Urbanization: Source of heavy metals pollution

By. Asifa Manzoor, M.phil Biotechnology


Heavy metals (HM) are the compounds having specific gravity >5 that of water. These heavy metals are found to be toxic for human health as well as to environment. Toxic heavy metals are Cadmium (Cd), Lead (Pb), Nickel (Ni), Mercury (Hg) and Chromium (Cr). Term of Heavy metal is linked with the contamination and toxicity of the environment, which is causing carcinogenicity, mutations and polyploidy etc.

Heavy Metals (HMs) make a critical commitment to ecological contamination because of human exercises, for example, mining, purifying. HM pollution influences the biosphere in numerous places around the world. HMs can influence plant development and production in many ways by repressing various physiological processes in plants. These were appeared to cause metal aggravation in plants and affect protein digestion through affecting nitrate and sulfate decrease.

Why to be addressed?

Environmental pollution is one of the biggest concern now a days. By increase in population and different human activities like mining and smelting, tearing of tires, fossil fuel burning etc. increasing pollution in environment. Migration of people from rural area to urban areas bring industries in cities which is a big source of heavy pollution in the environment i.e. smoke. Effluents released from industries as wastes and discharged to water uncleaned and unprocessed, which is very dangerous to human health as it is containing most of the heavy metals in it which are highly toxic and if left unprocessed can cause severe health hazards.

Due to increased urbanization there is need to make more constructions which indirectly bring the brick kilns more in use. These brick kilns use rubber tires and coal as its fuel which increase the heavy metals concentration in the environment polluting air and soil. In developed countries there is great awareness to pollution and its effects on human health and environment.

Heavy traffic is also known to be the biggest source of heavy traffic in the environment. Smoke released from the vehicles cause spread of lead in the air, tearing of tires causes spread of lead and cadmium in the environment, industries that are manufacturing lead batteries are releasing Lead and Nickel in the environment. Heavy traffic is effecting the crops grown along roadsides badly. Theses heavy metals get deposited on the crops and put hazardous effects not only on plants but on living organisms too i.e. humans, animals.

If food contains excessive amounts of metals or nutrients that are needed in trace amounts by our body, it can cause severe health issues, because some micronutrients like iron, zinc and copper if cross the permissible limit can cause severe issues or can intermingle with normal functions of the body. Similarly if the metals like cadmium, lead and nickel are up taken in high concentration, can cause severe health hazards.

Movement of Heavy Metals in Food Chain

When water polluted with heavy metals irrigates the soil, the surface of the soil get contaminated with heavy metals. Following the theory of osmosis when the amount of heavy metals increases in soil these heavy metals start moving from water to ground water or solutions of soil and make it available for plants uptake. In this way these heavy metals move to another ecosystem and thus enter the food web and put hazardous effects on human health and plants. The exposure of soil to the heavy metals have increased due to anthropogenic activities in some areas by humans even on a large scale. Particularly, the soils are known to be long term reservoirs of heavy metals. These heavy metals can be variable in different regions depending upon the conditions and pollutants available.

These heavy metals get mixed with air, water and soil. These things are compulsory for plants, thus heavy metals enter in plants. Animals eat these contaminated plants, so these heavy metals get accumulated in those animals. When humans eat these animals or plants they become contaminated with heavy metals. Thus heavy metals enter in food chain, become part of it and remain in it for a long period.


To avoid heavy metals pollution and their contamination in food and crops, industries should be planted away from the agriculture lands. As the crops that were grown away from the road have less amount of heavy metals deposited, that’s why the crops should be grown away from the roads at particular distance i.e. 50m. Waste water treatment plants should be planted.


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