PM2.5 is a concentration measurement of particulate matter (PM) in the air with a diameter of 2.5 micrometers or less, roughly a 30th the width of a human hair.
In regards to human health, this measurement is of great importance. The relatively microscopic size of PM2.5 gives it the potential to lodge deep into the most sensitive part of the respiratory tract upon inhalation – triggering respiratory illnesses such as asthma, bronchitis, and emphysema. After this particulate matter is absorbed by cells in the lungs, it has the capacity to travel to the heart - increasing the potential for cardiovascular problems such as arrhythmic heartbeats and heart attacks.
Because PM2.5 is simply defined by it’s size, it can originate from both organic and inorganic sources. Common sources include: soil, diesel exhaust, combustion emissions, and industrial processes such as construction and demolition.
Similar to PM 2.5, PM 10 is suspended particulate matter which can appear in either a liquid or solid forms. PM 10 differs from PM2.5 only in terms of size.
While PM 2.5 is particulate matter that has a diameter of 2.5 micrometers or less, PM 10 is particulate matter with a diameter between 10 - 2.5 micrometers. Therefore, PM10 is the larger, coarser particles in the air.
PM10 is not as dangerous as PM2.5 because it’s relatively larger size prevents it from being easily absorbed into the bloodstream. It can, however, cause irritation to the eyes, nose, and throat.
Sources for PM10 include dust and dirt from roads, farms and dry land as well as inorganic combustion.
The Ozone molecule is a naturally occurring compound that plays a vital role in blocking out harmful ultraviolet light from the sun. At the ground level however, ozone is toxic.
While other pollutants are emitted directly into the air by various sources, Ozone is simply created by sunlight acting on nitrogen oxides (NO) and volatile organic compounds (VOC) in the air. For this reason, Ozone is the most pervasive and most difficult to control of the six pollutants.
Short term exposure to even low concentrations of Ozone significantly reduces lung function, often causing respiratory inflammation. Other symptoms can include chest pain, nausea, coughing, and pulmonary congestion. Long term exposure to high levels of ozone, on the other hand, can cause very serious and permanent structural damage to the the lungs.
Nitrogen Dioxide (NO2)
Nitrogen dioxide is the pollutant with the characteristic biting odor we associate with pollution. In high concentrations it appears as a reddish-brown gas.
While not particularly harmful in itself - it is the precursor for pollutants like ozone and particulate matter.
Nitrogen dioxide is either formed naturally during thunderstorms or from combustion processes, most commonly in running car engines. Indoor sources include unvented heaters and gas stoves.
Health effects include irritated lungs and lower resistance to respiratory infections like influenza. Short term exposure seemingly produces only mild effects, while long term exposure leads to increased incidences of acute respiratory illness.
Carbon Monoxide (CO)
Carbon Monoxide is typically formed from incomplete combustion in vehicles, heating, coal-fired power generation, and biomass burning.
High levels of carbon monoxide is dangerous because it prevents oxygen uptake in the blood, causing a lack of oxygen supply to the heart.
Short term effects are similar to that of oxygen deprivation: headaches, dizziness, fatigue, heart palpitations, nausea, confusion, visual disturbance and muscle twitches.
Meanwhile, long term exposure to carbon monoxide can cause symptoms resembling the flu - headache, fatigue, muscle aches, nausea, vomiting and a sensitivity to light, odor and taste.
Special attention should be paid to avoid high levels of CO during pregnancy as exposure can cause brain damage in newborns.
Sulphur Dioxide (SO2)
Sulphur dioxide is commonly responsible for acid rain and low visibility. It’s prevalence is almost entirely man-made. It is formed when energy sources containing sulphur, like coal and oil, are burned in industrial processes. It can also result from fuel combustion in vehicles.
When inhaled, sulphur dioxide can cause shortness of breath and chest pain. In the long term, it can cause acute respiratory illness and permanent changes in the lungs' biology.