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Fresh Reads from the Science 'o sphere!

Thursday, April 17, 2008

Health Advisory: Bisphenol A

An important news article in the Straits Times yesterday.

The United States National Toxicology Program (NTP) has published a report on the health effects of Bisphenol A (BPA) , an ingredient of polycarbonate plastics, which is commonly used to make plastic bottles.

The full report is 68 pages long and written mainly in technical language, so as part of Fresh Brainz public service, we have summarized important facts and key findings here:

1. What is BPA?

Bisphenol A is a chemical (C15H16O2) that is used in large quantities to make polycarbonate plastics and epoxy resins.

Polycarbonate plastics are commonly used to make drink bottles.

Other applications include CDs, impact-resistant safety equipment and medical devices.

2. How to tell if something is made of polycarbonate plastic?

Polycarbonate plastics are typically clear and hard and marked with the recycle symbol "7" or may contain the letters "PC" near the recycle symbol.

3. How do people get in contact with BPA?

The primary source of exposure to BPA for most people is through the diet.

BPA can migrate into food from food and beverage containers with internal epoxy resin coatings and from consumer products made of polycarbonate plastic such as baby bottles, tableware, food containers, and water bottles.

The degree that BPA migrates depends more on temperature of the liquid than the age of the container.

Hot liquids transfer more BPA than cold liquids.

4. Why is there cause for concern about BPA?

BPA has a molecular structure that allows it to mimic the female hormone estrogen - thus it has a potential biological effect.

In animal studies, high doses of BPA have adverse effects on the survival and growth of lab rodents.

What is of greater concern is that lower doses of BPA (similar to human exposure levels) have a variety of developmental effects in young lab animals.

These include behavioural changes, precancerous lesions in the prostate and mammary glands, altered prostate and urinary tract development and early onset of puberty in female mice.

While there is currently limited evidence for the adverse effects of BPA on the development of lab animals, the possibility that BPA can also alter human development cannot be ruled out.

5. What are the key conclusions?

A. The NTP concurs with the conclusion of the CERHR Expert Panel on Bisphenol A that there is some concern for neural and behavioral effects in fetuses, infants, and children at current human exposures. The NTP also has some concern for bisphenol A exposure in these populations based on effects in the prostate gland, mammary gland, and an earlier age for puberty in females.

B. The NTP has negligible concern that exposure of pregnant women to bisphenol A will result in fetal or neonatal mortality, birth defects or reduced birth weight and growth in their offspring.

C. The NTP concurs with the conclusion of the CERHR Expert Panel on Bisphenol A that there is negligible concern that exposure to bisphenol A causes reproductive effects in non-occupationally exposed adults and minimal concern for workers exposed to higher levels in occupational settings.

6. What does this mean for me? (Fresh Brainz opinion)

Infants and children should avoid using food and beverage containers made from polycarbonate plastics.

Adults, including pregnant women, are unlikely to be affected by BPA.

However, to be extra cautious, people should avoid using polycarbonate containers for hot food and drinks.

7. What are governments doing about this?

United States government - No official change in policy yet.

Canadian government - Health Canada will soon make an official announcement to designate BPA as a dangerous substance.

*Update (20 Apr 2008): Health Canada has announced a 60-day public comment period on whether to ban the importation, sale and advertising of polycarbonate baby bottles which contain Bisphenol A.

Would you like to know more?
Original draft report by NTP (PDF file)


Edgar said...

Do you know that Bisphenol A is in almost every tooth coloured filling there is on the market? Haha sounds like trouble if it was to be labelled dangerous.

Lim Leng Hiong said...

Interesting point. Not sure about the ubiquity of tooth-coloured fillings though, I assume majority of the dental work in Singapore use the standard silver amalgam type. All of my fillings are silver; that's the only type I can pay for.

Are there alternative tooth-coloured fillings that don't contain BPA?

Anonymous said...

I switched to using metal water bottles months ago. I dunno why, but it just suddenly occurred to me that plastic bottles might be dangerous. (I was using Nalgene bottles, which I thought was already very safe, but some reading up on the net put a question to that)

Cost me quite a bit, but I think it's worth it.

FB supporter

lh said...

Is it the same material used for those takeaways bowls/ packet drinks?

Edgar said...

A significant number of dental composites contain Bisphenol A in the Bis-GMA form. There has been a big shift from the silver-mercury amalgam fillings to the more aesthetic, adhesive kind of fillings. I believe most dentists place more tooth coloured restorations these days than dental amalgam fillings. There are alternatives to those without BPA but those with BPA are still very popular due to longevity, aesthetics and price.

You'd be surprised to find that tooth coloured fillings can cost as much as the silver ones.

This BPA thing has been around in the dental community for a while but the quality of research was rather dubious or cannot be easily extrapolated to an in vivo situation so it wasn't really a concern. However, with this report, more research might be directed towards finding the effect of chronic BPA exposure due to fillings 'cos its in the mouth 24/7.

Lim Leng Hiong said...

To FB supporter:

I used to have a polycarbonate bottle too, but it was a cheap type and sprung a leak, so I switched to a polypropylene bottle.

To LH:

No, takeaway bowls are made of polypropylene. I think that drink bags are made of polyethylene.

To Edgar:

Thanks for the interesting details. Yes, more research is needed to determine the long-term effects of BPA. In the meantime, parents should be aware of this report if their young children need to have tooth coloured fillings.

lh said...

Wiki says low density commercial polyethylene melting point is about 105-115 degrees. If the drink bags are made from them, won't those piping hot drinks almost melt them?

Anonymous said...

Is Nalgene polycarbonate or polypropylene?

And which brand are you using now? It's still plastic right?

FB supporter

Anonymous said...

Silver-MERCURY amalgam? Isn't mercury supposed to be poisonous? Luckily, I have no tooth filling. : P


Lim Leng Hiong said...

To LH:

I think its polyethylene, at least those plastic bags that I drink hot tow huay tsui from. I should save one of those bags and pour some boiling water inside to see what happens to it.

To FB supporter:

Check the bottom of the bottle. If there is a "PC" or "7" then it's polycarbonate. My current bottle is a "PP" / "5" plastic bottle. I don't believe there is any BPA in polypropylene.

I think mercury in tooth fillings is stabilized by other metals in the amalgam, Edgar knows more details.

Heh, if it's not one thing, it's another.