Babies may be exposed to millions of microplastic particles which are released from polypropylene feeding bottles during standard formula preparation, an Irish study suggests.

Researchers from Trinity College Dublin found plastic bottles release up to 16.2 million particles per litre of formula when they tested 10 common infant feeding bottles.

High heats used in sterilising significantly increased the microplastic release, and the effects last at least three weeks after first use, the study in Nature Food showed.

In addition, the researchers calculated that Australian babies could be exposed to an estimated 2-3 million microplastic particles a day, using a mathematic model that estimated exposure in different geographical regions.