David Suzuki, Canada’s high priest of all things natural is at it again, raising money that is. The David Suzuki Foundation is mailing out requests for donations with statements like “We must stem the flow of toxic chemicals into our bodies...” and a “Sustainable Shoppers Guide” that cautions you about “a dirty dozen ingredients to avoid in your cosmetics”. Today’s message is about cyclosiloxanes.
The Myth
It is obvious, neither Suzuki nor his disciples at the foundation know much about chemistry. Let’s look at the second of the bad dozen. The “guide” says:
CYCLOMETHICONE and siloxanes: Widely used in moisturizer, makeup, hair products, etc. May interfere with hormone function and damage the liver. Harmful to fish and other wildlife.
Silicon and its Chemistry
The element silicon (more correctly termed silicium) is widely found on earth. In fact, it is the second most common element in the earth’s crust and accounts for about 25% of all atoms there. Chemically, it is related to carbon and follows it in the period of the Periodic System of Elements. Therefore, like carbon, it connects via FOUR bonds with other elements, preferably oxygen atoms.
Cyclomethicone is a general term used for cyclic dimethylsiloxanes, a series of five or so structurally related compounds. Their formula can be described as [-O-Si(Me)(Me)-]X, where Me stands for a methyl group and n equals three to seven. The most common cyclomethicones have X being either 4 (a compound commonly referred to as “D4”), or 5 (D5).
Both D4 and D5 are synthetic silicon derivatives which have been around for several decades. They are common ingredients in caulking materials, water repelling substances, hair conditioners, shampoos, moisturizers, antiperspirants, body lotions, and the like. Environment Canada identified some 6,000 commercial products containing cyclomethicone compounds.
Past Reviews
Both D4 and D5 have been reviewed by various organizations for their health and environmental effects, for example, by the European Commission [1], Environment Canada [2], Health Canada [3], and the Nordic Council [4]. None of these reviews or other scientific papers found any problems for either compound in terms of cancer, mutagenic, teratogenic, or even acute toxic effects on any mammalian species. The Europeans concluded that “Cyclomethicone (D4, D5) does not pose a risk for human health when used in cosmetic products.” Health Canada concluded the same.
Health Canada concluded that “A careful analysis of exposure through cosmetic products showed that the substances D4, D5, and D6 do not present a risk to human health.”
Environmental Effects
In terms of effects on fish and wildlife, laboratory tests with prolonged exposure of Daphnia and similar species have shown toxic effects at around 0.01 ppm. The problem with such measurements, however, is that they cannot readily be used for an assessment in natural conditions. Such laboratory tests typically use water with little or no dissolved minerals and natural particulates as obtained from photosynthesis, or simply carried in by a tributary. In the presence of such particles, trace levels of either D4 nor D5 would rapidly become adsorbed to such and effectively be deactivated. In the absence of such natural particulates, the Daphnia organisms themselves become the adsorbing “particles”. There is a clear relationship between adsorption from water onto particles and the substance’s octanol water partition coefficient (Kow). Environment Canada uses for its considerations the extremely high value of logKow = 9.06. Any compound with such a high logKow value would very rapidly adsorb to any matter suspended in water. This is also apparent from experimental investigations by the Nordic Council’s Nordic Environmental Action Plan 2005-2008. Values in sewage sludge were in the order of several 1000 microgram/kg, while occurrence of D4, D5, and D6 in sewage treatment plant effluents was extremely low, mostly below detection limit [4].
Bioaccumulation in the food chain has also been shown to be absent. Experimental data show a value of less than one, meaning no bioaccumulation potential. No toxic effects could be observed for any higher organisms such as fish.
The US also permits the use of dimethylsiloxanes as ingredients in nonfood pesticide products, i.e. for use in pesticide applications [5]. Obviously, there is no concern about their environmental effects.
Cyclomethicones in the Canadian Environment
Environment Canada’s data on actual occurrence of D4 are those of the Nordic countries (references Norden, and Kaj et al, both 2005) and some US data from the 1980s and 1990s. The only report on actual field data in Canada are from an unreferenced personal communication, two reports by Powell with all values below detection limit (except for Toronto Harbour sediments) and zooplankton in Algonquin Park (also below detection limit).
Frankly, with all that expertise and staff available to Environment Canada at its premier Canadian research facility, the Canada Centre for Inland Waters in Burlington, Ontario, it ought to be able to do better. If these siloxane materials are nowhere to be found in the environment (except the highly polluted Toronto Harbour, where its source could be from foreign ships) why bother trying to regulate it at all? At best, this appears to be a half-hearted exercise in futility, at worst just another bureaucratic endeavor without benefit to anyone.
Environment Canada’s View
On Feb. 3, 2011, the Governor General of Canada, on the recommendation of the Ministers of the Environment and Health, ordered D4 to be added to the list of Toxic Substances in Schedule 1 of the Canadian Environmental Protection Act, 1999. In the justification, it was noted that “it was concluded that D4 does not pose a risk to human health” but also that “D4 poses a risk to the environment in Canada since concentrations in the environment near some discharge points from industrial operations and municipal wastewater treatment plants are believed to be sufficiently high to cause harm to sensitive organisms.”
Michael Brook, professor at the Department of Chemistry, McMaster University, Hamilton, Ontario, has been studying siloxanes for many years. His comments published in ACCN [6] are most illuminating. Environment Canada, which normally takes its cues from other organization’s findings, has “jumped the gun” and proposed to limit D4 in effluents to 0.017.3 ppm or 0.017 mg/L. Brook states that “there is no evidence that the proposed [Environment Canada] regulation will have any positive impact on the environment, although it will impose an economic penalty on D4 use in Canada.”
I would go further. The proposed regulation of these siloxanes in Canada is counterproductive and liable to cause more harm than good.
Conclusion
The Suzuki organization is trying to cash in on the widespread fear of “chemicals” with strange names, with innuendos, unproven associations and implications. This fear-mongering is bordering on superstition. Regrettably, Environment Canada seems to be falling for that fear too.
If you prefer facts over fiction, may I suggest: Rather than sending your money to that organization, RECYCLE their GUIDE and BUY a copy of my book CONVENIENT MYTHS instead.
References
[1]
European Commission, 2010,
[2]
Environment Canada, 2008,
[3]
Health Canada, 2010,
[4]
Nordic Council, 2005,
[5]
US EPA, April 2011,
[6]
ACCN, 2011,
