Baby Bottles Release Microplastics

Warm content increases levels of plastics in food two-fold



There is growing evidence to suggest that micro- and nano plastics are released into our food and water sources through the chemical and physical degradation of larger plastic items. Some studies have demonstrated the potential transfer of micro and nano plastics from oceans to humans via the food chain but little is known about the direct release of microplastics (MPs) from plastic products through everyday use.

Polypropylene (PP) is one of the most commonly produced plastics in the world for food preparation and storage. It is used to make everyday items, such as lunch boxes, kettles and infant-feeding bottles (IFBs). Despite its widespread use the capacity of PP to release microplastics was not acknowledged until now.

The research also indicates a strong relationship between heat and microplastic (MP) release; warmer liquids (formula or water used to sterilize bottles) result in far greater release, according to the findings in Nature Food and from investigators at from AMBER, the SFI Research Centre for Advanced Materials and Bioengineering Research, TrinityHaus and the Schools of Engineering and Chemistry at Trinity College Dublin.

Key findings:

Polypropylene infant-feeding bottles can release up to 16 million MPs and trillions of smaller nanoplastics per liter. Sterilization and exposure to high temperature water significantly increase release from 0.6 million to 55 million particles/l when temperature increases from 77 to 203° F.

Other polypropylene plastic-ware products (kettles, lunchboxes) release similar levels of MPs.

The team undertook a global survey and estimated the exposure of 12-month-old infants to microplastics in 48 regions. The team found that the overall average daily consumption of PP-MPs by infants per capita was 1,580,000 particles. Oceania, North America, and Europe have the highest levels of potential exposure, at 2,100,000, 2,280,000, and 2,610,000 particles/day, respectively.

What to Do

The level of MPs can be significantly reduced by following modified sterilization and formula preparation procedures

Sterilizing infant feeding bottles

Always allow to cool before filling

Prepare sterilized water by boiling in a non-plastic kettle/cooker (e.g. glass or stainless steel)

Rinse the sterilized bottle using room temperature water at least three times

Preparing infant formula

Prepare hot water using a non-plastic kettle/cooker

Prepare infant formula in a non-plastic container using at least 158° F water. Cool to room temperature and transfer prepared formula into a high quality plastic infant feeding bottle

Standard Precautions

Do not reheat prepared formula in plastic containers and avoid microwave ovens

Do not vigorously shake the formula in the bottle at any time

Do not use sonication to clean plastic infant feeding bottles

Global Issues

Given the global preference for PP-IBFs it is important to mitigate against unintended generation of micro and nanoplastics in infant formula. Based on their findings the team notes that, given the prevalence of plastic products in daily food storage and food preparation, and the fact that every PP product tested in the study (infant bottles, kettles, lunch boxes, and noodle cups), released similar levels of MPs, there is an urgent need for technological solutions.

As Professor John Boland, AMBER, CRANN, and Trinity’s School of Chemistry explains: “When we saw these results in the lab we recognised immediately the potential impact they might have. 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.

“We are calling on policy makers, however, to reassess the current guidelines for formula preparation when using plastic infant feeding bottles. Crucially, we have found that it is possible to mitigate the risk of ingesting microplastics by changing practices around sterilisation and formula preparation.”

Professor Liwen Xiao at TrinityHaus and Trinity's School of Engineering said: “Previous research has predominantly focused on human exposure to micro and nanoplastics via transfer from ocean and soils into the food chain driven by the degradation of plastics in the environment. 016-020-00171-y

“Our study indicates that daily use of plastic products is an important source of microplastic release, meaning that the routes of exposure are much closer to us than previously thought. We need to urgently assess the potential risks of microplastics to human health. Understanding their fate and transport through the body following ingestion is an important focus of future research. Determining the potential consequences of microplastics on our health is critical for the management of microplastic pollution.”

Lead authors, Dr Dunzhu Li and Dr Yunhong Shi, researchers at CRANN and Trinity’s School of Engineering, said: “We have to accept that plastics are pervasive in modern life, and that they release micro and nano plastics 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.”

Dunzhu Li, Yunhong Shi, Luming Yang, Liwen Xiao, Daniel K. Kehoe, Yurii K. Gun’ko, John J. Boland, Jing Jing Wang. Microplastic release from the degradation of polypropylene feeding bottles during infant formula preparation. Nature Food, 2020; DOI: 10.1038/s43
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