Suspect Screening and Non-Targeted Analysis of Drinking Water Using Point-Of-Use Filters
Citation:
Newton, S., R. McMahen, J. Sobus, K. Mansouri, A. Williams, A. McEachran, AND M. Strynar. Suspect Screening and Non-Targeted Analysis of Drinking Water Using Point-Of-Use Filters. ENVIRONMENTAL POLLUTION. Elsevier Science Ltd, New York, NY, 234:297-306, (2018).
Impact/Purpose:
Safe drinking water supplies are critical for public health and it has been estimated by the World Health Organization (WHO) that a 10% reduction in worldwide disease could be achieved by improvements related to drinking water alone, including sanitation, hygiene, and water resource management (Prüss-Üstün et al. 2008). Furthermore, it is estimated that 70 – 90% of disease risks are due to difference in environments (Rappaport and Smith 2010), which includes direct exposures via consumption of drinking water. Chemicals that are present in water supplies can increase risk for disease and adverse health outcomes over long-term exposure periods (WHO 2013). It has been demonstrated for various chemical classes, including perfluorinated chemicals, that drinking water can be one of the most important pathways for human exposure (Egeghy and Lorber 2011; Lorber and Egeghy 2011). Even so, it has been estimated that only 40% of US consumers used any kind of water purification device in 2014 (Anumol et al. 2015). Certain chemicals are regulated under the Safe Drinking Water Act, but these chemicals constitute only a small fraction of the number of chemicals present in drinking water (US EPA 2016). New compounds can be added to this list if they are discovered and deemed to pose a threat to human health. These additions, however, require developing and validating “targeted” methods, which is a slow and expensive process. Furthermore, this process requires some a priori knowledge of the compounds for which methods should be developed. As of yet, there is no reliable mechanism to identify and prioritize novel compounds. There are needs, then, for: 1) a more complete picture of chemical exposures via drinking water consumption; 2) methods of rapidly identifying emerging chemicals that may be of importance to human health; and 3) means with which to properly assess exposure-disease relationships and risks to human health (Villanueva et al. 2014).
Description:
Monitored contaminants in drinking water represent a small portion of the total compounds present, many of which may be relevant to human health. To understand the totality of human exposure to compounds in drinking water, broader monitoring methods are imperative. In an effort to more fully characterize the drinking water exposome, point-of-use water filtration devices (Brita® filters) were employed to collect time-integrated drinking water samples in a pilot study of nine North Carolina homes. A suspect screening analysis was performed by matching high resolution mass spectra of unknown features to molecular formulas from EPA's DSSTox database. Candidate compounds with those formulas were retrieved from the EPA's CompTox Chemistry Dashboard, a recently developed data hub for approximately 720,000 compounds. To prioritize compounds into those most relevant for human health, toxicity data from the US federal collaborative Tox21 program and the EPA ToxCast program, as well as exposure estimates from EPA's ExpoCast program, were used in conjunction with sample detection frequency and abundance to calculate a “ToxPi” score for each candidate compound. From ∼15,000 molecular features in the raw data, 91 candidate compounds were ultimately grouped into the highest priority class for follow up study. Fifteen of these compounds were confirmed using analytical standards including the highest priority compound, 1,2-Benzisothiazolin-3-one, which appeared in 7 out of 9 samples. The majority of the other high priority compounds are not targets of routine monitoring, highlighting major gaps in our understanding of drinking water exposures. General product-use categories from EPA's CPCat database revealed that several of the high priority chemicals are used in industrial processes, indicating the drinking water in central North Carolina may be impacted by local industries.
