Most infant feeding bottles on the market across the world are either made of polypropylene or include polypropylene-based accessories. This is one of the most versatile types of plastic, due to its toughness, durability, and low cost. However, a new study found that the combination of hot water and mechanical shaking during the formula preparation process can cause the shedding of 1-16 million plastic microparticles per liter. It’s not clear at the moment if this is any cause of concern as the overall impact of microplastic ingestion on human health is unknown.

Microplastics and minihumans

Microplastics are any pieces of plastic smaller than 5 millimeters. Due to rampant plastic pollution, these tiny fragments are virtually everywhere. According to a 2019 study, every liter of ocean water contains 8,300 microplastics. And since plastic virtually last forever, microplastic accumulation will increase sharply with our consumption of plastic and plastic-wrapped goods.

From the water, the microplastic is ingested by creatures and travels higher up the food chain, eventually ending up in humans. Despite the ubuiquitos nature of these environmental contaminants, little is known about the effects of microplastics in human health.

What’s certain is that it’s everywhere, and microplastics exposure may start from the time we’re babies.

In a new study, researchers at Trinity College Dublin in Dublin, Ireland modeled the potential global exposure of infants to microplatics. The team led by Dunzhu Li mined data on the sales of plastic infant formula bottles, finding that polypropilene bottles account for 82.5% of the global bottle market.

The researchers then purchased ten types of plastic bottles that covered nearly 68% of the global online infant feeding bottle market across 48 countries. They then prepared formula in each bottle using guidelines from the World Health Organization (WHO), which recommends mixing the formula with hot water at a minimum of 70°C in order to reduce bacterial loads. Tests were also performed with fluid at 25°C and 95°C.

Using an optical microscope, the researchers counted the number of particles caught in a filter. This analysis showed that the overall average daily consumption of microplastics by infants per capita was 1,580,000 particles per liter of formula, most of which were smaller than 20 micrometers. This exposure increases proportionately with temperature and varied wildly among the bottles, up to 16.2 million particles per liter.

“We were surprised by the quantity, and the temperature dependant nature of the results. Based on research that has been done previously looking at the degradation of plastics in the environment we had a suspicion that the quantities would be substantial – but I don’t think anyone expected the very high levels that we found,” the authors of the new study told ZME Science in an email.

The researchers, however, stress that parents shouldn’t be alarmed. For now, these findings don’t mean anything from a health standpoint.

“Around the potential health implications – the simple answer is – we just don’t know. This is a new and rapidly evolving area of research and the data on the potential impact on human health is not well developed. The indications from natural habitats, and in particular oceanic environments of microplastic (MP) and the impact on the ecology and health of the species we share the planet with would suggest that we should take steps to remedy MP release. This is an area of research we’re actively pursuing,” researchers said.

“Several studies have indicated that high exposure of Poly Styrene MPs could have an adverse impact on mice’ health. However, there is no data available around the impact of Poly Propylene -MPs on human health. Looking at the fate and transport of microplastics through the body is our next step. We are going to collaborate with colleagues in the areas off immunology and biochemistry to try to figure out the exact consequences, if any, of micro, and also, and very importantly, nanoplastics on the body. “

These findings show that the number of microplastics that infants are exposed to has been greatly underestimated, which should inform manufacturers to improve their standards. Ultimately, this is yet another reason for the removal of microplastics from the environment.

“This study is another piece of the puzzle that illustrates that microplastics problem is likely much bigger than we think. This issue is something we need to start really getting to grips with sooner rather than later,” said Prof. Oliver Jones, Professor of Analytical Chemistry and Associate Dean of Biosciences and Food Technology, RMIT University In Melbourne Australia, who was not involved in the study.

The findings appeared in Nature Food. .