Canadian Plastics

Understanding BPA

If you're reading this month's rant looking for another tech tip, I'm going to ask your indulgence in a little side track. This month, I'm going to briefly talk about a chemical compound that's a hot ...

November 1, 2008   By Jim Anderton, Technical Editor

If you’re reading this month’s rant looking for another tech tip, I’m going to ask your indulgence in a little side track. This month, I’m going to briefly talk about a chemical compound that’s a hot news item again in Canada: bisphenol A (BPA).

BPA has been classified by Health Canada as “toxic to human health,” and as industry professionals, it’s vital that we understand this issue. If you’re like me, friends and family have already asked you about the controversy. We need to defend the Canadian industry, regardless of where we fit into the plastics sector, so here’s the truth about BPA.

BPA is a chemical compound made by a “condensation reaction” of acetone, a common solvent, (e. g. nail polish remover) and phenol, a common alcohol. Phenols are more common that you think: many sore throat medicines use phenols as a major ingredient.

The resulting BPA molecule has three primary uses in our industry. The first is as a basic monomer from which polycarbonate resin is made. The second is as a precursor in epoxy resin manufacturing and the third is as an additive.


Additive uses are typically as an antioxidant in plasticizers and as a polymerization inhibitor in PVC production. If BPA use was restricted to vinyl siding, there probably wouldn’t be an issue, but the use of PC in baby bottles, sports water bottles and the common application of epoxy resins as a liner in “tin” cans used in the food industry means that human exposure is inevitable. And “exposure” is the key word.

Unfortunately, the media paint BPA as “unsafe” even though the issue is far from black and white. The truth is that exposure generates risk factors, a statistical measure of the likelihood of a disease or illness, a concept more difficult to sell compared to the simplicity of well-known health threats like ionizing radiation or cigarette smoking.

Threshold exposure levels that cause harm vary widely depending on the study, with the U. S. EPA establishing a threshold level of 50 micrograms per kilogram of body weight as a safe maximum. Typical exposure of an infant (the most potentially vulnerable population) feeding from a PC baby bottle is on the order of 13 micro- grams per kilogram, although some studies suggest that even this low exposure may be dangerous.

Although the science is inconclusive, the media coverage has been negative enough to drive major retailers like Wal- Mart, Toys-R-Us and Mountain Equipment Co-op to demand BPA-free formulations.

Expect BPA to disappear as an additive, but remember that it’s also a monomer used in PC polymerization. Even with the removal of BPA in additives, trace amounts are still detectable if PC products are exposed to conditions that degrade the plastic.

This does not mean that PC products are unsafe. If consumers are worried about the trace amounts of detectable BPA in PC consumer goods the answer is simple: clean them according to the manufacturer’s directions and keep them out of the microwave oven.

The more the public knows about BPA and polycarbonates in consumer goods, the better off the industry is, regardless of the resin you’re processing.


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