Contaminants of Emerging Concern

Abstract

To paraphrase what the famous alchemist Paracelsus said about 500 years ago: all things are toxic; it is the dose that makes the poison. With the evolution of science over the past several hundred years, analytical chemists continue to detect more drinking water contaminants and at lower concentrations. As dose is a key element of risk, the question becomes, which contaminants can cause harm from drinking water exposure? This issue of Journal AWWA begins to answer this question by initiating a series of articles on contaminants of emerging concern (CECs). Trace contaminants often become causes célèbre when they are detected in drinking waters. The risk posed by CECs is complicated by the effect of media reports, and even some technical publications can contribute to misperceptions and confusion if they do not provide a complete picture of the science, toxicology, and technology associated with a particular chemical. In truth, while some chemicals are found at concerning levels, many others are measured at such low concentrations in drinking water that it is challenging to demonstrate any health effects. Because of this, it can be difficult for practitioners to develop a clear understanding of the key issues regarding the presence of drinking water contaminants. Our goal is to provide summaries of authoritative information produced and reviewed by experts in articles that provide a reasonable current perspective for readers, many of whom are not specific subject matter experts but whose work may be affected by CEC reports. This series of articles will address several of the most discussed chemicals, as well as some that are likely on the horizon for discussion, and identifies where more information must be developed before consensus can be reached. This series is by no means comprehensive, and readers are encouraged to recognize that issues with CECs will continue to evolve. The summary assessments to be published in this and subsequent issues of Journal AWWA cover a number of topics. In this month's issue, Katie Porter and Erin Mackey provide an overview of 1,2,3-trichloropropane and discuss treatment considerations (page 31). A discussion of modeled de facto reuse and CECs in source waters is presented by Thuy Nguyen et al. (page 26). Finally, Eaton et al. provide a review of an Unregulated Contaminant Monitoring Rule (UCMR) sampling frequency (page 13). In addition to these articles, others are being prepared for upcoming issues of Journal AWWA to discuss the latest information on hexavalent chromium toxicology, guidelines, and mode of action; 1,4-dioxane toxicology and mode of action; cyanotoxins; perfluorooctanoic acid, perfluorooctane sulfonic acid, and other per- and polyfluoroalkyl ether acids; and GenX. It is important to be able to distinguish hazardous chemicals from meaningful chemical risks. Almost any substance, including pure water, has a hazard profile, but risk is an indication of the probability that harm could occur under some condition of exposure. We hope that the articles published in Journal AWWA will help water professionals obtain useful information about those CECs that they frequently encounter, and that this information will help them stay up to date and conversant on CECs.