Restricted substances-Cadmium

Naturally occurring cadmium is composed of eight isotopes, of which two are known to be radioactive and three are completely stable. Cadmium is highly toxic and is an occupational hazard associated with industrial processes such as production of batteries, pigments, plastics and other synthetics. The toxicity issues Annually about 25,000 tons of cadmium is released into the environment. Half of this is released naturally into rivers through weathering rocks and some is released into the air because of forest fires and volcanoes. The rest, however, is due to manufacturing. Currently, according to HSE guidelines, it is recommended that 7 micrograms per kilogram of bodyweight per week is the maximum safe level of cadmium intake. Cadmium is a highly toxic metal and is mainly absorbed by humans through food. A greater exposure can occur with people who work in factories where cadmium is used and can be breathed in as dust. There are different degrees of toxicity depending on type and length of exposure. If ingested, it can firstly be transported by the blood to the liver and in turn to the kidneys. The cadmium accumulates in the kidneys, where it damages the filtering mechanisms and can result in severe kidney damage. If inhaled, it can severely affect the lungs. High levels may cause lung inflammation (pneumonitis) or fluid in the lungs (pulmonary oedema). If an individual is subjected to cadmium in these ways for a long time then they could develop kidney dysfunction, anaemia and lung conditions. Cadmium is relatively abundant in our everyday life through diet, fertilised soils and cigarette smoke. Being exposed to it in the workplace could also prove to be a significant health risk. Industrial uses Three quarters of the cadmium produced is used in the production of nickel-cadmium batteries. The rest of the stock is used for pigments, coatings and plating and as stabilisers for plastics. Cadmium freely forms various salts, the most common being cadmium sulfide which is used as a yellow pigment and another common one is cadmium selenide, used as a red pigment. Other uses of cadmium include:

• Electroplating, because cadmium has a high level of lubricity and easy solderability.
• A barrier against nuclear fission.
• Cadmium-containing compounds are used in black and white television phosphors and also in blue and green phosphors for colour television picture tubes.
• The pigments from the compounds of this metal achieve very vibrant colours and so are favoured by painters and other industries such as leather and textiles. The colours can get so potent that during production they have to be toned down before they are mixed with oils and binders. It is recommended that a barrier cream is used on the hands when handling these paints.
• To stabilise plastics such as pvc.

Considering this metal is just a byproduct of another process, it is very widely used and so must be acknowledged as a health risk. Environmental impact There are many ways by which cadmium enters the environment, some of which have already been discussed. Cadmium waste streams from industry usually end up in soil through rivers, but they can also end up in the air through waste combustion and the burning of fossil fuels. Currently, only very small amounts enter the environment through household and industrial processes because of regulations being put into place. Another major source of cadmium is in the production of artificial phosphate fertilisers when they are applied to farmland. The cadmium either ends up in the soil from the fertiliser or in surface waters when the waste from the production company is dumped. When cadmium is present in soil it can become very dangerous as the uptake through food will increase in both humans and animals. The importance to the leather industry Cadmium is a restricted substance worldwide. According to the EU directive 76/769/EEC, the maximum limit of cadmium to be found in any finished product is 100mg/kg (100ppm). In order to comply with the above mentioned legislation, products must be tested under EN 71-3 which also covers the EU directive 88/378/EEC - safety in toys. This restricts the extractable value to 75ppm in any product which is appealing to a child. In the leather industry this problem would mainly arise from using cadmium-containing pigments. Another way that they could appear is as heat and UV stabilisers in plastics such as pvc, which in turn would contaminate the surface covering of some leather products. When thinking about the level of cadmium in finished products it is important to make sure that the packaging is also taken into consideration. Conclusions Cadmium is a toxic metal, is potentially a very harmful element and needs to be controlled in industrial applications. The leather industry must be diligent in ensuring cadmium based chemicals are kept to a minimum. Cadmium testing is available at BLC. For more information contact BLC Leather Technology Centre Ltd on info@blcleathertech.com