Study: High levels of microplastics released by infant-feeding bottles

19 Oct 2020

Image: © Africa Studio/

Researchers from Trinity have found significant levels of microplastics in common infant-feeding bottles, especially in warmer liquids.

New research into the amount of microplastics released by infant-feeding bottles has shown higher levels are being released than previously thought.

In a study published to Nature Food, researchers from Trinity College Dublin (TCD) and AMBER, the Science Foundation Ireland research centre, looked at the potential release of microplastics from polypropylene infant-feeding bottles during formula preparation. They also estimated the exposure of 12-month-old infants to microplastics in 48 countries based on recent available data.

An immediate impact

The researchers followed international guidelines for infant formula preparation for 10 infant-feeding bottles that account for 68.8pc of the global infant-feeding bottle market. Their study showed that these common feeding bottles release up to 16m microplastics and trillions of smaller nanoplastics per litre.

When the bottles were sterilised and exposed to high-temperature water – up to 95 degrees Celsius – the number of microplastics increased significantly to 55m particles per litre. At 25 degrees Celsius (which is well under international guidelines for sterilisation or formula preparation) 600,000 microplastics per litre were generated.­­­

Analysis across the 48 countries showed that the average daily consumption level for infants is in excess of 1.5m microplastics. Oceania, North America and Europe have the highest levels of potential exposure, at 2.1m, 2.28m and 2.61m particles per day, respectively.

The researchers stressed that because the consequences of microplastics on human health – particularly infants – are still not known, more research is needed before a clear response can be formed.

“When we saw these results in the lab we recognised immediately the potential impact they might have,” said Prof John Boland of TCD and AMBER. “The last thing we want is to unduly alarm parents, particularly when we don’t have sufficient information on the potential consequences of microplastics on infant health.”

How to lower levels of microplastics

Despite this, the researchers devised and tested a series of recommendations for the preparation of baby formula that will help minimise the consumption of microplastics.

This includes advice such as preparing sterilised water by boiling it in a non-plastic kettle, such as a steel or glass container, and rinsing the cooled, sterilised bottle at least three times using this sterilised water at room temperature.

When preparing infant formula, the researchers recommend doing so in a non-plastic container using water at a temperature of at least 70 degrees Celsius (also prepared in a non-plastic container) and then allowing it to cool to room temperature before transferring to the feeding bottle.

Also, they advised against reheating formula in plastic containers, using microwave ovens, and vigorously shaking the bottle.

More research needed

Commenting on their findings, lead authors Dr Dunzhu Li and Dr Yunhong Shi said: “We have to accept that plastics are pervasive in modern life, and that they release micro and nanoplastics through everyday use.

“We don’t yet know the risks to human health of these tiny plastic particles, but we can develop behavioural and technological solutions and strategies to mitigate against their exposure.”

Dr Jing Jing Wang of AMBER’s microplastics group said this team will now investigate specific mechanisms of micro and nanoplastic release during food preparation in a host of different contexts.

“We want to develop appropriate technologies that will prevent plastics degrading and effective filtration technologies that will remove micro and nanoplastics from our environment for large scale water treatment and local distribution and use,” Wang said.

Colm Gorey was a senior journalist with Silicon Republic