of azo-type textile dyes do not bind to the fabric during the dyeing process, and are released into wastewater which is commonly used in developing countries for the purpose of irrigation in agriculture [121]. The use of these azo compounds affects negatively to germination and growth of plants and to soil microbial communities [117, 121]. The textile dyes, along with a large number of industrial pollutants, are highly toxic and potentially carcinogenic which makes them environmentally degrading and are the cause of various diseases in animals and humans [122, 123]. Whereas, the textile sludge reveals problems related to surplus volumes and unwanted composition, high loads of organic matter, micronutrients, heavy metal cations and pathogenic microorganisms [109]. Often sludge is sent to the landfills, as a result the toxic chemicals present in synthetic dyes percolate polluting ground water resources.
According to studies conducted by Clark, the acute toxicity of textile dyes is caused by oral ingestion and inhalation, especially by exposure to dust causing triggering irritations to the skin and eyes [19, 124]. The workers are prone to contact dermatitis, allergic conjunctivitis, rhinitis, occupational asthma or other allergic reactions due to producing or handling reactive dyes [125]. A conjugate forms between human serum albumin and the reactive dye, which acts as an antigen producing immunoglobulin E (IgE) antibodies, which combine with histamine and causes all these diseases [19, 125]. The greatest potential long-term hazard to human health is the genotoxicity of textile dyes [19, 126]. For example, the strong genotoxic effects of textile dyes, pointed out by Tiwari et al. in their study on A. cepa root cells exhibiting chromosomal aberrations. The carcinogenesis is comprised of multiple stages favored initially by mutagenic factors [125, 127]. The textile dyes, especially those of the azo and nitro type, may offer carcinogenicity, and its effects show themselves over time [128].
1.13.1 Overview
Globalization of the world market encouraged the textile industries for large scale production and application of synthetic dyes. These dyes are non-degradable, complex in nature, and a major reason of environmental contamination and serious public health concern. All above research investigations highlighted the impact of environmental, contamination and health hazards of flora, fauna and human beings by enormous use of synthetic dyes. Generally, the long list of synthetic dyes are toxic to humans and environment. In this discussion only three examples of dyes are given here with research evidences as Sudan I, Basic Red 9 and Crystal Violet dye to show their impact on organisms and ecological balance. Many scientists investigated the harmful effect in micro and macro-organisms as well as human beings to be aware of the production, exposure and disposal of these dyes. The synthetic dyes and their effluent discharge are responsible for little danger of skin irritation to cancer of different body parts. During textile processing, inefficiencies in dyeing result in large amount of the dye stuff being directly lost to the wastewater which ultimately finds its way into the environment. This is the picture of most of the developing countries. Approximately 10–15% dyes are released into environment during dyeing process making the effluent highly colored, unpleasant and toxic. As far as human health and environmental hazards are concerned, important prerequisites for risk should be assessed. Nowadays authorities, scientists and general public is aware to potential risk of production and exposure of synthetic dyes. Textile industries are liable to establish the treatment plants for wastewater before being disposed into the environment. But efficiency of treatment plants, honesty of workers, reliability of industry and implementation by government affect the extent of residual amounts reach to the environment. Export demands associated with low cost labor prevalent in India; determine the existence of small-scale textile factories that clandestinely release toxic dyes into water bodies [129].
The effluent disposal of synthetic dyes in water resources causes bio magnification, effects aquatic life where toxic chemicals enter in their bodies later goes to humans via food chain. Another bitter example of wastewater release from dyeing industry is their uses in irrigation by poor, illiterate, innocent farmers in agriculture enable the harmful chemicals of synthetic dyes reach to both animals and human beings through food chains.
1.13.2 Legislative Regulations for Synthetic Dyes
Though, stringent environmental legislations do exist in most of the countries, the will to implement these laws faithfully is needed to overcome the human health and environmental hazards of synthetic dyes [130]. The ministry of environment and forests, government of India has prohibited the handling of 42 Benzidine based dyes from 1993 onward. In January 1997 the use of Azo dyes was banned in India under the clause of Environmental (Protection) Act 1986. Indian legislation prohibited import ofhazardous Azo-dyes on 31 March 2002. In Europe Sudan I an Azo-dye was banned in 2009. However Sudan I, III and IV have been classifild as category 3 carcinogens. Many Benzidine based dyes are prohibited but Basic Red 9 dye is still in industrial use, which is carcinogenic and genotoxic to humans other mammals and aquatic fauna. As recent research studies showed the harmful effects of Crystal Violet dye on humans, rats and fishes with dangerous carcinogenic disorders. This alarming situation suggests us to ban the use of Crystal Violet dye with immediate effect. Despite of prohibition of many dyes, they are still in use.
1.13.3 Sustainability Aspects of Natural Dyes
Sustainability can be defined as the processes and actions through which mankind avoids the depletion of natural resources to keep an ecological balance so that society’s quality of life doesn’t decrease. Sustainability is the foundation for today’s leading global framework for international cooperation- the 2030 agenda for Sustainable Development Goals (SDGs). The 17 SDGs were adopted by all United Nation Member States in 2015, with 169 targets to reach 2030. International Institute for Sustainable Development (IISD) focus areas are mainly climate, economies, resources and some of the global goals are clean water, economic growth, industry, responsible consumption and production, climate action, life on land and below water etc. Use of natural dyes on large scale leads to Sustainable Development which meets the needs of the present without compromising the ability of future generation to facilitate their own requirements. Three pillars of sustainability are economy, society and environment. Therefore; if we discuss the connection between use of natural dyes and sustainability then we come to the highlight of profit, people and planet the three principles of sustainable development. There are certain precious points of natural dyes for environment, economy and society to combat threats of climate and restoration of sustainability.
i. Environment
The textile industry is the second most polluting industries in the world. Synthetic dyes contribute to a major part of this pollution, with nearly 20% of global water pollution being linked to the textile dyeing processes.
Benefits of natural dyes are as follows
Renewable resources.
Non-hazardous
Biodegradable waste, easily decompose
No negative impact on food supply or water.
ii. Economy
The worst scenario of clothing industry is over consumption and unsafe manufacturing. Hence, the economy can be boosted by use of natural dyes because
Some of the natural dyes are obtained from waste and by-products of plants and vegetables.
They will provide extra source of income for rural farmers.
Natural dyes collection can provide income source for locals.
The process of collection of dyes also requires skilled workers.
iii. Society
Sustainability
