New approaches to identifying substitutes for hazardous chemicals
When the use of a hazardous chemical is restricted by regulations, it is critical to avoid replacing it with another problematic chemical. However, a proper assessment of the environmental and human health hazards of novel alternative chemicals is usually hampered by the lack of data. Ziye Zheng presents in his thesis novel approaches for identifying less hazardous chemical alternatives in an efficient way with computational methods.
Text: Ingrid Söderbergh
Ziye Zheng, PhD student at the Department of Chemsitry.
With the rising concern on chemical safety in the past decades, an increasing number of hazardous chemicals are restricted or banned. Industry replaces those with chemicals of similar functions, while in many cases the hazards of novel alternatives are not understood due to lack of experimental data. As a result, many alternative chemicals have later been identified as “regrettable substitutes”, as they are equally or even more hazardous compared to the original ones. To minimize the risk of regrettable substitution, Ziye Zheng has combined chemical alternatives assessment with computational methods that provide data for novel chemicals with limit experimental data.
"We are interested in the general hazard level of each chemical alternative, both the potential effects to human health and the hazard impacts to the environment, so experimental data can hardly cover all desired aspects even for chemicals on market, let alone the novel alternatives. As a result, we decided to work with quantitative structure-activity relationship (QSAR) models, as they can be developed to predict hazard properties for unknown chemicals from known chemicals. In our study, we took a set of flame retardants as our case chemicals to study how QSAR models can be used to develop a hazard ranking tool for chemical alternatives assessment", says Ziye Zheng.
During his doctoral studies, Ziye has developed QSAR models to study how to use these models properly, and then he combined these with open source QSAR models to provide data covering various hazard properties.
“Considering that the modeling data generally have a higher uncertainty compared to experimental data, we compared three different multicriteria decision analysis (MCDA) methods trying to take the model uncertainties into consideration. With the combination of QSAR models and MCDA methods, we were able to develop an efficient and transparent hazard ranking tool for chemical alternatives, and successfully identified the less hazardous alternatives for the case of flame retardants. We also further developed the tool to take chemical transformation into consideration”.
Besides general hazards of chemical alternatives, Ziye also studied how the chemical alternatives differ in their emission properties from products, and how the emission process is related to their chemical properties.
“I developed with my colleagues in our research group a novel measurement method for the emission processes using a Quartz Crystal Microbalance and we were able to record the emission of various flame retardants from different polymer films. We were also able to develop mathematical models to describe the emission processes, and these models helped us to identify critical chemical properties that control the emission process”, says Ziye.
"While there are remaining challenges, we are now able to reduce the risk of regrettable substitution having a better understanding on how to identify less hazardous chemicals with the help of computational methods. We hope this study provides useful tools and a basis for future development of chemical alternatives assessment frameworks".
Ziye Zheng comes from China. He holds a Master's degree in Environmental Chemistry from Stockholm University and a Bachelor’s degree in Environmental Engineering from Tongji University, China.
On Thursday 6 of May Ziye Zheng, Department of Chemistry, Umeå University, defends his thesis entitled: Improving alternatives assessment of plastic additives: exploring in silico tools to identify less hazardous flame retardants.
The defense will take place at 09:00 am in Glasburen in the KBC building, Umeå University and online via Zoom.
The faculty opponent is Professor Gerrit Schüürmann, Department of Ecological Chemistry, UFZ Helmholtz Centre for Environmental Research, Leipzig, Germany.