'Our children are our future', it is not only a slogan of politicians, but also a faith most people in the world have. New generation benefit a lot from the advances of the 20th century. Yet this progress has come with many unpredictable consequences. In the last 50 years, 75000 chemicals have been developed and introduced into the environment. The overall incidence of childhood cancer increased 10% from 1975 to 1994, which is one of the scientific evidence clearly demonstrates our children are vulnerable to environmental hazards. The exposure to air pollutants is at the greatest risk as we cannot stop breathing, and children breathe more air than adults, which means that they receive higher doses of pollutants in air. Thus the internal organs of teenagers are more susceptible because of immaturity. Therefore, studying the effects of air pollution on children is so important to raise the awareness on the issue thus to protect them from the hazards.
             Many studies have shown that the exposures to common air pollutants are associated with the increased respiratory illnesses and symptoms, aggravation of asthma and decrease in lung function in children. Those common pollutants include ozone, particulate matter, nitrogen dioxide sulphur dioxide and airborne lead. Ozone is formed as a result of complex chemical reactions involving volatile organic compounds and oxides if nitrogen in the presence of sunlight. Particulate matter is fine dust, metal, soot, smoke, dirt and liquid droplet suspended in the air. The dioxides are formed during the combustion of fuel. The major sources of those harmful pollutants include motor vehicles with leaded gasoline exhaust, coal-burning power plants, refineries, industrial facilities, metal smelters and even from old paint in homes. In 1999, a figure from the World Health Organization (WHO) alarmed us that over 60% of the children population in the world lived in areas with air quality that did no...