Many ocean pollutants remain in the water for a long time. A new study suggests that exposure to some of them may be linked to faster aging in dolphins.
Small amounts of metals, such as zinc and copper, can enter the ocean from factories. The same is true of a large group of chemicals called PFAS. People often call them "forever chemicals" because they remain in the environment for a very long time.
Researchers studied common dolphins that had been exposed to these pollutants. Their paper appeared online in June, but it has not yet been reviewed by other scientists. According to the researchers, it is the first study to examine whether these pollutants are associated with faster aging in a marine mammal.
Age can be measured in two ways. One is chronological age, or the number of years an animal has lived. The other is biological age, which reflects changes in the condition of the animal's DNA over time. Stress and pollution may cause these changes to happen more quickly.
The team examined liver and kidney samples collected from 75 dolphins between 2000 and 2023. The researchers compared the levels of metals and PFAS in the samples with the difference between each dolphin's chronological and biological ages.
At first, the researchers expected the total amount of pollutants to be associated with faster aging. Instead, they found that only certain groups of metals and PFAS helped explain the difference between the dolphins' two ages.
PFAS includes thousands of chemicals. PFBA, a chemical associated with some nonstick products, showed the strongest link among the PFAS examined. Another chemical called PFNA was also associated with faster aging.
Among the metals, selenium showed the strongest link. Animals need a small amount of selenium, but too much can be harmful. Zinc, copper, aluminum, and manganese were also associated with faster aging.
Together, these metals and PFAS explained more than half of the variation in the gap between the dolphins' chronological and biological ages.
The findings suggest that the effects associated with these pollutants may extend beyond the organs where they collect. However, the study does not prove that the pollutants caused the dolphins to age faster. Dolphins are also rarely exposed to just one pollutant at a time.
The researchers say the next step is to understand how these substances may work together and whether they directly affect the aging process.