he current 50-μg/L maximum contaminant level (MCL) for arsenic in drinking water was first set by the US Public Health Service in 1942 and was adopted by the US Environmental Protection Agency (USEPA) in 1975.1 The standard was based primarily on toxic effects resulting from short-term or acute exposure to arsenic.2 Subsequent investigations have linked arsenic in drinking water with skin cance...

Nitrogenous disinfection by-products (N-DBPs) are far more cytotoxic and genotoxic than carbonaceous DBPs (Plewa & Wagner 2009). Among the N-DBPs, nitrosamines have been shown to be probable human carcinogens associated with 10–6 lifetime cancer risk at ng/L levels (USEPA 2002). An increasing number of water treatment plants (WTPs) in the United States have been using or considering chloraminat...

The US Army's need for a reliable and field-portable drinking water toxicity sensor was the catalyst for the development and evaluation of an electric cell-substrate impedance sensing (ECIS) device. Water testing technologies currently available to soldiers in the field are analyte-specific and have limited capabilities to detect broad-based water toxicity. The ECIS sensor described here uses r...

Discussions and applications of the policies and practices of the U.S. Environmental Protection Agency (USEPA) in ecological risk assessment will benefit from continued clarification of the concepts of assessment endpoints and of levels of biological organization. First, assessment endpoint entities and attributes can be defined at different levels of organization. Hence, an organism-level attr...

Toxicologically-based quantitative risk assessment is concerned with estimating human risks based upon experimental data linking an environmental agent to a known outcome (tumor incidence, acute toxicity, etc.). For dichotomous outcomes dose-response curves are modeled as complex functions of dose which often require specialized software to estimate. The SAS procedure NLMIXED readily allows for...

The primary objective of this paper is to describe the most common methods used to measure (i.e., sample and analyze) total suspended solids (TSS) and associated metals and phosphorus in urban runoff and to identify issues that may influence the accuracy of the results. This paper also discusses the availability of particle size distribution data from different developed and developing areas of...

The assessment and management of uncertain risks is an essential component of science, engineering, medicine, business, law and other modern disciplines. I. Good argues that risk science based on the evaluation of probabilistic events has been useful in saving and improving lives throughout history, “since the assessment of uncertainty incorporates the idea of learning from experience which mos...

The USEPA is revising the Total Coliform Rule (TCR) and is considering new possible distribution system requirements as part of these revisions. As part of this process, the USEPA is publishing a series of issue papers to present available information on topics relevant to possible TCR revisions. This paper was developed as part of that effort. The objectives of the issue papers are to review t...