Balloons released into the air are killing seabirds and sea turtles because they are clogging up their insides, a new study warned.
The must have party decorations are made from soft plastic which are easily swallowed by birds such as the majestic albatross.
But unlike hard plastics which pass more easily through the birds, soft plastics are “more likely to become compacted and cause fatal obstructions.”
Soft plastics account for just one in 20 cases where the seabirds have swallowed plastics – but they are to blame for killing two fifths.
The humble balloon and fragments when they burst have been identified as the number one risk of causing death from floating rubbish by University of Tasmania scientists.
They found a seabird ingesting a single piece of plastic had a 20 per cent chance of mortality, rising to 50 per cent for nine items and 100 per cent for 93 items.
PhD student Lauren Roman said the study found that although hard plastic accounts for the vast majority of debris ingested it is far less likely to kill than soft plastics such as balloons.
She explained: “Marine debris ingestion is now a globally recognised threat.
“However, the relationship between the amount or type of debris that a seabird ingests and mortality remains poorly understood.
“Among the birds we studied the leading cause of death was blockage of the gastrointestinal tract, followed by infections or other complications caused by gastrointestinal obstructions.
“Although soft plastics accounted for just five per cent of the items ingested they were responsible for more than 40 per cent of the mortalities.
“Balloons or balloon fragments were the marine debris most likely to cause mortality, and they killed almost one in five of the seabirds that ingested them.
“As similar research into plastic ingestion by sea turtles has found, it appears that while hard plastic fragments may pass quickly through the gut, soft plastics are more likely to become compacted and cause fatal obstructions.”
Co-author Senior Research Scientist Dr Chris Wilcox said the approach taken in the study was first developed for turtles before being applied to seabirds.
He added: “These two applications are the first time there has been a robust estimate of the impact of plastic ingestion on free living marine species.
“This is a critical step in triggering action to address plastic pollution.”
Ms Roman said that although the study showed that soft items like balloons are more dangerous, all plastics pose a mortal threat to seabirds.
She said: “If seabirds eat plastic their risk of mortality increases, and even a single piece can be fatal.
“While hard plastics are less likely to kill than soft plastics they were still responsible for more than half of the seabird deaths identified in our study.
“The evidence is clear that if we want to stop seabirds from dying from plastic ingestion we need to reduce or remove marine debris from their environment, particularly balloons.”
The study was published in the journal Scientific Reports.