A study found that the lifespan of fish was apparently significantly reduced by pesticides.
Even low levels of common agricultural pesticides can hamper the long-term lifespan of fish, according to research by Jason Rohr, a biologist at the University of Notre Dame in Indiana.
Signs of aging accelerated when fish were exposed to chemicals, according to the study published in 2018 scienceswhich can have effects on 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. The researchers said that low doses of pesticides are widespread in the environment, so their effects should be studied and understood.
Researcher Cai Huang, who also worked on the study, combined field observations of more than 20,000 lake fish in China as levels of the common pesticide chlorpyrifos continue to decline.
The research found that fish from lakes affected by pesticides showed shortened telomeres, the caps at the end of chromosomes known as the biological clock of aging.
When they shorten, it is a sign of cell aging and a decreased ability of the body to regenerate.
The lake populations are composed of younger fish, suggesting that pesticides have contributed to shortened lifespans. Laboratory experiments confirmed the results and showed that chronic exposure to low doses reduces fish survival and leads to degradation of telomeres. These effects did not appear with acute exposure to high doses.
“Given the conserved mechanisms of telomere biology across vertebrates, chronic exposure to low doses of these chemicals may pose similar risks associated with aging in humans, which may contribute to age-related diseases,” the researchers wrote.
“When we examined telomere length and lipofuscin deposition in fish livers — well-established biological markers of aging — we found that fish of the same chronological age were aging faster in polluted lakes than in clean lakes,” Rohr said.
Chemical analysis showed that chlorpyrifos, which is banned in the UK and EU but used in the US and China, is the only compound found in fish tissue that is consistently linked to signs of aging. These included shortened telomeres and deposition of lipofuscin – an accumulation of insoluble proteins often described as cellular “junk”.
Rohr said the worrisome aging effects occurred at concentrations below current U.S. freshwater safety standards, suggesting that the effects of chemicals and pesticides could occur 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. Exposure to low levels can silently accumulate harm over time by accelerating biological aging, highlighting that chemical safety assessments must go beyond short-term toxicity tests to provide adequate protection for environmental and human health.”
While short-term exposure to high doses did not appear to cause these aging problems—although it did cause high toxicity and death in the fish—the researchers concluded that it was long-term exposure to low doses that led to these changes.
The scientists added that reduced lifespan is a particular problem because older fish often contribute disproportionately to reproduction, genetic diversity and population stability.