A pesticide commonly used in agriculture may be shortening the lives of fish by speeding up the aging process, according to a new international study.
The research, led by University of Notre Dame biologist Jason Rohr, found that fish exposed for long periods to low concentrations of the insecticide chlorpyrifos showed signs of accelerated cellular aging, even though the exposure levels were below those known to cause immediate harm.
The study emerged from long-term fieldwork in China, where researchers analysed fish populations from lakes with varying degrees of pesticide contamination. In lakes with higher contamination, older fish were notably scarce, whereas fish in cleaner lakes were found to span a broader age range.
The absence of older fish initially raised questions about reproduction, but evidence pointed instead to shortened lifespans.
Rohr, Chair of Notre Dame’s Department of Biology, said: ‘When we examined telomere length and deposition of lipofuscin in the livers of the fish, well-established biological markers of aging, we found that fish of the same chronological age were aging faster in the contaminated than clean lakes.’
Telomeres protect chromosomes from damage, while lipofuscin accumulates as cells age and lose the ability to clear waste.
When researchers analysed fish tissues, chlorpyrifos stood out as the only chemical consistently associated with these aging indicators.
To test whether the pesticide itself was responsible, the team designed laboratory experiments that replicated the low concentrations detected in the lakes.
Fish exposed to these doses experienced telomere shortening, increased cellular deterioration and lower survival rates – effects that were strongest among fish already showing physiological signs of aging.
The researchers considered whether unobserved high-dose exposure events in the wild could explain the findings, as Rohr explained: ‘Although the laboratory results closely matched the field observations, it was possible that a missed high-dose [chlorpyrifos] exposure event in the field, rather than chronic low-dose exposures, caused the reduced lifespan’.
A follow-up experiment helped resolve the question. Fish subjected to short-term, high-dose chlorpyrifos exposure died quickly from toxicity but did not exhibit accelerated aging.
Rohr is satisfied that this showed ‘long-term accumulation of exposure to extremely common low concentrations – not brief high-dose spikes – was responsible for the observed aging.’
Although chlorpyrifos has been largely banned in the EU, it remains widely used elsewhere. Notably, the aging effects observed occurred at concentrations below current US freshwater safety limits.
Rohr concluded: ‘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 aging, highlighting that chemical safety assessments must move beyond short-term toxicity tests to adequately protect environmental and human health.’
The full research can be accessed here.
Photo: Sara Kurfeß / Unsplash
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