ALTERNATIVE TECHNIQUE FOR USING SYNTHETIC DYES INSTEAD OF NATURAL COLORANTS

Introduction

Dyes are coloured compounds capable of being fixed to fabrics, mats and wooden toys which do not wash out with soap and water or fade on exposure to light. Today most of the available dyes are synthetic ones prepared from aromatic compounds. The chemicals used for the synthesis of dyes are hazardous for human life. The metabolism occurs primarily in liver and the metabolites formed are transported in the blood where they can form protein adduct or undergo renal filtration in urinary bladder lumens where at acidic pH, they can react covalently with DNA and the carcinogen DNA adducts formed cause disorders in the whole metabolic reactions. Many of the synthetic dyes are harmful to living organism and few of which contain toxic heavy metals such as lead, mercury, chromium, zinc, cobalt and copper and harmful organic compounds such as benzene and formaldehyde. Toxic effects of synthetic dyes can be categorized as acute toxic effects and chronic toxic effects. Acute toxicity refers to exposure of short duration, e.g. a single oral administration. Studies have shown that there is very little evidence of acute oral toxicity in most synthetic dyes especially the vat dyes and pigments which have very low solubility in body fluids and they pass through the digestive system without absorption in the blood stream. Chronic toxicity is due to regular exposure over a prolonged period. The most serious concern is to induce cancer. There is concern in recent years over potential carcinogenicity of certain azo dyes. The reductive cleavage of the azo group gives aromatic amines from which the dyes are derived. Many aromatic amines which are used for dye manufacture are well known carcinogens. It is well established that benzidine and 2-naphthylamines are potent human carcinogens. In certain European countries research has been undertaken to examine the cancer causing potential of azo dyes particularly the amines produced by reductive enzymatic cleavage of azo group. In Germany the approach has been to ban manufacture and import of all dyes derived from aromatic amines. A number of non-permitted colours like Auramine (1), Blue VRs (2), Congo Red (3), Malachite Green (4), Metanil Yellow (5), Orange II (6), Rhodamine B (7), Sudan II (8) and Sudan III (9) are still used very commonly because of their ready availability and relative cheapness constituting a serious health hazard.

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(9)Malachite green and its major metabolite, leuco-malachite green has been reported to have mutagenic and carcinogenic effects. The effects of malachite green on fish eggs have also been tested and it has been shown that a twofold increase in the concentration of malachite green could lead up to 20 times the mortality rate in rainbow trout eggs. Congo red itself is moderately toxic [LD50 intravenously is 190 mg/kg in rats], there may be problems with the blood-brain barrier, and perhaps some derivative might be more effective. In California, Rhodamine B is suspected to be carcinogenic and thus products containing it must contain a warning on its label. Feeding of Sudan III to young rats retarded the growth of the thymus, testes, and ovaries. Postmortem examination showed no trace of dye in the brain, spleen, or heart; but its presence was noted in the liver, pancreas, and kidney. Daily ingestion of 3% Metanil yellow for 90 days produced a degenerative changes in the gametogenic elements of guinea pig testis. The exposure of some of the harmful chemicals and metals namely arsenic, cadmium, chromium, cobalt, copper, lead, manganese, nickel and zinc in excess from synthetic dyes may cause serious health effects are as follows:-Arsenic: Symptoms of arsenic poisoning start with mild headaches and can progress to lightheadedness and usually, if untreated, will result in death. Arsenic poisoning can lead to a variety of problems, from skin cancer to keratoses of the feet. Chronic exposure to inorganic arsenic may lead to cutaneous hyper pigmentation.Mercury: Mercury can be easily absorbed through skin or inhalation. It affects the immune system, alters genetic and enzyme systems, damages the nervous system. Particularly damaging to developing embryos, which are 5 to 10 times more sensitive for adults. Lead: Lead can be easily absorbed through skin or inhalation. It impacts nervous system. Even low levels of lead can reduce IQ level and cause behavior problems.

Chromium: Chromium is necessary for insulin activity and an essential trace metal but exposure at toxic levels causes squamous cell carcinoma of the lung. Manganese: Manganese affects liver function. On the other hand, more than 95% of manganese is eliminated by biliary excretion. Any existing liver damage may slow this process, increasing its concentration in blood plasma. The exact neurotoxic mechanism of manganese is uncertain but there are clues pointing at the interaction of manganese with iron, zinc,aluminum HYPERLINK "http://en.wikipedia.org/wiki/Manganism" \l "cite_note-Lai1999-18#cite_note-Lai1999-18"

, and copper. Based on a number of studies, disturbed iron metabolism could underlie the neurotoxic action of manganese. Copper: The massive exposure of copper can cause fatigue, insomnia, osteoporosis, heart disease, cancer, migraine headaches, seizures also creat mental disorders include depression, anxiety, mood swings, phobias, panic attacks and attention deficit disorders. Nickel: Exposure to nickel metal and soluble compounds should not exceed 0.05mg/cm. Nickel is an important cause of contact allergy, partly due to its use in jewellery intended for pierced ears. Cadmium: Cadmium is extremely toxic to humans because of its inhibition of various enzyme systems; primary target organ is the kidney; but it also causes lung cancer; testicular damage and male sterility. Chronic exposure is associated with renal disease.

Need for Eco-friendly natural dyes alternative to synthetic dyes

The exposure of significant amount of harmful chemicals from synthetic dyes, through breathing and contact with mouth would increase the risk of cancer and other health effects, but most of the natural dyes are almost perfectly safe and which do not contain toxic aromatic compounds and harmful metal ions. The environmental argument support the use of natural dyes as this will lead to exploitation of renewable resources and offering secure to human health. Presently there is a renewed interest in the application of natural dyes mainly due to their environmental friendly characteristics. Throughout the whole world there is now a great stress on the protection of environment, particularly the damage caused by effluents containing synthetic dyes. Regulations concerning the effluents of industries are becoming stricter everyday. The industries are being forced to develop and adopt the non-polluting technologies. Thus, there is a need to realize the importance and develop the use of natural dyes and an effort to reassess and promote the use of natural dyes technology deserves encouragement. Hence it is recommended to replace the harmful synthetic dyes with risk-free suitable natural dyes for craft works especially for mat weaving and toys making industries. Natural dyes and stains can be obtained from the roots, leaves, barks, rinds, rhizomes, fruits and woods of various plants (Table 1). Table 1. List of plant sources for obtaining natural colours instead of synthetic dyesS.NoColour Name of the plant source

1OrangeAllium cepa L - (Onion skin), Daucus carota L - (Carrot), Juglans cinerea L - (Butternut), and Punica granatum - (Pomegranate).

2.BrownQuercus - (Oak bark), Rhus - (Sumac), Taraxacum cass - (Dandelion), (Juglans L) Walnut, Juniperus drupacea - (Juniper Berries), Foeniculum vulgare Mill-(Fennel), genera Quercus (Acorns), Lawsonia inermis (Henna), Terminallia arjuna (Arjuna), Mimusops elengi (Spanish-cherry) and Bixa orellana (Annato).

3.BlueCrocus sativus (Saffron), Vaccinium (Blueberries), Prunus (Cherry), Rubus leucodermis (Raspberry) and Indigofera tintoria (Indigo).

4.RedBeta vulgaris (Beets), Malus Tourn - Crab Apple, Rosa glauca - Rose, Prunus virginiana - (Chokecherries), Rubia cordifolia (Madder) and Hibiscus rosa-sinensis (Hibiscus)

5BlackFicus racemosa (Cluster fig), Psidium guajava (Guava), Ceratonia siliqua - (Carob pod) and Quercus acutissima (Sawthorn Oak)

6PinkBauhinia purpurea (Camels foot tree)

7Reddish pale brownFicus religiosa (Peepul tree) and Caesalpinia echinata - Brazil wood

8.Brownish redPterocarpus marsupium - (Indian Kino)

9.Red-Purple Phytolacca acinosa (Pokeweed), Hemerocallis altissima (Daylilies), Carthamus tinctorius L (Safflower), Haematoxylum campechianum (Logwood) and Solanum melanocerasum - (Huckleberry).

10.GreenArtemisia abrotanum (Artemisia), Cynara cardunculus (Artichokes), Camellia sinensis (Tea Tree), Spinacia oleracea - (Spinach), Rumex acetosa (Sorrel), Digitalis cariensis (Foxglove), Syringa vulgaris (Lilac), Camellia assimilis (Camellia), Antirrhinum australe (Snapdragon), Pennisetum setaceum - (Grass), Acacia greggii (Mulga Acacia).

11.YellowPeganum harmala (Syrian Rue), Rudbeckia hirta (Yellow cone flower), Medicago sativa (Alfalfa), Salix (Willow), Daucus carota (Queen Annes Lace), Arctium lappa - (Burdock), Apium graveolens (Celery), Solidago virgaurea minuta (Golden Rod), Houttuynia cordata (Cameleon plant), Mimosa pudica (Mimosa), Maclura pomifera (Osage orange), Narcissus jonquilla (Daffodil flower), Carya glabra (Hickory leaves), Capsicum annuum (Paprika), Helianthus annuus (Sunflowers) and Curcuma longa (Turmeric).

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