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Bottle and Can Chemical Linked to Heart Problems

It’s estimated that nearly everyone carries the plastics chemical Bisphenol A in their bodies. However, those with the highest levels have the highest risk of heart disease, according to the latest findings.

Bisphenol A (BPA) is one of the world's most heavily produced chemicals. 2.2 million tonnes are produced every year, and it’s used to make PVC pipes, epoxy resins that line food cans, food packaging and baby feeding bottles.

The insides of some food cans contain BPA. This coating allows canned food to be heated to kill off bacteria without the metal in the can contaminating the food.

Animal studies suggest BPA can have a wide range of health effects. However, it's not clear whether these animal studies are relevant to humans.

Two studies

In 2008, Professor David Melzer of the Peninsula Medical School at the University of Exeter led a research team that analysed data from the Centres for Disease Control and Prevention in the US.

They found that high BPA levels were linked to a higher risk of heart disease, diabetes and elevated liver enzymes.

Critics pointed out that, because the original study looked at so many things, something was bound to seem risky just by chance. So, the question that needed answering was whether the link between BPA and heart disease was anything more than a statistical blip.

Link to heart disease ‘confirmed’

No, says Professor Melzer. His team analysed a new set of data from the US collected in 2005-2006. Surprisingly, average BPA levels were 30% lower in the new study. Yet people with the highest BPA levels still had a significantly higher risk of heart disease.

"It is very clear that the connection is still there," says Professor Melzer. "It underlines the question mark we found between BPA and human health."

To estimate the size of the risk they found, Professor Melzer calculates that a 60-year-old man in the top third of BPA levels (over 3.5 nanograms/millilitre urinary concentration) has a 10.2% chance of having heart disease. A 60-year-old man in the lowest third of BPA levels (under 1.4 ng/mL urinary concentration) has a 7% chance of having heart disease.

"As urinary concentrations of BPA are an approximate marker of longer-term BPA exposure, we expect these figures underestimate the true effect size. We can’t say by how much, as no long-term exposure data are available," says Professor Melzer.

It's not clear why BPA levels were lower in 2005-2006 than in the earlier study. Professor Melzer notes that public awareness of possible BPA health effects may have contributed to the decline, though nobody really knows.

But, at these lower overall BPA levels, there was a trend – but no significant association – between BPA and diabetes or liver enzymes. However, when data from both years was pooled, these links were highly significant.

While the latest study shows a link between BPA and heart disease, it doesn’t prove that BPA causes heart disease. Such proof may be hard to come by, as definitive studies would mean giving people BPA to see what happens. But longitudinal studies that track people with high BPA levels over time might provide clearer answers.

More answers needed

Professor Tamara Galloway, Professor of Ecotoxicology at the University of Exeter, and senior author of the paper, says "We now need to investigate what causes these health risk associations in more detail and to clarify whether they are caused by BPA itself or by some other factor linked to BPA exposure.

“The risks associated with exposure to BPA may be small, but they are relevant to very large numbers of people. This information is important since it provides a great opportunity for intervention to reduce the risks."

BPA: Possible health effects

According to the Food Standards Agency (FSA), Bisphenol A is one of a large number of substances that may have the potential to interact with human hormone systems. These substances are referred to as 'endocrine disrupters'.

The FSA says particular concern has focused on the sex hormones because of their important roles in the development of our reproductive systems. It says that, although there is evidence that some wildlife species have been affected by coming into contact with endocrine disrupters, there is still no conclusive evidence that exposure to these chemicals is harmful to humans.

What regulations protect consumers?

European rules lay down general safety requirements for all materials that come into contact with foods. These regulations (European Framework Regulation (EC) No. 1935/2004) require that materials and articles containing BPA, such as some can coatings, do not make food harmful. The regulations also make sure that they do not change the nature, substance or quality of the food.

In addition, The Plastic Materials and Articles in Contact with Food (England) (No.2) Regulations 2006 permit the use of BPA in the manufacture of plastic materials and articles intended to come into contact with food, provided that no more than 0.6 mg/kg migrates into the food.

Hattie Lambrou, a spokeswoman for the Food Standards Agency, tells us by email that the FSA, together with the European Food Safety Authority and the European Commission, have concluded that “exposure of UK consumers to bisphenol A (BPA) from all sources, including food contact materials, is well below levels considered harmful”.

She says “The EFSA assessed the health impact of BPA in 2006 and established a tolerable daily intake (TDI), which is the amount that can be eaten every day, over a whole lifetime, without causing appreciable harm.

“In July and October 2008 EFSA confirmed that this TDI would also apply to infants and pregnant women. The FSA has estimated that a 3-month-old bottle-fed baby that weighs around 6 kg would need to consume more than four times the usual number of bottles of baby formula a day before it would reach the TDI.”

The latest study by the University of Exeter team appears in the online journal PLoSOne.