A police officer near a pool of wastewater from the abandoned dumpsite near Chalongkrung Police Station.

Toxic fumes from an abandoned dumpsite have made life a misery for police officers in Bangkok's Lat Krabang district. Environmental officials said the site released methane that caused vomiting and unconsciousness after prolonged exposure.

Visitors to Chalongkrung Police Station often see officers wearing masks to cover their noses as they work amid the foul smell the seeps through their air-conditioned office from the nearby garbage mountains.

The police station was built in 2003 on four rai of land donated by the dump's owner, near the 50-rai dump that had been abandoned for more than a decade.

Most of the precinct's 125 officers have had health problems including nose irritation, sore throats, dizziness and vomiting. Some have also had rashes and those with chronic illnesses have been most affected.

The smell is particularly strong at night and during winter, while the garbage mountains often produce smoke.

Sgt-Major Sommat Permpul said he was diagnosed with pneumonia in 2004 and still took medication today. The former smoker said the foul smell caused his condition to worsen.

Sgt-Major Supachai Naksuk said he used to be fit and strong when he was a patrolling officer, but now that he worked at the police station on a daily basis, his health was weakening, with occasional fainting, dizziness, vomiting and respiratory problems. "I'm afraid I will develop a respiratory disease by being exposed to this foul smell every day," he said.

Sergeant Somkiet Janthakuman said there was a pool of wastewater at the rear of the police station that produced a chemical-like foul smell in the radio room all the time. After three years of putting up with the smell, he felt weak and nauseous and had developed rashes.

Colonel Sanapok Boonyakalampa said 40 officers worked regularly at the precinct and suffered from the foul smell of garbage and polluted water.

Several years ago, the Pollution Control Department inspected the area but did not inform police of whether there was any toxic contamination, he said.

The police are planning to set up a substation at Lat Krabang Industrial Estate to get away from the smell.

"After working here for only six months, my body became less fit. I often had a sore throat, so I had a health check-up and was diagnosed with atherosclerosis [a condition affecting the arteries]. I bought an air purifier for my office," Sanapok said.

He said he worried about suspects held at the station because the cells had no air-conditioners and were near the wastewater, so he considered it better to release people on bail when that was possible.

Lat Krabang district's environmental official Mongkol Kongdee said the area was an abandoned site where garbage was buried - a method which meant it took longer to dissolve - and the wastewater came from rainwater running down the waste.

The garbage dissolution produces methane, which causes nausea and unconsciousness in cases of prolonged exposure, he said.

An unnamed Pollution Control Department official said the garbage burial method could cause flammable but odourless methane and once it caught fire, the piles would always glow from inside unless the gas was removed.

The glowing garbage fire could affect nearby residents, the official said, adding that the department had in the past contacted the Bangkok Metropolitan Administration to find out what type of garbage was dumped there so it could determine what the toxins were.

Faikham Hannarong of Greenpeace Southeast Asia said Thailand still had no clear procedure for garbage separation and all kinds of waste were buried in one place.

She believed separation at the Lat Krabang site was poor and it had used substandard materials on the dump's bottom, allowing toxins to leak and contaminate the environment.