The lifespan of fish appears to be drastically reduced by pesticides, a study has found.
Even low levels of common agricultural pesticides can stunt the long-term lifespan of fish, according to research led by Jason Rohr, a biologist at the University of Notre Dame in Indiana.
Signs of ageing accelerated when fish were exposed to the chemicals, according to the study, published in Science, which could have implications for other organisms.
Chemical safety regulations tend to focus on short-term exposure to high doses of pesticides and other chemicals, but the study focused on long-term exposure. Low doses of pesticides are widespread in the environment, so their effects should be studied and understood, the authors said.
Researcher Kai Huang, who also worked on the study, combined field observations of more than 20,000 lake skygazer fish from lakes in China with laboratory tests of persistent low levels of the common pesticide chlorpyrifos.
The research found that fish from pesticide-affected lakes showed shortened telomeres, the caps at the end of chromosomes that are known as the biological clock for ageing.
When they shorten, it is a sign of cellular ageing and a decline in the body’s regenerative capacity.
The lake populations consisted of younger fish, indicating that the pesticides contributed to shortened lives. Laboratory experiments confirmed the findings and showed chronic low-dose exposure reduced fish survival and degraded telomeres. These effects were not seen with acute high-dose exposure.
“Given the conserved mechanisms of telomere biology across vertebrates, chronic low-dose exposure to these chemicals may pose similar ageing-related risks in humans, potentially contributing to age-associated diseases,” the researchers write.
Rohr said: “When we examined telomere length and deposition of lipofuscin in the livers of the fish – well-established biological markers of ageing – we found that fish of the same chronological age were ageing faster in the contaminated than clean lakes.”
Chemical analysis showed chlorpyrifos, which is banned in the UK and the EU but used in the US and China, was the only compound found in the fish tissues that was consistently associated with signs of ageing. These included shortened telomeres and lipofuscin deposition – a buildup of insoluble proteins often described as cellular “junk”.
The worrying ageing effects occurred at concentrations below current US freshwater safety standards, Rohr said, suggesting the effects of chemicals and pesticides could be occurring at low levels over the long term.
He said: “Our results challenge the assumption that chemicals are safe if they do not cause immediate harm. Low-level exposures can silently accumulate damage over time by accelerating biological ageing, highlighting that chemical safety assessments must move beyond short-term toxicity tests to adequately protect environmental and human health.”
While short-term exposure to high doses did not appear to cause these ageing issues – though it did cause high toxicity and death in fish – the researchers concluded that it was long-term exposure to low doses that drove the changes.
The scientists added that reduced lifespan was particularly problematic because older fish often contribute disproportionately to reproduction, genetic diversity and population stability.
