How harmful is it to drink from a plastic water bottle?

A recent study into a substance linked to low birth weight in newborns shows, again, that drinking from plastic bottles – and reusing them – can be dangerous.

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There is a growing appetite for reusable food and drink storage products that are safe to use. You only have to visit your local supermarket to see some of these products screaming "BPA-free" on their accompanying labels. After all, it's ridiculous (economically and environmentally) to constantly buy bottled water only to throw the bottle away each time. And even if you end up reusing those bottles, they could still potentially be harmful due to the leaching of chemicals into the water.

New research published in Environment International shows pregnant women exposed to bisphenol A (BPA) in high doses can potentially lead to low birth weight (LBW) in newborn children. BPA, first introduced in the Fifties, is used in the manufacturing of everyday plastics such as food containers, goggles, helmets, paper receipts, and the coating of metal tins and cans used to store food. Because of its wide use, almost everyone carries the compound in their blood at varying levels. 

The investigators analysed urine samples collected from the mother after delivery, and information on the newborns was collected using their birth certificates. A total of 452 mother-infant pairs took part in the study, which was carried out between 2012-2014. LBW babies made up 113 of these pairs, whereas the remaining 339 were matched controls. 

BPA has been shown as toxic in humans in previous studies. For example, the substance is known to be disruptive to the endocrine system, or the hormonal system, through the thyroid gland. The thyroid is a large gland in the neck, regulating growth by secreting hormones.

The compound has been implicated in the increased occurrence of obesity, where urine analysis was also used to compare BPA exposure with body mass index measurements. It's also been shown to affect brain and behavioural development in children. 

Another recent study shows similar correlation between BPA and LBW newborns, and that the link is more pronounced in baby girls. Led by Dr Almudena Veiga-Lopez of Michigan State University, this particular experiment tested the mother's blood for the substance during the first trimester, at the time of delivery and also from the umbilical cord after delivery. The tests were carried out to show levels for BPA and conjugated BPA, the form of the substance once it's been processed by the body.

The findings show for every two-fold increase in BPA in the mother's blood, babies (both male and female) weighed an average 55g less, but up to 183g less in female pregnancies. 

Governments and health regulators across the world have varying positions on the harmfulness on BPA, emphasising the need for researchers to continue investigating whether the substance is truly toxic. 

Canada has banned the use of BPA, whereas Sweden and Turkey have issued a partial ban, preventing its use in baby food and drink containers. However, the US and EU, including the UK's Food Standards Agency, still allow its use, stating current levels found in humans is below those which can cause harm. The substance has been reviewed for three years in a row by America's Food and Drug Administration (FDA) and the EU released their latest opinion in January this year. 

Although there is no definitive proof linking BPA exposure to low birth weight, this is still concerning given the greater potential health risks with children born with lower weight measurements. These include obesity, infertility and heart risks.

There is no doubt these experiments further the evidence of widespread contamination from plastic. In fact, a Harvard study showed participants' BPA levels increase after just one week of drinking from plastic bottles. But even removing just this one compound may not be enough.

Polyethylene terephthalate (PET) is the main polymer used to produce plastic bottles, and has previously been shown to affect the hormonal system.

Research has shown BPA can mimic the neurological properties of oestrogen. However, a more recent investigation published in Environmental Health Perspectives has shown that in some cases, BPA-free PET containers might leach more oestrogen-like chemicals.

There have been hoaxes stating BPA in plastic food and drink containers can lead to cancer, but the World Health Organisation has dismissed this, stating there is a lack of "convincing evidence" for this claim.

These latest studies will continue to add pressure on governing bodies to act, especially as consumers become aware of these hazards. Is this an issue in which the public will lead the way? Only time will tell.

Emad Ahmed writes about science and gaming. He tweets @ThisIsEmad.