Important toxic pollutants that affect the city


Toxic pollutants of the parts comprising urban environment (air, water, soil) imposes harmful influence not only on human health, but city biodiversity. Apart from human, the vegetation existing (or, planted) in city and its suburbs and its dwellers (birds, animals, fish, insects and etc.) are also exposed to toxic pollutants, which results in their degradation.

What are individual pollutants, their emission/transportation routes and subsequent influence on living organisms?

Heavy metals

The following substances from this class are especially important for urban environment (unless we take into account the existence of some particular enterprise):

- Pb (lead) as a pollutant enters urban environment mainly as a result of the combustion of leaded gas in engine exhausts, industrial processes of metal casting, solid wastes (throwing of batteries), leaded paints and others. Lead goes into the human's organism mainly (in case if there is no point source of pollution) through polluted food, air.

- Cd (cadmium) enters environment from landfills, fertilizers, and solid wastes. For the urban environment the important source of Cd are building materials, in particular, paints, and also atmospheric sedimentation. This pollutant enters the human body through obtaining the polluted food: internal organs (liver, kidney of domestic and wild animals); marine food (organisms with armor and mussel, for example, crawfish), some of seed cultures and others.

Chlorine-containing compounds

- Pesticides are means of the protection of plants. Their appearance in the urban environment occurs as a result of local purposeful use in the city, suburb, region or even from farther distances. From this class of substances the great attention is given to POPs representatives, from which DDT is especially important.

- DDT (dichlor-diphenil-trichlorethane) is a pesticide (insecticide), the use of which in various countries, including Georgia, is prohibited or restricted. Its emergence in the environment occurs as a result of unconscious (or, essential) use or transportation on large distances.

- Hexachlorbemzol (HCB) is a fungicide, which is prohibited for use in Georgia (as in many countries). It enters environment as a result of illegal (or, unconscious) use, also as a result of the combustion of fuel and production of some pesticides (by-products), with the transportation on long distances. Enters human body by means of polluted food (especially, fish).

- Polychlorbyphenils (PCB). Used in electric transformers, hydraulic installations, oils and others. These substances enter environment exactly during the incorrect use of these technologies and/or safe disposal and installations out of use. This pollutant enters human organism through polluted food, especially, fish, meat and milk products.
 
- Dioxins and Furans (more exactly, polychlor dibenzoldioxine and polychlor dibenzofurans) are polluters of the environment, which origin mainly as a result of chemical processes and various thermal processes.

These substances emerge during the chemical synthesis of chlorine containing compounds (production of some pesticides, herbicides) and frequently their entering the environment occurs in form of byproducts. An important source is burning processes: burning of chlorine-containing fuel, wastes (garbage), fires, paper production (process of whitening), exhaust of motorcars working on liquid fuel and others. These pollutants enter human body through products of polluted food, especially, fish, meat and milk products.

- Polycyclic aromatic hydrocarbons (PAH), for example, benzapirene, originate as byproducts of different processes and enter environment as a result of incomplete combustion of liquid fuel (oil, mazut (black oil) and others), combustion of other organic substances and solid wastes. These substances emerge in industrial fields as well, which are connected with combustion processes: coke productions, metal smelting, oil processing. Non-industrial sources of these substances are wood combustion, cigarette smoke, fried (or steamed) meat, fish and other food.

If, for example, a human for the purpose of aimed use of pesticides, and then dioxins/furans specially produces DDT (and HCB-pesticide), PAH, HCB and PCB enter environment as a result of other human activities: either as unintentional and or inevitable, undesirable byproducts or because of use and unsound management of unadjusted technologies.

POPs

Chlorine-containing organic pollutants (POPs) are distinguished by special sustainability in the environment (and living organisms). After entering the environment they eventually enter human's organism. Main transferring areas of these substances are air and water (municipal water supply, rivers, lakes and etc.). When entering water reservoirs because of the nature of bioaccumulation and biomagnification, their concentration increases in the upper link of food chain and enters human's body mainly through food (or respiratory system).

What kind of harmful influence may POP-pollutants impose through nourishment or breathing air?

POPs are carcinogenic, mutagenic, they cause depression of immune system, and affect human's reproductive system, cause disturbance of children's development and others.