From March to May, the winds are westerly or south–westerly in the western half but south-south easterly in the eastern half. Occasionally Nor’westers, of course, change the wind direction and bring relief from the dull heat.

From June to September, the winds are not all southerly, much of it being south-easterly, and even easterly.

In October the winds are very variable, but there is a definite strengthening of the northerly winds at the expense of the south-easterlies. The Inter-Tropical Convergence Zone is in the north of Bangladesh during the four monsoon months and thus it is a pronounced field of air mass convergence.

The season Monsoon is predominant among all other seasons in Bangladesh, where wind direction reverse completely with season. In winter, the prevailing wind is from north east and hence pollution even from Gobi desert can affect from Bangladesh. During the premonsoon season say March to May the wind can come from North west and pollutants even from Balucchistan desert can affect us. Thus sometime we experience hot "Loo" wind in this season. In summer the wind is predominantly from southwest southeast, which mainly comes from the sea, and our sea is perhaps free form lot of pollution and hence Bangladesh experience less pollution during summer.

In Bangladesh no study has been conducted on Atmospheric Transport of Air Pollution as yet. Some researcher claim that the degradation of Sunderban the largest mangrove forest of the world, which is now, a world heritage, site is being destroyed by Transboundary airborne pollution. Some even suggests the pollution may move towards China. But as there is no systematic study on those matters, it is mere predication. So thorough study on these matters need to be done and Bangladesh is eager to participate in this study.
 
 

2) Industrial units not located in designated industrial area shall not discharge or emit any pollutant, which may deteriorate the air quality in the area (c) & (d) of Table-4.1.

3) Suspended Particulate matter (SPM) means airborne particles of diameter of 10 microns of less.
 
 

Suspended particulate that measures 10 microns or less remain in the atmospheric longer than large particles and are small enough to be inhaled deeply into the respiratory tract. Hence, particulate matter can contribute to respiratory to illness, with the toxic effect dependent on the chemical nature of the particulate and gases that may be absorbed on particulate surfaces or absorbed within particulate.
 
 

Children and both healthy and at-risk adults are vulnerable to SO₂ emissions, depending on health status, individual sensitivity, and activity level. Individual who suffer from chronic respiratory diseases such as bronchitis, emphysema, and asthma may experience coughing and difficulties in breathing when the SO₂ concentration rises from 0.1 to 0.2 PPM. It has been documented that asthmatics are up to 20 times more sensitive to atmospheric SO₂ than healthy adults.

The effect of SO2 on beans and tomatoes is very sever. Sulphur Dioxides enter the stomata directly and the plants cells in the mesophyll. It converts to sulphite and latter to sulphate.
 
 

Nitrogen dioxides is a respiratory irritant that also causes irreversible ling damage to persons exposed to it for long periods of time. Other ill effects include chest tightness, burning of the eyes, and headaches. People wit asthma is particularly vulnerable to these effects and to bronchitis. Recurrent exposure to high concentrations of NO₂ is more damaging than constant exposure to lower-level concentrations.

NO₂ causes suppressed growth in beans and tomatoes.
 
 

Currently, the World Health Organization suggests that a level of 20 microgram of metal per decilitre of blood (20 micro gram/dl) is the maximum acceptable concentration. Other studies consider that the detrimental effects of exposure to lead appear at concentration of between 10 and 15 micro gram/ dl. It is not necessary; however, to have been exposed to major doses of lead contract lead poisoning. The body tends to accumulate lead over a lifetime and can release it only slowly. Hence even exposure to small concentrations of lead over a long period can produce harm. It is the total body burden of lead that is related to adverse effects.

Recently a descriptive cross sectional study have been conducted by a researcher of Department of Occupational and Environmental Health of NIPSOM on Rickshaw pullers, Baby taxi drivers, Traffic police, Tempo assistants, Petrol pump operators and motor vehicles serving men of some selected areas of Dhaka city. In this study it was found that, the mean blood lead levels of Rickshaw pullers was 248 m g /dl (range 154-344 m g /dl), of Baby Taxi drivers 287 m g /dl (range 161-372 m g /dl), Traffic polices 272 m g /dl (range 152-32 m g /dl). Tempo assistants 255 m g /dl (mean 177-49.9 m g /dl), petrol pump operators 249 m g /dl (mean 177-314 m g /dl) and Motor vehicles serving men was 264 (mean 207-342 m g /dl). The mean blood lead level on of among all these risk group was found to be higher than the accepted value. The traffic police group was the worst affected. The study also noted that blood lead levels increased with the duration of exposure. It was also observed that there was a relationship between increased blood lead levels with some signs and symptoms of respondents exposed.

Note: So far no study has been conducted in Bangladesh on impacts of air pollution on livestock, corrosion of materials, buildings and monuments; impacts of gases (mainly SO2 and ozone) on crops; forests or natural vegetation; acidification of soils and surface waters by acidic deposition; impacts due to the excessive build-up of nitrogen in ecosystems (eutrophication); Visibility and impacts on water quality (e.g. salinisation).