Methods used to derive water quality regulations for persistent, bioaccumulative, and toxic substances (PBTs) in the United States have evolved substantially over the past 50 yr, leveraging current understandings and assumptions about the nature and magnitude of partitioning and accumulation of substances in water, sediments, and organisms. In the United States and across the world, environmental regulations continue to evolve into more refined water quality criteria protective of aquatic life and human health. The present review provides historical context on the establishment of aquatic life and human health water quality criteria in the United States by compiling information from regulatory agencies and peer‐reviewed literature on methods used to characterize and quantify bioaccumulation of substances in aquatic organisms and humans. Primary data needs and assumptions for various methods, as well as their application in setting criteria by the US Environmental Protection Agency over the past half century, are highlighted. Our review offers an important retrospective on the data and methods used to derive water quality criteria for PBTs and provides commentary on the future of US criteria development. Environ Toxicol Chem 2021;40:2394–2405. © 2021 SETAC

Under the terms of the Clean Water Act, criteria for the protection of human health (Human Health Ambient Water Quality Criteria [HHWQC]) are traditionally derived using equations recommended by the US Environmental Protection Agency (USEPA) that include parameters for exposure assessment. To derive "adequately protective" HHWQC, USEPA proposes the use of default values for these parameters that are a combination of medians, means, and percentile estimates targeting the high end (90th percentile) of the general population. However, in practice, in nearly all cases, USEPA's recommended default assumptions represent upper percentiles. This article considers the adequacy of the exposure assessment component of USEPA-recommended equations to yield criteria that are consistent with corresponding health protection targets established in USEPA recommendations or state policies, and concludes that conservative selections for exposure parameters can result in criteria that are substantially more protective than the health protection goals for HHWQC recommended by USEPA, due in large part to the compounding effect that occurs when multiple conservative factors are combined. This situation may be mitigated by thoughtful selection of exposure parameter values when using a deterministic approach, or by using a probabilistic approach based on data distributions for many of these parameters.

Sustainability has become a key element of environmental management programs at most forest products companies. However, describing sustainability in terms of natural resource use and management can be challenging, owing to the evolution of practices deemed to be consistent with the concept. This paper provides quantitative and qualitative assessments and discussion of water resources as they relate to the activities of the forest products industry. Water resource use and management from the forest, through manufacturing, and on to potential effects of treated effluents on receiving waters is considered. Important findings from this work are that forests act to process precipitation into high-quality surface waters, and in North America, most surface waters are derived from forested areas. Forest management can affect water quality, but the use of forestry best management practices greatly minimizes harmful effects. Manufacturing of pulp and paper is water-use intensive relative to most other industries, although the amount of water consumed (i.e., evaporated or exported with product or residuals) represents a small fraction of the overall water used. The potential for treated effluent to affect receiving water systems has been widely investigated, and while effects are sometimes observed, aquatic community structures most commonly are not altered by well-treated mill effluents. Water profile results and water sustainability metrics are also briefly compared.

Development and maintenance of mill- and wastewater treatment system-specific programs aimed at optimizing use of supplemental nutrients for purposes of minimizing residual nutrients in treated effluents have evolved in recent years and are summarized. Suggestions for monitoring of nutrient forms in wastewaters prior to and during biological treatment are presented, as are approaches for determining supplemental nutrient requirements, monitoring biomass characteristics, and achieving minimum nitrogen and phosphorus residuals in treated final effluents while maintaining targeted levels of biological treatment. Aspects of nutrient management relevant to activated sludge (AS) and aerated stabilization basin (ASB) systems are presented, and ASB configurations operated in part to minimize nutrient levels in treated effluents are highlighted.

The connections between forest products operations and water resources in the United States is considered and, where possible, quantified. Manufacture of wood, pulp, and paper products and the influences of forest management and forest products manufacture on water quality are discussed. Most fresh water in the US originates in forested areas. Responsible harvesting strategies, best management practices, and forest re-growth combine to minimize or eliminate changes in water availability and degradation of water quality due to harvesting. Relative to alternative land uses and large-scale disturbance events, forested areas produce the highest quality of fresh water. Water inputs for the manufacture of forest products total about 5.8 billion m(3) per year, an amount equal about 0.4% of the surface and groundwater yield from timberland. Approximately 88% of water used in manufacturing is treated and returned directly to surface waters, about 11% is converted to water vapor and released during the manufacturing process, and 1% is imparted to products or solid residuals. Extensive study and continued monitoring of treated effluents suggest few or no concerns regarding the compatibility of current effluents with healthy aquatic systems.