California, Bisphenols & Direct Thermal Labels

First Published: January 26, 2024

I read a news item this week that the Tag and Label Manufacturer’s Institute (TMLI) has formed a Direct Thermal Task Force to keep members up to date with proposed regulations that will affect the use of bisphenols in direct thermal products in California and Washington, D.C.

This caught my attention because bisphenols have been in the news for a while, mainly focusing on plastic packaging, where bisphenols are proven to be harmful.

BPA and its lesser known relative, bisphenol S (BPS), are also often found in direct thermal materials in concentrations that cause concerns as well.

What is BPS?

Bisphenol S in Food Causes Hormonal and Obesogenic Effects Comparable to or Worse than Bisphenol A

The National Library of Medicine

Bisphenol A has been widely used as a component in food packaging and storage.

Bisphenols are endocrine disruptors that can interfere with the body’s hormonal systems. Studies have shown that exposure to bisphenols can have adverse effects on growth, brain function, the reproductive system, and the immune system.

Studies as far back as 2007 identified BPA as being particularly problematic and due to these concerns, there has been a push to regulate and phase out the use of BPA and related compounds in products that come into contact with food and other sensitive areas.

Bisphenol S (BPS) is part of polyethersulfone (PES) plastic and has been commonly used as an alternative to BPA – a lot of so-called BPA-free materials contain BPS as a substitute. Many of these substitutions were introduced without extensive testing of BPS, which has a very similar chemical structure to BPA.

As a result of studies undertaken since 2020, some states, such as California, Washington, and Washington, DC, are proposing to restrict the use of BPS in food packaging and related products in a similar way to how BPS is regulated.

At the end of 2023, BPS joined BPA as being listed under California’s Prop 65 as a reproductive toxiant.

What’s the Connection With Direct Thermal Labels?

Direct thermal labels are commonly used in logistics, for receipts and for use in retail for price labeling and other applications.

Direct thermal labels are chemically treated so that they change color when heated – this is how the dark print is formed on a white label background.

Bisphenols, particularly BPA, but also BPS, have traditionally been used in the production of direct thermal labels due to their color-developing properties when exposed to heat. The Bisphenols act as a developer in the heat-activated printing process, reacting with proto-dye to produce a dark color.

The concern with the labels containing high concentrations of bisphenols is that it has been shown the chemicals can leach into food products and they also can be harmful for people handing the labels.

Alternatives to Bisphenols in Direct Thermal Labels

For some time, BPS had been considered an alternative to BPA in labels, but now this has been discredited, new solutions are needed.

There are a number of label constructions that claim to be BPA free – some of them presumably incorporating BPS as as alternative.

Direct thermal materials that are bisphenols free are also available – such as this one from Avery Dennison. This material is in compliance with the EU regulations that allows for a trace amount of 0.02% of bisphenols.

What’s Next

Direct thermal labels have evolved over the years to be an excellent way of providing print on demand capability for a lot of applications.

Of course, now that we are aware of the health risks of using bisphenols in the label construction, the industry is going to need to come up with viable alternatives.

There are sure to be more states and countries tightening their regulations for BPA and BPS, so it is good to see TLMI getting a team of industry stakeholders together to address this.

Further Reading

Article on BPS from The National Library of Medicine

How nasty chemicals from grocery labels can leach into foods

Oh, I’m sorry about the spelling in the image – I blame the AI 😂

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