Developing novel methods for fate assessments of chemicals of emerging concern: to be or not to be? That is the question

Chemicals are essential for our modern lives and many functions of our society. The production, use and trade of chemicals is growing in all regions of the world, and the global chemical production is expected to double by 2030. The problem is that we are missing information on most chemicals. One of the key factors for assessing environmental concern is whether the chemical is resists degradation and thus persist in the environment. Pollution from persistent chemicals is difficult to reverse, and if they are also toxic, it is only a matter of time before the concentration is high enough to cause harm. A tiered testing strategy, including different types of biodegradation tests, are used to determine how persistent a chemical is in the environment. These tests are known to give variable data, being time consuming, laborious, and not suited for high throughput screening of many chemicals. The principle behind all biodegradation test set-ups is to expose a natural microbial community to a chemical to see if they will break it down. Thus, understanding microbial community dynamics, in both the laboratory tests and the natural environment can help validate, improve and design new tests for accurately assessing persistence of chemicals. So far in the project, three different strategies are under development to improve the possibilities for assessing degradation versus persistence of chemicals: 1. A laboratory method for screening readily degradable chemicals in a format that enables high throughput screening. The principle of the method is to measure the growth of bacteria that consume the chemicals as nutrition measured with the use of flow cytometry. This method provides more insight into how the bacterial communities react with chemicals, i.e., if they inhibit growth of the bacteria. 2. Laboratory experiments to test the degradation of a type of chemical that is a by-product of amine-based carbon capture: nitramines. The experiments will also try to elucidate which factors promote the degradation of the nitramines, and which microorganisms may be involved. This work is a collaboration with the project Future Drinking Water Levels of Nitrosamines and Nitramines near a CO2 Capture Plant, FuNitr (NFR code 336357). 3. Update on the CLP regulation means that substances that are persistent need to be labelled accordingly, if they are also mobile or bioaccumulative. The new classifications are persistent, mobile or bioaccumulative and toxic (PMT or PBT) or very persistent and very mobile or bioaccumulative (vPvM or vPvB). To try to understand how many chemicals this concerns, a tool developed in a project for the Environmental Agency will be used and further developed. This tool is called PikMe is combining databases of information about chemicals with computer models to predict properties such as degradability for prioritization of chemical contaminants for environmental monitoring. This tool will be further developed by finding several parameters that can be used to predict either readily degradable or persistent chemicals based on both computer models and curated lists of classified chemicals. The information will be combined using a weight of evidence approach.

The main objective of the project is to improve the assessment of biodegradation and persistence of chemicals of emerging concern. This will be achieved by improving current standardized laboratory tests, or by developing new tests if required. The focus for improvement is on the microbial inoculum used in these tests. There is a need for a better understanding of microbial community dynamics during biodegradation testing in the laboratory and under different environmental scenarios. The microbial dynamics will be monitored in laboratory tests where different water samples, containing different microbial communities, will be conditioned to laboratory settings and exposed to various chemicals. Flowcytometry will be used for cell counts to monitor growth patterns of bacteria, supplemented with microscopic identification of bacterial predators such as protozoa. A set of reference chemicals spanning from readily biodegradable to inherent biodegradable and persistent will be used for benchmarking optimal conditions for the inoculum. Diversity and variability in microbial communities in the environment, mesocosms (Aquaponics) and laboratory experiments will be analysed using metabarcoding for assessing dynamics in community composition under the different treatments. Finally, the implication for persistence assessments and comparison to current practice for environmental risk assessment will be performed for a set of selected environmental pollutants.