Great white sharks can live into their 70s, more than three times longer than previously thought, US researchers have found.

Experts used radiocarbon dating technology to examine the backbones of four male and four female adult white sharks from the north-western Atlantic Ocean.

The largest male was found to be 73 years old and the largest female was 40, according to the report by scientists at Woods Hole Oceanographic Institution (WHOI) in Massachusetts, United States.

"Our results dramatically extend the maximum age and longevity of white sharks compared to earlier studies," said Li Ling Hamady, lead author of the study.

Previous research on growth bands in sharks' bones, which are similar to rings in trees that signify age and growth, presumed each band was equal to about a year.

By those measures, the oldest white sharks ever found were a 22-year-old from the south-western Pacific Ocean and a 23-year-old from the western Indian Ocean.

However, the latest study measured their ages by searching their bones for radiocarbon residue from nuclear tests carried out by nations including the US and Soviet Union during the 1950s and 1960s.

Bomb carbon from these tests, which were banned after 1963, got into the atmosphere and ocean.

Sea creatures incorporated the radiocarbon into their tissues, which helps to determine the ages of those that lived during the thermonuclear tests.

The bones studied came from sharks caught in the north-western Atlantic Ocean between 1967 to 2010.

Great white sharks are considered a vulnerable species worldwide, and researchers say knowing more about how fast they grow and how long they live can assist conservation efforts.