Holy Smoke! Well, not exactly. But smoke has certainly been the main topic of conversation here in Stara Zagora since last summer.

It all started with a very strange yellow cloud that covered the city's atmosphere.  And, yes, people were hacking and coughing.  Asthma and bronchitis cases boomed.

The question is, what is it and what caused it?

Suspicion first descended upon the destruction of Bulgarian military Scud rockets as per the country's agreement with NATO.  It was surmised that possibly the fuel that was destroyed was gassing the people here. For months, there was speculation, but nothing concrete ever was discovered.

Next, the theory was the local Bulgarian military base possibly caused the gas.  What could it have been and what was it?

Then there was the idea that perhaps it was fumes drifting over from Maritsa Iztok from Gulovo.

Not only did the Bulgaria authorities study Stara Zagora's bad air, but so did NASA.  The culprits have not been found and speculation continues to this day.

When the weather turns hot, again the yellow cloud appears.  What could it possibly be? A hot air inversion from auto pollution?  Some factory polluting the air with their smokestacks? The destroyed rocket fuel?  Bulgarian military waste being burnt?

The mystery remains unsolved to this day. However, that is small comfort to the people of Stara Zagora having to inhale the yellow haze.

That said, the main suspects remain: 1) fumes from Maritsa Iztok, 2) burnt rocket fuel, and 3) pollution from a nearby military base.

What can be done?  First, if the culprit is Maritsa Iztok, why wouldn't the smoke have been here years before?  Why it just happen this past year? Secondly, if it is fumes from destroyed rocket fuel, why would it drift all the way southwest to Stara Zagora?  Next, if it is the military base, what would the fumes exactly be?

Popular suspicion is that it is the rocket fuel.  So, if this is the culprit, then it brings us to the next question.  Why was the fuel destroyed so close to a major city?  Also, if the pollution is due to the fuel, why was the fuel not first burned at a high temperature so there were no fumes left?  This is regularly done for other contaminate items and leaves nearly no pollution at all.

Also, why not burn the fuel somewhere near the southern Black Sea? Few people live there and the wind factor would completely dissipate the fumes.

Whatever the specific reason for the air pollution is, the problem remains. 

The pollution problem in Stara Zagora got on to the political agenda when right-wing political party the Democrats for a Strong Bulgaria, led by former prime minister Ivan Kostov, held a seminar on the weekend of March 11 and 12 about the problem.

Earlier, in February, Union of Democratic Forces leader Petar Stoyanov called on the Government to say whether there was another source of pollution in the Stara Zagora region besides the Maritsa East complex, and to take the necessary measures.

"The question is whether we have fully reconciled with the fact that Maritsa East is the only pollution source," Stoyanov said, according to a report by Focus news agency.

"Representatives from the ruling coalition carried out two campaigns, for local and parliamentary elections, on the basis of this problem. And we will not stop asking them this question. Someone will finally have to tell the people of Stara Zagora which is the real source of the pollution," Stoyanov said.

In September last year, Parliament gave the Cabinet two months to stop the gas pollution in Stara Zagora. MPs also recommended that the Cabinet set up a single centre monitoring all possible sources of pollution and draw up a single cadastre of the at-risk areas in Bulgaria, using aerial and other information.

The report identified the Maritsa East energy complex as the main polluter, with sulphur dioxide. It said that, in 2004 and 2005, the Government had failed in a number of ways to deal with the problem, including failing to screen children for illnesses related to air pollution.

The parliamentary report recommended a number of steps, including expert monitoring of the town's air, reduction of production capacity in the Maritsa East basin during unfavourable weather conditions, and the rapid phasing-in of desulphurisation equipment.

In August, it was reported that respiratory diseases in Stara Zagora region had risen four per cent in a month. In the summers of 2004 and 2005, sulphur dioxide emissions were much higher than permissible levels.

In July 2005, about 60 per cent of Stara Zagora residents had respiratory and throat problems. There were also increases in bronchial asthma and skin allergies.