The popular plastic toy may leave a much longer-lasting impression on Earth than in the memories of children around the world. According to new research, LEGOs have the potential to last in the ocean for more than a millennium.

It is estimated that around 440 billion LEGO parts and pieces have been manufactured since the Danish company started production in 1949. Nearly 30 years ago, a container carrying the small plastic pieces slipped into the sea, dumping millions of LEGO pieces that continue to wash up on the beaches of South West England.

To determine how long the toys might last in the marine environment, researchers from the University of Plymouth focused their analysis of 50 weathered LEGO pieces made from a common polymer known as acrylonitrile butadiene styrene (ABS). Each part was collected by local organizations along the beaches of South West England and identified using their “distinct studs and tubes and, in many cases, specific design numbers within the interior structure.”

Although plastic in the ocean is “persistent”, the authors write in the journal Environmental Pollution that it will still go through photo-oxidative degradation and physical stress when exposed to the elements, such as discoloring and a loss of mass. Each LEGO was washed, weighed, measured, and compared with similar blocks that had not been exposed to the elements. Researchers then used an X-ray fluorescence (XRF) spectrometer to confirm the age of each piece based on its chemical makeup.

Based on these measurements, the researchers deduce that an individual LEGO block may linger in the environment anywhere from 100 to 1,300 years. Older LEGOs had visible wear on them and exhibited lesser structural strength and weight as well as evidence of fracturing and a reduced average stud height.

"The pieces we tested had smoothed and discolored, with some of the structures having fractured and fragmented, suggesting that as well as pieces remaining intact, they might also break down into microplastics. It once again emphasizes the importance of people disposing of used items properly to ensure they do not pose potential problems for the environment,” said Dr Andrew Turner, associate professor (reader) in Environmental Sciences, in a statement.

A comparison with other LEGOs suggests that the average oceanic toy was around 40 years old. In theory, the blocks are denser than coastal seawater and should sink, but it appears that this plastic is beached under certain tidal and meteorological conditions like getting stuck in kelp or washed up after strong onshore winds and large swell. Because plastic is still so new to the world, the authors add that it is difficult to determine the long-term effects of plastic in the environment and how long it may last in the world’s oceans.

"LEGO is one of the most popular children's toys in history and part of its appeal has always been its durability. It is specifically designed to be played with and handled, so it may not be especially surprising that despite potentially being in the sea for decades it isn't significantly worn down. However, the full extent of its durability was even a surprise to us,” said Turner.