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SCIENCE & RISK ASSESSMENT
In order to assess the safety of substances and understand potential human health or environmental risks resulting from exposure, science plays a crucial role. Bisphenol A (BPA) is one of the world’s most studied chemical substances.
A multitude of laboratory and regulatory studies have been conducted over the years to better understand the impact from exposure and potential health effects from BPA.
For science to responsibly guide the perceptions of the public, the media, and regulators, they have to be assessed on the basis of three elements:
- Study design
- Laboratory quality practices
- Robust statistics and data transparency
Such parameters ensure that studies are easy to reproduce by other laboratories and scientists and observations remain consistent.
While thousands of studies have been published over the years on BPA, not all meet the above criteria. The American Chemistry Council compiled a list, while not intended in being exhaustive, which includes a summary of key studies that can have been considered significant because of their scope, findings or that have generated significant public interest.
The main themes covered in the majority of studies analyzing BPA’s exposure include the following topics: low dose theory, migration and endocrine disruption.
In recent years, some scientists have advanced a hypothesis which suggests that exposure to extremely low doses of certain substances could cause adverse health effects in humans, whereas no such effects would be observed at higher doses of the same substance.
Scientists call this a non-monotonic dose-response (NMDR), meaning that the response does not always increase/decrease as the dose increases/decreases.
In toxicity testing on animals, a conventional "monotonic dose-response" shows a consistent increase in (adverse) effects along the dose range. The slope of a NMDR curve, however, changes direction along the dose interval studied resulting, for example, in U-shaped or inverted U-shaped curves. Low dose effects are non-monotonic responses occurring at lower doses than those used in regulatory toxicity studies.
This "low-dose hypothesis" has been thoroughly tested for BPA with a series of comprehensive studies. These studies have been undertaken by governmental agencies, independent laboratories and the industry, using accepted test methods and rigorous Good Laboratory Practices (GLP) guidelines.
The weight of scientific evidence provided by comprehensive multigenerational studies using accepted measures and quality protocols clearly supports the safety from exposure to BPA-based applications. They confirm that there is no basis for human health concerns from exposure to low doses of BPA. Regarding any studies that demonstrated opposite conclusions, experimental data often contained errors. Conclusions are often based on possible statistical mistakes rather than on actual biological phenomena.
More than 99% of all BPA produced worldwide is converted into polymers, mainly epoxy resins and polycarbonate.
Like with any chemical process, unavoidable trace levels of BPA (so-called free or residual BPA) can occur in the final polymer. The amount of free BPA in the polymer, however, does not play a key role in the question of BPA-migration. This is because in many cases the dominant mechanism responsible for the release of BPA from the polymer surface into the contacting aqueous liquid is hydrolysis, not the amount of free BPA monomer.
Several high quality migration studies on BPA, which included daily use conditions such as heating, microwaving, machine-dishwashing, rinsing, sterilizing, have repeatedly shown that migration from BPA-based polycarbonate is very low and far below the safety levels set by the authorities. It does not pose a health risk to the consumer under normal handling and use of the products.
In fact, scientific studies have demonstrated that trace amounts of BPA that might enter the human body are rapidly "metabolised" into an inactive form, no matter how old the person is. These tiny traces of so called conjugated BPA are then excreted from the body within a day with no health effect whatsoever.
The World Health Organisation (WHO) defines an endocrine disruptor as a “substance or mixture that alters function(s) of the endocrine system and consequently causes adverse health effects in an intact organism, or its progeny, or (sub) populations.”
Certain natural, the so-called "phyto-estrogens", and man-made substances, co-called “endocrine active” substances, can exhibit properties that mimic hormones’ properties.
Like many naturally-occurring substances and everyday foodstuffs, BPA shows very weak, estrogen-like activity, but only at extremely high levels to which humans realistically can never be exposed to. This measurable estrogen-like activity is still significantly lower than that of natural phyto-estrogens, contained in every day food, e.g. in soy beans, coffee, or carrots.
For BPA, a comprehensive scientific evaluation, following weight-of-evidence principles was carried out by the European Food Safety Authority (EFSA) in 2015. EFSA reviewed all available scientific studies on BPA, including the literature on potential endocrine-related effects of BPA. On endocrine disruption, EFSA’s expert panel concluded that “based on the WHO criteria, it is not possible to conclude that BPA is an endocrine disruptor”.
In its screening exercise in the context of the development of criteria for identifying endocrine disruptors, the European Commission found no conclusive evidence of endocrine disrupting effects for BPA with respect to human health. In each of the investigated options based on the WHO-criteria, BPA is not identified as an endocrine disruptor with regards to human health.
Scare stories about avoiding polycarbonate plastic or epoxy resins for fear of adverse health effects due to BPA continue to be published. However, none of these adverse health claims have been proven to be relevant for human health.
The weight of scientific evidence regarding BPA is clear: Consumers may only be exposed to very low levels of BPA and there is no risk to humans, wildlife or the environment from products made from BPA-based materials in their intended uses.