The textile industry is witnessing a paradigm shift towards sustainability to circumvent ecological dilemmas and human health jeopardies arising from textile processing. Therefore, the review paper herein focuses on the role of green chemistry in synthesizing the natural biological pigments and biomordants for textile substrates such as Sarsasapogenin and soyasaponin from areetha nut extract. Concurrently, the overview aligns the data on the chemical characterization of these plant-based renewable pigments for textile processing that is chlorophyll, carotenoids, flavonoids others. Likewise, the subtle and vital role of bioactive biological compounds in plant pigments for functional textiles applications for example antibacterial, analgesic, and more is succinctly accentuated. The review paper identifies the substantial surplus reserve of plant-based materials that could be conserved for sustainable implications in the textile field. However, there is a prodigious scope of research and development in the same and therefore concludes by citing the multi-disciplinary research as future work to mitigate declared climate emergency for international thrive ability. Likewise, the responsibility of conserving biodiversity, adhering to sustainable development goals, and cradle-to-cradle theories are reinforced in the review paper.

Keywords: Green chemistry, Biological pigments, Bioactive, Functional fabrics, Sustainable textiles.

Climate emergency and human health perils from textile emissions and effluents Today a well-organized and established textile pigment and dye industry exist. However, there are environmental and human health hazards associated with it namely, the emissions of volatile organic compounds (VOCs), Chlorofluorocarbons (CFCs), greenhouse effect gas emissions namely sulfur dioxides and nitrogen oxides. The accumulative consequences are global warming, ozone layer depletion, summer smog, and acid rain which damage vegetation and aquatic life [1]. Ellan MacArthur Foundation affirms that the Emissions from the textile industry alone amounted to 98 million tons of carbon footprints in 2015 and the projected upraise is 300 million tons by 2050; refer to [Figure 1] [2].

Figure 1: Emissions from the Textile industry [4].

Greenpeace international initiated Detox My Fashion campaign in 2011 to ensure that the clothing was free from hazardous chemicals from make to finish. They promulgate transparency from manufactures to be evident to the consumers. Greenpeace International in collaboration with zero discharge of all hazardous chemicals (ZDHC) painstakingly works towards a clean process and safe chemistry [3] The Greenpeace International research findings concluded that the Citarum river, refer to [Figure 2], has chromium and copper-containing dyes of 0,005 mg/l and heavy metals from textile mills resulting in low levels of dissolved oxygen (DO) in the water of 2.45 mg/l. The minimum required DO is 4 mg/l to sustain aquatic life [5]. It took a heavy toll on aquatic life with 60% of fish dead also affecting surrounding flora and fauna. Even more, Greenpeace International investigations on wastewater samples from rivers around textile manufacturing and washing companies in Indonesia and Mexico have revealed the presence of detergents and surfactants 2,4,7,9-tetramethyl-5-decyne-4, 7-diol (TMDD), Nonylphenol (NP), and Nonylphenol ethoxylates (NPEs). These surfactants persistently contaminate the aquatic environment with hormone-disrupting properties [4].

Figure 2: Citarum river water coloured with unsafe textile dye chemicals waste seepage [3].

The well water near Citarum contains 4 times more mercury than recommended safe levels. The effluent water drinking, bathing, and working therein must be the foremost cause of the growing rate of cancer, mental illness, growth inhibition among children, and skin diseases among natives [6]. Also, the European Chemicals Agency (ECHA) and U.S. Environment Protection Agency (EPA) have stringently scrutinized the suspected carcinogens such as synthetic colourant aniline ‘Indigo’, textile additive titanium dioxide, and featured them under the restricted chemical lists (RSLs). They cause skin cancer and skin allergies associated with hypoxia and are toxic to marine life [7]. The clothing being second skin is exposed to textile dyes and additives that are cytotoxic, carcinogenic, genotoxic, and mutagenic causing DNA damage [8].

Greenpeace detox fashion agenda is dedicated to rehabilitating textile toxicity to the environment and human health, refer to [Table 1] for the Manufacturing Restricted Substances List or M-RSL by Greenpeace International, Germany, herein the focus is to substitute and eliminate the top eleven massively hazardous chemicals from the supply chain to mitigate the appalling harm done by the chemicals onto the environment and human health alike [3]. However, not all the synthetic is appalling or could be replaced, those from which, as listed in the M-RSL, resulting in enormous pollution and health problems require to be substituted. The negative impacts of overconsumption, over industrialization, and non-biodegradability due to fossil-based materials in the textile chain is to be addressed. The bio mimicry - and inspirations from nature, could greatly help us in the same.

Table 1: The Manufacturing Restricted Substances List or M-RSL by Greenpeace International [3].

Likewise, due to ozone depletion UV rays are causing skin ailments such as allergies, aging, carcinogenesis, and erythema [9]. Therefore, the Ultraviolet Protective Factor (UPF) of the fabric is calculated; refer to [Table 2]. The Ultraviolet Radiations’ (UVR) are electromagnetic radiations up to 400 nm, they are divided into 3 as per their strength, UVA (315-400 nm), UVB (280-315 nm), and UVC (100-280 nm). UVC and UVB (90%) are absorbed by the ozone layer, water, carbon dioxide, and oxygen in the stratosphere. Therefore, UVB (10%) and UVA reach the earth [10]. They pierce through the human skin and can prove to be detrimental. Ozone depletion has accelerated this process. Textile emission and effluents provide the momentum to ozone depletion. Therefore, it is essential to refute the dangers arising from the textile industry.

Table 2: The ultraviolet protection factor (UPF) [10].

Concurrently, textile materials are vulnerable to microbial bouts as they provide enough surface area and absorb moisture vital for bacterial colonies to multiply. Cellulosic and protein (keratin) fibers provide the indispensable elementary necessities of dampness, oxygen, food, and temperature for bacterial growth and reproduction. These bacteria proliferate repeatedly leading to the unpleasant odor, dermal contagion, product corrosion, allergic comebacks, and other associated ailments [11]. The expansion of eco-friendly and safe to humans, antimicrobial fabric finish is exceedingly vital as clothing stay in direct contact with the human body. The anti-microbial textile application would render the resultant cloth resistant to bacteria, fungi, and yeast attacks. Therefore, enhancing the fabric functionality, visual appeal and medicinal endue of the cloth. It would prevent the biodeterioration of the fabric due to mildew and mold growth and create a protective shield against bed bugs [11].

To render the textile substrate functionally protective against microbes’ wide range of textile goods such as synthetic antimicrobial agent’s triclosan, metallic salts, phenols, and quaternary ammonium compounds are commercially marketed. However, they are not ‘hygienic’ and cause negative side effects. Thus, alternative plant-based biomaterials are sought-after for antimicrobial applications. The natural chitosan and natural dyes are widely utilized for the same. Additionally, herbal extracts namely, aloe Vera, neem, tulsi leaves, tea tree oil, eucalyptus oil are utilized. An upsurge in plant-based bioactive components has opened new boulevards in this area of research for textile healthcare applications [11].

Plant-based bioactive antimicrobial coatings for cotton fabrics are an evolving technology in the production of medical clothes. They impart colour to the fabrics along with functional property. The pigments could be extracted from fungi and bacteria for colouration however they do not impart any functional property to the substrate. There is a huge proportion of humanity on earth they are religiously and ethically prohibited from the killing of any form such as Hindus, Jains, and Buddhists in India following the principle of Ahimsa. These sects could not favor microbial-coloured textiles for example red colour obtained from chiodectonic acid from lichens on textiles or bacterial enzymatic processing of textiles with laccase, amylases others. Hence, the plant-based renewable and exotic colorations would be a good natural alternative [12].

Rationally the synthesis of the literature review distills that the effect of the textile industry on the global environment and human health is an accumulative effect of the chemical, material, process, design, and product life cycle associated with it. Therefore, to mitigate the same the paper emphasizes an inter-disciplinary research approach for holistic sustainable outcomes. Also, in compliance with the above apprehensions, the overview reinforces the role of biological bioactive pigments for sustainable and functional textiles. Cohesively, the role of green chemistry is accentuated. The relevant and recent research studies are cogently cited to justify the same. Likewise, on critical analysis, the identified gaps in knowledge are intermittently specified as anticipated for future work.

Sustainable Measures

There are manifold strategies adopted by the textile research and development segment for an imperative shift towards sustainable alternatives for global benefits. In this overview, the approaches most relevant to the topic are discussed as follows.

Green chemistry

The United States Environment Protection Agency (EPA) defines green chemistry or sustainable chemistry as the strategy for chemical substances and methods to decrease or remove the usage and production of harmful elements. It mandatorily covers the entire life cycle of a chemical material. Green chemistry principally involves exerting at the iota scale of chemistry across all disciplines including textile chemistry. Green chemistry originates from the Pollution Prevention Act of 1990 in the USA and primarily emphasizes source reduction [13].

The twelve ideologies contented by Sustainable green chemistry are listed herein [13].

• Generate no waste material.
• Utilize the whole of the chemical.
• Produce no toxic chemical.
• Synthetizes safe chemical.
• Utilize safe additives and auxiliaries.
• Perform reactions at room temperature and pressure.
• Utilize renewable raw materials.
• Eliminate modifications and postulates.
• Utilize catalysts.
• Design degradable chemicals at the molecular stage itself
• Analyze on time and remove the formation of lethal by-products.
• Analyze, foreknow and eliminate the chemical accidents potentially poisonous to the environment and human health.

The research studies cited hereafter represent plant-based green chemistry in textile processing that would prodigiously propel the sustainability agenda with functional textiles. For example, herbal saponins from Areetha nut and Shikakai would be a sustainable alternative that would benefit the textile manufacturing and washing companies, refer to [Table 3]. They are not only biodegradable and renewable sources of surfactants, but also aromatic, soft to the skin, and functionally healing as investigated by Thakker, refer to [Figures 3 and 4] illustrating green chemistry [14].

Table 3: Bioactive herbal saponins from areetha nut and Shikakai for sustainable and functional textiles [Thakker A].

Figure 3: Functionally efficient saponins from areetha nut and shikakai extracts [14].

Figure 4: Functionally efficient saponins from Areetha nut and Shikakai extract [14].

Concurrently, an inter-disciplinary study is envisaged wherein the author investigates on anti-microbial and anti-fungal properties of banana, bamboo, and merino wool fibers treated with natural biomaterials Syzygium aromaticum (Cloves), Curcuma amada (Mango ginger/Amba Haldi), and Juglans nigra (Walnut leaves) for prospective implications in medical textiles and day-to-day protection from ubiquitous pathogens. The three herbs in research are hypothesized to be strongly functional and aromatic. They also impart colour to the fibers as shown in [Figures 5-8] [15]. The sustainable chemical structures of bioactive chemical components that impart functional properties and coloration to textiles substrates are also illustrated below [15].