Ô nhiễm kim loại nặng là một hiện tượng trên toàn thế giới. Trong số các kim loại nặng, chì (Pb), thủy ngân (Hg), cadmium (Cd), asen (As), crôm (Cr), kẽm (Zn), đồng (Cu) là đáng quan tâm nhất, mặc dù ba kim loại là những dưỡng chất thiết yếu trong động vật và dinh dưỡng con người. Những kim loại này được sử dụng rộng rãi trong ngành công nghiệp, đặc biệt là lao động bằng kim loại hoặc kim loại mạ, và trong các sản phẩm như pin và điện tử. Họ cũng được sử dụng trong sản. | CHAPTER 8 Heavy Metals Pollution caused by heavy metals is now a worldwide phenomenon. Among the many heavy metals lead Pb mercury Hg cadmium Cd arsenic As chromium Cr zinc Zn and copper Cu are of most concern although the last three metals are essential nutrients in animal and human nutrition. These metals are widely used in industry particularly in metal-working or metal-plating and in such products as batteries and electronics. They also are used in the production of jewelry paint pigments pottery glazes inks dyes rubber plastics pesticides and even in medicines. These metals enter the environment wherever they are produced used and ultimately discarded. Heavy metals are very toxic because as ions or in compound forms they are soluble in water and may be readily absorbed into living organisms. After absorption these metals can bind to vital cellular components such as structural proteins enzymes and nucleic acids and interfere with their functioning. In humans some of these metals even in small amounts can cause severe physiological and health effects. In this chapter we will consider Pb Cd and Hg the three heavy metals widely recognized as the most toxic in our environment. LEAD Lead Pb is one of the ancient metals and has been used by humans for several thousands of years. Pb plays an important role in the economy of all industrialized countries in the world. In the . the industrial consumption of Pb is estimated to be about million tons per year with a concomitant annual emission of about 600 000 tons of Pb into the environment NAS 1980 . Additional amounts are added through mining smelting manufacturing disposal and recycling processes. Furthermore until recently huge amounts of Pb and its compounds had been emitted into the atmosphere as a result of leaded gasoline combustion. Consequently Pb is ubiquitous in our environment. Because Pb is toxic to humans at high doses levels of exposure encountered by some members of the population constitute a .
