What are Azo Dyes?
Azo dyes is a general term which refers to a group of synthetic dyes composed of a chemical azo group. They are mainly produced in developing nations such as China, India, Korea and Argentina.
So you may now be wondering why you should care about these dyes. Azo compounds are widely used in the dyeing of every type of fibres, natural, artificial and synthetic in order to colour a variety of things; from textiles and plastics to cosmetics and food. In fact, studies have found that they are used in approximately 70% of all organic commercial dyes today. The issue however is that they have also been shown to have extensive environmental and health consequences.
Why are they used?
Azo dyes are used so commonly as they are able to dye the cloth at a lower temperature than azo-free dyes. They also offer a wider range of colours, allowing for brighter clothing, which will not run in the wash. This means that the colour of the clothes that you buy will last longer, and is easier to produce for the company as it requires lower temperatures.
What’s wrong with them?
Approximately 4- 5% of Azo dyes can cleave to form compounds known as aromatic amines, which are potentially dangerous to human health and have therefore been regulated. They are considered to be dangerous as there has been a relation found between these aromatic amines and cancers. Specifically, they have been seen to cause bladder and liver cancers.
These Azo dyes can come into contact with human bodies through three different pathways: inhalation, ingestion and dermal absorption. In regards to textiles, the dermal absorption would be the most relevant, especially in regards to textiles that come in direct contact with skin and sweat. For example, if you wear a t-shirt for a day that is created with azo-dyes, it will sit on your skin for many hours, and the azo-dyes will slowly be absorbed into your skin. If for any reason you sweat, the azo-dyes will begin rapidly leaving the shirt, and will rub off of the shirt.
Azo dyes practically do not degrade under natural environmental conditions. When the waste water has been released from the factory, it will bio-accumulate in the environment. Posing issues not only in the water which it has been released into, but also affecting the entirety of the ecosystem. For example, Azo dyes have been connected to growth reduction, neurosensory damage, metabolic stress and death in fish, and growth and productivity in plants. Contamination of the water which is released from these factories therefore effects downstream water use, not only in terms of drinking water for humans and animals, but also negatively effecting any farming, fishing or tourism and recreation industries.
In 2007, a study linked an Azo dyeing plant as one of the sources of mutagenic activity detected in the Cristais River in Brazil, a source of drinking water for 60,000 locals. Though the drinking water was treated in a plant 6km downstream of the discharge site, testing confirmed the presence of carcinogenic aromatic amines after it had been released from the treatment plant, and was considered to be safe. This was unknown prior to the testing, and may have had health impacts upon the 60,000 people who had previously relied on this water.
One of the issues with Azo dyes is that it looks clear when it is released and therefore the polluted nature of the water cannot be seen when you first look at it, making them hard to detect until they it is too late. In addition, these Azo dyes will sometimes accumulate in a concentrated sludge, posing a significant secondary disposal problem, which can produce toxic end-products, meaning that these products are hard to dispose of, especially in places with limited resources. The economic resources required to clean up some of this environmental damage are huge, and companies do not want to spend more money than necessary. With the lax environmental regulations in these areas, companies are creating
The harmful effects of Azo dyes have not gone unnoticed. In 2002, the European Commission put regulations in place which limited the use of azo dyes which, “may release one or more carcinogenic aromatic amines that may come into direct and prolonged contact with the human skin or oral cavity.” Regulations have also been implemented in other first world countries, such as Canada and the United States, but for the most part have not been regulated abroad.
Although the effects of using Azo dyes has been shown to be extremely damaging to local people and ecosystems, the regulations have been lacking in producing countries. Little equivalent regulations are present oversees and the expulsion of hazardous dyes. The expulsion of dyes into the environment has continued despite mounting evidence that this continued practice is damaging local ecosystems, with potential detriment to human health and wellbeing.This means that although they have been regulated in certain countries, they have not been regulated in many of the countries where the production is taking place. Therefore the impact of Azo dyes on countries such as China and India can not be discounted.
Overall, Azo dyes have severe environmental impacts as well as health impacts not only on the local community, but also on anyone who is coming into contact with products created by Azo dyes. They are harmful, and the regulations that have been put in place are not addressing many of these major issues. New regulations should be put into place to address these concerns, to protect not only the consumer but also the people producing the textiles and those in the surrounding environment who will be affected by the waste. The time for Azo dyes to be common in our clothing has passed, we need to make a change in order to get rid of this harmful product.