When a city running out of air

Beijing shrouded in smog again , three days after the city raised the orange alert for air pollution . The problem is something that is common in Asia and around the world . So what exactly is the smoke , and how it can be dangerous ?
Recently, reports of haze across Asia have made headlines . In fact , in the Chinese capital Beijing scientists have deemed the air quality is so bad that they consider the city " barely fit " to live .The word " smoke " coming from the early 20th century and is the construction of English words , smoke and fog . Smoke comes up most often when a cold front hits a densely populated city . The cold air moves under warm air which previously had been in the area . The cold front is heavier and sits on the city like a blanket .Before too long , the warm air above began working as a cap on the bottle and air movement between the two levels is almost stopped . It's called " weather inversion " is very important to form smog . This is also the reason why the smoke form more easily in winter than in summer .The other 'ingredients' in the smoke pollution , something that used to exist in large cities in large numbers . Pollutants emitted into the air from burning fossil fuels in power stations and vehicle engines and smoke from industrial and household and exhaust .The importance of the boundaryOver the years , the World Health Organization has warned that the fine particles of matter , ozone , nitrogen monoxide and sulfur dioxide are very harmful , repeatedly urged that a specific limit for each was introduced to protect the inhabitants of large cities .China struggling with a severe smog problemDuring the winter period the smoke , particulate matter , which comes from vehicle emissions , is a major issue . Particles 2.5 micrometers in diameter and can enter the lungs and heart attack .In the summer smoke , ozone becomes more of a problem . Nitrogen oxides and hydrocarbons , which are part of the emissions of the car , undergoes a chemical reaction when subjected to sunlight and form ozone . This gas is colorless and - despite protect us against the sun when at the top of the atmosphere - it is very toxic down at ground level .The risk of air pollutionMost people do not know how dangerous the actual smoke , " said Benedikt Steil of the Max Planck Institute for Chemistry in Mainz . Every year , in Germany , more than 40,000 people die from diseases related to air pollution . Figure is much higher than the number of deaths from traffic accidents .Long-term exposure to particulate matter , nitrogen dioxide and sulfur dioxide can cause chronic respiratory problems , according to the International Agency for Research on Cancer . Lung cancer and bladder cancer , for example , can increase the exposure to smoke .Health risks associated with smog also worse in developing countries than in industrialized countries . Many pollutants are generated during the process of energy production .In order to keep the air clean in cities such as Berlin and New York , the government has set up a low emission zone and build more public transport over the past decade . Steil said that , in developing countries , more and more people have to use bicycles for short trips . It will not solve the problem , he said , but it will be the beginning .