Health Canada just published the results of its survey of bisphenol A (BPA) in canned drink products. Seventy-two canned soft drink products (all carbonated except for four tea products), representing a Canadian market share of 84% or more, were analysed for BPA. Health Canada isn’t concerned; should you be?
The assay method could detect 0.045 mcg/L (note: 1 mcg/L = 1 part per billion). Two samples of each product were analysed (each sample was divided into two subsamples) and the results averaged.
BPA was detected in samples from all but two products; the exceptions were tonic water products containing quinine, a chemical that may interfere with the BPA assay. BPA concentrations were reported as being “low” – ie.,
- < 0.5 mcg/L (75% of products);
- < 1 mcg/L (85% of products);
- average BPA concentration (all products): 0.57 mcg/L
Take a look at the Table that accompanies the study – find how much BPA is in your favourite brand of pop!
Health Canada opines that the range of concentrations (0.032 – 4.5 mcg/L) could be due to differences in the coatings of the drink cans (e.g., type used, amount) or sterilization conditions (e.g., temperature, length of time) used by the different companies. The report also suggests that exposure of the cans to sunlight (e.g., during storage) could increase the concentration of BPA that leaches into the drinks.
Health Canada tells us not to worry. The provisional tolerable daily intake (TDI ) is 25 mcg/kg of body weight per day. Health Canada provides a nice calculation that indicates that to reach this TDI, the average 60 kg adult would have to drink 940 cans of soft drinks per day. But take a look at a few of our calculations, below, based on a higher intake of sodas with higher BPA concentrations.
Why are we concerned?
- Health Canada tells us that this is a “snapshot” of what’s in the drinks – i.e., perhaps not a representative sample. What would a more comprehensive study reveal?
- Is Health Canada’s safety limit (TDI) robust? Some authors suggest that much lower concentration thresholds need to be set, as even very low concentrations of BPA could be harmful.
- What are the reasons for the huge range in BPA concentrations in the various products? Can liners? Exposure to heat or sunlight during storage? Something else?
- Why should consumer products like canned drinks contain any chemicals like BPA?
- Remember that soft drinks are just one source of BPA – we are being exposed to this chemical through many other consumer products.
In our September blog about BPA, we wrote that one of missing pieces of the BPA puzzle is how much BPA is actually present in consumer products – it is encouraging that studies like this one are being done and reported to the public. In October 2008, we reported that the federal government had decided to take a precautionary approach in characterizing the risk from BPA. But is that really what they’re doing with soft drinks?
| What are we drinking? Here’s Health Canada’s calculation for a 60 kg person 1 can/day with BPA 0.057 mcg/L : 0.57 mcg/L x 0.355 L = 0.202 mcg BPA/can. This means 0.202 mcg/60 kg person = 0.003 mcg/kg/day or 0.012% of the TDI. But what if the person drank 6 cans of the more BPA-laden soda each day? A couple of brands of soda contained BPA in a concentration of 1.1 mcg/L: 1.1 mcg/L x 0.355 L = 0.39 mcg BPA/can. Six cans would contain 2.34 mcg BPA. 2.34 mcg/60 kg = 0.039 mcg/kg/day or 0.156 % of the TDI A couple of brands of soda contained BPA in a concentration of over 4 mcg/L – the highest concentration was 4.5 mcg/L:
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And some of us weigh less than 60 kg.; for smaller people, the effect would be worse.
For more information:
Health Canada’s Survey of BPA in canned drink products. March 2009:1-8. http://www.hc-sc.gc.ca/fn-an/alt_formats/hpfb-dgpsa/pdf/securit/bpa_survey-enquete-can-eng.pdf
Update on Canada’s Chemicals Management Plan (includes Bisphenol A) – to January 30, 2009:
http://www.chemicalsubstanceschimiques.gc.ca/challenge-defi/batch-lot_2_e.html#Update
BPA research & monitoring activities: This site mentions a targetted survey of BPA in packaged drink products (e.g., glass, plastics, cans – includes soft drink products)
http://www.chemicalsubstanceschimiques.gc.ca/challenge-defi/BPA_Research_fs_e.html
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What the heck is a “mcg”? My guess is it’s a “millicentigram” or 100,000th of a gram in which case 1 mcg/L = 0.00001 g/L or 0.01 mg/L which equals 10 ug/L or, loosely speaking (which lawyers should never do) = 10 ppb, not 1 ppb. Strictly speaking, the terms “ppm” or “ppb” should not be used in describing the concentrations of solutions since you are comparing “apples with oranges”, the apple being a weight unit (in grams) and the orange a volume unit (in litres). Great info in your news letter, Dianne, thanks!
Dear Dr. Duncan – Thanks for your comments. In my “other” world as a pharmacist, instead of typing ” ug ” (using the symbol for “mu”), which means “microgram”, we always use “mcg” (also meaning microgram). This avoids possible errors in medication dosing (as ug can be misinterpreted as mg, not a nice factor by which a patient could be overdosed). As well, I have done lots of research examining toxic levels of chemicals, and find that “ug” and “mg” are frequently (and inappropriately) interchanged, so I find “mcg” the safest and clearest abbreviation to use.
And while I agree that “ppb” should not typically be used in this context, since Health Canada’s report stated, on page 2, in its footnote, that
“1 ug/L is equivalent to 0.000001 g/L or 1 part per billion (ppb)”, I thought it would be helpful to provide the alternative terminology. We would appreciate your bringing it to the attention of Health Canada that they erred in their report by providing an incorrect conversion factor.
Jackie Campbell
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