Tag Archives: fluorinated chemicals

Removing fluorines from chemicals = greener CFCs?

Removing stubborn fluorines detoxifies CFCs.

Jun 17, 2010

Douvris, C, CM Nagaraja, C-H Chen, BM Foxman and OV Ozerov. 2010. Hydrodefluorination and other hydrodehalogenation of aliphatic carbon-halogen bonds using silylium catalysis. Journal of the American Chemical Society 132(13):4946-4953.

Synopsis by Adelina Voutchkova
A new method for removing fluorines from fluorinated chemicals offers a promising method to detoxify some types of organohalogen pollutants, such as CFCs.

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A new method to take the fluorine atoms off of fluorinated chemicals may be a promising way to detoxify them, according to an article published in the Journal of the American Chemical Society.

The new method would selectively remove fluorines from chemicals, such as chlorofluorocarbons (CFCs), a class of compounds notorious for causing global warming. Removal of fluorines is considered highly challenging as fluorine atoms are known to bind very strongly to a molecule’s carbon framework.

The method could be more broadly applied to other organofluorines, including perfluorinated compounds (PFCs) such as PFOA and PFOS. PFOA is a chemical used in nonstick cookware and PFOS was used in anti-stain fabrics and water resistant coatings. They do not biodegrade and can only be partially recycled, therefore, defluorination to polyethylene (nylon) would be one strategy to avoid accumulation of PFCs.

Many organofluorine compounds have been banned or removed from manufacturing or industrial use due to their severe potential hazard. CFCs, for instance, were taken out of refrigerants because they can destroy the Earth’s protective ozone layer. Some others that were phased out include polychlorobiphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF). The compunds contaminate the environment and contribute to global problems. CFCs and some of their chemical cousins that replaced them have tremendous global warming potentials. So much so they have been called “super-greenhouse gases.”

In addition, harmful derivatives of these chemicals can persist in the environment where they travel through food chains and accumulate in animals and people. The health effects associated with the compounds are varied but include cancer, reproductive problems and developmental changes.

Removal of fluorines from chemicals – a process called defluorination – has been generally viewed as a way to neutralize existing over stocks of these chemicals.

Researchers from Texas A&M and Brandeis University developed the chemical defluorination technique. They used silicon and boron-containing solids to efficiently defluorinate CFCs under mild conditions.

Although this is an advancement, the technology has some significant drawbacks. The process requires large amounts of a sacrificial chemical to abstract the fluorine. The disposal of this by-product would itself be problematic, and there is no evidence it can be recycled. In addition, the report indicates that tetrafluoromethane, the smallest fluorinated chemical and commonly used in refrigerants, resists defluorination under research conditions.

Future endeavours will undoubtedly be aimed towards developing defluorination processes that overcome these drawbacks.

Towards shorter – and safer – fluorochemicals?

Towards shorter – and safer – fluorochemicals?

Posted by Adelina Voutchkova and Heather Stapleton at Mar 16, 2010 10:20 AM | Environmental Health News

A recent article in Chemical and Engineering News deems the new replacements for the widely used fluorocarbons as “safer” than their predecessors, but does not delve into the seemingly lack of evidence.

The newest replacements for the ubiquitous chemicals that repel grease, water and stains on fabric, cookware and food packaging are regarded as “safer” than their predecessors, reports Stephen K. Ritter in a recent Chemical and Engineering News article. The detailed article explores the chemical and regulatory history of an ongoing effort to find safer alternatives for the perfluoroalkyl compounds (PFCs), specifically the perfluorinated sulfonates (PFSAs) and perfluorinated carboxylate acids (PFCAs). Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA or C8) are the best known of these.

Due to concerns about bioaccumulation, persistence and toxicity, PFCs are being phased out through a now voluntary program headed by the U.S. Environmental Protection Agency (EPA).

While Ritter does a good job of covering a complicated story, the article could have emphasized that the reported safety claims for the new replacements are seemingly premature and made without enough solid research evidence.

Ritter explains that the new chemicals – reformulated with fewer carbon atoms and thus called “short chain” fluorocarbons – are an intermediate step on the path to finding less toxic solutions. He goes on to say that these replacements are just as persistent as the prior chemicals but “aren’t as bioaccumulative and appear to have a better toxicity profile—which is still being confirmed by testing—and are thus considered sound replacements.”

These and other statements throughout the article hint that not enough is known about the toxicity of the replacements.

PFCs are ubiquitous in animals, people and the environment – including places as remote as the Arctic – due to their high production volumes and worldwide transport in water and air. This emphasizes that global, rather than local, approaches to reducing environmental concentrations of these fluorinated chemicals are necessary. Animal and very limited human studies link high exposures to a number of health effects, including developmental problems, liver toxicity, immune system problems and thyroid disease.

Industry and the EPA are both supporting the shift to new, shorter chain replacements. This could be because research suggests the molecules with six or fewer carbons may bioaccumulate less. While that sounds positive, it is not at all clear how fewer carbons will affect bioavailability and toxicity.

In addition, EPA’s Office of Pollution Prevention and Toxics has not yet decided if importing long-chain PFC chemicals, in raw form or in consumer products, will continue. This may represent a significant concern given the large amounts of imports from countries like China, which still produces, uses and sells PFOS.

Although initiatives that aim to introduce safer alternatives to existing commercial chemicals should certainly be encouraged, the safety profiles of the alternative chemicals should be evaluated conclusively before widespread production and use of the new chemical begins. We have witnessed prior cases where lack of such thorough analysis of an alternative chemical has had dire consequences on human and environmental health. In the case of this article, further critical analysis about the safety of replacements is needed when so little is known about the health and environmental risks of the new versions.