Should I worry about microplastics in my infant feeding equipment?

Our tweet thread on microplastics was so popular that a few people requested it in blog format! So, here it is. Let’s answer the question using the power of science!

Should I worry about microplastics in my feeding equipment?

That is the question on many lips after a study looking into it was (badly) reported this week. We mean you Daily Mail. Read on for the key study findings and for info on washing, sterilising & using plastics for infant feeding.

First, it’s important if you’re bottle feeding your baby breastmilk or formula, or expressing, please ensure your gear is properly sterilised. If you’re worried about heat, you can cold water sterilise.

If you’re using infant formula, it’s also crucial that you prepare it in water of at least 70°C as recommended by the NHS. As you’ll see below, it’s temperatures above 70°C that are suggested to have the biggest impact on microplastic release.

The study causing concern looked at how feeding items release microplastics; wee bits of plastic <5mm in size that are released as the plastic in bottles, pump parts, tubes, cups & plates break down. 

Microplastics are released from water bottles, tea bags & many other plastic items we all use on a daily basis. The introduction to the study states that they focused on baby bottles due to high temperature exposure and the shaking that is common during formula prep. 

To simulate formula prep, the researchers soaked ten infant feeding products – 8 bottles and two accessories - in 95°C deionised water for 5 min, dried them, then added 70°C water and shook for 1 minute at 180 rpm. It’s not exactly how most of us would prepare a bottle of formula; if you shook every bottle that fast for a min you’d have the biceps of Michelle Obama!

After they shook the items way more vigorously than a polaroid picture (or indeed a normal bottle of formula), they filtered the water & counted the microplastics on a selected area of the filter. They didn’t count the microplastics on the whole filter, which the authors acknowledge in the supplementary material is a limitation of the study.

The researchers also did a test in which they added formula to the bottle, shook it, promptly poured it all out and added tap water, assuming the formula would remain on the bottle as a protective film. You can be the judge of how likely that would be.

In a surprise to nobody, there was no reduction in microplastics in bottles that had an Aptamil rinse versus water only bottles. So, sticking with water only analysis, the researchers found a lot of microplastics in water from items that had gone through the simulated formula preparation process.

The authors note the amount of microplastics in the samples were higher than amounts the WHO reported in drinking water, although they note that levels were similar in lunch boxes, noodle cups and kettles in their experiment.

It’s interesting that microplastics in the three bottles further tested increased at temperatures above 70°C, suggesting it was the hot sterilising process that caused more release compared to using 70°C water to prepare the formula. A way to overcome this ‘in real life’ would be to cold sterilise your feeding equipment. 

To estimate babies microplastic exposure, breastfeeding rates, formula intakes & the market share of each of the items tested was used to calculate daily microplastic exposure:

Daily MP exposure = (1 – BF rate) x market share of product x avg MP released from the product in that region x est. daily milk intake

Now, to me, this reads like the estimated daily microplastics exposure as an average for all babies across a region, which is a strange way to report the data to me. Surely either a baby will use that product or not? In that case would the daily microplastic exposure for a single baby not just be calculated by looking at the estimated milk volume intake x amount of microplastics found in fluid from the specific feeding item that baby uses? But honestly, I’m not sure!

We need a brain like Gideon Meyerowitz-Katz (aka @GIDMK) to explain this equation! For the UK, ’daily microplastic exposure’ from the feeding items tested ranged between 80,000 – 3 million per day. Reader, if you can shed some light on this equation please let me know! 

The lovely Gideon responded on twitter to point out that the best rule here is probably to apply the @BBCMoreOrLess question - is that a big number? He said

It seems to me that the crude number of particles is a terrible metric for microplastic exposure, because they vary in size. If a baby is exposed to 16,200,000 particles a day but they are all 0.00000000001mm in size, it might be less worrying than if they had 100,000 particles that were 0.001mm, for example. I think the question of whether that's a lot depends mostly on the total volume of microplastics.

The conclusions of the study were that there are high amounts of microplastics in baby bottles, increased by heat sterilising. It also pointed out that the cleaning, sterilising & reheating of breastmilk is likely to release microplastics into pumped milk too.

So, back to the question, should we be worried about this?

We’d conclude a cautious no.

WHO said last year that there is no evidence yet that microplastics are harmful to human health but it’s clearly something we should be looking into.

We know that improperly prepared formula carries contamination risk, albeit small. We can also assume that microplastics have been released from infant feeding equipment for as long as we’ve been using it with no detriment to health.

Together with the WHO statement we conclude ‘don’t panic’ and keep doing what you’re doing if it works for you. Keep making formula in hot water at 70°C – this is really important - and if you are concerned about microplastics, you can cold sterilise your formula/breast feeding/pumping equipment and/or switch to glass bottles!