The tangle of traffic that knots up downtown Kabul almost everyday is one of the few hints of the invisible killer stalking the city.
Another is the large number of pedestrians who cover their faces with masks or scarves.
Shamshullah is one of them, unmasking only to answer a question.
"I cover my face because of all the dust and pollution, to try to ward off the illness," he said.
He has real reason to worry.
The Afghanistan government estimates that air pollution is responsible for 3,000 deaths every year in Kabul.
That is nearly as many as the number of civilians killed in Afghanistan last year as a result of the ongoing war.
Vehicles are a big part of the problem.
Most of the tens of thousands of them that choke the city's roads are old, run on leaded gasoline and have dodgy exhaust systems.
They also drive over a lot of unpaved roads, kicking up clouds of dust.
And all these polluting cars are crammed into a city that is badly overcrowded.
Ghulam Mohammed Malikyar, a senior adviser at Afghanistan's Environmental Protection Agency, believes Kabul's population of five million is five times too big.
"Kabul is built for maximum one million population. The geographical limitation — it is very very limited city in a mountainous area," he said. "During the past 30 years most people from rural area migrated to Kabul city because of security or education or other purposes."
The city's swelling size has led to other sources of pollution as well, according to Malikyar.
People build illegal homes, then use diesel generators to power them.
Those who can't afford a generator will burn tires, plastic bags or other garbage as fuel.
The result is a nearly permanent smoky haze over the city.
As recently as the 1980s, Kabul was known for its crystal clear air and spectacular views of the snow-capped mountains that rise up around it.
Malkiyar is saddened by the fact that they are rarely visible these days.
"Of course, I was a child here and I was raised in this situation. I was involved in environmental protection since 1992 so from that time to now I see the changes — many changes," he said.
Those changes have a human cost, one that can be seen in a Kabul hospital, where Noor Ahmad lies on a bed, as an IV drips antibiotics into his arm.
His doctor Naseetar Zanaksay, who is seeing an increasing number of patients like Ahmad, said he came to the hospital after feeling ill for weeks.
In fact, he said he has been coughing so much he has been unable to sleep at night.
According to Afghanistan's health ministry, cases involving respiratory problems tripled between 2005 and 2011 to nearly 500,000.
And a 2006 report from the United Nations Environment program found that even then 60 percent of Kabul residents were exposed to high concentrations of dangerous particulate matter, nitrous oxide and sulfur dioxide.
Zanaksay said even as his list of patients grows, he does not see any real efforts to tackle the problem.
"Sometime as a doctor we think this is sad for us, but there is no way to solve the problem, or how to control the diseases," he said.
In fact, the government is making at least some effort to solve the problem. It has tried to ban older cars with damaged exhaust systems and it has proposed emission standards for vehicles and industry.
Last year, it even started closing government offices one day a week to try to reduce traffic. Still, the EPA's Malikyar said there is one critical part still missing.
"Of course, political will and political support is very low."
That is not surprising, perhaps, in a country torn apart by decades of war and facing many more immediate challenges than an enemy that is not easy to see.
Still, Malikyar said, it means there is not nearly enough money to tackle the problem.
Recently, for example, Kabul installed a new air quality monitoring station.
Malikyar said the city would need ten more to do the job properly.