What is Air Pollution

Air pollution is made up of many kinds of gases, droplets and particles that reduce the quality of the air. 

Air can be polluted in both the city and the country. In the city, air pollution may be caused by cars, buses and airplanes, as well as industry and construction. Air pollution in the country may be caused by dust from tractors plowing fields, trucks and cars driving on dirt or gravel roads, rock quarries and smoke from wood and crop fires.

Ground-level ozone is the major part of air pollution in most cities. Ground-level ozone is created when engine and fuel gases already released into the air interact when sunlight hits them. Ozone levels increase in cities when the air is still, the sun is bright and the temperature is warm. Ground-level ozone should not be confused with the "good ozone" that is miles up in the atmosphere and that protects us from the sun's harmful radiation.

What symptoms does air pollution cause? Air pollution can irritate the eyes, throat and lungs. Burning eyes, cough and chest tightness are common with exposure to high levels of air pollution.

Different people can react very differently to air pollution - Some people may notice chest tightness or cough, while others may not notice any effects. Because exercise requires faster, deeper breathing, it may increase the symptoms. People with heart disease, such as angina, or with lung disease, such as asthma or emphysema, may be very sensitive to air pollution exposure, and may notice symptoms when others do not.

Is air pollution bad for my health? Fortunately for most healthy people, the symptoms of air pollution exposure usually go away as soon as the air quality improves. However, certain groups of people are more sensitive to the effects of air pollution than others.

Children probably feel the effects of pollution at lower levels than adults. They also experience more illness, such as bronchitis and earaches, in areas of high pollution than in areas with cleaner air.

People with heart or lung disease also react more severely to polluted air. During times of heavy pollution, their condition may worsen to the point that they must limit their activities or even seek additional medical care. In the past, a number of deaths have been associated with severely polluted conditions. Pollution this bad is rare today in the United States.

The health effects of long-term exposure to low levels of air pollution are being studied.

What can I do to protect my family and myself? Check the predicted PSI in your area. Be careful if the PSI is greater than 100. Be careful also if there are high-risk weather conditions, such as a hot, sunny day, and you begin to develop symptoms like chest tightness, burning eyes or a cough.

You can protect yourself and your family from the effects of air pollution by doing the following:

• Stay indoors as much as you can during days when pollution levels are high. Many pollutants have lower levels indoors than outdoors.

• If you must go outside, limit outside activity to the early morning hours or wait until after sunset. This is important in high ozone conditions (as in many large cities) because sunshine drives up ozone levels.

• Don't exercise or exert yourself outdoors when air-quality reports indicate unhealthy conditions. The faster you breathe, the more pollution you take into your lungs.

These steps will generally prevent symptoms in healthy adults and children. However, if you live or work close to a known pollution source, or if you have a chronic heart or lung problem, talk with your doctor about other ways to protect yourself from air pollution.

Air Quality Index - AQI

The AQI is an index for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health effects might be a concern for you. The AQI focuses on health effects you may experience within a few hours or days after breathing polluted air. EPA calculates the AQI for five major air pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution (also known as particulate matter), carbon monoxide, sulfur dioxide, and nitrogen dioxide. For each of these pollutants, EPA has established national air quality standards to protect public health.

How Does the AQI Work? Think of the AQI as a yardstick that runs from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health concern. For example, an AQI value of 50 represents good air quality with little potential to affect public health, while an AQI value over 300 represents hazardous air quality.

An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level EPA has set to protect public health. AQI values below 100 are generally thought of as satisfactory. When AQI values are above 100, air quality is considered to be unhealthy-at first for certain sensitive groups of people, then for everyone as AQI values get higher.

Understanding the AQI The purpose of the AQI is to help you understand what local air quality means to your health. To make it easier to understand, the AQI is divided into six categories:

Each category corresponds to a different level of health concern. The six levels of health concern and what they mean are:

• Good - The AQI value for your community is between 0 and 50. Air quality is considered satisfactory, and air pollution poses little or no risk.

• Moderate - The AQI for your community is between 51 and 100. Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people. For example, people who are unusually sensitive to ozone may experience respiratory symptoms.

• Unhealthy for Sensitive Groups - When AQI values are between 101 and 150, members of sensitive groups may experience health effects. This means they are likely to be affected at lower levels than the general public. For example, people with lung disease are at greater risk from exposure to ozone, while people with either lung disease or heart disease are at greater risk from exposure to particle pollution. The general public is not likely to be affected when the AQI is in this range.

• Unhealthy - Everyone may begin to experience health effects when AQI values are between 151 and 200. Members of sensitive groups may experience more serious health effects.

• Very Unhealthy - AQI values between 201 and 300 trigger a health alert, meaning everyone may experience more serious health effects. "Hazardous" AQI values over 300 trigger health warnings of emergency conditions. The entire population is more likely to be affected.

There are 2 types of AQI Guides:

• Air Quality Guide for Ozone

• Air Quality Guide for Particle Pollution

The Pollutants

Hazardous air pollutants - also known as toxic air pollutants or air toxics - are those pollutants that cause or may cause cancer or other serious health effects, such as reproductive effects or birth defects, or adverse environmental and ecological effects. EPA is required to control 188 hazardous air pollutants. Examples of toxic air pollutants include:

• Benzene [which is found in gasoline]

• Perchlorethlyene [which is emitted from some dry cleaning facilities] and; 

• Methylene chloride [which is used as a solvent and paint stripper by a number of industries]. 

The Sources

Most air toxics originate from human-made sources including:

• Mobile sources (e.g., cars, trucks, buses) 

• Stationary sources (e.g., factories, refineries, power plants)

There are two types of stationary sources that generate routine emissions of air toxics: 

• "Major" sources are defined as sources that emit 10 tons per year of any of the listed toxic air pollutants or 25 tons per year of a mixture of air toxics. These sources may release air toxics from equipment leaks, when materials are transferred from one location to another, or during discharge through emission stacks or vents. 

• "Area" sources consist of smaller-size facilities that release lesser quantities of toxic pollutants into the air. Area sources are defined as sources that emit less than 10 tons per year of a single air toxic or less than 25 tons per year of a combination of air toxics. 

Though emissions from individual area sources are often relatively small, collectively their emissions can be of concern - particularly where large numbers of sources are located in heavily populated areas.

• Indoor sources (e.g., building materials and activities such as cleaning). 

(Source: FamilyDoctor, EPA & AirNow)