Heavy metal is a relatively large atomic weight of metal element, the proportion is greater than 5.0 g/cm3 such as mercury, lead, cadmium, etc. But it is not our traditional sense of the metal (such as steel and other alloys, a number of alloys containing heavy metal elements). Arsenic does not form part of heavy metals, but their sources and hazards are similar with heavy metals, so it is usually included in the category of heavy metals to examine and discuss.

Heavy metal contained in the textile is not in a free state, which not cause harm to human body. Soluble heavy metal are extracted under the conditions which simulate the material remaining in contact with acid sweat solution for a period of time after contacting with skin. The concentrations of the soluble elements which may cause harm to human health, are determined by ICP, AAS, UV-Vis, etc.

Lists of soluble heavy-metals in the Oeko TexStandard 100-2009 are Antimony(Sb), Arsenic (As),Lead (Pb),Cadmium (Cd),Chromium (Cr), Hexavalent Chromium (CrVI),Cobalt (Co), Coppper (Cu),Nickel (Ni),Mercury (Hg).

Harm

Trace concentrations of heavy metals can be toxic (usually 1 ~ 10 mg/ L, mercury, cadmium is 0.01 ~ 0.001 mg/ L),translated into more toxic organic metal compounds by the microorganism effect  (such as the ocean - methylmercury ), and bio-accumulation through the food chain into the human body, causing chronic poisoning.

The sulfophile heavy metal elements (such as mercury, cadmium, lead, copper, arsenic, etc.) have particularly affinity with certain sufhydryl enzymes in human tissues, inhibit the activity of enzymes. The siderophile elements(such as nickel) can be accumulated in the body of the kidney, spleen, liver, inhibit the activity of arginine enzyme. Lead is a highly toxic substance, its greatest hazards that affect children’s intellectual development, there will also harm the nervous system, heart and respiratory system. Hexavalent chromium may be the precipitant of protein and nucleic acid, inhibit cell glutathione reductase, lead to methemoglobin and cancer.

Source    

·Usage of metal complex dyes is an important source of heavy metals in textiles.

·Dye-processing and printing -dyeing processing may also be a source of heavy metals. 

·Absorbing heavy metals from the soil or air during the growth process of natural plant fiber.

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In order to reduce the risk of consumer products on human health and environmental, while limiting the content of harmful substances in waste, provide a good environment for the development of human society, a series of directives and requirements are drafted in various countries and regions.

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