The Centre for Science and Environment (CSE) has challenged the Council for Scientific and Industrial Research’s (CSIR) recent conclusions based on the draft findings of a joint study that buses running on CNG may be more hazardous to health than diesel buses.

“The CSIR has claimed, without presenting the full study and the facts in the public domain, that CNG buses emit more ultrafine particles than diesel buses and are a health hazard,” according to press statement by CSE.

The ultrafine emissions from CNG buses are higher than only the Canadian diesel buses with advanced particulate traps meeting one of the global best standards, the statement pointed out.

CSIR’s own findings have shown the conventional CNG buses have already achieved emissions levels for all pollutants, including ultrafine particle number very close or better than Euro VI emission standards that are yet to be implemented, while diesel buses are far behind, the release added.

The study was jointly carried out by CSIR, IIP-Dehradun and University of Alberta.

‘Defying science’ “This motivated campaign against CNG buses in India, and defiance of what science is saying, will harm not only the CNG bus programme that has given enormous public health benefits but also jeopardise policy decision to leapfrog emissions standards roadmap to Euro VI by 2020 to cut dangerous diesel emissions,” the release added.

The study carried out real world emissions tests on two Indian buses running on CNG and two diesel buses, one of Canadian make meeting current US Tier II standards (higher than Euro VI norms) fitted with advanced particulate trap, and one Indian diesel bus without diesel particulate trap.

“Ultrafine particle emissions from the Indian diesel bus without particulate trap were at dangerous levels emitting 600 to 2,000 times more than the Indian CNG bus,” the CSE release said.

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