Pollution

Pollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms . Pollution can take the form of chemical substances, or energy, such as noise, heat, or light energy. Pollutants, the elements of pollution, can be foreign substances or energies, or naturally occurring; when naturally occurring, they are considered contaminants when they exceed natural levels. Pollution is often classed as point source or nonpoint source pollution.

The Blacksmith Institute issues annually a list of the world's worst polluted places. Humankind has had some effect upon the environment since the Paleolithic era during which the ability to generate fire was acquired. In the Iron Age, the use of tooling led to the practice of metal grinding on a small scale and resulted in minor accumulations of discarded material probably easily dispersed without too much impact. Human wastes would have polluted rivers or water sources to some degree.

However, these effects could be expected predominantly to be dwarfed by the natural world. The European Dark Ages during the early Middle Ages probably saw a reprieve in wide spread pollution, in that industrial activity fell, and population levels did not grow rapidly. Toward the end of the Middle Ages populations grew and concentrated more within cities, creating pockets of readily evident contamination. In certain places air pollution levels were recognizable as health issues, and water pollution in population centers was a serious medium for disease transmission from untreated human waste.

Since travel and widespread information were less common, there did not exist a more general context than that of local consequences in which to consider pollution. Air pollution was largely from wood burning which must be properly ventilated. Septic contamination or poisoning of a clean drinking water source was very easily fatal, and contamination was not well understood. Bad septic contamination and pollution contributed greatly to the Bubonic plague. The first medium warranting official policy measures in the emerging western world would be the most basic: the air we breathe.