The arrival of the monsoon is literally a breath of fresh air for Kathmandu residents. The rains flush out the pollutants, and air quality is much cleaner. This natural phenomenon is clearly reflected in the data collected by newly established monitoring stations in Kathmandu measuring the concentration of fine dust particles in the air.
Just before this year's monsoon arrived in mid-June, the Putali Sadak station recorded 461 micrograms per cubic meter concentration of dust particles less than 10 microns, also known as PM10.

This is almost four times higher than the national ambient air quality standard (NAAQS) which is 120 micrograms per cubic meter for particles that size. The WHO guideline for PM10 used to be 70 micrograms per cubic meter (WHO does not have a guideline value for PM10 anymore because it says there is no safe limit for such fine dust).

But within a few days of the start of the monsoon, the PM10 concentration at Putali Sadak had gone down to less than 100 micrograms per cubic meter. The conclusion: the monsoon is the healthiest time for Kathmandu Valley residents, at least as far as breathing is concerned.

Records from major hospitals in Kathmandu indicate the prevalence of diseases related to air pollution is on the rise. At Patan Hospital, the number of patients admitted with Chronic Obstructive Pulmonary Disease (COPD) has almost doubled in the past five years. Similar increases are observed at Bir Hospital and Teaching Hospital. The number of COPD cases shoot up in the winter when the air quality is especially bad (see graphs).

From November to May, PM10 levels along Putali Sadak and Patan Hospital exceeded the national standards on 99 percent of days. At these locations, the air could be classified as "unhealthy" more than 9 out of 10 days, "very unhealthy" in 7 percent of the days and "hazardous" in 2 percent of the days. These numbers should be sending out alarm signals to anyone breathing Kathmandu's air.

The data also indicates that the air quality has deteriorated significantly over the past few years. In November 1993, Environment and Public Health Organization (ENPHO), a local NGO, took several 24-hour measurements of PM10 in Putali Sadak and reported an average value of 92 micrograms per cubic meter. Ten years later, the figure for PM10 in November had shot up to 270 micrograms per cubic meter.

Danish air quality expert Karsten Funglsang says that in Western countries, this level of pollution would cause the government to issue an emergency health alert requiring people to stay at home.

The main culprit in Kathmandu is vehicular emissions that get trapped because of poor air circulation. The dispersion of pollutants is especially bad in the winter when thermal inversion (where cold air flowing down from the mountains is trapped under a layer of warm air) creates a lid that keeps the pollutants sealed within the Valley.

The main sources of air pollution used to be the Himal Cement Factory, brick kilns and vehicles. Now, with the closure of the cement factory and the possibility of new environment-friendly brick kilns replacing old polluting chimney bhattas starting next year, vehicles are becoming the main culprits.

The Ministry of Population and Environment estimates that the PM10 emission from vehicles in Kathmandu has gone up by more than 5 times, from 570 tons per year to 3,259 tons per year, in the past ten years.

At the alarming rate of 16 percent per year with which vehicles are being added to Kathmandu's congested streets the number will double in five years. It is clear that neither Kathmandu's road infrastructure, nor its air is ready to handle this kind of increase. Still, hundreds of vehicles, especially polluting diesel vehicles, are added to the streets every day while new electric vehicles have been stuck at the customs for over a year.

While drafting the National Ambient Air Quality Standard this year, the government promised to meet the threshold within three years-a target that is very ambitious, but not impossible. If the government is serious it needs to take more bold decisions and have the will to implement them. The citizens also need to raise their voices, after all it was this that led to the banning of the appalling Vikram diesel tempos. Till that happens, here are a few things individuals can do to make a difference:

. Maintain your vehicle. A poorly maintained vehicle may consume up to 50 percent more fuel and emit 50 percent more pollutants than a well maintained one.

. Use public transportation, especially the electric vehicles we have in Kathmandu. Our city has the largest fleet of public electric vehicles. Use them.

. For short trips (most trips in Kathmandu are short) leave your car at home and ride a bicycle or walk. Walking or pedaling is good for your health as well as your wallet.

. Raise your voice, since everyone's health is affected.

Bhusan Tuladhar is Executive Director of Clean Energy Nepal.

Danger : PM10

PM10 is the most dangerous pollutant in the air because it is tiny enough to enter deep into the human respiratory system, it is often coated with highly toxic compounds and metals and it hangs around in the air for a long time. In fact, the smaller the size of the particles the more dangerous they become. Fine particles not only damage the lungs but they can also enter the blood stream and cause problems in the heart and the nervous system. PM10 is the main concern in Kathmandu in terms of air quality because its levels are way above national and international standards.

Deadly Diesel

Until recently, diesel was considered to be a relatively clean fuel because it is up to 20 percent more fuel-efficient than petrol. But in the past 10 years diesel has taken a severe beating and now diesel exhaust is considered a deadly pollutant and a carcinogen.

The first alarm rang when experts found up to 100 times more particulate matter in diesel exhaust than petrol. Then researchers in the UK found that 90 percent of the particles emitted by diesel engines are very tiny or less than 1 micron. This means that almost all the particles in diesel exhaust, which are surrounded by toxic compounds such as polycyclic aromatic hydrocarbons (PAHs), are small enough to go deep into the human body.

This was followed by studies indicating that of all the air pollutants, fine particles are the most deadly. To make matters worse, in 1997, Japanese scientists discovered the most potent carcinogen found as of date in diesel exhaust. As a result, the California Air Resources Board (CARB) declared diesel exhaust to be toxic air contaminants and said that chronic exposure to just 1 microgram per cubic meter of diesel exhaust will lead to additional 300 cases of lung cancer per million people.

Environmentalists all over the world are now campaigning to ditch diesel vehicles and some countries such as Brazil, Taiwan and Egypt have banned private diesel cars. French journalists and the famous Indian environmentalist the Late Anil Agarwal called diesel vehicles "Engines of the Devil".

In Nepal, however, diesel continues to enjoy subsidies and driving a heavy diesel powered SUVs is fashionable. It's not, it's deadly. Kathmandu-based international aid agencies are the largest users of these cars, followed by government ministers, projects and members of parliament who all ordered one during the Pajero scandal. Ironic, isn't it, that agencies promoting sustainable development are the ones who use these cars the most.

Keeping tab of Kathmandu air

Adults breathe 25 kg of air in and out of their lungs every day. Kathmandu residents have felt the pollution in this air as irritation in the throat or the dirt on clean shirts. Now we can tell exactly how bad the air is, thanks to the six monitoring stations set up by the Ministry of Population and Environment with help from the Danish government. Two of these stations are located on busy roads (Putali Sadak and Patan Hospital), one in a residential/tourist area (Thamel), two in urban backgrounds (Bhaktapur Durbar Square, Tribhuban University) and one as a Valley background (Matsegau). The state-of-the-art stations measure PM10 levels round the clock, data is tabulated every week and released on Tuesdays through MOPE's web site (www.mope.gov.np) and a newly installed electronic board on Basantapur. Nepali Times begins publishing some key results starting this week on Kathmandu Air Quality.