PEGs – Haters gonna hate but there is another side to this story.
PEGS or Polyethylene Glycols are on many brands ‘avoid’ lists either because they don’t want anything made from unsustainable resources (petroleum) or because they have done their google research and found them to be terribly bad, pure evil in fact.
As with most things in life, I feel it is all a bit more complex and interesting than that.
Before I go on I want to make it quite clear that I recognise that yes, these PEG’s are made by big chemical companies some of whom have been implicated in some very bad things. I’m also sure that there are some who would claim that despite any awesome technological breakthroughs the world would be a better place if these companies had never existed. But these companies do exist and so do PEGS and as such it makes sense for me as a cosmetic chemist and teacher to try, at least a little bit, to understand these chemicals so that we (me, my clients and my students) might better be able to relate to these mis-understood molecules either to dismiss them completely, to learn from them or to actually safety use them. With that in mind, for the purposes of this scientific investigation I am going to separate the chemistry from the company (s), just so we can get our minds into a more neutral and open space and focus on the technology that’s on the table.
So, what are PEGS?
P=Poly (many, usually hundreds or thousands of something stuck together and is short for ‘polymer’).
E = Ethylene (A hydrocarbon – a chemical that is made from just two things 1) hydrogen and 2) carbon. It is a colourless gas that is usually derived from petroleum. It smells sweet and is widely used in the chemical industry to help with reacting one thing with another and especially in building polymers such as PEGS)
G = Glycol (the family name for a bunch of chemicals that belong to the alcohol family – not the alcohol we drink but another type of alcohol. These alcohols have two OH groups attached to different carbons whereas ethanol (The drinking alcohol) has only one OH (hydroxyl group).
PEGS = Polymers of Ethylene Glycol. Ethylene Glycol = This is what you get when you combine a particular glycol with ethylene (there is more than one type of glycol). It transforms the ethylene gas into a liquid that retains its sweetness and can be further reacted to form materials as diverse as fabrics for clothing, plastics for packaging, cosmetic ingredients and pharmaceutical medicines.
While pretty much all of the ethylene glycol pumping through your friendly local chemical factory is petroleum derived it doesn’t HAVE to be. Ethylene, a key starting material in this synthetic chemical is produced naturally by plants as they ripen and age so we could capture that rotting veg and channel it into our factories if we so wished. Chemical producers Dupont Tate and Lyle nailed the ‘natural chemical’ process for glycols back in 2008 with the launch of Zemea (1,3-propanediol) showing that there is a space in the green future for all-natural PEGs, well, chemically anyway. Public acceptance doesn’t always follow as these things still sound and read like those dreaded chemicals…..
So PEGS are polymers of ethylene glycol and we have found out that these things COULD potentially be made from sustainable sources so we can tick the ‘environmentally responsible’ box but what are they used for?
There are many different PEGs used in many different industries but those that we are most interested in are those making their way into the pharmaceutical and cosmetic industries. Here they are prized for their safety (chemical inertness – very low potential to react with other things, very low impurity levels) and flexibility – you can create polymers of different sizes and shapes to cover a whole range of actions including:
- Solubilising of actives – this helps to ensure that the active in your product actually gets to the site where the action is going to happen be that on the skin or hair or in the body (Suppositories etc)
- Humectant – PEGS have an affinity for water but without any of the stickiness found with glycerine, propylene glycol or sorbitol. This can help prevent creams and ointments from drying out and also help the skin and hair feel good.
- To help prevent bars of soaps from drying out and to make them more plastic in nature for ease of moulding and added stability.
- Wetting agents to help improve the flow of a product across the skin or hair.
- To help bind salts and dry cleansing ingredients together such as those found in denture cleaners, dry shampoo and bath salts.
- As a non-volatile active carrier for deodorant sticks. They help to deposit the active onto the skin without leaving the skin feeling dry.
- To replace alcohol in cough syrups etc as solubilisers for the active.
- Great slip so used as lubricants and for products to help relieve constipation.
- For tablet coatings to help with both stability and product integrity and also ensure the tablet is easy to swallow.
It is also important to note that PEG functional groups are often added to oils to produce cosmetic ingredients that have both oil loving features and water-loving features (the PEG bit loves water). This can be utilised in all sorts of things from hair and skin conditioning to essential oil solubilisation and detergency. The safety dossiers available in relation to PEGs is absolutely HUGE as you might expect given their use both inside and on the body and that is one thing that always strikes me as being one of the ‘inconvenient truths’ of my life as a cosmetic chemist. No matter how much we might feel emotionally drawn to natural materials their safety is always going to be more complex and nuanced than their laboratory made cousins.
PEGS play a role in many life-saving medical treatments:
A quick search through a few medical news releases shows us that PEGS are both extremely useful and even life-saving at times helping to treat anything from chronic constipation to preventing brain damage in a stroke victim. Fascinating stuff!
PEGS have been used to help prevent overoxidation and cell breakdown after traumatic brain injury or stroke by rapid neutralisation of free radicals and normalisation of cellular energy – often cells burn out due to the oxidative damage caused during these medical emergencies meaning that even if the patient survives, quality of life can be severely impaired.
Injecting donor organs with PEG based antifreeze increases lifespan and gives an extended window for donation and implantation.
But they have a dirty little secret – Carcinogenic contaminants…..
Like all chemicals, natural or synthetic the PEG family are not a panacea for everything and neither do they come without a down side that must be carefully managed. The manufacture of PEGS involves the use of ethylene oxide and ethylene oxide is a known carcinogen which is rather worrying given that all you want from your cosmetic or pharmaceutical product is a cure and not a cancer, but like many other known risks in life it can be managed down to levels that are widely agreed to be safe. Ethylene oxide is a flammable gas that dissolves easily in water making the biggest environmental problem with this its migration into waterways. Factories using this gas must carefully monitor their air quality as while there is a ‘safe’ level of exposure, breathing in the gas is not to be recommended and extended exposure of relatively high levels (higher than you would ordinarily get) will likely lead to adverse health outcomes. Skin contact with the ethylene oxide can cause blisters and burns and as such factory workers are always advised to use protective clothing. Controlling Ethylene Oxide in the factory environment is something that any GMP (Good Manufacturing Practice) site will have covered and risk-assessed. But that’s only one side of the story.
Ethylene Oxide in the Environment.
Ethylene Oxide has been found to be more transient than persistent in the atmosphere, soil and/or water. In the atmosphere UV rays break it down to harmless by-products, in the soil it tends either to be broken down by soil organisms over time or it leaches into ground water. In water it has a low to moderate aquatic toxicity and can be broken down by one of many different processes.* None of this means it is harmless and if discharged into the air, soil or water in large doses (say an accidental spill or leak) there would be negative consequences but the same could be said of many other chemicals including most essential oils, natural (and allowed in organics) surfactants, even some whole herbs. * One of the ways Ethylene Oxide breaks down in water is by hydrolysis which turns it into a glycol. This ethylene glycol by-product is also readily biodegradable and is broken down aerobically and anerobically in a very short period of time. In soil this process takes less than a day and can be processed by wastewater treatment plants.
The other trace impurity is 1,4-Dioxane.
1-4 Dioxane is a contaminant from the PEG making process and it is listed as a possible human carcinogen which might make it sound less of a problem than Ethylene Oxide (a known carcinogen) but it isn’t as simple as that. While ethylene oxide rapidly degrades and has a low potential for bioaccumulation, 1,4-Dioxane can take years to degrade in groundwater where it could build up. In contrast in surface water (where there is a plentiful air supply) Dioxane has been found to degrade within a range of 1-6 months (Howard et al 1991) which shows us that keeping this out of the ground water supply is a priority and if we can do that we can manage this impurity. In the air 1,4-Dioxane has a half-life of less than 7 hours so air-exposure is less of a concern. Laboratory studies of 1,4-dioxane in surface water has found it to be practically non-toxic to aquatic organisms (fish, micro-organisms, invertebrates) and has not been found to bioaccumulate in fish under normal circumstances. Normal circumstances being what we would usually expect given how much of this chemical is used and makes its way into the environment.
So this chemical is not readily biodegradable but it won’t bioaccumulate in organisms? That seemed weird to me…..
OK so I’ve just been reading this and had to stop and think – so I’m being told that 1,4-Dioxane has a preference for settling in water, can leach into groundwater where it takes a long time to bio-degrade and yet it has no effect on fish etc meanwhile still being toxic enough to cause cancer in lab animals and humans? It doesn’t make sense… The missing link in all of these reports is the groundwater biodiversity – fish and the other species used to test toxicity and bioaccumulation are surface water-dwelling. Ground water is water that is underground – the environment is different but still alive. I was sure that there would be a less happy ending down there in the stygofauna and so I kept reading…. I found this report confirming that 1,4-Dioxane can leach into the groundwater where it can occur as a xenobiotic component of the environment (basically that means it is an alien – foreign component in groundwater) and that it is something that water treatment plants are onto (as one would expect). The bottom line, it appears is that while 1,4-Dioxane is a carcinogen it can be processed by the bodies of both humans and animals great and small if they are not overwhelmed by it. In other words there is a relatively ‘safe’ or tolerable level. Exceed that for a short time and there is discomfort and short-term health issues, exceed it for an extended period of time and lung (if breathed in), liver and kidney tumours could develop (animal studies usually focused on the dioxane being injected intravenously or eaten). In terms of personal care exposure where products are applied topically results found that dioxanes can penetrate the skin but as one would expect they penetrate better through occluded skin – like if you put on a dioxane enriched cream then put cling wrap (glad wrap) over the top or if you had a dioxane rich, thick water-in-oil formula with up to 3.2% of the applied dose absorbed. These conditions are not normal and under non-occluded conditions only 0.3% of the applied dose was absorbed. Both were rapidly metabolised and excreted.
Where does all of this leave me?
This article has taken me two days to write because of what it has brought up. I, like many bloggers thought I had all of the answers to this “PEG issue” before I started writing. I was triggered into writing this because I heard a scientist on ABC radio talking about a new treatment for blasting arterial plaque cells with a chemical made from PEGS. My ears immediately pricked up and I started to feel that this was a good angle for a ‘PEGS – not all bad are they’ story. I had my bias, I had been using these chemicals for years and while I’m not keen on anything non-sustainable I appreciated that they had their place. But then I started writing….. I had not anticipated how complex it would be to get a grip on the life-cycle of these chemicals to assess their safety. I had not left much time for the layering of question after question that I found myself bringing up. That said I’m glad I’ve stuck with it as I now feel that I do have a better understanding of this family of chemicals.
So can these risks be managed or should we ditch PEGS once and for all?
The majority of PEG based chemicals on the market are still made from petroleum derivatives. That is a fact and it is a fact that will prevent many from wanting to use them – not wanting to support an unsustainable industry. PEGS do contain unsavoury contaminants and there is no denying that they need careful environmental management but we can and do manage them. Vacuum stripping, ozone treatment and good manufacturing practices can make these risks more than manageable and in the process open our eyes to how amazing our body and environment are at processing and re-balancing themselves. I was inspired enough by the heart story to write about PEGS but during the course of my research have found that they are much more widely used and amazing than I had first given them credit for. Finally I feel that I’ve got a better grip on how to explain all of this to my students and get them thinking and that is just great. Amanda x