OMA
Smog-Wise Information Program – Backgrounder
In light of new health studies, which have further examined the impacts of smog, the Ontario Medical Association has updated our smog advisory health information for physicians and their patients. What follows is a general overview of the health risks associated with elevated smog levels, accompanied by fact sheets offering advice to smog-vulnerable groups (The OMA's Smog-Wise Information for Parents can be found at www.oma.org/phealth/smogwisekids.htm and OMA's Smog-Wise Information for Seniors athttps://www.oma.org/phealth/smogsr.htm
Few things are as important as the air we breathe, but our breathing has been increasingly threatened by smog. Smog is a complex mixture of pollutants, mainly ground-level ozone and fine particulate matter.
Ground-level ozone is different from the stratospheric, "ozone layer", which protects us from the sun's harmful ultraviolet rays. At ground-level, ozone gas is toxic to the respiratory system, and is the pollutant that has historically triggered nearly all of the smog alerts in Ontario. Fine particulate matter are tiny specks of either liquid or solid particles, which are suspended in the air. They consist of soot and acids, which can lodge deep in our lungs.
The main sources of the man-made chemicals that make up smog are automobile emissions, coal-burning power plants and other heavy industries. They are emitted locally and from sources as far away as the United States and drift across the Ontario landscape on the prevailing winds.
Since polluted air masses cover large areas, and usually move slowly, the smog problem is not only confined to cities and industrial centres. Smog builds up in both urban and rural areas, blanketing southern Ontario, from Windsor to the Quebec border, along the Lake Huron shoreline, and as far north as Sudbury and North Bay. Smog episodes can also last for days at a time.
We are most familiar with elevated smog concentrations in the summer, especially on hot, sunny days, because that is when ozone is at its worst, but now that fine smog particles have been added to Ontario's Air Quality Index, a smog day can happen at any time. It is likely, though, that most will still be in the summer.
Ground-level ozone is invisible, but particulate matter often gives the air the hazy appearance that we associate with a smoggy day. The yellowish-brown colour in the sky on polluted days is the result of nitrogen dioxide, a poison on its own and one of the building blocks of ozone and particle pollution. Whereas ground-level ozone concentrations are higher in the late afternoon and evening, these smog particles can be high at any time of the day.
The Ontario Ministry of the Environment reports several times a day on the Air Quality Index (AQI) and provides three-day air pollution forecasts. When smog levels are forecast to be high, the ministry issues a smog alert, which is widely reported via television, radio and newspapers. Smog alerts are targeted at the general population, so for those of you who are most vulnerable (e.g., asthmatics and heart patients) there can be significant health impact at lower pollution concentrations, i.e., less smog will trigger a physical reaction.
It is important to not be confused by the different names used for a smog alert. It is also sometimes called a Smog Watch, Smog Warning, Air Quality Advisory, or Air Quality Alert. Some of these terms refer to different forecast timeframes, so it is important to note the day for which the alert is being issued and to plan accordingly, but they all mean that you should take precautions.
Smog alerts are often accompanied by health advice on the possible risks associated with smog exposure, and although it is important to pay attention to these health warnings, they are not fully protective for all parts of the population. It is important that those who are vulnerable to the effects of smog, pay heed to these warnings, but remember that this system is not perfect. The combined effects of these different pollutants on our cardiac and respiratory systems has not been factored in to these warnings. We also know that many people are affected at smog concentrations below the designated "poor air" level. There is no threshold for smog's health effects, so don't mistake smog concentrations below the smog 'alert' level as "safe".
It is now accepted that smog affects a range of cardio-respiratory health problems. Smog increases the number of people affected by asthma, it increases the number of asthma attacks and makes them worse. Smog over-burdens the heart, but can also cause relatively minor irritation of the eyes and throat. Smog's health impact includes increased emergency room visits and hospital admissions, and even premature death.
The health evidence against smog continues to grow stronger all of the time. Recent studies have shown that athletic kids living in polluted cities are more likely to develop asthma, have linked smog particles to lung cancer, and found that increased concentrations of these particles increases heart attack risk. Although everyone can be affected by smog, some groups are much more sensitive. These include individuals with cardiac conditions such as heart failure and arterial sclerosis, or respiratory diseases such as asthma, emphysema and chronic bronchitis. Any elderly individual may also be at increased risk. Children are at greater risk than adults because they take more breaths and, in summer, spend more time active outdoors. Adults who are exercising outdoors, such as joggers and cyclists, as well as outdoor workers, may also be at increased risk because they draw more polluted air through their lungs.
Heat and humidity, which are often a problem at the same time as smog, add synergistically to the stress on the cardio-respiratory system from smog, especially in those with pre-existing cardiac and respiratory compromise.
To protect yourself from smog you must become aware of when smog levels are high.
AQI readings are available on the Ministry of the Environment's Air Quality in Ontario web site (http://www.airqualityontario.com). Daily AQI values and forecasts are also available from the Ministry of the Environment by calling (416) 246-0411 in Toronto, and toll-free at 1-800-387-7768 (English) or 1-800-221-8852 (French).
You can also listen and watch for the smog advisories in local weather reports on the TV or radio, but also pay attention to the weather itself. If a hot and hazy day is forecast, the air quality is not likely to be very good, whether a smog alert has been called or not.
If you can't access a weather report, it is easy to basic sense of the air quality yourself. In general, the hotter it is - the worse the ozone level; the hazier - the worse the smog particle concentrations. Haze on rainy days isn't usually as bad because rain washes some of the pollution out of the atmosphere.
Since individual health responses to smog vary widely, it is important to pay attention to your breathing and the breathing of those in your care. The fact that you are breathing freely does not mean that your children will respond to these pollutants in the same way.
Common sense suggests that very hot, hazy days are not the best days for outdoor exertion even if smog was not a factor, so taking the precaution of limiting strenuous activity can reduce your exposure and help in a number of ways. If you feel the immediate effects of air pollution, trust what your body is telling you and don't push yourself beyond a comfortable physical limit.
We are still learning about the short and long-term effects of smog, but we do know that reducing your exposure on high pollution days is appropriate preventative medicine.
A clean and cool environment is the most comfortable place to be on smoggy days. Putting off strenuous outdoor activities until it feels more comfortable makes good health sense.
For more detailed health-protective suggestions, please refer to the OMA Smog-Wise Information Program Fact Sheets for those who are most vulnerable to smog.
Please visit www.oma.org/phealth/smogmain.htm