(Health impacts of major air pollutants as defined by the WHO)
Epidemiological studies have shown that symptoms of bronchitis in asthmatic children increase in association with long-term exposure to NO2. Reduced lung function growth is also linked to NO2 at concentrations currently measured in cities of Europe and North America.
The highest levels of ozone pollution occur during periods of sunny weather.Ozone at ground level is one of the major constituents of photochemical smog. It can cause breathing problems, trigger asthma, lung diseases or reduced lung function.
The most health-damaging particles are those with a diameter of 10 microns or less, (≤ PM10), which can penetrate and lodge deep inside the lungs. Chronic exposure to particles contributes to the risk of developing cardiovascular and respiratory diseases.
SO2 can affect the respiratory system and the functions of the lungs. Inflammation of the respiratory tract causes coughing, mucus secretion, aggravation of asthma and chronic bronchitis and makes people more prone to infections of the respiratory tract.
Carbon monoxide (CO) poisoning is the most common type of fatal air poisoning in many countries. CO is colorless, odorless, and tasteless, but highly toxic. It combines with hemoglobin which usurps the space in hemoglobin that normally carries oxygen, but is ineffective for delivering oxygen to bodily tissues. Exposures to CO may cause damage to the heart and central nervous system, as well as severe adverse effects on the fetus.
The main health hazard associated with methane is that it is highly combustible. Mixtures of 5 to 15 percent methane in air can be explosive. Large concentrations of methane in enclosed areas can lead to suffocation as large amounts of methane will displace oxygen in the air. The effects of oxygen deficiency are nausea, headaches, dizziness, and unconsciousness. Methane does not present any long-term, or chronic, health effects.
Ammonia vapour has a sharp, irritating, pungent odour that acts as a warning of potentially dangerous exposure. Exposure to very high concentrations of gaseous ammonia can result in lung damage and death. Although ammonia is regulated in the United States as a non-flammable gas, it still meets the definition of a material that is toxic by inhalation and requires a hazardous safety permit when transported in significant quantities.
Some VOCs are dangerous to human health or cause harm to the environment. However, not all VOCs are hazardous, and since not all hazardous materials are VOCs, the term HAP comprises those things that fall in that area. Harmful VOCs typically are not acutely toxic, but have compounding long-term health effects. Because the concentrations are usually low and the symptoms slow to develop, research into VOCs and their effects is difficult.