Ecotoxicological properties of principal pollutants

This section discusses toxicological aspects of different chemical species, which are of great concern in the various environmental compartments in the Asian region. The description of toxicological features of other chemical compounds can be found in S. Manahan (2000) and Chapters 12-14 of this book. 

Heavy metals are the metals with atomic mass 56 units. They (see also Chapter 12) are particularly toxic in their chemically combined forms and some, notably mercury, are toxic in the elemental and organic forms. The toxic properties of some of the most hazardous heavy metals and metalloids are discussed in this sub-section. 

Beryllium (atomic mass 9.01) is not truly a heavy metal, but this is one of the more hazardous toxic elements. Its most serious toxic effect is berylliosis, a condition manifested by lung fibrosis and pneumonitis, which may develop after a latency period of 5-20 years. Beryllium exposure also causes skin granulomas and ulcerated skin and is a hypersensitizing agent. 

Elemental mercury vapor can enter the body through inhalation and be carried by the bloodstream to the brain, where it penetrates the blood-brain barrier. It disrupts metabolic processes in the brain causing tremor and psychopathological symptoms such as insomnia, shyness, depression, and irritability. Divalent ionic mercury, Hg +, damages the kidney. Organometallic mercury compounds such as dimethylmercury, Hg(CH3)2, are also very toxic. 

Cadmium affects adversely several important enzymes. It can cause also painful bone disease, osteomalacia, and kidney damage. Inhalation of cadmium oxide dusts and fumes results in cadmium pneumonitis, which are characterized by edema and pulmonary epithelium necrosis. 

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