When the United Nations Environment Program did a study that included air sampling, in 2008, it found plenty to worry about, but mostly what would be expected of a traffic-congested city: a lot of sulfur dioxide and nitrous oxides. Plus a very high concentration of particulates, known in the trade as PM 10 — which means particles smaller than 10 microns, small enough to penetrate deeply into the lungs, and an important indicator of air pollution — but no specific fecal bits.

A study by the Asian Development Bank and the Afghan government’s environment agency in 2007 similarly found the atmosphere thick with the usual suspects in any city, especially in an underdeveloped country where fuel quality is very poor, but it made no mention of flying feces — although toxic levels of cadmium were noted.

In fact, when the Canadians investigated the matter in response to their worried soldiers, the investigators said that some fecal matter in the air was normal — even in Canada. Some of it could just be bird and flying-insect droppings.

While Kabul might have more because of open sewers and burning dung, that still was not a problem for two reasons: ultraviolet radiation from the sun kills most microbes, and even those that might survive in airborne fecal matter are not the type to invade the body by air; they are the type more likely to infect victims through the mouth or skin.

The investigators were also unable to find the original studies that supposedly found such high levels of fecal matter in the air. “I’d like to point out that I have a vested interest in this,” said a Canadian colonel who was among the debunkers, quoted by Canada’s National Post. “I’m breathing this air, too.”

Kabul may not have an aerial fecal problem, but it is far from off the hook on air pollution. “Any kind of pollution is a problem,” the mayor said.

Kabul’s geography is a big part of that: the city sits on a 6,000-foot-high plateau that looks like the bottom of a bowl, encircled by much taller mountains. The result is atmospheric inversions during fall and winter that trap airborne pollutants.