Research Background

Non-stick cookware with Teflon coatings uses compounds of perfluorooctanoic acid (PFOA). These compounds are highly stable to chemical and thermal impacts resistant to hydrolysis, photolysis, and microbial degradation. Their half-life in the environment is 41 years. Therefore, according to the Stockholm Convention, PFOA belongs to the class of persistent organic pollutants.

Animal studies have shown that PFOA is quickly absorbed with food, accumulates in the body, and leads to internal organ damage. It has been proven that these compounds are toxic to the liver and nerve cells, cause diabetes, immunodeficiency, cancer, and disrupt the function of the thyroid gland and central nervous system.

There is insufficient data on the impact of perfluorooctanoic acid on humans. However, it is known that the half-life of PFOA in the human body is about four years. The European Food Safety Authority has established a tolerable daily intake of PFOA at 150 ng/kg/day.

Previous studies have shown that household cookware with Teflon coatings can release various gases and perfluorinated compounds during cooking.

An international group of scientists investigated how much PFOA enters food from the Teflon layer under various cooking conditions. The researchers hypothesized that the leaching of PFOA from Teflon into food significantly depends on the products’ acidity and the frequency of cookware use.

Study Design

The study focused on popular cookware from the Tefal brand with DuPont Teflon non-stick coating. The diameter of the selected pot model was 24 cm, and the bottom thickness was 3 cm.

Tomatoes, peeled and seeded, were used as acidic food. White beans were used as non-acidic food. All initial products were tested for the absence of PFOA before the experiments to ensure the purity of the study.

Tomatoes were cooked until 75% of the liquid evaporated. Beans were pre-soaked for three hours and then stewed until done.

Experiments were conducted under two cooking conditions: with table salt (NaCl) and without it.

The researchers prepared 20 portions of each product type in the preliminary stage. Each portion size was 500 g. The first 10 portions were sequentially cooked in one pot. The other 10 portions were sequentially cooked in another pot but with the addition of 5 g of table salt. The scientists then measured the amount of PFOA in the first, fifth, and tenth portions of the cooked products. Each experiment was repeated three times.

The researchers were also interested in the dynamics of Teflon layer degradation during cooking. To study the dynamics, they compared the structures of the non-stick coating of a new pot and pots after ten uses for cooking tomatoes and beans under conditions with and without table salt. The researchers used X-ray diffraction, X-ray microanalysis, and scanning electron microscopy.

Image source: https://wjarr.com/content/impact-household-cooking-release-fluorinated-compounds-pfoa-and-pfos-tefal-coated-cookware

Study Results

After ten uses of cookware with Teflon coatings, Acidic foods contain 5% more PFOA than non-acidic foods. Adding table salt increases PFOA content by an additional 15%. After ten uses, the non-stick coating releases nearly four times more PFOA than in the first use.

PFOA content (ng/g) in the cooked product depending on the frequency of cookware use and cooking conditions:

Usage Frequency Tomatoes without salt Beans without salt Tomatoes with salt Beans with salt
One time 13.7 13.1 18.3 18.1
Five times 31.2 29.2 39.6 36.2
Ten times 52.1 50.0 60.3 57.2

The degradation of the Teflon layer by the tenth use of the cookware is shown in electron microscope photographs with a magnification of 1500 times. Figure A – before the first use. Figure B – after ten uses for cooking tomatoes without salt. Figure C is similar to Figure B but with the addition of salt. Figure D – after ten uses for cooking beans without salt. Figure E – identical to Figure D but with the addition of salt:

Image source: https://wjarr.com/content/impact-household-cooking-release-fluorinated-compounds-pfoa-and-pfos-tefal-coated-cookware

Conclusions

Repeated use of cookware with Teflon coatings leads to a significant increase in PFOA content in cooked products, which is particularly relevant for acidic foods and when adding salt. The results highlight the importance of further research to assess the health risks associated with using Teflon coatings for cooking.

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