NGO Centre for Science and Environment has critically analyzed a Council of Scientific and Industrial Research study, jointly carried out by Indian Institute of Petroleum and the University of Alberta, on presence of pollution-causing nanoparticles in CNG and diesel bus exhausts.
This was in response to claims made by M O Garg, director general of CSIR, who had recently shared the findings of the study—that the number of nanoparticles released from CNG buses is higher than that from diesel buses but the mass of nanoparticles emitted from CNG buses is relatively lower.
CSE’s analysis, however, reveals that the CSIR study findings are different from what Garg’s briefing may have conveyed. Garg had been referring to nanoparticle emissions from an Indian CNG bus and a Canada-made diesel bus meeting advanced US tier-II standards. US tier-II norms are tighter than Euro VI norms.
CSE accessed the draft study by CSIR only to find that CNG buses performed way better than diesel on almost all pollution parameters—including nanoparticles. CNG’s performance is close to or better than Euro VI emission standards for diesel that are yet to be implemented in India.
“This motivated campaign against CNG buses in India will harm not only the CNG bus programme that has given enormous public health benefits but also jeopardize the policy decision to leapfrog emissions standards to Euro VI by 2020 to cut dangerous diesel emissions. The government of India is dragging its feet in face of strong opposition from the diesel industry,” CSE’s statement issued on Monday said.
The study involved carrying out emission tests on two Indian CNG buses and two diesel buses (when they were mobile)—one of a Canadian make that meets US tier II standards fitted with advanced particulate filters and another an Indian diesel bus without any filter or diesel trap.
The results showed that nanoparticle emissions from Indian diesel buses were 600 to 2,000 times more than those from the CNG bus. But when the CNG bus was compared with the Canadian diesel bus with particulate matter traps and advanced nitrogen oxides control meeting US tier-II standard, the study found nanoparticle levels for CNG to be 12-40 times higher. The Indian diesel bus without particulate matter trap was found emitting 28,000 times more nanoparticles compared to the Canadian bus.
CSE highlights that CNG performed much better on other pollution parameters as well—carbon monoxide, non-methane hydrocarbons and nitrogen oxides. Both CO and NMHC emissions from CNG buses in use are close to the limit values of Euro VI norms.
“CSIR should have put out a red flag immediately and urged the government to leapfrog to Euro VI emissions standards for diesel. Nanoparticles, being of 0.1 micrometres in width, are 25 times smaller than PM2.5 and go directly into the bloodstream. In conjunction with PM2.5 and PM1, they cause irreparable damage. PM2.5 is already the fifth largest killer in India,” a CSE researcher added.
Anumita Roy Chowdhury, head of CSE’s Clean Air campaign, said, “CSIR has omitted to mention the serious health risk associated with diesel emissions. It is now well known that WHO has concluded that diesel exhaust is a human carcinogen and is in the same class as tobacco for its strong link with lung cancer.”
In its report on August 8, based on interviews with Garg and other experts, TOI highlighted that CNG is far cleaner than non-low sulphur diesel. Its nanoparticle numbers, though, can be marginally higher than that in emissions from low-sulphur diesel vehicles meeting Euro V/VI norms.