BPA in Food Cans - and a discussion about limit values.

In principle, food products should be as free from harmful substances as possible. After all, I am also a consumer and I want this to be the case. At the moment there are warnings against eating tinned food in Germany because, according to press reports, it is heavily contaminated with the plasticiser bisphenol A.

Stiftung Warentest quotes the maximum permissible levels for a person weighing 60 kg from two different institutes. This is because both the European Food Safety Authority (Efsa) and the German Federal Institute for Risk Assessment (BfR) have re-evaluated the risk of bisphenol A and come to very different conclusions. There is still a scientific dispute between the two institutes, but also among medical experts, about the accuracy and significance of the respective test series. I have therefore included the FDA (Food and Drug Administration USA) values as an additional third piece of information to give a better picture. The total tolerable daily intake (TDI) for a person is usually determined in a similar way, with about half of the intake coming from sources such as contact with plastics or tap water, and the other half from food.

For your information:

Milligram (mg): 10^-3 gram or 0.001 gram. Microgram (μg): 10^-6 gram or 0.000001 gram. Nanogram (ng): 10^-9 gram.

Limit values:

Elfsa 0.2 nanograms/kg body weight x 60kg = 12 nanograms per person/day (down to 1/20,000 of the previous value).

BfR 200 nanograms/kg bodyweight x 60kg = 12,000 nanograms = 12μg (at 1/20 of the previous value)

FDA 5 mg/kg bodyweight x 60kg = 300mg = 300,000 micrograms = 300,000,000 nanograms or 0.3g

According to my research, the FDA has not yet set a limit, only a draft, which can be found on the FDA website under BPA, effective 05/2023. Several petitions from citizens' groups to revise the limit have been rejected as unreliable.

So we have limits from the world's leading institutes ranging from 12 nanograms to 300 million nanograms, or 0.3g TDI.

To be honest, as a consumer I find this a bit difficult.

As an engineer, I tend to prefer the median. This is the value that lies exactly in the middle of a data distribution, and in our case it is the BfR value.

However, as far as I know, all the headlines in the magazine have referred to the Elfsa value, which has recently been reduced to one 20,000th of the old value. According to this value, all tins (51) are highly contaminated, except condensed milk (7). Condensed milk has such good values because, like tinned fruit, it probably has no inner coating.

The BfR classifies only 14 cans as significantly to highly contaminated and points out that only long-term consumption is problematic.

The FDA limit says all cans are safe.

I think the recommendation in the press that 'the less canned food, the better' is a bit ill-considered. It is not just bisphenol A that is dangerous to the consumer, but a host of other plasticisers, photoinitiators, bacteria and viruses. It's sub optimal that the type of packaging that offers the greatest safety in this respect is caught in the crossfire.

The advice to avoid frozen food could be also a problem, as plastics with plasticisers are also used. These plasticisers need to be active at sub-zero temperatures, otherwise the packaging will become brittle. Plasticisers in can coatings must also be able to withstand 240°C. Switching to glass bottles can only help to a limited extent. The closures of glass packaging has a lid with an inner coating that also contains plasticisers, but the contact with the base and sidewall is more intense of course.

Tinplate packaging (including lids) has an advantage here because almost all of the substances mentioned (except BPA) are evaporated at 200-240°C for 10-12 minutes during the manufacturing process and then incinerated at 700°C. This is already a very high level of safety, that other packaging materials cannot offer, or only to a limited extent.

Plastics in composites or as film in freezer packaging can withstand autoclaving at up to 120°C, but metal packaging is exposed to twice that temperature during production. This is undoubtedly an advantage, and the Nestlé guidelines therefore allow UV inks for metal packaging if a final production step of at least 200°C is carried out in the drying oven.

Nevertheless, the magazines warn against cans. This is probably scientifically correct, but at least statistically increases the risks elsewhere.

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