ISLAMABAD, Oct 30: Air pollution level in various cities of the country has either crossed safe limits or reached the threshold due to the presence of excessive suspended particulate matters (SPM) in the ambient air.

According to an official report of the Ministry of Environment, Local Government and Rural Development and other documents of international agencies, major urban air pollutants include SPM, sulphur dioxide, carbon monoxide, nitrogen dioxide, hydrocarbons and heavy metals.

These pollutants are produced by vehicles, industry, burning of solid waste, brick kilns and natural dust, said the ministry report.

Air pollution has been identified primarily as an urban issue, where the density of industry, buildings and vehicles prevents the pollutants from being dispersed.

The Pakistan Environment Protection Agency carried out a study with the assistance of Japan International Cooperation Agency (JICA) to investigate the ambient air quality in three major cities, Lahore, Rawalpindi, and Islamabad, and to find out pollution levels in traffic-congested areas.

The study showed that the average suspended particulate matter in the cities was 6.4 times higher than the World Health Organization (WHO) guidelines and 3.8 times more than Japanese standards.

The levels of sulphur dioxide, oxides of nitrogen and carbon monoxide were found in excess of acceptable standards in some areas, but, the average levels were found below WHO guidelines. Presence of such a high level of suspended particulate matter in the air is certainly a matter of concern due to its serious health implications for public, the ministry report said.

These pollutants, environmentalists say, are responsible for the increase in bronchial irritation and asthma. These can also cause irritation in the eyes, besides respiratory diseases.

Deliberating on the adverse impact of various pollutants, the environmentalists said, sulphur dioxide was a precursor of acid rain and was an irritant to the eyes, nose, throat and lungs.

Sulphur dioxide content is normally the highest at Peshawar Road and Marir Chowk. Aldehydes are particularly noteworthy for their foul smell.

Carbon monoxide is considered to be the most toxic common urban air pollutant since it reduces the oxygen carrying capacity of the blood. Exposure for about eight hours to the levels of carbon monoxide prevalent in our cities, the health experts and environmentalists believe, can cause impairment of nervous system functions. In Rawalpindi and Islamabad, the average hourly concentrations is around five to six parts per million that is extremely toxic.

Nitrogen dioxide, whose safe limits are 0.05 parts per million in most parts of Rawalpindi and Islamabad, are in the range of 150 to 240 parts per million.

Health experts say brief exposure to nitrogen dioxide in laboratories can cause illness, whereas extremely high contents as found in our cities can be fatal.

Lead, another pollutant, has been identified as being responsible for reduction in the intelligence quotient (IQ) of urban people.

Lead on being ingested can be deposited in the brain and its emissions are particularly hazardous for inner-city residents, living, working or playing around busy urban roads.

The report, while mentioning some of the causes responsible for slow dilution of pollution, states that Pakistan is an arid country with rainfall ranging as low as 80mm in the south to as high as 1,600mm in the north. Moreover, the wind speed, which is essential for eliminating pollution, is also low in the cities.

In the dry and low wind days, natural dust and anthrapogenic pollution, when generated in access, takes longer time to disperse. Over the last few years, the average rainfall has declined in many parts of the country. The level of suspended particulate matters and other pollutants, which have active co- relation with meteorological conditions, are likely to increase if the dry air condition prevails.—Zahra Syed