Pollution
Everyone has a general idea of what pollution is, to the point where sometimes people can identify something as it or not, but they might struggle to define the word. Pollution is, at its essence, when harmful substances are added to the environment. Those harmful substances, known as pollutants, can vary in the way they are introduced and their effect. When discussing pollutants, their persistence refers to how long the chemical lasts in the environment and it can vary based on environmental factors and the unique chemical properties of the pollutant.
Pollutants can be described as coming from a point source (a single, identifiable source that you can "point" to) such as a smokestack, or a nonpoint source (an area that is diffused where it can be difficult to identify the exact spot the pollutant is coming from) such as urban or agricultural runoff.
How much pollution is too much?
Each species has its own range of tolerance for various environmental conditions, and this includes pollutant levels. The range of tolerance applies to both individuals as well, with some individuals of a species having a slightly different range than others.
Dose response studies are done in order to examine the effect of a specific pollutant at varying dosages on a population. This data is shown via a dose response curve (see below), which can be used for both pollutants or drugs that are meant to have medicinal effects.
The threshold dosage is the lowest dose that has a measurable effect on the organism.
The ED50, or effective dose, is where 50% of the population experiences a non-lethal effect. This is often used for pharmaceuticals and measures the therapeutic effect.
The TD50 measures the toxic dosage, where 50% of the population experiences a toxic, but nonlethal effect.
The LD50, or lethal dose, is the dose concentration that results in 50% of the population dying.
How does this affect human health?
When it comes to effects on humans, it can be difficult to pinpoint the exact effect of the pollutant on our health. That is because we are exposed to so many things that it can be difficult to identify the effects of a single one. In addition, synergism occurs when multiple substances interact and their combined effects are even worse than the sum of their separate effects.
Below are some examples of conditions on human health caused by pollution of some kind.
Dysentery is a disease that is caused from untreated sewage contaminating water, which results in food/water being contaminated with fecal coliform bacteria. It results in intestinal swelling and bloody diarrhea and kills over one million people annually.
Mesothelioma is caused by exposure to asbestos. It is an aggressive type of cancer that forms on the mesothelium, tissue that covers internal organs, mainly the pulmonary pleurae which surround the lungs and chest cavity.
Tropospheric ozone inhalation irritates the muscles of the respiratory tract, resulting in constricted airways and impairing lung function. This worsens respiratory ailments such as asthma, emphysema, bronchitis, and COPD.