Heating just one food item in a plastic container creates more nanoplastic than a whole lifetime of drinking mineral water from plastic bottles

[Hip]

SUMMARY: By my calculation (given below), if you drank one litre of mineral water from a plastic bottle every day for your whole life, you would still consume far less nanoplastic than you get from eating just one food item in a plastic container that was heated up in a microwave.

So it might be prudent to take microwave meals out of their plastic containers, and to place them on a plate, before microwaving them.

A study found that microwave-heating food for 3 minutes in a plastic container releases 2.11 billion nanoplastic particles and 4.22 million microplastic particles per square centimetre of plastic area. Article about the study here.

So if you are microwaving some ready-made food from a supermarket — like a microwave meal that comes in a plastic container with around 250 square centimetres of plastic surface in contact with the food — you are going to be ingesting about 500 billion nanoplastic particles, and about 1 billion microplastic particles. So that's half a trillion nanoplastic particles from one microwave meal!

The study tested polyethylene and polypropylene plastic containers. This article indicates that ready-made microwave meal plastic trays are made of polypropylene or CPET.



By comparison, a study found that a litre plastic bottle of mineral water contains around 240,000 particles of plastic, 90% of which is nanoplastics, and the remaining 10% microplastics. Thus that would be around 216,000 nanoplastic particles and 24,000 microplastic particles per bottle.

So if you drank a litre bottle of mineral water every day for 100 years, you would consume around 8 billion nanoplastic particles over that time, and approximately 1 billion microplastic particles.

Thus clearly you ingest far more nanoplastic by microwaving just one food item in a plastic container than you would from a lifetime of drinking mineral water. And this single heated food item will give you about the same amount of microplastic as a whole lifetime of mineral water.

Thus it would seem advisable to remove food from plastic containers, placing the food on a plate or in a bowl, before microwaving it.

EDIT: there is a correction to the above calculation in this post below.



Nanoplastics are thought potentially more dangerous to human health than microplastics, because due to their smaller size, they can easily enter the bloodstream when ingested, can cross the blood-brain barrier, traverse the placental barrier, and can enter into cells.

Estimates for the amount of microplastic and nanoplastic particles ingested into the body per year are:

• 121,000 particles of microplastic are ingested by each human per year from food, drinks and breathing air. Ref: here
• 22 million particles of microplastic and nanoplastic are inhaled by each human every year. Ref: here

If the first estimate is correct, it shows that microwave meals have massively higher levels of plastic particles compared to the average yearly exposure, around 4 orders of magnitude higher.



Due to the accumulation of microplastic and nanoplastic in the body, human brains now contain about 0.5% plastic by weight, with brains accumulating plastic at levels 10 to 20 times higher than other organs like the liver and kidneys. Ref: here

The health impacts of microplastic and nanoplastic particles in the body are still not clear, but it is thought they may potentially lead to a range of health issues, including respiratory disorders like lung cancer, asthma and hypersensitivity pneumonitis, neurological symptoms such as fatigue and dizziness, inflammatory bowel disease and even disturbances in gut microbiota, according to this study.

And this paper lists many potential ill effects, including the following:

[Nanoplastics and microplastics] pose a substantial risk to the endocrine system by interfering with hormone production, release, transport, metabolism, and elimination. This interference can lead to a range of endocrine disorders, including metabolic, developmental, and reproductive disorders such as infertility, miscarriage, and congenital malformations.

Furthermore, research is ongoing to understand the potential impact of microplastics on the human immune system, and evidence has been found of chronic inflammation and homeostasis disturbances in animal studies and the activation of innate immunity in human lung cells.

Collectively, cellular and animal experiments have elucidated the role of microplastics in inducing oxidative stress, disrupting cellular structures, triggering inflammatory responses, lipid metabolism disturbances, gut microbiota dysbiosis, and neurotoxicity.

 

[Hip]

Plastic tea bags are also a source of microplastic and nanoplastic particles, as again you are heating the plastic in boiling water in order to make a tea.

One study found a single plastic tea bag released about 3.1 billion nanoplastic and 11.6 billion microplastic particles into the hot water. Ref: here

Apparently paper tea bags may also release some plastic particles, as they can have plastic components.



So a cup of tea made from a plastic teabag will contain around 14,000 times more nanoplastic particles than a litre plastic bottle of mineral water.

And food in a plastic container heated in a microwave will contain about 2 million times more nanoplastic particles than a plastic bottle of mineral water.



It's quite likely that nanoplastics and microplastics have a certain half-life in the body and organs, meaning that they may be slowly cleared out of the body by natural processes. So if you avoid the highest sources of nanoplastics, you will likely lower your body load over time.

 

[Artemisia]

I only ever see one type of tea bag but idk if it's plastic or not. Seems like paper but plastic seems to be added to everything. Even toilet paper has a plastic feel now.

Are most tea bags plastic or paper?

 

[Hip]

Are most tea bags plastic or paper?

Nylon tea bags I have seen are a bit more difficult to tear with your fingers, compared to paper tea bags which are easily torn. The plastic material is stronger. So that's one way to distinguish them. Plus the nylon bags look and feel like plastic. You could not mistake them for paper.

 

[bad1080]

Are most tea bags plastic or paper?

the regular (flat) ones are paper but those new ones (tetrahedron or similarly shaped) are plastic

 

[Viala]

That's the thing people should know. I think most are wary about plastic bottles but not many about other plastics, tea or rice.

I was suspicious about boil ready rice bags long time ago and always opened them and put rice directly in the water. For tea there's an infuser, so we can always open a tea bag. It takes no more than 20 seconds, but not many people want to do it because it's too much.

 

[Wishful]

I'm wondering about the physics of it. The microwaves shouldn't heat the polymers directly. Does hot water release those nanoparticles? Do the fats, sugars, or other components of foods break polymer bonds?

 

[Hip]

I'm wondering about the physics of it. The microwaves shouldn't heat the polymers directly. Does hot water release those nanoparticles? Do the fats, sugars, or other components of foods break polymer bonds?

I think it is simply the heat which releases these nanoplastic and microplastic particles, not the microwaves per se. I think if you heated the same ready-made meal in a conventional oven, you would get similar results.

 

[Wishful]

So, is that plastic bag heating in the sunlight releasing extra nanoparticles? Is there no point in worrying about heat'n'serve dinners is it's only a tiny portion of the nanoparticles we're exposed to every day? The story looks like a demonization attempt, where the "amazingly dramatic" finding is taken out of context of the total environmental exposure to the harmful factor.

 

[bad1080]

is that plastic bag heating in the sunlight releasing extra nanoparticles

there's usually a curve to those kinda things. any heat will release it and some particles will dissolve on their own without any extra heat (see the water bottles). but the heat from a microwave is rather punctual (that's why some parts of your food are still cold after microwaving it) and thus concentrated so my guess is that's why it releases a lot of microplastics.
the sun would introduce stuff like UV light which could set another reaction in motion.

 

[Hip]

The story looks like a demonization attempt, where the "amazingly dramatic" finding is taken out of context of the total environmental exposure to the harmful factor.

Provided above are some yearly environmental exposure estimates taken from studies. The estimate for the total amount of microplastic ingested by the average human each year from food, drinks and breathing air is 121,000 particles.

The amount of microplastic ingested from heating just one microwave meal in a plastic tray is 1 billion particles, which is nearly 4 orders of magnitude higher than the 121,000 figure.

So people who have say two microwave meals a week are exposing themselves a yearly microplastic dose of 100 billion, which is 6 orders of magnitude higher than the 121,000 figure.

Clearly this could potentially be a concerning issue. But we don't know at this stage, because research into the ill effects of plastic particles in the body is still in its infancy.

I consume around one ready-made meal per week, and from now on, I am going remove the food from the plastic tray and microwave it on a plate, just to be on the safe side.

 

[mattie]

Pukka tea bags are made from unbleached, plastic-free, compostable materials.

1. Tea Bag Material:

• Made from a natural blend of abaca (a type of banana plant fiber), wood pulp, and plant cellulose fibers.

• Free from plastic, including polypropylene.

2. String and Tag:

• The string is made from organic cotton.

• Tags are printed with vegetable-based inks and attached without metal staples.

3. Seal:

• The tea bags are stitched together with organic cotton.

4. Outer Packaging:

• The box is recyclable and made from sustainably sourced cardboard.

 

[junkcrap50]

You would be surprised how much food is cooked in its plastic packaging before you ever take it home. Basically, if it's a product that's already cooked, you should assume it was cooked in its packaging, or at least put into its packing hot.

 

[Hip]

You would be surprised how much food is cooked in its plastic packaging before you ever take it home. Basically, if it's a product that's already cooked, you should assume it was cooked in its packaging, or at least put into its packing hot.

Would you have any references for that?

 

[Hip]

There appears to be a commentary paper linked to the original study I referenced in the first post.

The authors of the commentary do not question the accuracy of the study, but say:

However, MH [microwave heating] is characterized by a rapid heating rate, achieving higher temperatures within the same time compared to conventional heating methods. Additionally, a high temperature is an important risk factor for microplastic release.

It is necessary for us to point out, therefore, that the release of MNPs in the MH group might be caused by the high-temperature heating of the plastic containers. MH, a fast and convenient heating method, is widely used in everyday heating scenarios. We are worried that their statements might misdirect consumers about the unsafe use of microwaves in food heating.

So if I understand it correctly, the commentary is suggesting that the high amount of plastic particles released by microwave heating of baby food containers may not necessarily apply to microwave heating of food containers.


The commentary authors did their own experiments, and found that baby food containers heated by microwave or by water bath resulted in both cases in around 10 million nanoplastic particles per square centimetre being produced, and 1 million microplastic particles per square centimetre.

So the commentary authors found a lot less nanoplastic particles compared to the original study (about 100 times less nanoplastic), but around about the same amount of microplastic particles.

We can thus revise my statement in the first post, which said that on microwave meal produces about 500 billion nanoplastic particles, to a new figure of 5 billion nanoplastic particles per microwave meal. This new figure is still a lot, as it is equivalent to the amount of nanoplastic you would ingest from drinking 23,000 mineral water bottles.

 

[Wishful]

The estimate for the total amount of microplastic ingested by the average human each year from food, drinks and breathing air is 121,000 particles.

What I'm wondering is the accuracy of that estimate. If it's based on the same assumptions that plastic food containers wouldn't release significant amounts of MP or NP, then it's meaningless. Then the article would be demonizing a couple of measured items when the exposure might be comparable or even less than many other everyday encounters with plastic items. How many particles come off a styrofoam cup when you add hot beverage? Then stir it with a plastic spoon or stick.

I'm just wondering if the actual typical annual exposure is high enough that the 5 billion per meal is trivial. ~100k particles per year seems absurdly low.

 

[Hip]

How many particles come off a styrofoam cup when you add hot beverage?

That's a good question. I just found one 2022 study which detected 1 trillion nanoplastic particles per litre in plastic beverage cups filled with boiling water and then left for 20 minutes. That is significantly worse than microwave meals.

Another 2023 study found a few thousand microplastic particles were generated in plastic cups containing water at 95°C for 20 minutes.

I am not sure why the nanoplastic levels are so much higher than the microplastic levels in these plastic cups. In the case of plastic tea bags detailed in this post above, the amount of microplastic and nanoplastic particles were similar, and in the few billion range. It could be that researchers are using different measurement methods for these particles, which then results in wildly different particle number figures.

What I'm wondering is the accuracy of that estimate. If it's based on the same assumptions that plastic food containers wouldn't release significant amounts of MP or NP, then it's meaningless.

My guess is that the yearly estimates for microplastic exposure will not have taken into account the high levels of microplastic found in microwave meals, or in plastic cups containing hot water, since the studies which found these high levels are quite new.

Thus this appears to be new information. In the light of this new information, new estimates for human yearly plastic particle exposure may need to be given. Though estimates for human exposure might be wildly different depending on whether or not someone consumes microwave meals and hot beverages in plastic cups.


What seems clear is that hot food or hot beverages in contact with plastic results in very high levels of plastic particle release, compared to other sources.

So if one wants to reduce the plastic particle load in their body, avoiding these items would seem like a good idea.

 

[Hip]

Looks like electric kettles that are made from plastic release around 10 million microplastic particles per litre of water when they are boiled, according to this study.

Electric kettles are uncommon in the US, but almost every UK household has one, due to the popularity of drinking tea in the UK.

So glass or stainless steel kettles may be a better option than plastic ones, if you want to minimise microplastic exposure.

 

[Hip]

Interestingly enough, according to research on marine sediments, microplastic and nanoplastic particles started polluting our environment from the 1980s onwards, with a dramatic increase in microplastic abundance from about 1998.

It may be a coincidence, but the 1980s also saw an 8-fold increase in the incidence of ME/CFS.

Autism rates also dramatically increased from 1990s onwards (though this might in part be due to greater awareness of autism and better diagnostic infrastructure). One mouse study found a potential link between autism and microplastic.

This 2024 study about the the toxic effects of microplastics on the immune system concludes:

The universal presence of MPs in our environment has become a significant challenge to human health, particularly to the immune system. This review highlighted the complex impacts of these particles on various immune cell types, from myeloid to lymphoid lineages. The cytotoxic effects and immunomodulatory potential of MPs underscore the urgent need to develop intervention strategies to cope with such harmful effects.

As our understanding of the interactions between MPs and the immune system expands, a multidisciplinary approach to combine environmental science, immunology and materials engineering is crucial to address this global issue.