Nav: Home

Pesticides: Improved effect prediction of low toxicant concentrations

November 15, 2019

Toxic substances such as pesticides can cause effects on sensitive individuals in concentrations up to ten thousand times lower than previously assumed. This was shown by Researchers at the UFZ in their latest study published in Scientific Reports. For understanding these results, one must consider that the level of stress plays an important role. Most surprisingly: not only too much, but also too little stress can lead to a higher sensitivity to toxicants!

Whether a toxicant harms or kills an organism, and if so to which extent, depends on its concentration and the sensitivity of the individuals exposed: the dose makes the poison. "But that's not all," says UFZ ecotoxicologist Prof. Dr. Matthias Liess. „Also, the magnitude of environmental stress is very important to determine the effect of a toxicant." Toxicant concentration, individual sensitivity and environmental stress thus interact in a triad of effects. In their current study, the researchers have investigated the role of these individual components. They wanted to find out how sensitive individuals can be better protected by risk assessment. "Previous model calculations could not sufficiently predict the effects of low toxicant concentrations on sensitive individuals and species," explains Liess. "But this is very important in both human and ecotoxicological risk assessment". This is because sensitive persons - such as children, sick or elderly people - or more sensitive species of an ecosystem obviously suffer damage even at much lower concentrations than previously assumed.

Our extensive investigation was triggered by an observation: "At very low pesticide concentrations - far below concentrations that led to effects in previous studies - effects on sensitive organisms were observed," says the ecotoxicologist. These effects have hardly been observed since such low concentrations are very rarely tested. Previously, it was assumed that pollutants only elicit effects in high concentrations after a threshold value has been exceeded. However, at such extremely low concentrations this is obviously not the case. Liess said: "We observed these unexpected effects at very low concentrations in almost all existing studies in which effects of such concentrations of toxicants were investigated. Also, in their own investigations in which they exposed the crustacean Daphnia magna to very low concentrations of the pesticide esfenvalerate (is used as an insecticide with contact and feeding action in plant protection products in fruit, vegetable and arable farming and is approved in the EU). The question that arises is: which process can induce effects in these low concentration ranges? The hypothesis of the UFZ scientists is that toxicant stress meets internal stress. But what does that mean?

Under the influence of environmental stress - such as predation pressure, parasites and heat organisms become more sensitive to toxicants and therefore can be affected, or die at much lower toxicant concentrations than in the absence of environmental stress. "We were already able to quantify this relationship in earlier studies," says Liess. "Additionally, we are now able to show that individuals develop internal stress when they are exposed to too little stress from the environment. In fact, it seems like organisms are adapted to a certain degree of "external" stress. If it is missing, they develop "internal" stress. "And since external and internal stress add up, the sensitivity to toxicants increases drastically," explains Liess. The result: Sensitive individuals already react to extremely low concentrations of toxicants. These can be up to 10,000 times lower than the concentrations previously considered harmful so far. "Thus, too much - but also too little - stress increases sensitivity to pollutants," says the UFZ researcher. "Optimal with regard to resilience against toxicant exposure would therefore be some fluctuating environmental stress, which reduces internal stress.

In order to make effects visible at low concentrations, the scientists developed a model that enables a calculation of the internal stress and the resulting survival. Liess: "We hope that our study will contribute to a more realistic environmental and human risk assessment - especially for sensitive individuals".

The model of the UFZ researchers can be used in generally accessible and free software: http://www.systemecology.eu/indicate/
-end-


Helmholtz Centre for Environmental Research - UFZ

Related Stress Articles:

Red light for stress
Researchers from the Institute of Industrial Science at The University of Tokyo have created a biphasic luminescent material that changes color when exposed to mechanical stress.
How do our cells respond to stress?
Molecular biologists reverse-engineer a complex cellular structure that is associated with neurodegenerative diseases such as ALS
How stress remodels the brain
Stress restructures the brain by halting the production of crucial ion channel proteins, according to research in mice recently published in JNeurosci.
Why stress doesn't always cause depression
Rats susceptible to anhedonia, a core symptom of depression, possess more serotonin neurons after being exposed to chronic stress, but the effect can be reversed through amygdala activation, according to new research in JNeurosci.
How plants handle stress
Plants get stressed too. Drought or too much salt disrupt their physiology.
Stress in the powerhouse of the cell
University of Freiburg researchers discover a new principle -- how cells protect themselves from mitochondrial defects.
Measuring stress around cells
Tissues and organs in the human body are shaped through forces generated by cells, that push and pull, to ''sculpt'' biological structures.
Cellular stress at the movies
For the first time, biological imaging experts have used a custom fluorescence microscope and a novel antibody tagging tool to watch living cells undergoing stress.
Maternal stress at conception linked to children's stress response at age 11
A new study published in the Journal of Developmental Origins of Health and Disease finds that mothers' stress levels at the moment they conceive their children are linked to the way children respond to life challenges at age 11.
A new way to see stress -- using supercomputers
Supercomputer simulations show that at the atomic level, material stress doesn't behave symmetrically.
More Stress News and Stress Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Meditations on Loneliness
Original broadcast date: April 24, 2020. We're a social species now living in isolation. But loneliness was a problem well before this era of social distancing. This hour, TED speakers explore how we can live and make peace with loneliness. Guests on the show include author and illustrator Jonny Sun, psychologist Susan Pinker, architect Grace Kim, and writer Suleika Jaouad.
Now Playing: Science for the People

#565 The Great Wide Indoors
We're all spending a bit more time indoors this summer than we probably figured. But did you ever stop to think about why the places we live and work as designed the way they are? And how they could be designed better? We're talking with Emily Anthes about her new book "The Great Indoors: The Surprising Science of how Buildings Shape our Behavior, Health and Happiness".
Now Playing: Radiolab

The Third. A TED Talk.
Jad gives a TED talk about his life as a journalist and how Radiolab has evolved over the years. Here's how TED described it:How do you end a story? Host of Radiolab Jad Abumrad tells how his search for an answer led him home to the mountains of Tennessee, where he met an unexpected teacher: Dolly Parton.Jad Nicholas Abumrad is a Lebanese-American radio host, composer and producer. He is the founder of the syndicated public radio program Radiolab, which is broadcast on over 600 radio stations nationwide and is downloaded more than 120 million times a year as a podcast. He also created More Perfect, a podcast that tells the stories behind the Supreme Court's most famous decisions. And most recently, Dolly Parton's America, a nine-episode podcast exploring the life and times of the iconic country music star. Abumrad has received three Peabody Awards and was named a MacArthur Fellow in 2011.