Aquatic exposures of chemical mixtures in urban environments: Approaches to impact assessment

Abstract

Urban regions of the world are expanding rapidly, placing additional stress on water resources. Urban water bodies serve many purposes, from washing and sources of drinking water to transport and conduits for storm drainage and effluent discharge. These water bodies receive chemical emissions arising from either single or multiple point sources, diffuse sources which can be continuous, intermittent, or seasonal. Thus, aquatic organisms in these water bodies are exposed to temporally and compositionally variable mixtures. We have delineated source-specific signatures of these mixtures for diffuse urban runoff and urban point source exposure scenarios to support risk assessment and management of these mixtures. The first step in a tiered approach to assessing chemical exposure has been developed based on the event mean concentration concept, with chemical concentrations in runoff defined by volumes of water leaving each surface and the chemical exposure mixture profiles for different urban scenarios. Although generalizations can be made about the chemical composition of urban sources and event mean exposure predictions for initial prioritization, such modeling needs to be complemented with biological monitoring data. It is highly unlikely that the current paradigm of routine regulatory chemical monitoring alone will provide a realistic appraisal of urban aquatic chemical mixture exposures. Future consideration is also needed of the role of nonchemical stressors in such highly modified urban water bodies. Environ Toxicol Chem 2018;37:703-714. C

Prospective mixture risk assessment and management prioritizations for river catchments with diverse land uses

“…Each scenario layout was modeled for 20 yr, with daily quantifications of PECs for the each of the studied chemicals. Details are in the Supplemental Data (section 1) and the scenario reviews (Holmes et al 2018; Diamond et al 2018; de Zwart et al 2018). …”

“…The aims of the present study were to combine the land‐use scenarios of the associated manuscripts of the Pellston workshop, references Holmes et al (2018), Diamond et al (2018), and de Zwart et al (2018), to investigate these questions for catchments with different combinations of land use.…”

“…Prospective, catchment‐scale prioritization of chemical mixture risks can assist decision‐making regarding risk‐mitigation strategies (Ginebreda et al 2013; Coppens et al 2015; Sobek et al 2016; Brack et al 2017). The present study expands on and integrates 3 detailed analyses of land use–related scenarios, investigating the specific chemical signatures of an agriculture scenario (emissions from agricultural land dictated by rainfall, soils, and PPP use [Holmes et al 2018]), a treated domestic wastewater scenario (daily use of household chemicals [Diamond et al 2018]), and an urban runoff scenario (rainfall‐mediated emissions from city surface areas [de Zwart et al 2018]).…”

Prospective aquatic risk assessment for chemical mixtures in agricultural landscapes

“…Examples of the single‐unit scenarios are feedlots, fields, pasture, aquaculture production areas, and potentially other inputs from nonagricultural point discharges (de Zwart et al 2018; Diamond et al 2018), as in case study 1.…”

“…The aims of the present study were to investigate these questions using standard agricultural aquatic exposure models and scenarios. Associated articles adopted the same working hypothesis to evaluate the risk of chemical mixtures from 2 other land‐use types (de Zwart et al 2018; Diamond et al 2018), whereas a combination of the 3 land‐use scenarios was generated to investigate these questions for catchments with different combinations of land use (Posthuma et al 2018). …”