PFAS in non-stick pans: how fast does it migrate to food?

PFAS has been shown to have adverse health impacts when over a toxicity treshold. I go through research relating to non-stick cookware and PFAS transfer into food.

This is a blog where I go in-depth into questions and topics, I am personally interested in related to contamination and toxicity. The goal is to break down and interpret the actual data behind many of these compounds in the news for a non-chemist like me. Each blog is based on secondary research, primarily from published articles found through Google Scholar and known academic journals, and experience formed during my work with chemical analysis.

TLDR

1. 3 research papers assessed imply a very wide range of PFAS transfer during cooking from non-stick pans to food.

2. The numbers imply that between 4 and 70 meals a day cooked with a non-stick pan can take you into the toxic zone.

3. Some secondary insights are: PFAS transfer seems to increase with repeat usage of the same pan. And salt in food seems to accelerate PFAS transfer.

PFAS recap

PFAS is a family of ~5k molecules (and ever growing), known as “forever chemicals”, which are made of fluorine and carbon and usually have an extremely long shelf life. Some of the compounds, which fall under PFAS are PFOA and PFOS but also many others. Very few of the many compounds are thoroughly researched for human impact, but what we know are:

• They take a very long time to break down and have a tendency to accumulate in the body, which in itself is a risk factor.

• CDC data shows that once regulations around specific compounds, called PFOS/PFOA, kicked in, it took 10-20 years for the population to clear the compounds from the blood.

• There is a probable link of PFOA exposure and increased risk of cancer and other diseases.

• As a result, PFOA has been phased out from PTFE (often branded as Teflon), which is a variation of plastic, formulations.

• Even when cleared from the body, these compounds are fairly indestructible and likely accumulate in the soil.

More around PFAS structure, risks and background can be found in my earlier post on PFAS and waterproof clothing.

PFAS in pans - levels of release to food

I recently started using enamelled cast iron for cooking. But oh, do I miss the good old non-stick pans - despite the enamel, making an omelette in a cast iron pan is a task too tall for it not to stick.

So, let’s actually look at the PFAS and the non-stick frying pans through the numbers lens.

Assumptions

In this section I rely heavily on the following assumptions:

1. Safe exposure limit. Going back to research in my previous post, let’s take the 0.070 mg/day = 70 μg/day quantity of PFOS specifically as a level of concern for human exposure. This is actually based on CDC report citing mice studies by weight and at that level induces “suppressed immune response”. While not directly human attributed, better to be conservative on this assumption.

2. Transfer rate from pan to food. I took three different papers, all with different numbers of transfer to get a better sense.

3. Today we are cooking a 300g / 315ml tomato sauce, which is assumed as an average portion size.

Transfer rate: paper 1

A paper which examined cooking using non-stick utensils, specifically from the Tefal company, found the following migration from pan to food:

• 18 to 60 ng/g of PFOS migration from the non-stick pan surface to tomato sauce with salt.

• The migration was 15-25% less when not using salt. Let’s go with the numbers with salt as we would use it more often than not.

• The migration levels increased which each subsequent cooking repetition. 18 ng/g represents the first go, while 60ng/g was reached on the 10th attempt. Presumably there is a trajectory of increase over time rather than decrease.

We are making some tomato sauce at home today (Source)

Eyeballing an average food serving size, let’s go with a 300g average cooked meal (Source). Thus cooking with PTFE coated cookware, on the 10th attempt, an average meal of tomato sauce will contain 300g x 60ng = 18,000ng = 18μg of PFOS.

Ok wow, that’s quite a bit.

So doing 4 meals like that a day will equal to 18 x 4 = 72μg everyday, taking us over the 70 μg/day safe limit for PFAS related compounds. That’s 4 meals leading to “supressed immune response” already.

Transfer rate: paper 2

Let’s take another example for the 2nd assumption. The following paper in Table 2 cites migration of PFODA (one of the other PFAS compounds) to a food-like sample at 3.05 μg/L rate:

• Ok so 300g of tomato sauce is approximately 315ml in volume (based on this online calculator)

• This translates to 0.96μg ~ 1μg of PFODA in our tomato sauce. Ok, that’s many times less than the previous study at 18μg.

• In this case, we would need to cook 70 meals a day like that to take us over the safe exposure limit (assuming the same limit as for PFOS).

Transfer rate: paper 3

Another paper looked at various food preparation trays (rather than frying pans) and found PFOA migration at levels of between 3.15 and 22.3 μg/kg. The variation was due to the manufacturer of the tray. Let’s estimate both extremes:

• On the safer end, 3.15 μg/kg will equal 0.9μg of PFOA for our 300g tomato sauce. That’s unlikely to be an issue.

• On the higher end, 22.3 μg/kg will equal ~6.7μg of PFOA for the 300g tomato sauce. So we need around 10+ meals a day to get into the risk zone. Ok so this is not likely, but also not that far off the risk zone to be fully comfortable.

Recap

Based on different research sources, it will take us between 4 and 70 meals a day using non-stick / PFAS coated cookware to get us into a danger zone for health and toxicity. There is some evidence that with each repeat use of the pan, the amounts of PFAS transferred to food increase.

Is it still a thing today?

Is PFOS/PFOA even in today’s cookware? I was not sure if it was still a thing, given that these specific compounds are very strongly associated with health risks.

EPA says that “PFOA and PFOS has been replaced in recent years”. This is based on a voluntary agreement between producers and EPA. Although I could find some questions online if in fact this is true in the industry (Press release from an advocacy group).

It turns out changes in the EU regulations are only fairly recent, coming into effect in 2019 (Source) and limiting PFOA contents to 0.025 mg/kg with a maximum concentration of 1 mg/kg for a combination of PFOA-related compounds. This relates to total product, such as frying pan, composition rather than migration from it.

Let’s sense check this:

• In a Teflon 12-inch (30cm) non-stick pan, that’s around of 3.4lb (1.5kg) in weight (Source).

• So, the EU limit would be a maximum of 1.5mg per a 30cm Teflon pan of PFOA-related compounds.

• Given the safe exposure limit of 70 μg/day, the pan would need to migrate up to 5% of its PFOA weight a day into food to be toxic.

• That feels like a lot and would mean that in 20 days there is no more PFOA left in the coating, presumably meaning a loss of non-stick ability. Not something I have observed in practice.

• All of this assumes regulation compliant cookware.

Let’s try to assess this against a typical lifespan of such pans:

• The same Teflon pan came with 1.5mg of PFOA out of the factory.

• Let’s say that in 1 year we have none of the coating left (e.g, as in this Reddit post), assuming that actually we have depleted PFOA.

• Assuming we cook with this pan every day (that’s probably on the extreme end) and that all of the PFOA transferred to food (some of it certainly would go into sewage through the washing), we would have to be releasing ~4μg/day.

• That’s 17.5 times under the dangerous exposure limit.

In summary

I tried sense checking the numbers in different ways. In conclusion, research papers assessed show it would take between 4 and 70 meals cooked with non-stick pans a day for it to become toxic. This is a huge variation and that gives cause for doubt whether that range can actually be broader, particularly if on the more toxic side.

Lastly there’s a John Oliver segment on PFAS from a few years ago below. John Oliver actually says (around the 15th minute) that non-stick frying pans is not an issue if not overheated or scratched, but does not go into more detail.