The compressed natural gas (CNG)-run buses are harmful for humans as they emit "nanocarbon" particles which can cause cancer.

The compressed natural gas (CNG)-run buses are harmful for humans as they emit "nanocarbon" particles which can cause cancer, according to a study conducted by Council of Scientific and Industrial Research (CSIR).

Though the study was conducted on a very limited sample size in Delhi, CSIR took the findings seriously owing to the health hazard it poses to humans and alerted the central government for further follow up, CSIR's director general Dr MO Garg said on Thursday.

According to him, the study can change the perception that natural gas is a clean fuel as it does not emit any visible smoke, which is in contrast to smoke emitted by diesel-run vehicles and perceived as harmful for humans.

"Natural gas is supposed to be a clean fuel when used in internal combustion engines, right? But, I don't think people realize that what you see (smoke) is perhaps better than what you don't see (no smoke from CNG vehicles)," said Garg during his address at the Global Green Energy Conclave held here.

"We did a study with a professor of Alberta University, who have developed a device to measure and analyze particles emitted by vehicles. We have installed this machine on the exhaust of a natural gas-run DTC bus in Delhi," he said.

"Can you imagine that we found nanocarbon particles coming out of from natural gas combustion. These particles are moving around in the atmosphere and going straight into your lungs through your nose. It then enters into your blood through membranes," Garg said.

According to him, these nanocarbon particles are carcinogenic. Garg also said that he has alerted the government about its effects.

"These nanoparticles are rich in polynuclear aromatic, having huge surface area. They are also carcinogenic. I have been telling government that we need to look at this situation more seriously," he said.

"Imagine what will be its effect when all the commercial vehicles, such as buses, run on natural gas in Delhi. You can see smoke coming out from diesel engine and tell that it is dangerous. But, nanocarbon particles coming out from vehicles is something we need to look at," Garg added.