Heavy Metals in the Environment

Heavy metals are found naturally and in very small amounts in living ecosystems. These elements are simple, stable pollutants that, unlike their compounds, do not break down in nature through biological or chemical processes. One of the important consequences of the persistence of heavy metals is their increase along the food chain; as a result of this process, their quantity in foods can increase to several times the amount found in water or air. Many of these elements are not only unnecessary for biological life but are also highly toxic. Living organisms require, in trace amounts, certain heavy metals such as iron, cobalt, copper, magnesium, molybdenum, vanadium, strontium, and zinc for continued growth and survival. These elements are termed trace elements, and if their amounts exceed the minimum required, they cause poisoning and growth disorders. Other heavy metals such as mercury, lead, and cadmium are not vital elements and have no beneficial effects on life; their accumulation in the bodies of living organisms, especially mammals, causes dangerous diseases. One of the most important ways heavy metals are released into the environment is emission through polluted air in industrial areas. These elements enter the soil and surface and groundwater through precipitation and subsequently, by flowing into oceans and seas, also cause environmental pollution. Toxic heavy metals have many destructive effects on health. There are more than 20 different types of toxic metals that are harmful to human health, and each has different physiological behaviors and effects on the exposed person. The degree and severity of the toxicity of heavy metals on the body's cells or tissues depends on the type of toxin and the duration of contact with it. Characteristics of heavy metals To date, 48 metals and 18 non-metals have been identified among these elements. Metals are elements that easily lose electrons to become positive ions. Among the characteristics of heavy metals are conductivity of electrical current, malleability, high density, and great weight. Sources of heavy-metal emissions Heavy metals have two origins, natural and human. For example, the natural sources of cadmium mainly include sedimentary rocks, marine phosphate rocks, active volcanoes, and natural sources; human sources include emissions from industries that consume cadmium-containing products such as nickel-cadmium batteries, plastics, ceramics, glass, paint, enamel work, polyvinyl chloride stabilizers, and so on. Effects of heavy metals on the environment Environmental pollution caused by heavy metals is increasingly growing as a result of the development of urbanization and industries, which leads to an increase in the quantity and quality of the wastewater and effluent produced. Currently, the emergence of severe poisonings in human and animal communities that consume water and agricultural products has become one of the important issues in the world. Heavy metals, in various forms and concentrations, mainly find their way into the environment through the discharge of industrial effluents and urban sewage into rivers, as well as the drainage of agricultural lands fed with fertilizers made from sewage sludge; they not only threaten aquatic organisms and fish but also cause changes in the ecosystem that humans have formed with their surrounding environment and at the top of which they themselves stand. Effects of heavy metals on humans Unnecessary heavy metals or toxic metals leave destructive effects in the body. In general, heavy metals present in the environment are regarded as a potential danger to living creatures. In other words, heavy metals are among the environmental pollutants, and human exposure to some of them through water and food can cause chronic and sometimes dangerous poisonings. For example, mercury is one of the heavy elements that is harmful to the body and is considered among the toxic substances. This element combines with the body's internal enzymes and causes disruption in the functioning of enzymes. If heavy metals enter the body through respiration, food, or skin absorption, and accumulate in tissues at a speed greater than the body's detoxification rate, they gradually reveal their toxicity. Finally, one of the most fundamental issues related to heavy metals is their failure to be metabolized in the body. After entering the body, these elements are not excreted, or are excreted in small amounts; rather, they are deposited in tissues such as fat, muscles, the liver, bones, and joints, and this leads to numerous diseases and complications. Heavy metals can also replace the body's salts and minerals (for example, in the case of a zinc deficiency in food, cadmium replaces it). In general, neurological disorders (Parkinson's, Alzheimer's, depression, schizophrenia), various cancers, nutritional deficiencies, allergies and asthma, endocrine-gland disorders, infertility, anemia, gene destruction, hair loss, premature aging, osteoporosis, and in acute cases death, are among the effects of heavy metals entering the human body. Source: Book: Heavy Metals in the Environment Publisher: Hak Publications (member of Tarfeh Holding)