Dyeing for a change
Since the invention of aniline purple in the 19th century, synthetic dyes have been employed in a wide variety of industries to alter the colour of textiles, papers, foodstuffs, and numerous other materials.
Many dyes have medical value, and are used as drug colourants, in vital staining, tracing, and histopathology. More modern applications include the production of photosensitisers, light-sensitive drugs which react with molecular oxygen to cause biochemical disruption. By carefully timing light exposure and ensuring that the ratio of photosensitisers is greater in diseased tissue than in healthy tissue, such compounds can be used in photodynamic therapies to treat cancers and infections.
Unfortunately, some dyes have been shown to exhibit carcinogenic and mutagenic properties. One pivotal study in the 1980s found that workers in chemical dye factories in England were between 100 and 200 percent more likely to develop bladder cancer. As recently as 2008, a report by the International Agency or Research on Cancer (IARC) concluded that hairdressers and barbers were “probably” at greater risk from bladder cancer, due to their exposure to hair dyes containing benzidine-based dyes.
To this day, exposure to industrial chemicals remains the second biggest risk factor for bladder cancer after smoking, and may account for around 25% of cases. Compounds particularly associated with an elevated risk of bladder cancer include 4-aminobiphenyl, benzidine, and o-toluidine, all of which have historically been used in the dyestuff industry.
Synthetic dyes also rank amongst the most significant root causes of environmental pollution. In the event of a spillage, dyes that cut off sunlight can impair the photosynthetic processes of aquatic plants or algae. High concentrations of dyes can reduce the reoxygenation capacity of a body of water, thereby upsetting aquatic life, not to mention rendering that water undrinkable for neighbouring populations. “I have workers in my factory who spend two to four hours everyday going to collect water, with no guarantees they’ll even find it,” one Indian clothing factory owner told The Guardian in 2015.
Amidst the complexities of the industrialised world, dyes are a problem that is far from ‘black and white’.
In Bangladesh, meanwhile, the world’s second-largest garment manufacturing hub, the fashion industry is responsible for up to one fifth of industrial water pollution. “wastewater is commonly dumped directly into rivers and streams,” a report published last September noted. “The discharge is often a cocktail of carcinogenic chemicals, dyes, salts and heavy metals that not only hurt the environment, but pollute essential drinking water sources.”
Amidst the complexities of the industrialised world, dyes represent an equally complex problem that is far from ‘black and white’. There are many hundreds of pathways into circulation - from textile factories and industrial emissions to plastic bag degradation, tattoos, and curry sauces - and each of these must be covered by its own set of regulations.
In Europe, these include those drafted by the European Regulation on Registration, Evaluation, Authorisation, and Restriction of Chemicals (REACH), the Toy Safety Directive, and the EU Food Contact Material Framework, whilst in the USA there are many examples of state legislature pertaining to dye exposure, including California’s Proposition 65, Washington’s Chemicals of High Concern to Children (CHCC) list, and Vermont’s own, separate CHCC list.
At the federal level, the Food and Drug Administration (FDA) maintains an extensive summary of dyes approved for use in foodstuffs, drugs, cosmetics, and medical devices, alongside details of their respective maximum residue levels (MRLs).
Scientists have been developing methods to help remove dyes from the environment for some time. These include the synthesis of dye-fixing peptides, and the use of a polymeric natural carbohydrate of turmeric powder adsorbent. Needless to say, should these technologies prove scalable, they could revolutionise dye clean-up efforts around the world.
In one study, published in December 2020, a team of researchers employed multiwalled carbon nanotubes functionalised with L-tyrosine (CNT-TYR) as nanoadsorbents to remove methylene blue (MB), a toxic dye with medical applications in the treatment of methemoglobinemia. At 25 °C and pH 6, a >95% level of adsorption was observed with seven minutes of contact time. “The results indicate that CNT-TYR has high efficiency for the removal of dyes and various other toxic contaminants present in water,” concluded the study’s authors.
Some dyes pose a threat to the health of bodies of water, and the people who depend on them.
Needless to say, the work has only just begun - approximately 17-20% of industrial water pollution is owed to fabric dyes and treatments, worldwide. Without well-informed regulatory oversight, further environmental contamination is inevitable. Sites like Citarum River, the longest river in West Java, Indonesia and amongst the world’s most polluted rivers due to the more than 2,000 industrial facilities concentrated along its banks, including 200 textile mills and garment facilities, could become widespread, leading to not only environmental devastation but untold consequences for human health.
For the sake of consumer and environmental health, therefore, it’s vital that your laboratory is able to produce reliable results when analysing dyes in environmental samples and foodstuffs. LGC’s range of Dr. Ehrenstorfer reference materials help you do just that.
LGC is proud to announce the addition of a number of new dye and metabolite reference standards to the Dr. Ehrenstorfer portfolio, which now includes a comprehensive range of almost 300 dye and metabolite products. To view our full portfolio of dye and metabolite reference standards, click here.
High quality reference materials are essential for accurate analytical measurement and quality control, ensuring sound decisions are made based on reliable data. The majority of our Reference Materials and Certified Reference Materials are produced under the scope of our ISO 17034 accreditation and verified in accordance with ISO IEC 17025 to guarantee the highest quality.
Recent additions to our extensive portfolio include:
Used as a coupling partner in the preparation of some azo dyes.
Derivative of 2-naphthol. Common precursor to azo dyes and pigments.
Colorant used in the paper and textile industries.
Colorant used in multiple industries.
Commonly used as a cotton, leather, and paper dye.
Methylthioninium chloride[Methylene blue]
Medication and dye, mainly used to treat methemoglobinemia.