Eighteen private well users in North Carolina were recruited to test the performance of under‐sink, activated carbon block water filters to remove per‐ and polyfluoroalkyl substances (PFAS). Monthly sampling was conducted for 8 months. Filters were certified for removal of perfluorooctanoic acid and perfluorooctanesulfonic acid under NSF International certification P473, but not for additional short‐chain perfluoroalkyl acids or perfluoroalkyl ether acids (PFEAs) evaluated in this study. Out of 47 targeted analytes, 17 PFAS were detected in filter influent samples (influent ∑PFAS 4.7–131 ng/L). Mixed‐effects Tobit regression models showed that the filters effectively removed 97%–99% of all influent PFAS, including short‐chain PFEAs, for the entire manufacturer‐recommended lifetime of the device. The prevalence of PFAS above the minimum reporting limits was reduced by 99.5%, and the prevalence of any PFAS above the method detection limits was reduced by 92%. The results provide increased confidence in NSF P473‐certified filters for the removal of PFAS from private well water.

Limited information is available regarding chemical water quality at the tap in Guatemala City, preventing individuals, water utilities, and public health authorities from making data-driven decisions related to water quality. To address this need, 113 participants among households served by a range of water providers across the Guatemala City metropolitan area were recruited as participatory scientists to collect first-draw and flushed tap water samples at their residence. Samples were transported to the U.S. and analyzed for 20 metals and 25 per- and polyfluoroalkyl substances (PFAS). At least one metal exceeded the Guatemalan Maximum Permissible Limit (MPL) for drinking water in 63% of households (n = 71). Arsenic and lead exceeded the MPL in 33.6% (n = 38) and 8.9% (n = 10) of samples, respectively. Arsenic was strongly associated with groundwater while lead occurrence was not associated with location, water source, or provider. One or more PFAS were detected in 19% of samples (n = 21, range 2.1–64.2 ppt). PFAS were significantly associated with the use of plastic water storage tanks but not with location, water source, or provider. Overall, the high prevalence of arsenic above the MPL in Guatemala City tap water represents a potential health risk that current water treatment processes are not optimized to remove. Furthermore, potential contaminants from premise plumbing and storage, including lead and PFAS, represent additional risks requiring further investigation and public engagement.

Thallium (Tl) can be released as a byproduct of smelting, mining, and other industries, causing human exposure. There are knowledge gaps on the toxicity of thallium compounds, so the National Toxicology Program is investigating the toxicity of thallium (I) sulfate in rodents. We developed and validated a method to quantitate Tl in rodent plasma and secondary matrices. Primary matrix standards and validation samples were digested with nitric acid and analyzed for Tl by inductively-coupled plasma – mass spectrometry (ICP-MS). Method performance was validated for linearity, accuracy, precision, and other criteria. Calibration was linear from 1.25 to 500 ng Tl/mL plasma; accuracy (RE) was −5.9 to 2.6% for all calibration standards. The lower limit of quantitation (LLOQ) was 1.25 ng Tl/mL plasma, and the limit of detection was 0.0370 ng Tl/mL plasma. Intra- and interday RE and precision (RSD) were −5.6 to −1.7% and ≤0.8% (intraday) and −4.8 to −1.3% and ≤4.3% (interday), respectively, at three sample concentration levels. Standards up to 10.0 x 10³ ng/mL could be analyzed by dilution with digested blank matrix, with −6.4% RE and 5.4% RSD. Method was also evaluated in post-natal day 4 (PND4) Hsd:Sprague Dawley SD (HSD) dam and pup plasma, gestation day 18 (GD 18) HSD rat fetal homogenate, HSD rat urine, female HSD rat brain homogenate, female B6C3F1 mouse plasma. Background Tl was detected in control fetal and brain homogenates and urine at < 30% of LLOQ response. Results demonstrate that the method is suitable for determination of Tl in rodent matrices for toxicology studies.

Drinking water contributes 1.2-61% of perfluoroalkyl and polyfluoroalkyl substances (PFAS) exposure, but little information is available on PFAS in private wells serving 17% of the U.S. population. Well users (n = 271) from four U.S. states collected tap water samples for analysis of 25 PFAS. Participants received results report comparing their water to PFAS health guidelines and recommending water filters when guidelines were exceeded. Follow-up surveys asked respondents what actions they took in response. To identify potential PFAS sources, we computed distances from households to PFAS sources recorded in EPA's PFAS Analytic Tools and other public databases and used spatial regression models to analyze relationships between these sources and water quality. PFAS were found in 15% of wells in the area with no known sources, some above a health guideline, and 53-88% of wells at sites with known sources. Total PFAS concentrations were significantly higher in wells closer to PFAS production facilities, Superfund sites, spill sites, and federal facilities. When recommended, 49% installed filters, while none did where water met the guidelines. Our study sheds insight into geographic variation in PFAS in private wells, the influence of potential PFAS sources on well water quality, and private well user decision-making in response to PFAS water quality information.

Human exposure to vanadium (V) is anticipated because it is a drinking water contaminant. Due to limited data on soluble V salts, the National Toxicology Program is investigating the toxicity in rodents following drinking water exposure. Measurement of internal V dose allows for interpretation of toxicology data. The objective of this study was to develop and validate an inductively coupled plasma-mass spectrometric method to quantitate total V in rat plasma. The method was linear (r ≥ 0.99) from 5.00 − 1,000 ng V/mL. Intra- and inter-day relative error (% RE) and relative standard deviation (% RSD) of spiked plasma samples were 8.5% to 15.6% RE and ≤ 1.8% RSD and 7.3% to 11.7% RE and ≤ 3.1% RSD, respectively. The limit of detection was 0.268 ng V/mL plasma and absolute percent recovery was 113%. Standards up to 7,500 ng V/mL plasma were diluted into the validated range (5.6% RE, 0.9% RSD). V in extracted plasma samples over 15 days at ambient and refrigerated conditions was from 97.7 to 126% of day 0. Determined plasma V concentrations after three freeze-thaw cycles and after frozen storage for up to 63 days ranged from 100 to 106% and 100 to 122% of day 0, respectively. The method was extended to rat urine (accuracy and precision −2.0 to 0.3% RE and <0.6% RSD, respectively for same linear range). These data demonstrate that the method is suitable to quantitate V in rat plasma and urine.