Carbon monoxide (CO) is a colourless, odourless gas that is produced by the incomplete burning of carbon-based fuels including petrol, diesel, and wood. It is also produced from the combustion of natural and synthetic products such as cigarettes. It lowers the amount of oxygen that enters our blood . It can slow our reflexes and make us confused and sleepy.
Carbon dioxide (CO2) is the principle greenhouse gas emitted as a result of human activities such as the burning of coal, oil, and natural gases.
Chloroflorocarbons (CFC) are gases that are released mainly from air-conditioning systems and refrigeration. When released into the air, CFCs rise to the stratosphere, where they come in contact with few other gases, which leads to a reduction of the ozone layer that protects the earth from the harmful ultraviolet rays of the sun.
Lead is present in petrol, diesel, lead batteries, paints, hair dye products, etc. Lead affects children in particular. It can cause nervous system damage and digestive problems and, in some cases, cause cancer.
Ozone occur naturally in the upper layers of the atmosphere. This important gas shields the earth from the harmful ultraviolet rays of the sun. However, at the ground level, it is a pollutant with highly toxic effects. Vehicles and industries are the major source of ground-level ozone emissions. Ozone makes our eyes itch, burn, and water. It lowers our resistance to colds and pneumonia.
Nitrogen oxide (NOx) causes smog and acid rain. It is produced from burning fuels including petrol, diesel, and coal. Nitrogen oxides can make children susceptible to respiratory diseases in winters.
Suspended particulate matter (SPM) consists of solids in the air in the form of smoke, dust, and vapour that can remain suspended for extended periods and is also the main source of haze which reduces visibility. The finer of these particles, when breathed in can lodge in our lungs and cause lung damage and respiratory problems.
Sulphur dioxide (SO2) is a gas produced from burning coal, mainly in thermal power plants. Some industrial processes, such as production of paper and smelting of metals, produce sulphur dioxide. It is a major contributor to smog and acid rain. Sulfur dioxide can lead to lung diseases.
There are many different sources of chemical pollution, including:
- domestic sewage
- industrial discharges
- seepage from waste sites
- atmospheric fallout
- domestic run-off
- accidents and spills at sea
- operational discharges from oil rigs
- mining discharges and
- agricultural run-off.
However, the chemicals that are probably of most concern for everyone are the persistent pollutants: those substances that enter marine food chains and are eventually passed along the chain to the marine top predators in increasing amounts. Persistent pollutants include pesticides, such as DDT, and industrial chemicals, most famously the PCBs.