Читать книгу Sustainable Practices in the Textile Industry - Группа авторов - Страница 42

The contribution of textile industry is spread globally with 7% of the total world exports and employs 35 million workers, generating around 1 trillion dollars economy around the world [108]. The textile industrial sector is one of the biggest global polluters that consume high amounts of fuels and chemicals [109] despite its undeniable importance. The special emphasis is placed on the enormous use of drinking water in various operations of its production chain such as washing, bleaching, dyeing among others [110]. The textile industry is responsible for an extensive list of environmental impacts [111]. Some of the research studies are given below to access the impact of synthetic dyes on overall nature. Air water and soil pollutions are major environmental hazards of synthetic dyeing industries. Where air pollution caused by particulate matter, dust, oxides of nitrogen, sulfur and volatile organic compounds.

The water is an essential resource for life on the planet and for human development. The textile industries discharge untreated effluents into water bodies [109]. Most of the residual waters of textile industry create high levels of biochemical oxygen demand (BOD) and chemical oxygen demand (COD) [112]. The effluent sample collected from Karur, a textile city in Tamil Nadu (India) showed dark violet color, objectionable odor, high TDS, alkaline PH, high amount of chlorides, nitrate, sulfates, heavy metals, and low amount of dissolved oxygen (DO), all parameters exceeded the BIS (Bureau of Indian Standard) limits [113]. The active, direct, basic and acid dyes are soluble organic compounds [114]. Their high solubility in water makes it difficult to remove them by conventional methods [115]. They impart color to a given substrate due to the presence of chromophoric groups in its molecular structures [116].

The reduction in the rate of photosynthesis and dissolved oxygen levels affecting the aquatic biota are due to the color present in textile dyes that not only causes aesthetic damage to the water bodies, but also prevents the penetration of light through water [112, 115, 117]. The textile dyes are toxic, mutagenic and carcinogenic agents that act as environmental pollutants and cause biomagnifications by entering in food chain. Organisms at higher tropic levels show higher levels of contamination compared to their first level [30, 118–120]. Here it is necessary to mention that around 15–50%, 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].