Researchers from PlastiPure, CertiChem, and Georgetown University tested products made from polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polylactic acid (PLA), polyethylene terephthalate glycol (PETG), and polyethersulfone (PES) and said that all show detectable EA levels.

PlastiPure (Austin, TX) has created and markets a line of plastics it says are EA free called PlastiPure-Safe. CertiChem, also based in Austin, develops testing assays for detecting hormonal activity in different materials, including plastics. At the 2010 SPE Polyolefins conference in Houston, PlastiPure presented preliminary testing that it says showed EA in various plastics.

The researchers used what they called a "sensitive, accurate, repeatable" testing method, built around a roboticized MCF-7 cell proliferation assay to quantify the EA of chemicals that leached into saline or ethanol extracts. MCF-7 is a breast cancer cell line that was isolated in the 1970s and is accepted as estrogen responsive.

Some of the plastic samples were exposed to common-use stresses for the products they were contained in, including microwaving, UV radiation, and/or autoclaving. The plastic samples consisted of 4-mm squares cut from various products and sterilized prior to testing to remove any bacteria.

The researchers claim that even when EA-free monomers and additives are used in the production of a resin, the final plastic item must still be tested for release of chemicals having EA because manufacturing processes or common-use stresses can convert EA-free chemicals to chemicals having EA.

EHP, which is a peer-reviewed journal published by the National Institute of Environmental Health Sciences, published the paper on March 2. The paper's authors say their research is groundbreaking because its quantifies levels of EA across multiple BPA-free materials and consumer plastic products.

The paper found that 92% of the individual plastic product samples that were tested came back positive for EA, even when not exposed to common-use stresses, including baby bottles, water bottles, rigid food packaging, bags, deli containers, and flexible wrap.

BPA, or bisphenol A, which is a component of polycarbonate (PC) plastic, had successfully been targeted by consumer, environmental, and public health groups, resulting in a de facto ban on PC for use in items like water bottles, with makers of such bottles switching to new materials and prominently displaying "BPA-free" labeling on their products after many retailers announced that they would not carry BPA-containing bottles. 

 * Number of unstressed plastic items with contents having EA using standard EtOH Extraction Protocol