EDCs contaminate our water supplies
The quality of drinking water is critical to public health, and Denmark prides itself on the purity of its water. However, recent studies show a worrying trend: more and more potentially hazardous compounds are being discovered in Danish freshwater sources [1].
This issue came to our attention during the recent Nordic Waste scandal in Denmark. A thunderstorm caused a landslide at the Nordic Waste facilities. This caused millions of tons of contaminated soil to slide towards the nearest river, presenting a massive threat to the near water supplies [2]. This story made us aware that water pollution is a real problem in Denmark. Some important statistics about the Danish groundwater are listed below:
50% of drinking water boreholes in Denmark contain pesticide residue or other pollutants.
10% of the boreholes exceed the acceptable limit values [3].
70% of our youngest groundwater reservoirs contain hazardous pollutants [4].
None of this affects the Danish consumer yet. This is due to the waterworks working tirelessly to ensure that our drinking water is clean. Currently, when drinking water contains contaminants, the water is either diluted with clean water or cleansed. But oftentimes it is expensive to cleanse, so they just close down the water wel [3].
However, as more water wells become polluted, we can’t keep diluting forever.
Among the most hazardous pollutants present in our waters are endocrine-disrupting compounds (EDCs). These pollutants can interfere with the hormonal systems in humans or wildlife, leading to serious health issues like fertility problems [5]. EDCs function by binding to endocrine receptors, disrupting processes controlled by nuclear hormone receptors (androgen, progesterone, thyroid, and retinoid) and non-nuclear receptors (dopamine, norepinephrine, and serotonin) [5].
Notable EDCs reported in drinking water, groundwater, and wastewater include bisphenol A (BPA), diethylstilbestrol, octylphenol, nonylphenol and exogenous hormones [6]. These pollutants often originate from cleaning agents, pesticides, and plasticizers like bisphenols and phthalates [2, 5].
“The contamination of Danish drinking water has reached a critical point. If we want clean drinking water for our children, something must be done now.”
Press release by Danish Regions [5]
While political and systematic solutions are very important, advancements in water treatment methods and detection technologies will be crucial to ensure clean drinking water in the future [3]. To pave the way for more sustainable solutions, the first step for bioremediation is detection.
Current testing procedures are problematic
Currently, when testing drinking water, ground water or wastewater, most compounds are measured individually At the same time, the laws defined by the EU mainly restrict individual compounds, which comes with various limitations.
Issues with current testing procedures for EDCs
Cocktail Effect
Current regulations fail to address the cocktail effect, which describes the cumulative effect of multiple pollutants. They may be more harmful than the individual compounds alone [7].
Unknown EDCs
Testing mainly focuses on compounds that are legally restricted, leaving many potentially hazardous and unregulated endocrine-disrupting compounds (EDCs) undetected [8].
High Costs
Testing for each compound is expensive, and the cost increases over time as more compounds are added to the list of regulated compounds every year [8].
Modifications
Companies can slightly modify restricted compounds to create new variants that bypass regulations. This allows the harmful compounds to stay in the environment.
Limited Discovery
By focusing only on single, already-known compounds, the current system limits the discovery of new hazardous compounds [8].
These limitations can be addressed by shifting regulations towards broader groups of compounds, rather than regulating each compound individually. To ensure relevance and applicability of our project, we have worked with stakeholders from various areas, which guided our work immensely as described on our Integrated Human Practice page.
We found it important to address these issues through our project. Specifically, our project will work on developing a method for detecting EDCs to overcome some of the listed limitations of the current testing methodologies.
Our proposed solution
Gene regulatory elements such as transcription factors as well as receptors have been evolved to have natural sensitivity to environmental changes, including high sensitivity to specific target molecules. So-called biosensors have been developed based on these regulatory elements because of its versatility and customizability as well as sensitivity.
As part of our solution, we propose a broad cell-free biosensor targeting many EDCs. This system could allow rapid screening of samples to identify groups of EDCs before deciding on more specific tests to apply. This will reduce both time and cost of the testing procedure, while accounting for the cocktail effect and enhance discovery of new pollutants. A cell-free system is required to use it on-site as it will not be a GMO-based system, and it allows for quicker testing [10].
For the design of EndoSense, we were inspired by the ROSALIND system [10, 11] which is a systematic approach to using allosteric transcription factors in biosensors. We adapted this general method by using nuclear human hormonal receptors instead of the basic allosteric transcription factors described by the authors [11]. These receptors bind directly to response elements (RE) on DNA after interacting with their corresponding hormone (or EDC). By using these hormonal receptors as the base of our biosensor, it is possible to sense all the EDCs that normally bind them [12].
We don’t search for specific compounds. We search for the biological effect!
For read-out, our system uses the Broccoli aptamer, previously described in iGEM [13], which functions as a reporter transcribed by the T7 RNA polymerase. The full system design is shown in the animation above.
This project will provide a new method to reduce time and cost of testing for EDCs. To ensure a structured workflow, we adhered to the engineering cycle as described on our Engineering page. In the first iteration, we aimed to demonstrate a preliminary proof of concept for the sensing-part of our system. Here, we drew inspiration from a protocol by Edwards, T. M. [12], which describes an in-cell system using the human estrogen receptor.
During the initial stages of designing our project, we encountered challenges linking EDCs to their respective receptors. This inspired us to develop SENTINEL, a database we built in order to identify and connect molecular targets with their respective and chemical, but also their methods of action.
Our vision is to use SENTINEL to automate the scientific literature mining using NLP-based techniques to gather the desired information of interaction between different molecules and their targets and their modes of action all in one database.The development of this tool is described on ourr Software page.