When the Old Way Isn’t the Best Way: Reimagining a New Approach to Environmental Risk Assessment
Scientific research is often about control – controlling as many variables as possible so that you can be confident that your data is accurate and reproducible. In other words, you want to be sure that your results weren’t an “accident.”
That axiom is being turned on its head by researchers in the Department of Integrative Biology – at least when it comes to measuring the impact of potential toxins on the environment.
Before any new chemical or compound can be marketed, it must undergo an environmental risk assessment that includes toxicological testing. For over half a century, these tests have been based on the response of a few representative species that are carefully exposed to different concentrations of the compound to gauge its level of toxicity. The results are then used to establish regulations and safety measures meant to protect non-target organisms from the compound, whether it be an agricultural pesticide, an industrial chemical, or any other potential environmental contaminant.
“Being able to reliably translate what happens in the lab to what happens at the population level in nature is essential for assessing environmental risk. But our current methods have serious flaws,” says Dr. Rene Shahmohamadloo, a postdoctoral fellow in the lab of Dr. John Fryxell.
Historically, toxicity tests have relied largely on readily available lab strains that lack genetic diversity – in fact, clones with zero genetic diversity are typically used. While this certainly provides greater experimental control, Shahmohamadloo says it doesn’t adequately reflect what would happen in nature, where is there much more genetic variation.
“Relying on a single strain of a species for these tests overlooks the inherent genetic diversity that can dictate a species’ true response to a hazardous substance.”
In a recent study published in Scientific Reports, Shahmohamadloo and colleagues measured just how much genetic variation can influence the response of Daphnia magna, a small aquatic crustacean, to a toxin. The researchers found that when genetically diverse Daphnia had the same toxic exposure, in this case to a naturally occurring bacterial toxin, their outcomes ranged from barely being impacted to extremely negative responses in terms of survival, growth, and reproduction. What’s more, this variability in response became even more pronounced at a higher level of toxin exposure.
“Our data confirm the importance of genetic variation, even within a population from a single locality, on predicting toxicological responses,” says Shahmohamadloo. “Toxicity tests form the cornerstone of environmental regulations. If these tests overlook this variation, they are mostly likely providing inaccurate insights and reducing the effectiveness of risk management strategies.”
The study provides the first concrete demonstration of how genetic variation can impact the “real world” accuracy of toxicity tests. The researchers hope it will serve as a widespread call to improve toxicity predictions by using genetically diverse samples in future testing protocols.
And, as an added bonus, it is typically much more cost-effective to simply collect samples from the wild rather than paying for genetically homogenous lab strains, creating a win-win scenario for everyone – including the environment.
Read the full study in the journal Scientific Reports.
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