Trends in 1,4‐Dioxane Analyses: Implications for Identification and Characterization of Contaminated Groundwater Sites

Abstract

1,4‐Dioxane is a contaminant of emerging concern, and there is significant uncertainty about how its environmental occurrence in groundwater is being assessed given the various analytical methods available. This study compiled public sampling records from 2000 to 2019 that included >106,000 analyses of 1,4‐dioxane from 822 different U.S. sites. The 1,4‐dioxane detection frequency in the entire dataset (including all methods) was 45%, and the median detected concentration was 10 μg/L, highlighting the dilute nature of 1,4‐dioxane in environmental media and the importance of selecting methods with adequate sensitivity. The annual distribution of samples analyzed by each method type confirmed a shift towards methods designed for semi‐volatile compounds (Method 8270 and Method 8270 SIM) that exhibited consistently lower reporting limits (median reporting limit for each year typically ≤1 μg/L). In contrast, the method designed for volatile compounds (Method 8260) exhibited less sensitivity for 1,4‐dioxane (median reporting limit per year between 40 and 100 μg/L) and its use declined significantly over time with increasing use of the moderately sensitive Method 8260 SIM in later years. This shift contributed to an increase in the 1,4‐dioxane detection frequency over time, with a strong correlation between the annual detection frequency and the median reporting limit. Sites where 1,4‐dioxane was analyzed but not detected overwhelmingly used less‐sensitive methods that may not have been adequate for the expected concentration levels. Given the sub‐μg/L groundwater criteria issued for 1,4‐dioxane by some regulatory agencies, more sensitive and accurate methods will be increasingly needed to assess compliance.

The California GeoTracker Database: A Unique Public Resource for Understanding Contaminated Sites

“…In addition, 7 of the 14 studies published prior to 2020 (50%) have been cited in 10 or more subsequent publications (four of these have been cited more than 50 times) indicating that many of these studies are influential. As shown in Table 5, over the last 10 years, the GeoTracker dataset has been used as the primary data source to explore a wide set of research topics including overall progress in remediation of contaminated sites (McHugh et al 2014), contaminated site risk drivers (O'Reilly et al, 2021), drinking water system vulnerability (Best et al 2021), the vapor intrusion pathway (Kolhatkar et al 2019; Lahvis and Ettinger 2021), individual contaminants 1,4‐dioxane, ethanol, and hexavalent chromium (Adamson et al 2014, Adamson et al 2015, Adamson et al 2021; O'Rielly et al, 2016; Hausladen et al 2018), the effect of ambient temperature on source attenuation rates (Kulkarni et al 2017), and the impact of sample container contamination on analytical results (McHugh et al 2018). This diversity in topics highlights the utility of the GeoTracker database for supporting a wide range of research applications.…”

Application of Response Surface Method for Determination of Optimized Conditions for Quantification of 1,4-Dioxane in Model System of Polyethylene Glycol 200

“…For example, in Canada, it has been rejected for use in cosmetics, and, in Europe, it is a substance subjected to regulation [13]. The permitted concentrations in the U.S. are anticipated to vary from state to state, often at low parts-permillion to parts-per-billion levels [14]. In the U.S., the California DTSC (Department of Toxic Substances Control) has identified 1,4-dioxane as a chemical that merits additional study in order to remove it from consumer products due to the numerous issues associated with it in the environment [15].…”

Occurrence in France of 1,4-dioxane, an emerging pollutant of high concern in drinking water

“…Covering three years, the data set showed that 1,4-dioxane was present in 21% of the public water systems sampled (4,864 public water systems). Compared with other contaminants investigated in UCMR 3, the detection frequency of 1,4-dioxane was relatively high, resulting in 6.9% of observed concentrations exceeding the US EPA reference concentration of 0.35 µg/L (Adamson et al, 2017;Adamson et al, 2021). More recently, the systematic occurrence of 85 volatile compounds was investigated in aquifers feeding US public water supplies.…”

“…The analysis of 1,4-dioxane in water is challenging, leading to analytical methods with high quanti cation limits and low recovery rates (Hayes et al, 2022;USEPA, 2017). Thus, the US and German reference levels (0.35 and 0.1 µg/L) in drinking water cannot be easily achieved (Adamson et al, 2021).…”