Polyfluoroalkyl chemicals – An environmental and health impact comparison to short chain perfluorocarbon monomers used in Presspart/Portal plasma process.
Polyfluoroalkyl chemicals (PFAS) and pre-cursors such as perfluorooctanoic acid (PFOA) and perfluorooctanoic sulfone (PFOS) are used in several industrial applications such as carpeting, upholstery, textiles and sealants. PFOA serves as a surfactant in the emulsion polymerisation of fluoropolymers such as polytetrafluorethylene (PTFE).
Perfluorooctanoic acid (PFOA)—also known as C8—is a perfluorinated carboxylic acid produced and used worldwide as an industrial surfactant in chemical processes and as a material feedstock. Highlighted as a health concern by regulatory bodies it is subject to regulatory action and voluntary industrial phase-outs.
Polyfluoroalkyl chemicals (PFAS) have been found to be a potential environmental and human health hazard, due to their bioaccumulation properties.¹
PFOA has been detected in the blood of more than 98% of the general US population in the low and sub-parts per billion (ppb) range. Levels are shown to be higher in chemical plant employees and surrounding subpopulations. A study of workers living near a DuPont Teflon plant found an association between PFOA exposure and two kinds of cancer as well as four other diseases².
PFOA has been detected in the eco-system on every continent.
PFOA can form as a breakdown product from a variety of precursor molecules. In fact, the main products of the fluorotelomer industry – fluorotelomer-based polymers, have been shown to degrade to form PFOA and related compounds, with half-lives of decades. It has been argued that fluorotelomer-based polymers (such as PTFE) already produced might be major sources of PFOA globally for decades to come³.
The gaseous fluorocarbon pre-cursor used in the Pressart/Portal plasma coating system is a short chain (<C5), cyclic perfluorocarbon. It is synthesised by the dimerization of tetrafluoroethylene. Due to its volatility and chemical inertness, the fluorocarbon pre-cursor used can be found in some aerosolized foods⁴. The fluorocarbon pre-cursor is an ultrapure gaseous product with no added stabilisers or surfactants present. It has low toxicity and no potential chronic health effects⁵.
The Presspart/Portal plasma coating process uses both hydrocarbon and perfluorocarbon pre-cursors. The polymerisation of the monomers in the plasma process (carried out in a vacuum system) leads to the formation of a polymeric, highly cross-linked fluorocarbon outer layer. The formation of polymeric PFAS such as PFOA is not achievable in the process due to the random structure formation in the plasma environment, and because the pre-cursor gases are much shorter chain than C8 in the PFOA/PFAS structures.
The shorter perfluorocarbon/hydrocarbon chain pre-cursors produce an exceptionally stable, highly crosslinked structure when polymerised in the plasma process.
The level of crosslinking is in excess of 50%, an order of magnitude greater than typical polymer structures and as such is not susceptible to degradation⁶.
GC-MS extractive studies⁷, using methods universally accepted by the pharmaceutical regulatory bodies, of plasma coated pMDI’s show that fluorine containing extractables and leachables are not detected.
The resultant coating is uniform across the canister surface in the nanometre thickness range. Utilising just micrograms of ultra-pure gaseous material during each batch production cycle, the thin film coating deposited provides a solvent free continuous barrier.
This barrier layer is chemically inert, with c.200 x less material used than traditional FEP spray coatings for example. Furthermore, waste material and other harmful emissions associated with traditional spray coatings are eliminated alongside the potential for PFAS environmental and health impacts.
¹Emerging Contaminants Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoic Acid (PFOA) (Report). EPA. March 2014. 505-F-14-001
²Nicole, W. (2013). “PFOA and Cancer in a Highly Exposed Community: New Findings from the C8 Science Panel”. Environmental Health Perspectives. 121 (11–12): A340
³Washington JW, Jenkins TM (2015). “Abiotic hydrolysis of fluorotelomer polymers as a source of perfluorocarboxylates at the global scale”. Environ. Sci. Technol. 49 (24): 14129–14135
⁴It is listed by the Codex Alimentarius under number 946 (E946 for EU).
⁵Airgas safety data sheet Halocarbon C318
⁶European patent application No: 18203323.3 Portal Medical Ltd Carbon barrier layer
⁷Smithers extractable analysis of pMDI cans AA0220