Near the start of his third year of graduate school, Kazi Albab Hussain became a father.
A PhD student studying environmental engineering at the University of Nebraska-Lincoln, Hussain鈥檚 time was soon consumed between his research into plastic contamination and raising his son. 鈥淎t the time, we were using lots of baby products (containing) lots of plastic and we would even sometimes put it in the microwave,鈥 he told the Star.
Inspired by his new life development, and building on previous research that found from their plastic feeding bottles, Hussain decided to investigate whether his baby鈥檚 food packaging could be similarly harmful. The results, he said, were 鈥渟hocking.鈥
Hussain and his team鈥檚 study, recently , found 鈥渕icrowave-safe鈥 baby food containers made of polypropylene (a common type of plastic) can inject millions of microplastics and billions of tinier nanoplastics into their food contents after just three minutes in the microwave.
While the exact health impacts are unknown, Hussain asserts the plastic shards show signs of toxicity; direct exposure to high concentrations of the particles killed 75 per cent of cultured human cells over two days, according to his paper.
Microwaving plastic baby food containers releases billions of toxic fragments
For the experiment, Hussain鈥檚 team purchased two common brands of baby food containers made of polypropylene (both labelled 鈥渕icrowave-safe鈥 by the U.S. Food and Drug Administration) and one flexible pouch of polyethylene 鈥 two of the most common plastics used in food containers today, outside experts said.
Both are approved for use in food packaging , and other regulators around the globe.
The containers were filled with either purified water or mild acetic acid, to simulate watery or acidic food contents. They were then subjected to FDA-approved conditions to simulate microwaving and storage at room temperature or in the fridge, to mimic everyday use.
After treatment, the containers鈥 contents were filtered and analyzed for particles. In the microwaved samples, the team counted up to 4.71 million microplastic particles and up to 2.11 billion nanoplastic fragments 鈥 released from just one square centimetre of polypropylene.
Notably, the polyethylene pouch was not microwaved, as it wasn鈥檛 deemed microwave-safe.
The scientists found hotter temperatures caused more particles to shed, although experiments simulating a six- to 12-month stay in the fridge found the containers still released up to 577,000 microplastics and 21.5 million nanoplastics. For a similar stay at room temperature, numbers shot up to 841,000 and 34.9 million micro and nanoplastics, respectively.
Although Health Canada acknowledges microplastics can seep into food and water, it hasn鈥檛 indicated a 鈥渟afe鈥 level of ingestion. Its website reads: 鈥淓xposure to microplastic pollution was 鈥
鈥淚t was so shocking for me because at the time I first started getting results from my experiment, my baby was one (or) two months old,鈥 Hussain said. 鈥淎ll I was thinking was 鈥極h my gosh, my baby is eating all these plastic particles.鈥欌
His family has since stopped microwaving plastics and is avoiding as many plastic food containers as possible.
How much plastic is your infant consuming?
Hussain鈥檚 team went further and estimated how many toxic particles infants and toddlers eat daily, should they consume different products prepared in plastic containers.
The greatest level of estimated daily ingestion came from drinking microwaved water or dairy products stored in a polypropylene container, both averaging over 20 nanograms of particles per kilogram of body weight per day.
On the opposite end, the smallest amount of exposure came from veggies stored in plastic in the fridge, at under 0.001 ng/kg/day.
In general, the study found the polyethylene pouch released more particles than the two polypropylene containers; 鈥渢he exact reason for this difference is not certain,鈥 the paper reads.
Hussain鈥檚 findings correlate with previous research; a 2020 study in Nature Food found infants can ingest up to feeding bottles. Meanwhile, earlier papers estimate individuals consuming an average American diet .
Direct exposure to plastic container particles can kill human cells
Although Hussain is quick to note the exact health impacts of ingested plastic particles on the body are yet unknown, experiments show the fragments recovered from his earlier tests were toxic to cells.
Using the micro and nanoplastics recovered from baby food containers, Hussain鈥檚 team injected the particles at varying concentrations into dishes of cultured human embryonic kidney cells. He said these cells were chosen because the kidneys have more contact with plastics than other organs.
After two days, Hussain found the greatest concentration of plastics killed 75 per cent of all cells: over three times as many as the lowest concentration of plastics.
This might not reflect how the particles behave in the body, however, noted Roxana Suehring, a microplastics researcher and assistant professor of environmental analytical chemistry at 海角社区官网Metropolitan University unaffiliated with the study.
For one, the test concentrations contain far more particles than our cells would normally be exposed to in the body. Additionally, because the team tested the plastics on embryonic kidney cells, their results might not translate to infant or adult kidneys, as the cells undergo a great many changes during development, Suehring said.
鈥淥n top of that, if we ingest plastics, they first have to pass our gastrointestinal tract where they鈥檙e going to be in the stomach and the intestines,鈥 she added. 鈥淔rom there, they have to somehow get to the (kidneys), which obviously would be a tiny fraction of what was actually ingested.鈥
Hussain agreed this result should be taken with a grain of salt, but added that it was at least a signifier of what the particles were capable of.
Study not without flaws
Suehring believed the study was 鈥渞eally important鈥 and 鈥渨ell done,鈥 especially as it simulated everyday use scenarios. That said, it wasn鈥檛 without its flaws.
On top of the team鈥檚 cell-exposure experiments, Suehring noted the authors did not confirm whether all the collected nanoparticles were made of plastic 鈥 some may be additives instead of nanoplastics, for example, which might lead the study to overestimate how many were actually released. They did confirm the microplastics were plastic, however.
鈥淏ut that said, even the (verified) findings on the microplastics side are really important and interesting,鈥 Suehring continued. 鈥淚 found it surprising how high the numbers were.鈥
Suehring also wished the team was able to study more than two types of plastic, but noted that centring the paper on polypropylene and polyethylene was a good start, given their widespread use: 鈥淚f you want to know something about food containers, these are the two specific plastics I would start with.鈥
That said, Hussain hopes to analyze other plastics in the future.
Suehring and Hussain say his paper should serve as a wake-up call for companies to devise safer packaging and plastics, and for consumers to watch their own habits.
鈥淪omething I always do and I recommend for everyone 鈥 (is to) heat things up not in a plastic container but a dinner plate or glass container; you can empty (plastic food containers) into a bowl and heat that up.
鈥淚t鈥檚 an extra step, but it鈥檚 not something that I think will massively inconvenience anyone and it will substantially reduce your exposure.鈥
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