Team:Paris Bettencourt/About Perc
Integrated Human Practices
Human Practices are a noticeable part of iGEM and more broadly of synthetic biology and science. The idea behind Human Practices is to investigate how our work will influence the world, what impact it will have and what good could the society benefit from it. It starts with reverse thinking, how does the world influence your work? What problem(s) does our project tackle? Our project, Frank&Stain, aims to find a biological way to degrade wine pigments, anthocyanins. But why caring so much about stains? Wine stains, among other stains, are difficult to remove after some time and people usually send their stained clothes to dry cleaners.
PERC
What is PERC?
Perchloroethylene (aka tetrachloroethylene or PERC) is the main chemical found in products used for dry cleaning worldwide. It acts as a solvent to remove stains from all types of fabrics, since it is an excellent solvent for organic materials. It is volatile, highly stable and non-flammable, reasons for which it is so widely used in this industry.
The big selling point of this chemical is that it is quite effective and quite cheap, which means that almost all dry cleaners throughout the globe use it daily.
The problem is that PERC is quite toxic, both for humans and the environment.
Like many other chlorinated hydrocarbons, PERC acts as a central nervous system depressant, and due to its volatile character, it can enter the body through both the respiratory system and dermal exposure.
The World Health Organisation’s International Agency for Research on Cancer lists it as being a group A2 carcinogen, which means that it is “probably carcinogenic to humans”. It can also dissolve fats from the protective layer of the skin, potentially resulting in skin irritation.
Animal studies have already shown evidence that exposure to PERC increases the risk of developing Parkinson’s disease in ninefold, and the compound has been shown to cause liver tumours in mice, and kidney tumours in rats.
PERC is also labelled as toxic for the environment, since its degradation is quite slow, having an estimated atmospheric half-life of 100 days.
The predominant routes of exposure to PERC for the general population are the inhalation of the compound from both ambient and indoor environments, and ingestion, by drinking water contaminated with it. People working on the dry cleaning industry are, of course, exposed to higher levels of PERC than the general population, and, in addition, people residing near dry cleaning locations are also exposed to high levels, due to the volatile nature of the compounds and to vapour intrusion.
Because of all these reasons, the French government has set up for 2022 the complete banning of PERC from dry cleaning establishments situated close to residential areas. Similar laws had been already passed in Denmark and the USA.
What are the effects of PERC on human health?
PERC’s mechanism of toxicity differs from tissue to tissue. The main two targets of PERC, in the human body, are neurological tissues and hepatic tissues.
In the case of the neurological effects, experimental studies in rodents have shown that PERC alters the fatty acid pattern of the brain’s phospholipids and amino acids. This explains its neurotoxic effects.
Other studies propose that PERC might be incorporated into the brain membranes, hence altering the neural conduction velocity.
PERC can also interfere with the voltage-gated channels and neuronal receptors of the nervous cells. Shafer et al. (2005) showed that PERC disturbs whole-cell calcium currents as well.
In contrast with these neurological effects, which are a result of PERC itself, the hepatic effects are a result of oxidative metabolites including trichloroacetic acid and dichloroacetic acid, which accumulate on the liver.
What are the effects of PERC on the environment?
PERC is a compound that tends to volatise quickly when released into water or soil. Furthermore, it is also mobile in soil and therefore has the potential of leaching bellow the soil surface and reaching groundwater, hence contaminating it. The United States’ Health and Human Services identified PERC in approximately 4% of aquifers in the latest US Geological Survey, showing that aquifer contamination is indeed a problem.
It can biodegrade to tricholoethylene, dichloroethylene, vynil chloride or ethane through dechlorination, but these compounds are not safer than PERC itself.
What alternatives exist already to PERC?
There are already some existing alternatives to the use of PERC in dry cleaning, but the scientific community is divided regarding their safety.
The first alternative is the use of liquid silicon instead of PERC. Silicon is a commonly used solvent, which we find in products such as cosmetics, deodorants and shampoos. It is both odourless and colourless making it in theory a perfect alternative to PERC. However, some scientists have expressed their concern over the use of this chemical since no complete analysis of its impact on humans has been performed to date. Furthermore, only some countries, such as Canada and the UK, have declared liquid silicon as not harmful for the environment, which shows that there is no global consensus on its safety.
Furthermore, the European Chemical Agency has reported that liquid silicone is bioaccumulative. It is very difficult to break down and it is likely to accumulate in our bodies, which is why the EU’s Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) has called for further research.
Another existing alternative is wet cleaning. This method involves the use of gentle washing machines, water, biodegradable soaps and conditioners, and various types of pressing and re-shaping equipment specialised for different types of fabric and fibre types. This method is quite expensive because it requires the investment of acquiring different machines for different fabrics, and requires a lot of training for the operators.
Although a safe alternative for the environment, the specialised detergents and conditioners are mild and not as effective on getting rid of all stains, and many tailors do not recommend it as the process can harm sensible garments.
Another existing alternative is the use of KWL as a solvent. KWL is a petroleum-based solvent, which means that its use is not environmental-friendly. Furthermore, recent studies show that KWL is slightly toxic for human health and also that it is highly inflammable.
Similar data is found for another alternative, the solvent K. This is also a petroleum-based solvent, and is highly inflammable as well. This hydrocarbon is also uncommonly volatile for a compound of its class, which makes it very efficient for dry-cleaning, but hazardous for human health.
How would our product fit in the market?
To understand how our team could make a positive impact on the dry cleaning industry, we interviewed all the dry cleaners in Paris to gather information about the use of PERC and on the impact that the new rules will have on their businesses. For more detailed information on the questionnaire, visit our human practices page.
Overall, most dry cleaners expressed their concern about the compulsory changes, not only because of the economical impact of renewing their already established methods, but mainly because of their concern over the efficiency of the existing alternatives.
Those dry cleaners that had already made the change to the new alternatives told us that the new methods were highly less efficient than PERC itself, and that therefore they now were required to use pre-washing products specific to each type of stains. They also told us that amongst the most difficult stains to remove, red wine was a specially challenging one, especially on white and light coloured pieces of clothing.
We therefore decided to focus on red wine stains by trying to produce and enzymatic pre-washing product that would help washing the red wine stains away! For more information about the outline of our project, visit our project page!
Questionnaire for Dry Cleaners
From the beginning of our project, we had one thing in mind: making a product that suits the needs of those who will use it. It doesn’t really matter how efficient a product is, if it does not meet the needs of those for whom it has been designed for, it is worthless.
In order to create the best product possible, we created a survey designed to get to know the needs of the industry and also to assess the level of awareness of the people working on it. From this survey arose our Human Practices’ project.
We interviewed face-to-face all the dry cleaners in Paris (which means that we performed more than 200 interviews and walked or biked hundreds of kilometers). We got to know which are the most difficult stains to remove and which are the most problematic fabrics.
We also got to know their personal experiences on the use of PERC and the impact that the compulsory change would have on their business. We learnt that the already existing alternatives to PERC are not efficient enough.
Most of the dry cleaners expressed their concern over their business, being afraid that the new methodologies would result in a decrease of the quality of their services. Using the existing alternative to PERC means that it takes longer to remove the stains than it used to take when they used PERC. It also means that for the most difficult stains they need to use pre-washing products to be able to efficiently get rid of the stains.
We learnt that, among the most difficult stains to remove, red wine is a particularly difficult one to get rid off. This type of stains is especially difficult to remove without a trace on white fabrics, since it has very strong pigments. We therefore decided to focus on developing a pre-washing product for getting rid of the verrry Frrrrench red wine stains.
Our survey (original questionnaire in French or translated version in English) allowed us to create a better suiting product, but it also allowed us to assess the level of awareness of the dry cleaners regarding the dangers of using PERC. The interesting thing about Paris is that the city is divided into 20 neighborhoods, the 20 arrondissements. This division is very interesting for our study because it allows us to make not only a statistical analysis of our data, but also a socio-economical one based on the differences in styles of living in each arrondissement.
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