A chemical activity approach to exposure and risk assessment of chemicals

Abstract

To support the goals articulated in the vision for exposure and risk assessment in the twenty-first century, we highlight the application of a thermodynamic chemical activity approach for the exposure and risk assessment of chemicals in the environment. The present article describes the chemical activity approach, its strengths and limitations, and provides examples of how this concept may be applied to the management of single chemicals and chemical mixtures. The examples demonstrate that the chemical activity approach provides a useful framework for 1) compiling and evaluating exposure and toxicity information obtained from many different sources, 2) expressing the toxicity of single and multiple chemicals, 3) conducting hazard and risk assessments of single and multiple chemicals, 4) identifying environmental exposure pathways, and 5) reducing error and characterizing uncertainty in risk assessment. The article further illustrates that the chemical activity approach can support an adaptive management strategy for environmental stewardship of chemicals where "safe" chemical activities are established based on toxicological studies and presented as guidelines for environmental quality in various environmental media that can be monitored by passive sampling and other techniques. Environ Toxicol Chem 2018;37:1235-1251. © 2018 The Authors. Published by Wiley Periodicals, Inc. on behalf of SETAC.

Equilibrium sampling reveals increasing thermodynamic potential of polycyclic aromatic hydrocarbons during sewage sludge digestion

“…In addition, total concentrations are difficult to compare between similar matrices with very heterogeneous compositions (e.g., sludge or soil) and between different matrix types (e.g., air, water, soil, and human tissue). The freely dissolved concentration (C free ) and chemical activity (a) are thus more meaningful parameters for characterizing and quantifying exposure (Gobas et al, 2018). C free is proportional to chemical activity, which quantifies the energetic state of a HOC relative to its reference state (a = 1) and thus expresses its thermodynamic potential (Schwarzenbach et al, 2002).…”

Tunnel vision in current chemicals management cannot deal with the unknown risk of synthetic chemicals in aquatic systems

“…Many environments are primarily exposed to chemicals below the threshold level for compound-specific toxicity and on a global scale, baseline toxicity may determine the overall toxic effect exerted by mixtures of innumerable chemicals (Escher et al, 2002). Baseline toxicity is additive and directly related to chemical activity which is also additive (Gobas et al, 2018;Mackay et al, 2011) and relates chemical concentration to its maximum solubility in the environmental media. Chemical activity offers an additional concept to link exposure of complex mixtures to effects and is a proposed next-generation tool in monitoring that can be used to evaluate the total chemical burden of environmental matrices (Gobas et al, 2018).…”

“…Baseline toxicity is additive and directly related to chemical activity which is also additive (Gobas et al, 2018;Mackay et al, 2011) and relates chemical concentration to its maximum solubility in the environmental media. Chemical activity offers an additional concept to link exposure of complex mixtures to effects and is a proposed next-generation tool in monitoring that can be used to evaluate the total chemical burden of environmental matrices (Gobas et al, 2018).…”

Organic Contaminant Mixture Significantly Changes Microbenthic Community Structure and Increases the Expression of PAH Degradation Genes

“…Non-specific toxicity is induced by partitioning of contaminants to cell membranes, causing disturbance of the membrane. It is governed by the chemical's hydrophobicity, is additive and correlates to chemical activity (Mackay et al, 2011;Gobas et al, 2018). Chemical activity is a thermodynamic concept that relates the concentration (C; mol L −1 ) of chemical i to its maximum solubility (S; mol L −1 ) in the same environmental media (e.g., sediment porewater) (Schwarzenbach et al, 2002).…”