Researching the risk posed by antifungal azoles to aquatic ecosystems
Azoles are widely used as agricultural fungicides or pharmaceuticals for the treatment of mycoses, parasitic infections and cancer in humans. Initially designed to inhibit CYP51 enzymes, responsible for the biosynthesis of ergosterol in fungi, they also disrupt a broad range of other cytochromes (the CYPs) involved in steroidogenesis, for example CYP19, and xenobiotic detoxification like CYP1A in mammals and fish. These antifungal agents therefore have the capacity to act as endocrine disruptors and to affect the survival, development, growth, reproduction and behaviour of non-target organisms. Although a few of these compounds are routinely investigated and detected, an accurate exposure assessment for evaluating the associated environmental risk of most azoles is still lacking. The EXPOZOL project sought to widen scientists’ understanding of the exposure of aquatic ecosystems to antifungal azoles, and their occurrence and biotransformation in aquatic organisms and associated effects, to improve environmental risk assessment. This research was undertaken with the support of the Marie Skłodowska-Curie programme.
Confirmation of the exposure of aquatic organisms to azoles
Investigators employed cutting-edge high-resolution mass spectrometry technology (Q-Exactive by Thermo Fisher) to perform retrospective screening of azoles in archived digital samples and investigate their biotransformation. “Such technology is increasingly used in the field of environmental chemistry to get a full picture of the chemical complexity of the contamination, by investigating both known and unknown contaminants, for example biotransformation products,” says research fellow Nicolas Creusot. Results indicated that antifungal azoles are widely distributed in terrestrial and aquatic ecosystems in accordance with their wide range of physico-chemical properties. “We showed that biota from different trophic levels are exposed to these chemicals,” explains Creusot. “One of the key points is EXPOZOL confirms that linking exposure and effects is very important for improving chemical risk assessment.” In fact, risk quotient calculations also revealed the threat associated with exposure to antifungal azoles, especially if some of the investigated rivers and streams are used for drinking water production. In addition, scientists confirmed through toxicokinetic and toxicodynamic experiments that aquatic organisms can accumulate and transform azoles, which may trigger adverse effects such as a reduction in growth – and even death.
Importance of further investigation
Beyond the specific case of antifungal azoles, investigations clearly demonstrated that the retrospective analysis of data acquired by high-resolution mass spectrometry can improve current knowledge of exposure and the related risks attached to chemicals of emerging concern and can be effectively employed for such purposes in future. “We are now able to increase our knowledge of the spatial and temporal dynamic of thousands of chemicals that were not initially investigated,” Creusot emphasises. EXPOZOL showed that aquatic ecosystems and humans (through drinking-water consumption) can be at risk from contamination by antifungal azoles. “This should act as a warning sign by providing proof that these chemicals should be studied more closely with regard to occurrence and effects, in order to limit their impact on aquatic ecosystems and beyond,” Creusot concludes.
Keywords
EXPOZOL, antifungal azoles, aquatic ecosystems, biotransformation, endocrine disruptors, high-resolution mass spectrometry
