Smog

Major Components of Smog

Smogs Effect on Health

Smog

The word smog is a word that was coined in England to describe the combination of smoke and fog. In Ontario we experience a different kind of smog composed mainly of ozone and fine particles. Smog affects everyone and its components aggravate a wide range of health problems. The most common symptoms of exposure to high concentrations of smog are, coughing, wheezing and tightness of the chest. People most vulnerable to the affects of smog are the elderly, people with cardiac or respiratory problems, children and healthy adults who are highly sensitive to ozone. Children are especially affected by smog as they often play vigorously outside and as they need more oxygen for their size, they breathe faster.

The Ministry of the Environment and Energy (M.O.E.E.), in conjunction with Environment Canada, has developed a special program to warn Ontario residents when unacceptably high levels of ground-level ozone are either present or expected. Through this program, alerts are sent electronically to media resources and other major organizations for distribution throughout the region. Alerts issued to the media are added to radio and television weather forecasts. Air quality alerts are usually issued late in the afternoon the day before an ozone episode is expected. This allows residents an opportunity to take appropriate health precautions, and warns major pollution sources that they may need to reduce their emissions.

There are 2 two stages in a smog alert day. The first step is that the M.O.E.E. can issue the alert as either a smog watch or as a smog advisory. A smog watch is when there is a 50% likelihood that a smog day will occur within the next (3) three days. A smog advisory is when there is a strong likelihood that a smog day will occur within the next twenty-four (24) hours or when a smog day is about to happen or has happened without warning.

The second step is that the air quality is rated on a scale known as the air quality index (AQI). The air quality index is a public information device, used to inform residents about local ambient air quality conditions. To calculate the AQI, the M.O.E.E. monitors the airborne concentrations of several major pollutants, including carbon monoxide, nitrogen dioxide, ozone, sulphur dioxide, suspended particles and total reduced sulphur compounds. The monitoring is conducted at 33 locations in 27 Ontario cities. The air quality index scale is as follows:

• 0 to 15 indicates very good air quality.
• 16 to 31 indicates good air quality.
• 32 to 49 indicates moderate air quality.
• 50 to 99 indicates poor air quality.
• 100 and above indicates very poor air quality.

Smog is measured by the concentration of the pollutants in the air. The concentration of smog is usually expressed either in micrograms per cubic meter of air, or as parts per billion (p.p.b.), averaged over a given period of time. The pollution that most often exceeds the provincial ambient air quality criterion (AAQC) is ground-level ozone. Ontario's one-hour ozone criterion is 80 p.p.b. If forecasts indicate occurrences of ground-level ozone in excess of 80 p.p.b. over a wide geographic area, a smog alert is declared.

Smog is formed when airborne gases and fine particles react in the presence of intense sunlight and heat, which is why we get more of it in summer than in winter. From late spring to early fall, when the weather is hot and sunny, ground-level ozone is the leading component of smog. During cooler months, inhalable particulates comprise a higher proportion of the smoggy mix. Smog levels are strongly influenced by the weather, and the best conditions for the formation of ground-level ozone and smog are when:

• the air temperature is at or above 30⁰C (86⁰F)
• the solar radiation index is high
• there is little or no wind
• nitrogen oxides and volatile organic compounds are present in the air

In Ontario most smog producing pollutants are released as unburned by-products of the gasoline, coal and natural gas we use in vehicles, homes, businesses, industrial boilers and power plants. Vehicle emissions alone account for 40% of the total smog produced. Improvements in the design of vehicle exhaust systems have reduced pollution from individual vehicles, though total emissions are expected to increase because of the growing number of vehicles on the road.

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The Major Components of Smog

Nitrogen oxides (NO_x): a family of generally colourless and odourless gases (with the exception of nitrogen dioxide), are emitted from many sources, including motor vehicles, power plants, incinerators and a wide range of industries. High levels of nitrogen oxides irritate the lungs and can cause coughing, dizziness and headache. Nitrogen oxide emissions also contribute to acid rain and global warming.

Volatile organic compounds (VOCs): are released from a variety of sources including solvents and paints as they are being produced and used, motor vehicles being operated and wood while it is burning. The health effects vary according to the compound and range from relatively non-toxic chemicals to dangerous neuro-toxins and carcinogens. Volatile organic compounds are among the precursors of ground-level ozone and smog.

Ozone (O₃): a colourless gas with a sharp electrical smell is highly unstable and very reactive. A key ingredient in smog, ozone attacks the lungs and respiratory tract and depending on the concentration and a person's sensitivity, may cause coughing and other breathing problems, watery eyes, headache, reduced vision, fatigue and difficulty concentrating. Ozone can be broken down into two types, stratospheric and tropospheric ozone. Stratosphere ozone is produced when radiation from the sun splits oxygen molecules (O₂), which re-combine to form ozone (O₃). Stratospheric ozone is located in the earth's upper atmospheric layer, between 16 and 50 kilometers above the ground. Stratospheric ozone is considered "good" since it filters the sun's harmful ultraviolet (U.V) rays and protects people from sunburn and skin cancer. Tropospheric ozone also known as ground-level ozone, is produced by the combination of nitrogen oxides and volatile organic compounds in intense sunlight. Tropospheric ozone, located anywhere from ground level to 16 kilometers above the planet, is considered "bad" because of the damage it does to human health and the environment.

Particulates: high concentrations of particulates are responsible for the dirty haze of smoggy days and are classified according to size. Inhalable particulates, known as particulate matter PM₁₀, are smaller than 10 microns in diameter and are emitted directly into the air from many sources including dust and ash blown up from roads, construction sites and agricultural areas, forest fires, power plants, industrial processes and vehicle emission, particularly from diesel engines. The respirable particulates, particulate matter PM_2.5 are smaller still, less than 2.5 microns size, which means they can be drawn into the deepest parts of the lungs. The PM_2.5 fraction is derived primarily from common air pollutants and can also be formed in the atmosphere by the chemical reaction of gaseous pollutants, such as sulphates from sulphur dioxide, nitrates from nitrogen oxides and organic particles from volatile organic compounds.

Nitrogen dioxide (NO₂): is a toxic red-brown gas with an irritating odour and is emitted by all combustion processes. Nitrogen dioxide can irritate the lungs and lower resistance to respiratory infection. It can also damage materials and vegetation. When combined with water, nitrogen dioxide forms acid rains. It is also a component of smog and contributes to the formation of ground-level ozone and particulate matter.

Sulphur dioxide (SO₂): is a colourless gas with a pungent, distinctive odour. Exposure to high concentrations of SO₂ can cause breathing discomfort, respiratory illness and the aggravation of existing lung and heart disease. Sulphur dioxide can also be chemically transformed into acidic pollutants and fine particles, both of which pose health risks. The main source of airborne sulphur dioxide is from coal-fired generating stations and non-ferrous ore smelters.

Carbon monoxide (CO): is a colourless, odourless and tasteless gas that is released by combustion processes and found in automobile emissions. Carbon monoxide in the bloodstream can impair the transfer of oxygen to the organs and tissues of the body. High concentrations can cause blurred vision, clumsiness and even death. Lower levels can cause discomfort for people with heart or lung disease.

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Smog's Effect on Health

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