Where the fog comes from? The fog is triggered by temperature inversion - the formation of a static layer of cooler air close to the ground as the night time temperature drops. Normally, air closer to the ground is warmer than the air above it, and therefore the air rises. Inversions are frequent during winter nights after the ground has cooled down so much that it begins to chill the air closest to it often causing mist to form as water vapor precipitates on dust particles. Normally the morning sun swiftly breaks through the mist and heats the ground, which warms the air above it, breaking the inversion.
The fog phenomenon was studied for the first time in 1905. It was then described that a mixture of various gases with water vapors and dust cause the condition of fog. A large part of the gases that form fog is produced when fuels are burnt.
Fog phenomenon is experienced in Lahore, Faisalabad, Gujranwala, Gujrat and other cities situated in plains more because most of the cities have large number of registered vehicles, and many more come and go every day from out of these cities. Due to the concentration of heavy traffic, emissions of smoke and sculpture dioxide and nitrogen oxides are much greater than they are in adjoining rural areas. Some industrial concerns in and around cities also emit heavy amount of haze causing pollutants (mostly fine particles) directly into the atmosphere. Thick clouds of fog form when heat and sunlight react with the gases and fine particles in the air. Metrological Science experts say that air pollution can span broad geographic areas and be transported great distances, sometimes hundreds or thousands of miles.
Environmentalists attribute the heavy fog in the plains increasing in intensity as well as length of the fogy period every year to the constantly growing number of polluting vehicles that jam the roads. Many of the vehicles plying on the city roads are old vintage and have engines that guzzle petrol and diesel, and spew out poisonous fumes. Even heavy vehicle commute most city roads freely. But "the main threat is obviously cars. More so, when CNG is unavailable and everyone has to use petrol and or diesel. How can we improve air quality fast enough as in the absence of suitable city transport system more and more cars come onto the urban roads," says Metrological expert Faiz Rasool.
"What cities in plan areas are witnessing every winter since 1987 is the kind of killer fog that used to envelope cities like Los Angeles, London and Mexico City a few decades ago. While awareness about the dangers of pollution has resulted in improved emission standards in advanced countries, in Pakistan, we still do not have clean environment concerns," Faiz Rasool adds.
The calm puffs of air from plains does not help in blowing away much of the pollutants for winters and a large part of it remain hung a few hundred feet above the ground in the city. So, most mornings and evenings – especially in December through January - fog turned ‘smog’ defines the climate of the urban centers.
Smoke particles trapped in the fog give it a yellow black color and this often settles over cities for days causing poor visibility -- one of the most obvious indicators of pollution in the air. It often occurs as a result of fog that obscures the clarity, color, texture, and form of what people see. Result: The airports remains close during long hours of fog disturbing schedule of national and international flights. Motorway (M 2) has to be closed. Even railway schedule is affected.
The most harmful components of fog are ground-level ozone and fine airborne particles. Ground level ozone forms when pollutants released from gasoline and diesel powered vehicles and oil based solvents react with heat and sunlight. It is harmful to humans, animals, and plants. Not only that, the prime ingredient in fog, can come into the houses and combine with the other household pollutants that emanate from flooring, citrus scents or solvents in air fresheners, floor cleaners, deodorizers and furniture polishes and can enters the lungs. Hint for the health minded is to keep the windows and ventilate while vacuuming. Not to spray chemicals. Even putting on nail polish inside the house adds a bit to the indoor pollution. One should avoid even air fresheners or scented candles.
In winters, the vibrant and living cities get enveloped in fog from early morning and those suffering from lung ailments like asthma and other diseases are the worst sufferers. On many mornings, it fails to dissipate till even 10 AM or late. Doctors advise people to remain indoors, instead of going out on jogging or exercising out in the open. The last few days have seen hospitals reporting a large inflow of patients, especially children, suffering from lung ailments.
Relatively little has been done to control any type of pollution or to promote environmental protections until now in Pakistan. Today, smoke and sulphur dioxide pollution in cities is much higher than in the past. May be some government puts up a legislation to control pollution emissions. Or we keep getting used to the worsening situation. It is one of the very valid fields of scientific activities and political priorities elsewhere.
