EPA Researchers Develop Tool That Predicts How Organic Chemicals Transform in Different Environments
Published October 18, 2021
Ever wonder how and why chemicals change in different environments? Scientists have also grappled with this question and over the past few decades have greatly improved their understanding of how chemicals change in natural systems. To better assess risk from chemical exposures, EPA scientists developed the Chemical Transformation Simulator (CTS), a web-based screening tool that predicts how organic chemicals will transform in environmental and biological systems.
Traditionally, exposure and risk assessments for human-made, organic chemicals have only focused on chemicals in their manufactured form. CTS is revolutionary because it focuses on how chemicals interact and transform in different natural environments. For example, most organic chemicals change when they react with water, heat, microbes, and other environmental conditions. Organic chemicals can also metabolize into new molecules when they are ingested by humans or other animals.
“CTS helps users predict how organic chemicals change under various scenarios. For example, a user may be interested in chemical transformations within anaerobic aquatic environments or due to human metabolism,” said EPA scientist Caroline Stevens, Ph.D., who co-led development of the tool with EPA scientist Eric Weber, Ph.D.
CTS organizes organic chemicals, or most substances that contain carbon-hydrogen bonds, into collections of transformation pathways. Transformation pathways occur when chemicals change in composition due to changes in environmental conditions, such as changes in light exposure or the introduction of new substances.
When using CTS, one can enter a chemical’s name or structure into one of the three workflows: chemical speciation, physicochemical properties, or transformation products. CTS then searches through reaction libraries for matches to specific structural fragments within the chemical of interest to identify potential transformation pathways. Reaction libraries are composed of generalized reaction schemes that are based on specific examples published in peer-reviewed literature.
While the tool can be operated by anyone, interpreting the results requires some knowledge of physicochemical properties and how organic chemicals transform in different environments. Various audiences can use the tool’s three different workflows for different needs. For instance, chemical exposure and risk assessors can use CTS to support alternative assessment activities for manufactured chemicals. Scientists can also use the tool to address data gaps associated with chemical registration and assessment and help interpret field and laboratory studies.
Additionally, CTS can be used as a tool for more complex exposure assessment models for environmental fate, transport, bioaccumulation, and dose estimation. EPA scientists are currently studying how CTS can help inform the analysis of emerging perfluoroalkyl and polyfluoroalkyl substances (PFAS) and their transformation products in environmental and biological samples. Researchers are creating reaction libraries that will predict if and how PFAS could transform in various environmental or biological systems and generate reaction products that are not present in the original chemical formulations.
Ultimately, predictions from CTS can be used in a variety of ways to provide a more holistic evaluation of how the manufacture and use of organic chemicals can impact humans and ecological systems.