The sun still shines here in Dhaka, but more often than not, the Bangladeshi capital's millions of residents are oblivious to that because of the ever-present smog.

Indeed, Dhaka's air is now so polluted that its lead content is even higher than that of Mexico, which is often referred to as having the worst air quality in the world.

According to the Bangladesh Atomic Energy Commission, each cubic metre of air in Mexico City has an alarming 383 nanogrammes of lead, but Dhaka bests that with 463 nanogrammes.

As a result, Dhaka's nine million people are at risk of falling ill with a variety of sicknesses, with the city's children more vulnerable than others to succumbing to the effects of dirty air. One World Bank report even says that air pollution is to blame for some 15,000 deaths in the country each year.

The report also says that in the four major cities of Dhaka, Chittagong, Khulna and Rajshahi, the ''major disease is not diarrhoea, as is the general perception, but acute respiratory infections caused mainly by the polluted air''.

At the Dhaka Shishu (Child) Hospital, respiratory problems top the list of afflictions of the 450 outpatients the institution has each day.

Thousands of children who seek medical treatment in other hospitals across Dhaka are also often found to have illnesses related to lead poisoning, which may cause extensive damage to the brain and the nervous system.

At the very least, say experts, high lead in the blood of children retards their mental growth.

''Children of Dhaka are more at risk than the adults because their bodies are still developing,'' explains Dr Manzoor Hussain, director of the Dhaka Shishu Hospital. ''They tend to absorb pollutants more readily than adults do and retain them in the body for longer period of time.''

Most vulnerable

Manzoor also says that because the children's breathing rates are substantially higher than that of adults, the children are exposed to greater level of pollutants. He adds that children under six are most vulnerable to toxic effects of air pollution, as are youngsters who are malnourished.

Separate studies conducted by the Dhaka Shishu Hospital and the International Centre for Diarrhoeal Diseases and Research, Bangladesh (ICDDR, B) have found that children living in slums close to main city streets already carry dangerous levels of lead in their bodies.

In some children, the lead was found up to 30 to 40 microgrammes per decilitre of blood as against the permitted level of 10 microgrammes per decilitre.

Complicating the situation is the fact that children who have fallen ill because of lead poisoning are sometimes misdiagnosed and written off as suffering merely from malnutrition.

Says one paediatrician who declines to be identified: ''In Dhaka city, hundreds of children down with lead pollution are getting wrong treatment as the general medical practitioners are unable to diagnose the cause of their illness.''

Observers say the cause is evident enough in the streets, which is usually choked with fumes from about 200,000 cars and 50,000 auto-rickshaws fitted with two-stroke engines, as well as industrial emissions and brick-burning.

These translate to about 50 tonnes of lead being mixed with Dhaka's air annually, along with 73 tonnes of carbon monoxide, 17 tonnes of hydro-carbons,19 tonnes of nitrogen oxide and 4.2 tonnes of suspended particulates, says one Department of Environment report.

Address the problem

The previous government had tried to address the problem by banning the importation of leaded gasoline and two-stroke engines for the auto-rickshaws.

It also signed contracts for the import of modern passenger buses to replace the decrepit commuter vehicles plying the city's streets and established an environment court.

The present administration of Prime Minister Begum Khaleda Zia has followed these up with an announced phasing-out of the auto-rickshaws with the two-stroke engines.

In the past month, more than 2,000 outdated public and private vehicles have been withdrawn from the streets of Dhaka as part of the drive to combat air pollution.

The government has drawn up a comprehensive programme aimed at ridding all of urban Bangladesh of air pollution.

While that may sound like a tall order, Forest and Environment Minister Shahjahan Siraj has repeatedly said that the government is committed to present pollution-free cities to the people of Bangladesh.

Converted in phases

Under the plan, all petrol run vehicles will be converted into compressed natural gas (CNG) driven ones in all government and semi-government organisations in the next two years and other vehicles in phases.

The government is also planning to convert all petrol pumps into CNG pumps in the next two years. To quicken the conversion process, the government will extend full cooperation to the private sector by making it easier to get the loans they need and complete the required paperwork.

So far, however, little is being done about the hundreds of industrial establishments in and around Dhaka over the years, despite zoning laws that prohibit such to be set up close to residential areas.

Laments Manzoor: ''We are pitifully behind, not just scientifically and technologically, but more potentially in our ability to grasp the true nature of the problem.''

''This time,'' he says, ''if we fail to face the challenge of air pollution, there will be a man-made disaster — the cost of which will be unbearable for both (our) families and the nation.''