Paper problems continue: Bisphenol A replacement found in currency and paper products

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  • Published: Aug 1, 2012
  • Author: Steve Down
  • Channels: Base Peak
thumbnail image: Paper problems continue: Bisphenol A replacement found in currency and paper products

Alternatives to bisphenol A

Bisphenol S, one of the modern replacements for bisphenol A, has been measured in many different types of paper to establish baseline levels and estimate human exposure by handling the paper.

Bisphenol A (BPA) is one of those chemicals that was around for decades until its possible effects on human health came to light. The main points of contact for humans are via plastic food containers like bottles and storage containers, as well as the protective linings in food packaging and cans. BPA can leach into the food or drink before being taken in by the consumer.

There are other routes of exposure, principally via thermal paper like till receipts, labels and books, which affect humans by skin contact. However, the EU estimates that about 30% of thermal papers are recycled, so BPA turns up in many more paper products like newspaper, toilet rolls, kitchen rolls, advertising flyers and envelopes to increase points of contact with humans.

Now, the use of BPA is being limited, driven by its ability to disrupt the endocrine system and trigger a wide variety of disorders, including chromosomal and reproductive system abnormalities. It has also been implicated in cancer, adult-onset diabetes, early puberty, obesity and resistance to chemotherapy. As a result, the US EPA and the ESFA in Europe have established recommended human intake limits of 50 µg/kg body weight/day.

In order to comply with these restrictions, companies that use BPA in the manufacture of plastic food contact materials and paper products have begun to substitute other compounds in its place. One of them is bisphenol S, which, despite the similar name, is notably different in structure, with a central sulphonyl group in place of the isopropylidene group of BPA.

It is expected that humans will come into contact with BPS via recycled paper in the same way as with BPA, which is almost as worrying. Several bisphenol A analogues including BPS are also thought to be genotoxic and estrogenic, so the problem has not gone away, merely been reassigned to another compound. In addition, bisphenol S is much less biodegradable than BPA so will persist for longer.

One research team that reported the widespread occurrence of BPA in paper products has now turned its attention to BPS in the first study of its type. Kurunthachalam Kannan and colleagues from the State University of New York at Albany and the Yantai Institute of Coastal Zone Research, China, wanted to confirm the extent of BPS usage in paper and use the findings to estimate human exposure.

A proliferation of paper

The researchers collected 268 samples of 16 types of paper products from supermarkets, stores, banks, public libraries, gas stations and restaurants in four countries (USA, Japan, Korea, Vietnam). They included paper currency of 20 countries, thermal receipts, flyers, magazines, tickets, mailing envelopes, newspapers, food contact paper, food cartons, plane boarding passes, luggage tags, copying paper, business cards, facial tissue (napkins), kitchen rolls and toilet paper.

Small circles were cut from each sample with a hole punch and extracted with methanol before mixing with carbon-13-labelled BPA as an internal standard. Then each extract was analysed by LC-tandem-MS with electrospray ionisation in negative ion mode. BPS and labelled BPA were measured using the transitions from their deprotonated molecules to a dominant fragment ion.

A detection limit of 0.1 ng/g was achieved and the recoveries of BPS were complete after three successive methanol extractions.

Ubiquitous bisphenol S in paper products

Every one of the thermal receipt papers contained BPS across the range 13.8 ng/g to 22.0 mg/g, with a geometric mean of 0.181 mg/g. The levels were greatest in the US and Japanese samples, with those from Korea and Vietnam being much lower.

These values are similar to those that Kannan found in earlier studies on BPA in thermal receipt papers and there was a close negative correlation between the concentrations of BPS and BPA. Those samples containing high levels of one contained low or undetectable concentrations of the other, consistent with the replacement of BPA with BPS in the manufacturing process.

A total of 87% of currency bills also contained BPS but their levels tended to be lower than in the thermal receipts at a geometric mean of 0.029 µg/g. The most likely mechanism for its presence is transfer from thermal receipts when they are placed together in cash tills or wallets. There was more BPS at the centres of the currency than the edges, which might be due to removal from the edges by frequent handling and the more likely transfer from thermal receipts to the centre portions.

BPA was also found in all tickets, envelopes, boarding passes and luggage tags and in most flyers and food cartons but was absent from kitchen rolls and printing paper. The levels tended to be 4-6 orders of magnitude lower than BPS in thermal receipts.

The team used the findings to estimate that daily intake of BPS via dermal contact with the different types of paper was 4.18 or 312 ng/kg body weight/day for the general public and those occupationally exposed to them, such as people working at cash registers or in banks.

This is the first report of the distribution of BPS in different types of paper products but similar research should be carried out on food packaging to estimate the dietary exposure. This should be backed up by attempts to discover the environmental fate of BPS as well as its effects on human health so that a refined risk assessment can be carried out.

Related Links

Environmental Science and Technology 2012, 46, 6515-6522: "Bisphenol S, a new bisphenol Analogue, in paper products and currency bills and its association with bisphenol A residues"

Article by Steve Down

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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