Abstract

With the phase-out of bisphenol A (BPA) in thermal papers, bisphenol S (BPS) and several non-BPA color developers have become the dominant developers in thermal labels applied to food packaging. While dermal exposure from receipts has been widely studied, the contribution of thermal food labels to dietary bisphenol exposure has received far less attention. This work synthesizes a 2023 investigation in which 140 packaging materials from North American retailers were screened for BPS and alternative developers, and controlled migration experiments were conducted on fish packaged with their original thermal labels and plastic films. BPS was detected in 73% of thermal price labels, with mean and maximum loadings of 66 and 193 μg/cm², respectively, while BPA was not detected in any sample, confirming a shift to substitutes. In label–fish contact experiments, BPS reached concentrations up to 1140 ng/g wet weight in label-contact fish portions, frequently exceeding the European Union specific migration limit of 50 ng/g; D-8 and D-90 also migrated, although at lower levels, and PF-201 was measurable in selected samples. Residual migration tests using 95% ethanol as a simulant demonstrated substantially higher leaching of BPS and other developers from film areas located beneath labels than from non-label film regions, confirming a label → film → food pathway. These findings establish thermal labels on plastic packaging as a significant yet previously under-recognised source of dietary exposure to BPS and other color developers, and highlight the need for comprehensive risk assessment of BPA alternatives in the context of recent bisphenol bans and monitoring requirements.

Keywords

thermal food labels BPS exposure; bisphenol S; D-8; D-90; Pergafast 201; color developers; food packaging; migration into fish; dietary exposure; BPA alternatives; bisphenols regulation.

1. Introduction

Bisphenols are widely used industrial chemicals with crucial roles in plastics, resins and specialised paper coatings. Among them, bisphenol A (BPA) has attracted extensive scrutiny as an endocrine disruptor associated with developmental, reproductive and metabolic effects. Regulatory measures over the last decade have led to BPA bans or severe restrictions in sensitive applications such as baby bottles, can linings and thermal papers.

In thermal paper, BPA functions as a color developer in the heat-sensitive coating. Regulatory action, including the European Union ban on BPA in thermal paper from 2020, has driven rapid substitution with structurally related compounds, most prominently bisphenol S (BPS), and with so-called “BPA-free” non-bisphenolic developers such as D-8, D-90, TGSA and Pergafast 201 (PF-201). Although intended as safer options, many of these replacements display endocrine activity similar to or overlapping with BPA, and toxicological data remain incomplete.

Most exposure assessments for BPS and other alternatives have focused on:

• Dermal contact with receipts and labels; and
• Background contamination in food due to processing and packaging.

Recent evidence has highlighted thermal food labels applied on plastic-wrapped fresh products (fish, meat, cheese, produce) as potential sources of dietary BPS, but systematic migration data were lacking.

The study synthesised here addresses two critical questions:

1. How prevalent are BPS and alternative developers in real thermal labels and associated packaging components?
2. To what extent do these developers migrate from labels, through plastic films, into food under realistic storage conditions?

The answers bear directly on consumer exposure, regulatory compliance with specific migration limits (SMLs) and the broader problem of regrettable substitution, where BPA is replaced by equally problematic compounds without robust risk evaluation.

2. Materials and Methods

2.1 Packaging Sample Collection and Classification

A total of 140 packaging samples were collected from retail stores in North America (primarily Montreal, Canada, and selected United States locations) in 2021–2022. The sampling targeted typical fresh-food packaging configurations where thermal labels are applied to plastic-wrapped products. Materials were categorised as:

• Thermal price labels (n = 40)
• Other stickers (n = 29)
• Plain films (n = 39; typically cling wraps)
• Absorbent pads (n = 14)
• Trays (n = 18)

Each component was analysed separately to differentiate label-related from background packaging contamination.

2.2 Chemical Analysis

Target analytes included:

• BPA (as a legacy developer, though anticipated to be mostly phased out),
• BPS,
• D-8,
• D-90,
• TGSA,
• PF-201, and selected other developers and bisphenols where standards were available.

Samples were extracted and analysed using liquid chromatography–quadrupole time-of-flight mass spectrometry (LC-qTOF-MS):

• Column: Poroshell EC-C18.
• Mobile phases: water and methanol with appropriate volatile buffers (e.g. ammonium acetate).
• Detection: electrospray ionisation in positive and/or negative mode with exact-mass extraction (mass errors typically <3 ppm).

For packaging materials, 95% ethanol was used as an extraction medium, applied for 10 days at 20 °C, an approach consistent with EU food-contact migration protocols for fatty foods. Results were reported as μg/cm² of packaging material.

For fish samples, extraction was performed on freeze-dried tissue using methanol, followed by LC-qTOF-MS quantification. Concentrations were reported as ng/g wet weight (ww) of fish.

Method performance (limits of detection and quantification, recoveries, matrix effects, linearity) complied with standard validation criteria, with method detection limits (MDLs) in the range of 0.01–1.87 ng/cm² and recoveries generally 70–120%.

2.3 Migration Experiments with Fish

To quantify migration into food, the authors designed a storage experiment using real fish fillets with their original packaging and labels:

• Twenty-four packaged fish products (different species, including salmon, sole, tilapia and basa) were purchased from Canadian and US retailers.
• In the laboratory, each fish was subdivided as follows:
  1. Initial portion: a piece of the fillet was removed immediately upon opening the package to establish background levels of bisphenols and color developers (initial fish).
  2. The remaining fish was re-wrapped in its original cling film with the thermal price label intact.
  3. Fish were stored at 4 °C for five days, simulating typical retail or domestic refrigeration.
  4. After storage, the fillet was cut into:
     • Label-contact portion – region directly beneath the label area on the film.
     • Film-contact portion – region in contact with film only, away from the label.

All portions were separately extracted and analysed as described above.

2.4 Residual Migration from Films

To characterise residual migration potential from the plastic films themselves, the study conducted migration cell experiments according to European Regulation EU 10/2011:

• Film pieces were placed in MigraCell® cells with 95% ethanol as the food simulant.
• Contact conditions: 10 days at 20 °C.
• Two types of film areas were tested:
  • “Non-label film”: regions not covered by labels.
  • “Label film”: regions that had been directly under thermal labels during storage.

Migrated amounts were reported as μg/cm² of film surface.

2.5 Polymer Identification

ATR-FTIR spectroscopy was used to identify the polymer type of plastics (films, pads, trays). This allowed evaluation of whether certain polymers (e.g. PVC vs PE) were associated with different migration behaviours, although detailed polymer-specific modelling was beyond the scope of the study.

3. Results

3.1 Occurrence of BPS and Alternatives in Packaging

Across the 140 packaging components, BPA was not detected, indicating effective phase-out in the examined market segment.

In contrast, BPS was prevalent, particularly in thermal price labels:

• Thermal price labels (n = 40):
  • BPS detected in 73% of labels.
  • Mean loading: 66.0 μg/cm².
  • Maximum: 193 μg/cm².

Other color developers were also found in labels:

• D-8: present in 10% of labels, with mean levels around 124 μg/cm² when detected.
• D-90: 20% of labels, mean ≈ 6.0 μg/cm².
• TGSA: 18% of labels, mean ≈ 61 μg/cm².
• PF-201: 28% of labels, mean ≈ 38 μg/cm²; maximum ≈ 133 μg/cm².

Non-price stickers showed more variable behaviour:

• 21% contained BPS, but at substantially lower levels (mean ≈ 3 μg/cm²; maximum ≈ 17 μg/cm²).
• Stickers that lost colour during extraction tended to behave like thermal labels, while colour-stable stickers often contained little or no BPS.

Other packaging components—plain films, absorbent pads and trays—showed BPS and alternative developers occasionally and at much lower levels (typically ≤1 μg/cm²). The data therefore point to thermal labels as the primary reservoir of BPS and color developers in the tested packaging systems.

Store-specific analysis revealed that all retailers used BPS-containing labels, but the co-occurrence patterns of D-8, D-90, TGSA and PF-201 varied, reflecting different supplier formulations and label supply chains.

3.2 Migration of BPS and Alternatives into Fish

Initial fish portions, taken immediately upon opening the package, contained none or only trace levels of BPS, D-8, D-90 and PF-201 (generally <1.3 ng/g ww), confirming that the purchased fish were not materially contaminated before contact with their packaging.

After five days of storage at 4 °C in original packaging:

• Label-contact portions exhibited significantly higher concentrations of color developers than film-contact portions.

Maximum concentrations observed in label-contact fish were:

• BPS: up to 1140 ng/g ww (sole, USA) and 1090 ng/g ww (salmon, USA), with another sample around 437 ng/g ww (basa, Canada).
• D-8: up to 230 ng/g ww in tilapia from one US retailer.
• D-90: up to 3.41 ng/g ww in salmon.
• PF-201: 1.87 ng/g ww in label-contact fish, with 1.32 ng/g ww in the corresponding film-contact portion from one Canadian retailer.

In most samples, film-contact portions contained substantially lower, but often still measurable, levels. Statistical analysis indicated that for BPS, D-8 and D-90, label-contact concentrations were significantly higher than film-contact concentrations (BPS p < 0.001; D-8, D-90 p < 0.05), confirming the role of the label in driving migration.

Importantly, many label-contact fish samples exhibited BPS concentrations well above the EU specific migration limit (SML) of 50 ng/g, in some cases by more than a factor of twenty.

3.3 Residual Migration from Films With and Without Labels

Migration cell tests on plastic films further clarified the pathway:

• Films were tested after the 5-day storage, using 95% ethanol as a fatty food simulant.
• For BPS, migration from “label film” regions was markedly higher than from non-label regions, with maximum values around 33.8 μg/cm².
• D-8 and D-90 similarly showed enhanced migration from label film areas (e.g. D-8 up to ≈61.8 μg/cm²).
• For PF-201, elevated migration from label film was noted in some Canadian samples.

These findings demonstrate that color developers first transfer from label to plastic film, and then, as shown in the fish experiment, from film to food. The label therefore acts as a source, and the cling film as a conduit, rather than a barrier.

4. Discussion

4.1 Thermal Labels as a Dietary Exposure Route

The combined packaging, fish and migration-cell data converge on a consistent picture:

• Thermal price labels on plastic-wrapped foods are a direct source of BPS and alternative color developers in food.
• BPS concentrations in label-contact fish frequently exceeded the EU SML of 50 ng/g ww; D-8 and D-90 were present at lower but non-negligible levels.
• BPA was undetectable, indicating successful substitution—but the substitutes themselves are now present at levels that raise concern.

While earlier bisphenol research emphasised dietary BPA from can linings and dermal exposure from receipts, this work shows that packaging labels can significantly contribute to dietary BPS exposure, in some cases surpassing estimated dermal doses from handling receipts for the general population.

4.2 Role of Packaging Design and Materials

The study highlights several design factors that modulate migration:

• Location of labels: placing labels directly over edible portions, particularly fatty regions, promotes elevated migration into food.
• Film polymer type: although detailed polymer-by-polymer analysis is beyond the scope of the article, prior work and the present data suggest that PVC cling films are more permissive to BPS and D-90 migration than certain other polymers, whereas some PE-based wraps may offer better barrier properties.
• Label composition: the presence of multi-component developer systems (BPS with D-8, D-90, TGSA or PF-201) complicates both migration behaviour and toxicological assessment.

From a practical standpoint, several mitigation options emerge:

• Avoid locating thermal labels directly over food-contact windows; instead place them on trays, secondary flaps or non-food-contact areas.
• Where possible, introduce barrier layers (e.g. an extra film or paper layer between label and food-contact film).
• Shift to non-thermal labelling technologies (e.g. digital signage, laser-etched information, or non-migrating adhesive labels) for products requiring prolonged cold storage.

4.3 Regulatory and Toxicological Implications

The findings are particularly salient in the context of recent regulatory developments:

• As of January 2025, the EU has extended its restrictions on BPA in food contact materials and has initiated monitoring programmes for BPS and other bisphenols.
• In the United States, California Proposition 65 enforcement actions have increasingly targeted BPS in receipts and labels, with numerous notices issued for thermal label uses.

Despite these measures, toxicological profiles for D-8, D-90 and PF-201 remain incomplete, and evidence continues to accumulate that some BPA replacements can disrupt ovarian and other endocrine functions. The present migration data therefore underscore the importance of:

• Comprehensive risk assessment that explicitly includes labels as a distinct food contact material;
• Non-targeted analytical screening to capture emerging developers beyond the current target list; and
• Precautionary substitution, moving not only away from BPA but towards colour developers with demonstrably low migration and low endocrine activity.

4.4 Limitations and Future Directions

Several limitations should be recognised:

• The migration experiments focused on fish stored for five days at 4 °C; other food types (red meat, cheese, produce) and different time–temperature combinations may yield different profiles.
• The number of products per retailer and per polymer type is limited, restricting robust statistical comparisons between packaging materials.
• The study quantifies exposure, but does not provide new toxicological data; health impacts must be inferred from separate endocrine assays and in-vivo studies.

Future work should:

• Extend migration tests to a broader range of foods and packaging formats;
• Couple occurrence and migration data with in-vitro bioassays (e.g. estrogenic, androgenic, thyroid assays) on migrated mixtures;
• Develop and evaluate phenol-free and non-migrating label technologies that can maintain print performance without contributing to bisphenol exposure.

5. Conclusion

This synthesis shows that the transition away from BPA in thermal papers has shifted, rather than eliminated, bisphenol-related risks in the food packaging sector. Thermal food labels:

• Contain substantial amounts of BPS, often accompanied by D-8, D-90, TGSA and PF-201, while BPA is no longer detectable.
• Transfer BPS and other developers into fish stored under realistic refrigerated conditions, with label-contact portions frequently exceeding the EU SML for BPS.
• Use plastic films not as impermeable barriers but as pathways for migration from the label into the edible product.

In light of these findings, “BPA-free” labelling on packaged fresh foods does not guarantee bisphenol-free products, particularly when thermal labels are applied directly to food-contact films. Regulators, retailers and packaging suppliers must therefore consider thermal labels explicitly in food-contact regulations, broaden risk assessments to include BPS and alternative developers, and accelerate the development and adoption of low-migration, low-toxicity labelling solutions.

For consumers and industry alike, the evidence supports a simple principle: effective risk reduction requires moving beyond BPA, not only in name but in actual exposure and hazard profile of the entire labelling and packaging system.

Last Updated on 12/12/2025 by Jota Machinery