MOST commuters in Karachi have experienced getting stuck in traffic jams for an extended period during evening rush hour. The main concern of commuters at that time is reaching home in the shortest possible time. But now, the commuters have to worry about a potentially lifethreatening side-effect of getting stuck in gridlock.

In October, the International Agency for Research on Cancer (IARC), the specialised cancer agency of the World Health Organisation, announced that it has classified outdoor air pollution as carcinogenic to humans.

The IARC concluded that there is sufficient evidence that exposure to outdoor air pollution causes lung cancer.

It also noted a positive association with an increased risk of bladder cancer. Particulate matter (PM), a major component of outdoor air pollution, was evaluated separately and was also classified as carcinogenic to humans.

While it is already known that increased exposure to airpollution causes health impacts like lower respiratory, cardiovascular, and reduced lung function problems and probably lung cancer, this is for the first time that the agency has given definitive and confirmed findings of lung cancer caused by outdoor air.

So, as it turns out, the most widespread environmental carcinogen in Karachi, or for that matter in Hyderabad and Sukkur, is the air we breathe! Components of air pollution that are major threats to human health in causing lung cancer are PM2.5 and PM10.

To put a better perspective on the particle size, the size of a single hair from a person`s head is about 70 micrometers in diameter. That means a single hair is 30 times larger than the largest fine particle.

A large number of anthropogenic and natural sources contribute to airborne PM.

These include cement industries, quarries, power plants, smelters, motor vehicles, buses, minibuses, trucks, solid waste burning, dust andtobacco smoke.

While a systematic air quality monitoring network is not in place in Karachi, the level of PM2.5 in the city`s ambient air during traffic congestion and at busy spots like Empress Market, Plaza (M.A.

Jinnah Road) and Gurumandir, must be around 70 micrograms per cubic metre (ìg/m3). The WHO guideline value is 10ìg/m3 annual mean.

In addition to the threats posed by PM, airborne lead is also of major concern. A study conducted in 1989 in Saddar found blood lead levels in schoolchildren as high as 38ìg/dl (micrograms per decilitre). A study conductedin 2002 in Karachi showed that over 80pc of the children have blood lead levels of more than 10ìg/dl. Airborne lead is due to the use of leaded gasoline in vehicles.

Lead is implicated in neurological problems in children, including impaired cognitive, motor, behavioural, and physical abilities.

Normally, a blood lead level of 10ìg/dl is taken as a maximum permissible concentration.

Road traffic noise is also a nuisance in Karachi. Buses, minibuses, rickshaws and motorcycles produce noise of more than 100 dB(A) decibels on A-weightage scale.

Noise level of more than 65 dB(A) causes heart rate variability, hearing impairment, psychological problems, neurological complications including depression, sleep disturbance, ringing in the ears, annoyance and irritation.

There are a number of technical strategies that can be used, quite often in combination, to improve the ambientair quality in Karachi. An efficient and decent bus rapid transit (BRT) system is a longterm solution that will take people away from their cars and put them in decent public transport.

Other strategies include improved condition of roads; synchronisation of traffic signals; vertical extension of exhaust pipe; regular engine tuning and maintenance of ageing vehicles; car-pooling in schools and in offices; preventing on-street parking; staggered working hours (say in offices located along I.I Chundrigar Road) to lessen the traffic peaks; no-drive days (for example, no cars should be allowed in Saddar one day a week) and use of bicycles.

The Sindh Environmental Protection Agency (SEPA) has the mandate to control air pollution in the province. It needs to take action against the smoke-emitting and noisy vehicles, polluting industries and departments responsible for burning solid waste out in the open.-F.H. Mughal