bisphenol a
On April 18th of this year, Nalgene Outdoor, a division of Thermo-Fisher Scientific, announced plans to discontinue manufacturing its line of bisphenol A containing polycarbonate consumer products. The announcement coincides with Health Canada’s statement, released on the same day, of a 60 day public comment period on whether to ban the importation, sale and advertising of polycarbonate baby bottles containing bisphenol A.
Bisphenol A (BPA) was first synthesized by Aleksandr Dianin in 1891. It is a key monomer in the production of polycarbonate plastic and epoxy resins and is used to manufacture polymeric materials used for a variety of consumer products. BPA is used as an antioxidant in some plasticizers and as a polymerization inhibitor in PVC, polyvinyl chloride. It is used in the synthesis of polyesters, polysulfones, and polyether ketones. Bisphenol A is also an active component of thermal paper used for some types of duplication, like some cash register receipts. The epoxy resins are used to line food cans to prevent the food from taking on a metallic taste. Polyester-styrene, and polycarbonate plastics are used for some drink and baby bottles and other containers. These polymeric resins and plastics have also been used in some dental sealants and fillings, adhesives, protective coatings, flame retardants and water-storage tanks and supply pipes.
BPA is generally in its polymerized form when it is used to manufacture products but degrades into its monomeric form over time. This is a process that can be accelerated by heat exposure . The monomeric form can leach from its source into adjacent materials, such as into water or food products. Several studies have demonstrated detectable BPA levels in packaged foods that were contained in wrapping or cans coated with BPA.
Most human exposure to bisphenol A is believed to be via ingestion. This active form of BPA doesn’t appear to last long in the adult human biological system. It is believed that when adults ingest bisphenol A, metabolism primarily converts it to either bisphenol A-glucuronide or bisphenol A-sulfate in the liver, which is then excreted. Infants’ metabolism, however, is not as effective and some research suggests that active bisphenol A remains in their systems longer. In addition to being less effective at removing the chemical, there is evidence that infants are regularly exposed to disproportionately larger quantities of BPA.
There are several contributing factors that might explain why infants are exposed to a greater relative quantity of bisphenol A. Clear polycarbonate baby bottles containing BPA became very popular a few decades ago. In addition to using, scrubbing and reusing the bottles, often they are filled with formula that has been distributed in cans coated with epoxy resins. The filled bottles of formula are then heated in hot water or in the microwave. Infants and children have higher intakes of many widely detected environmental chemicals because they eat, drink, and breathe more than adults relative to their weight. In addition, infants and children spend more time on the floor than adults and may engage in certain behaviors, such as eating dirt or teething on plastic toys, that can increase the potential for exposure. What’s particularly concerning about these findings is that animal studies demonstrate that similar levels may result in neurodevelopmental and behavioral anomalies.
Bisphenol A was identified as having some estrogenicity in the 1930’s. Since then, more than a hundred studies investigating its endocrine disrupting properties have reinforced neural development concerns and suggested that in addition to developmental concerns, BPA may be linked to obesity and some forms of cancer. As with any difficult scientific investigation, there has been a great deal of discussion, debate and disagreement with the methodologies and the findings of various studies.
Health Canada’s public comment period follows a risk assessment process that was performed in consultation with a variety of stakeholders, including industry, as a part of Prime Minister Stephen Harper’s initiative known as the “Chemicals Management Plan.” The scientists involved reviewed all available data on bisphenol A and concluded in their assessment that bisphenol A exposure to newborns and infants is below levels that may pose a risk, but that the gap between current measured exposure levels and potentially detrimental exposure levels is not wide enough. Health Canada’s risk assessment does agree with the United States National Toxicology Program, under the National Institutes of Environmental Health Sciences and the European Union’s Food Safety Authority’s draft opinions in that there is a need for more studies.
In another agency, Environment Canada, scientists found that at low levels, bisphenol A can harm fish and aquatic organisms over time. This evidence of bioaccumulation brings into question the possibility of bioaccumulation in humans as well as the long term affects on the food chain. As global production is reported at over 3 million metric tons - and increasing in demand - it is reasonable to assume that if no action is taken, levels of bisphenol A in the environment, in ourselves and in our fetuses & infants will increase as well.
While many companies and government organizations are hesitant to take action, it is gratifying that some are willing to step forward and act, even if the information isn’t complete. Bisphenol A is an integral part of so many different consumer products that it would be difficult to find a single substitution for every application. Alternatives will be found on a case-by-case basis. There are already alternatives for drink containers and baby bottles. Developing new materials and alternatives for the other BPA products will be challenging. These challenges are great opportunities to discover Green Chemistry solutions to environmental, societal and industrial needs.