important tool for studying vapor intrusion. BPC has been used to distinguish subslab and indoor sources of vapor intrusion as well as to define reasonable worst case volatile organic compound mass discharge into a structure. Analyses have been performed both semi-quantitatively with concentration trends and quantitatively with more rigorous flux calculation and source attribution methods. This paper reviews and compares the protocols and outcomes from multiple published applications of this technology to define the key variables that control performance. Common lessons learned are identified, including those that help define the range of building size and type to which BPC is applicable. Differences in test protocols are discussed, recognizing that the complexity of the test protocol required depends on the particular objectives of each project. Research gaps are identified and tabulated for future validation studies and applications.

Variables affecting emissions of PCDD/Fs from uncontrolled combustion of household waste in barrels.

The uncontrolled burning of household waste in barrels has recently been implicated as a major source of airborne emissions of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). A detailed, systematic study to understand the variables affecting emissions of PCDD/Fs from burn barrels was performed. The waste composition, fullness of the barrel, and the combustion conditions within the barrel all contribute significantly to determining the emissions of PCDD/Fs from burn barrels. The study found no statistically significant effect on emissions from the Cl content of waste except at high levels, which are not representative of typical household waste. At these elevated Cl concentrations, the impact of Cl on PCDD/F emissions was found to be independent of the form of the Cl (inorganic or organic). For typical burn conditions, most of the PCDD/F emissions appear to be associated with the later stages of the burn when the waste is smoldering. Polychlorinated biphenyls (PCBs) were also measured for a subset of the tests. For the nominal waste composition, the average emissions were 76.8 ng toxic equivalency units (TEQ)WHO98/kg of waste combusted, which suggests that uncontrolled burning of household waste could be a major source of airborne PCDD/Fs in the United States.

Aquatic ecological risks due to cyanide releases from biomass burning.

Aquatic toxicity due to the creation and mobilization of chemical constituents by fire has been little studied, despite reports of post-fire fish kills attributed to unspecified pyrogenic toxicants. We examined releases of cyanides from biomass burning and their effect on surface runoff water. In laboratory test burns, available cyanide concentrations in leachate from residual ash were much higher than in leachate from partially burned and unburned fuel and were similar to or higher than the 96-h median lethal concentration (LC50) for rainbow trout (45 microg/l). Free cyanide concentrations in stormwater runoff collected after a wildfire in North Carolina averaged 49 microg/l, again similar to the rainbow trout LC50 and an order of magnitude higher than in samples from an adjacent unburned area. Pyrogenic cyanide inputs, together with other fire-related stressors, may contribute to post-fire fish mortalities, particularly those affecting salmonids.