If you’ve ever had the misfortune to step on a Lego, you know that plastic building blocks give you absolutely nothing. Now, scientists have discovered another unpleasant consequence of the indestructibility of toys: a single Lego could take hundreds of years to decompose in the ocean.
Earth’s oceans are full of plastic of all kinds, but estimating how long it takes for that trash to disintegrate into seawater is often challenging, because it’s hard to date pieces of debris of unknown origin; but it’s easy enough to identify a Lego piece by its distinctive shape, according to environmental scientists in England. Because the chemical additives used to make Legos have changed over time, the composition of each brick contains clues as to when it was made.
Researchers used an X-ray fluorescence spectrometer to measure the chemical compositions of washed-up Lego blocks, which had been collected by beach-cleaning volunteers in Cornwall, England, since 2010. Using the chemical fingerprints of the blocks, the team identified the manufactured bricks; Around the 1970s, a key chemical indicator was cadmium, used to make bright yellow and red pigments from the early 1970s until the early 1980s, when it was phased out due to its toxicity.
Researchers surmise that the stranded Legos were lost at sea at the time of their purchase; To measure the wear and tear of Legos stranded for 30 to 40 years at sea, due to factors such as abrasive sediments and exposure to sunlight, the researchers used their X-ray fluorescence measurements to compare the worn-out Legos with pristine versions. of the same bricks kept in collections since the 1970s.
Across 14 pairs of matching Legos, the weathered versions had between 3 and 40 percent less mass than their perfectly good counterparts — based on those measurements, it’s estimated that it will take anywhere from 100 to 1,300 years to fully decompose a single brick. of Lego, the researchers report.
Previous research has shown that plastic water bottles take decades to break down in the ocean, but since many plastic components used to make electronics and other consumer products are more like Lego bricks in thickness and strength than to water bottles, it is suspected that a time scale of several hundred years may be more representative of overall plastic degradation in seawater.