In an article published on December 30, 2026, in the journal Food Packaging and Shelf Life, Ziyun Xu and co-authors from McGill University, Montreal, Canada, reported that a wide variety of color developers is used in thermal food labels.
Thermal labels are commonly applied to food packaging to provide information such as price, barcode, and more. To activate the dye used in thermal printing, color developers are required. Bisphenol A (BPA; CAS 80-05-07) was a widely used color developer until the European Commission restricted its use in thermal papers to 0.02% by weight (FPF reported). Since then, BPA has been replaced by alternative bisphenols, but knowledge about their types and quantities has been limited. Therefore, Xu and co-authors aimed to identify these substances and their migration into food by investigating 247 thermal labels sourced from around the world for 28 known color developer chemicals.
The researchers detected nine out of the 28 tested chemicals in at least one of the analyzed thermal labels. They further reported that in each of the 247 labels, mostly one and sometimes two or three chemicals were dominant. Bisphenol S (BPS; CAS 80-09-1) was the most frequently detected color developer, present in 45 % of samples. Its mean concentration was 59.3 µg per cm2 of thermal label. BPS was found in higher concentrations and more commonly than BPA. Although BPS is commonly used as a substitute for the known chemical of concern BPA, it is of similar concern due to its endocrine disrupting properties (FPF reported) and related adverse health outcomes (FPF reported, here, and here)
Despite regulatory restrictions on BPA in many countries (FPF reported), it was detected in 2 % of samples. However, the dominance of BPS indicates “that it has been replacing BPA in food thermal labels globally,” Xu et al. state. In samples from Switzerland neither BPA nor BPS were detected, reflecting the country’s regulatory actions to ban both chemicals (FPF reported). The study is the first to report that N-(2-(3-phenylureido)phenyl)benzenesulfonamide (NKK-1304; CAS 215917-77-4) and 2,4-bis (phenylsulfonyl)phenol (DBSP; CAS 177325-75-6) have emerged as new alternatives with a mean concentration of 41.5 and 40.6 µg/cm2 and a detection frequency of 15 % and 11 %, respectively. NKK-1304 is known to be persistent in the environment and toxicity data is fragmented, e.g., it has not been tested for endocrine-disrupting properties. DBSP has been mentioned to be a BPS analogue but “it had only been detected previously in matrices such as river water and human urine.”
Xu and co-authors also tested whether BPS and bis(2-chloroethyl)ether-4,4′-dihydroxydiphenyl sulfone copolymer (D-90; CAS 9168-83-8) present in thermal labels migrated through the food packaging into the food. “Approximately 63 % of BPS and 31 % of D-90 in the labels were able to migrate across polyvinyl chloride (PVC) cling films,” which were used in 80% of the samples tested. Polyethylene (PE) films and paper wraps were found to limit migration to 0.01 µg/cm2, highlighting “the importance of both the cling film and paper properties in reducing the migration of chemicals from thermal labels and possibly from other stickers found on the food packaging.”
The scientists analyzed 247 thermal food labels and wrapping materials purchased on the market in 15 countries around the world. They extracted the samples with ethanol for 12 hours at room temperature before analyzing them for the presence of 28 different color developers, using liquid chromatography-mass spectrometry (LC-MS). To study chemical transfer into food, the scientists performed migration experiments with thermal labels containing BPS and D-90 affixed to PVC and PE films and paper wrap. Using different food simulants, samples were stored for 10 days at room temperature prior to chemical analysis.
Already in 2023, Ziyun Xu and co-authors had investigated 140 Canadian food packaging and thermal label samples. At that time, they were the first to demonstrate that BPS and alternative chemicals found in food labels migrate through the packaging materials into the food (FPF reported).
References
Di Duca, F. et al. (2025). “Global survey of bisphenol color developers in thermal food labels and a study of the role of food packaging materials in preventing color developer migration into food.” Food Packaging and Shelf Life. DOI: 10.1016/j.fpsl.2025.101687
