At the heart of a significant scientific breakthrough is zinc, a metal essential in many bodily processes and crucial for both animals and humans. Researchers have raised alarms about the widespread use of zinc oxide in tiny, particle forms (known as nanoparticles) in various products. Concerns are growing about how these particles might affect the health of the environment. To explore this, scientists have developed an advanced model using zebrafish, a type of small fish often used in experiments, to detect how these particles cause stress at low doses.
Researchers led by Dr. Aya Takesono and Prof. Charles Tyler, and their team including Dr. Sylvia Dimitriadou, Dr. Sulayman Mourabit, Dr. Matthew Winter, Dr. Tetsuhiro Kudoh from University of Exeter in collaboration with Dr. Nathaniel Clark and Professor Richard Handy from University of Plymouth conducted a novel study to understand the effects of these tiny particles on aquatic life focused specifically on how they affect the zebrafish’s sense of smell.
Their research, featured in the journal Environment International, emphasizes how sensitive the smell-related nerve cells in zebrafish are to zinc oxide nanoparticles. Dr. Aya Takesono shares, “Through detailed live-imaging analysis, we discovered that the development of nerve cells in the brain responsible for smell are especially sensitive to exposure to these nanoparticles.” This groundbreaking method revealed that even low, non-lethal doses of these nanoparticles cause considerable inflammation, disturbing the brain functions related to smell and leading to changes in the zebrafish’s smell-driven behavior.
The researchers exposed zebrafish embryos to levels of nanoparticles that one might find in polluted waters. Dr. Takesono points out, “We detected stress responses in the smell nerve cells at exposure levels as low as 33 μg/L, and these responses increased with the increasing doses of zinc nanoparticles.” Remarkably, these responses were observed without any noticeable impact on the growth or physical development of the fish embryos, highlighting the hidden nature of this toxicity.
Further investigations showed that exposure to these nanoparticles caused inflammation around the smell-related tissues, changed the spontaneous activity of nerve cells in the brain regions associated with smell, and hindered the zebrafish’s ability to avoid certain smells. Dr. Takesono adds, “Our findings indicate that white blood cells locate and possibly contribute to the inflammation around the nerve cells responding to these nanoparticles in exposed animals.”
The broader implications of this study are significant. The range of nanoparticle concentrations used in the research is consistent with what is found in the environment, particularly near industrial and mining areas. Considering the crucial role of smell in various animal behaviors, such as finding food, recognizing kin, evading predators, and mating, the disruption of this sense could have substantial ecological impacts. This study suggests that the harmful effects of zinc oxide nanoparticles could pose a risk to animals and possibly humans, emphasizing the need for more research on the long-term consequences of these particles on the sense of smell.
In summary, this extensive study uncovers the unseen dangers of zinc oxide nanoparticles, particularly their ability to disrupt the sense of smell in aquatic life, even at low exposure levels. These findings highlight the necessity for increased attention to the potential risks posed by metal-based nanomaterials in our environment.
Takesono A, Dimitriadou S, Clark NJ, Handy RD, Mourabit S, Winter MJ, Kudoh T, Tyler CR. Zinc oxide nanoparticles disrupt development and function of the olfactory sensory system impairing olfaction-mediated behaviour in zebrafish. Environ Int. 2023 Oct;180:108227. DOI: https://doi.org/10.1016/j.envint.2023.108227.