• Pollution can have devastating effects on the land, the water, and the air on which we rely. Air in particular is of crucial importance, since it is spread all around the globe by winds and jet streams. This means the release of airborne pollutants in one area can affect another area, even if it is thousands of miles away. And while these pollutants can cause damage to various aspects of the world in many different ways, they are especially detrimental to the human respiratory system.
  
  

Carbon Monoxide

• Carbon monoxide is an odorless, colorless gas that is formed by the incomplete combustion of carbon. According to a Hofstra University study, when you inhale carbon monoxide, it combines with the hemoglobin in your blood and forms carboxyhemoglobin. This substance prevents your body from absorbing oxygen, and over time--and in large enough quantities--will cause asphyxiation and death. According to the above source, just .5 percent of carbon monoxide in the air can cause death in less than half an hour, while smaller amounts will cause symptoms associated with poisoning, including respiratory and cardiovascular weakness.
  
  

Particulates

• Particulates refer to any suspended particles of matter that are not gaseous in form. These include the solids and liquids that make up dust, mist, smoke, and smog. According to a University of Michigan study, particulates almost exclusively affect the human respiratory system, and are incredibly detrimental to lung tissue. It is the small particulates (less than five millimeters in diameter) that are of the most concern, because they can bypass our respiratory defenses and penetrate deep down into our lungs. Particulates are also known to exacerbate preexisting respiratory and cardiovascular conditions.
  
  

Nitrogen Oxides

• There are three primary varieties of the gas nitrogen oxide: nitrogen dioxide, nitric oxide, and--the most toxic--nitrous oxide. However, according to a Hofstra University study, none of these gases (which are commonly released from combustion engines) are particularly harmful to humans in comparison to other pollutants. Still, in high enough concentrations, nitrogen oxides can cause respiratory irritation and infection.
  
  

Sulfur Oxides

• The sulfur oxides in our atmosphere--most of which are the result of humans burning coal--include sulfur dioxide and sulfur trioxide. The latter does not stay in the atmosphere for long, because it often combines with water to form sulfuric acid, one of the components of acid rain. According to a University of Michigan study, breathing in sulfur oxides usually results in mild respiratory distress such as coughing. However, in high enough concentrations, it can cause respiratory infections.
  
  

Hydrocarbons

• Hydrocarbons such as methane, formaldehyde, benzene, and gasoline vapor are compounds made of the elements hydrogen and carbon. In gaseous form, they are referred to as volatile organic compounds, or VOCs. According to a Hofstra University study, all hydrocarbons/VOCs are carcinogens, and in high concentrations can cause cancers, including those affecting the respiratory system, such as lung cancer.