Just the ticket? Alternatives to BPA in receipt paper

August 6, 2012 at 7:51 pm | Posted in Feature Articles | 3 Comments

Although there is not much information about the environmental performance of potential substitutes, the Swedish Chemicals Agency (KEMI) has nonetheless proposed banning the use of BPA in thermal paper. Here we outline some of the problems with securing data on chemicals used in manufactured goods, and why KEMI believes a ban on BPA is warranted even though information on alternatives is lacking.

In June 2012, the Swedish Chemicals Agency (KEMI) presented a proposal to the Swedish Government for a national ban on bisphenol A in thermal paper used in cash receipts and tickets.

This is an extension on current concerns with BPA, which have focused on food contact materials. Measures adopted to manage potential risk from BPA vary by authority, with France proposing the strongest restrictions, while the European Union and US Food and Drug Administration have only gone as far as prohibiting the use of BPA in baby bottles.

In thermal paper BPA is used as part of a thermosensitive coating which changes colour when heated but does not revert to white when it cools down. The coating is a mixture of a colourless dye, a colour developer, and a compound which is solid at room temperature and melts when heated to 45-65 degrees Celsius.

When the print head of the receipt printer heats the paper, the solid compound melts, allowing the colourless dye and colour developer to mix. The dye and developer react and change colour, to leave a legible impression in the paper.

The overall mix of substances within thermal paper is complex, consisting of about 20 different compounds including adhesives, solvents, sensitisers, stabilisers, dye and developer. BPA is used as a developer and, after use, remains in the parts of the receipt which have not changed colour.

The concern is that people may be exposed to potentially harmful levels of BPA in the process of handling receipts and KEMI’s risk assessment of BPA in receipts was to evaluate more precisely the likelihood of harm.

KEMI analysed data on the neurotoxicity of BPA to derive a range of reference doses to which people could be exposed without significant likelihood of harm. These doses were then compared with likely exposure to BPA via cash receipts to obtain a hazard value. If a hazard value exceeds 1, then KEMI considers a risk to be inadequately controlled.

KEMI’s analysis produced a range of results all of which exceeded the acceptable hazard value (the lowest being 1.05), requiring measures to lower the risk. In an occupational or industrial setting, this might amount to changes in process or the introduction of safety equipment. However, in the case of BPA in thermal receipts, because the use cannot reliably be controlled, KEMI concluded that a substitute has to be found.

Safer substitutes

Which leaves the question: are there compounds can be used instead of BPA, and is there sufficient evidence that they are any safer?

In April 2010, the U.S. Environmental Protection Agency (EPA) began a project “BPA Alternatives in Thermal Paper Partnership” to identify and assess alternative colour developers to BPA for use in thermal paper. The project, to produce a safer alternative, is a collaboration between a wide range of stakeholders, including NGOs, chemical manufacturers and retailers.

17 substances have been identified by the EPA as potential substitutes for BPA, and it is these compounds which KEMI assessed. The problem is that there is not much data out there to evaluate.

Using the EU chemicals Classification and Labelling Inventory, KEMI found there is not even basic hazard data on five of the potential 17 substitutes: BPS MAE (CAS 97042-18-7); D-90 (CAS 191680-83-8); a urea urethane compound (CAS 3217860-75-7); bisphenol AP (CAS 1571-75-1); and MBHA (CAS 5129-00-0).

Of the rest, several compounds are clearly toxic to aquatic organisms, although an environmental risk assessment would require more data about the extent to which the compounds would appear in the aquatic environment. One compound is a suspected carcinogen, and two may cause genetic damage. Some showed eye or skin irritation, and one is likely harmful if swallowed. And this is what the data showed; for other environmental health end-points, data was altogether lacking.

The data KEMI was able to access, however, is mainly from acute toxicity tests and material safety data sheets, primarily intended for managing risk in occupational settings. The data does not really correspond with concerns about BPA as an endocrine disruptor or how people are likely to be exposed on a day-to-day basis, so is not necessarily helpful in identifying a safer alternative.

Furthermore, data on some compounds was withheld. Mitsubishi HiTec Paper Europe GmbH produce a BPA-free thermal paper but would not disclose to KEMI the details of their formulations, except to that they are urea-based compounds instead of phenols. Similarly, Papierfabrik August Koehler AG would not disclose any information.

There is more data in the draft of the EPA’s own results, published for comment on July 31 this year. Data gathered on material properties, toxicokinetics, acute mammalian toxicity, carcinogenicity, genotoxicity, reproductive effects, developmental effects, neurotoxicity, repeated dose effects, skin and respiratory sensitization, eye and dermal irritation, endocrine activity and environmental fate.

Overall, however, the data again appears to be limited: most of the data concerns BPA, while assessments of other compounds are in many places based on “professional judgement” of the molecule’s likely properties given their resemblance to BPA, rather than on any specific data for the molecules themselves. Overall, the story seems to be that there are alternatives to BPA in thermal paper, which may or may not be on the market, for which there is insufficient data to perform a meaningful risk assessment.

The main contenders

Of the 17 chemicals, KEMI concluded that only two were being used on the Swedish market: Bisphenol S (BPS) and Pergafast 201, described by its manufacturer BASF as “suitable for use as a color developer in most grades of thermal paper, especially premium grades where high image stability is required.” (BASF 2012, BASF 2011)

2-dimensional structure for Pergafast 201

There are 19 citations (on 26/7/12) in PubMed for Bisphenol S. The studies examine human exposure, the presence of BPS in paper, how it degrades in the environment, leaches from plastic, and its estrogenic transcriptional activities. BPS is widely used in receipt paper and may be similarly oestrogenic to BPA, according to two in vitro cell assays and an in silico ER-alpha binding assay (Grignard et al. 2011, Kurutu-Niwa et al. 2005).

Pergafast 201 has been evaluated under the Australian National Industrial Chemicals Notification And Assessment Scheme (NICNAS 2004 PDF). There are indicators that it may be toxic to aquatic organisms and persistent in the environment, though not bioaccumulative. In a document submitted to the EPA, liver toxicity at high doses is reported.

According to the Substitution Support Portal (SubsPort) Pergafast 201 “carries none of the classifications associated with health hazards to humans; it could however be dangerous if released into the aquatic environment. Due to how receipts are handled, most of them will probably not reach the aquatic environment and this is therefore considered an acceptable risk”.

Pergafast 201 has also been evaluated by the EPA Thermal Papers project. The draft assessment draws its conclusion from confidential studies submitted to the EPA and “professional judgement” of likely toxicity by comparison with similar molecules. For some environmental health end-points, there is no data at all.

In terms of endocrine activity, one confidential study “similar to OECD 455” (which tests the affinity of a compound to the principle nuclear oestrogen receptor) shows Pergafast 201 to have very low potency in comparison to 17-beta-estradiol. There are no studies evaluating the affinity of Pergafast 201 for other hormone receptors. A PubMed search for Pergafast 201 yielded no results on 2 August 2012.

Overall, the extent of testing of Pergafast 201 appears minimal. Nonetheless, according to BASF the compound represents “the first real commercial alternative to BPA […] and confirms BASF’s position as a leading supplier for sustainable paper chemicals.”

The lack of data, however, makes it seem this statement about environmental performance has to be taken on trust – there is certainly insufficient public data on which to compare its performance with BPA. And there is the rub: do we want to substitute chemicals such as BPA with chemicals like BPS or Pergafast 201, for which we have very little data at all?

A precautionary approach

KEMI states that “current knowledge is limited”, that “a national ban on BPA would not limit the use [in cash receipts] of other chemical substances which may have an adverse impact on human health or the environment”, and that there is no guarantee that introducing regulation would improve safety or human health.

Nonetheless, KEMI argues that a ban is justified because “a regulation would facilitate and improve the information regarding which colour developers that are used in cash receipts” and “motivate further product development” which “may lead to safer products”.

The usual advice is to choose the devil you know, but this reversal of conventional wisdom makes sense if one thinks about it: a three- to four-year research period to identify a substitute should sort out at least a rudimentary test regime on which a risk assessment can be based, a fresh battery of information on the biological activity of the possible alternatives, and therefore ought to produce a substitute which has a reasonable chance of being safer.

The problem we have at the moment is that acquiring data requires an independent laboratory to be aware of a chemical and be able to generate research funding to look at it. BPS has some funding going its way, but Pergafast 201 seemingly has none. Not setting a sunset date for BPA would not change this situation.

Thermal paper also shows us how difficult it is to obtain information about many chemical products on the market. BASF is evidently under no obligation to publicly disclose its research into Pergafast 201, while formulations are a secret guarded even from regulatory agencies such as KEMI. Overall, there is little onus on a manufacturer to produce data, prior to market, which proves that a “better” thermal paper is safer than one which contains BPA.

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  1. […] The Swedish Chemicals Inspectorate (KEMI) argues that instead of encouraging bad decision-making, substitution targets are actually an important part of generating the data needed to improve the safety of chemicals in consumer goods. In discussing a ban on BPA in receipt paper, KEMI says that even if obvious safer alternatives do not yet exist, a substitution deadline encourages manufacturers to produce data on a compound and its alternatives, allowing an informed choice about substitutes to be made (KEMI 2012, see also H&E #51: Alternatives to BPA in Receipts). […]

  2. […] The Swedish Chemicals Inspectorate (KEMI) argues that instead of encouraging bad decision-making, substitution targets are actually an important part of generating the data needed to improve the safety of chemicals in consumer goods. In discussing a ban on BPA in receipt paper, KEMI says that even if obvious safer alternatives do not yet exist, a substitution deadline encourages manufacturers to produce data on a compound and its alternatives, allowing an informed choice about substitutes to be made (KEMI 2012, see also H&E #51: Alternatives to BPA in Receipts). […]


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