Pollution and Pollutants

“ Any undesirable change in the characteristics of the air, water, soil and food that can adversely affect the health, survival, or activities of humans or other living organisms is called pollution,” which also takes into account noise or thermal pollution in addition to pollution caused by chemicals or  materials. A ‘pollutant’ is a chemical or material out of place or present at higher than normal concentrations that has adverse effects on any organism.

The term ‘contaminated’ is often used synonymously with ‘polluted,’ although subtle differences in the differences in the definitions indicate that these are not interchangeable. ‘Contaminated’ implies that the concentration of a substance is higher than would naturally occur but does not necessarily mean that the substance is causing any harm. ‘Polluted’ refers to a situation in which the concentration of a substance is higher than would naturally occur but also indicates that the substance is causing harm of some type. By this reasoning, a soil could be contaminated but not polluted.

Unwanted Effects of Pollutants

Almost every part of the human body is affected by one pollutant or another. For example, lead and mercury affect the brain, arsenic the skin, carbon monoxide the lungs, and cadmium the heart. However, a toxin that affects the brain, such as mercury, causes a variety of other problems as well.

Unwanted effects of pollutants include :

• Disruption of life support systems for humans and other species,
• Damage to wildlife, human health, and property, and
• Nuisances such as noise and unpleasant smells, tastes, and sights. 

Factors determining the severity of the pollutants

There are many factors which determine the severity of a particular pollutant. These factors include:

Type and nature of the pollutant (organic or inorganic, ionized or nonionized, solubility whether in water or fat) ,Concentration , pH, Eh, Temperature, Wind, Persistence, Chemical forms, Volatility, Biodegradability, Water quality, Organic matter content, Soil properties, Bioaccumulation, Biomagnifications, Chemical interactions (antagonistic or synergistic),  and many more.

Synergism, an important concept in pollution problems, which refers to the interaction of different substances where the combined effect is greater than the sum of the effects of the separate substances. For example, sulfur oxides and particulates are both air pollutants. Either one taken separately may cause adverse health effects, but when they combine, as when sulfur oxide is adsorbed onto small particulates, they may be inhaled deeper than sulfur oxide alone and cause greater damage to lungs. Another aspect of synergistic effect is that the body may be more sensitive to a toxin if it is simultaneously subjected to other toxins and stresses.

When acid waters come into contact with certain chemicals and metals, they often make them more toxic than normal, e.g., fish that usually withstand pH values as low as 4.8 will die at pH 5.5 if the water contains 0.9 mg/L of iron. Presence of Al, Pb, Hg in acid water environment (pH of around 4.8-5.5) will far exceed the damages of these substances. Seawater tends to be more buffered because of the presence of different salts.