Moreover thousands of diesel-run vehicles, vehicles with faulty engines and industries are spewing toxic fumes to add to the worsening air pollution.

Millions of people especially children are the worst sufferers with various respiratory complications during this dry season. City clinics and hospitals are swarmed with patients complaining of various respiratory problems.

According to experts at the Air Quality Management Project (AQMP) in addition to toxicity, the city air is also polluted with huge amount of particulate matters generated by drought and also from industrial, such as the brick kiln wastes.

AQMP,s Director Dr Mohammad Nasiruddin said that constant exposure to such high concentration of particulate matters can cause cancer, hypertension, lung and heart problem and related diseases.

The main causes for air pollutions are continuous emission from thousands of faulty diesel-run buses, trucks and other vehicles, the 4,000 brick kilns around the city and haphazard re-rolling mills, factories and tanneries have turned it into a virtual "gas chamber", enveloping the metropolis with thick smog.

World Bank (WB) sources said that recent conversion of the brick kiln chimneys into 120 feet tall chimneys has 'not at all helped' the city environment. The kilns use 'worst quality coal with high sulphur', vehicle tyres, fuel wood and even discarded polythene bags as fuel. Fumes from the kilns contain an extremely high count of sulphur dioxide and ash.

Deterioration of air quality has reached its peak in the current lean period with scarcity of rain. People of all ages are exposed to various health hazards due to the toxic haze hanging in the atmosphere, another Department of Environment (DoE) source said.

"There is no consorted effort to combat air pollution. To combat air pollution we need effort from several ministries like Communications Ministry, Energy and Mineral Resources Ministry, Environment and Forest Ministry, Housing and Public Works Ministry and Industries Ministry," said an official Department of Environment.

To measure the variation of air quality in the AQMP has recently set up five satellite stations in Razarbagh, Tejgaon, Lalbagh, Narayanganj and in Tongi. The results of the study show that among the five areas air quality is the worst in Lalbagh.

According to Bangladesh standards the permissible level of particulate matters (PM)10 in the city air is 150 microgram per cubic metre (mg/m3). But the study conducted by AQMP shows that in Lalbagh during the month of November the PM10 rose to 230 microgram per cubic meter. The PM 2.5 in Lalbag reached to 160 microgram per cubic meter while the endurable air quality PM2.5 is 65 mg/m3.

Brick kilns, haphazard industries, unfit human haulers, foundries, polythene industries and diesel run launches are the worst polluters, said the sources.

During winter the concentration of particulate matters in the air is the highest due to climatic condition. Air pollution worsens from end of October and continues until the rains come.

"During the winter months, wind speed and velocity are reduced, for this reason, thermal pollution occurs and smog and fog appear, " said an expert.

According to Environment Ministry officials, the then government without introducing any substitution of transport, banned the two stroke three wheelers auto rickshaws in 2003 and introduced limited number of CNG-run four stroke three wheelers from January, 2003 to improve the air quality of the city.

As a result a vacuum occurred for the city dwellers in transport sector and taking advantage of the situation unfit vehicles took to the streets.

"We have again returned to the same situation as prior to 2003," the official said.

Dr Noor Alam, registrar of Medicine, Sir Salimullah Medical College & Mitford Hospital urged city dwellers to use protective mask during winter to avoid dust, smoke and respiratory diseases.