CNG emits cancerous particles?

Though perceived as an environmentally friendly fuel, CNG actually emits particles at higher rates and smaller sizes than diesel fuel, making it many times more harmful for the environment and human health, said the Suep general secretary Akhtar Hossain Babu, citing a study of the Harvard-based Centre for Risk Analysis.

The finer the particles, Babu explained, the easier they enter the human lungs, where they can cause cancer. While the fineness of diesel-emitted fine particles is 2.5 to 1 microns, CNG emits ultra-fine particles, meaning matter smaller than 0.056 microns, he said.

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Citing a recent survey conducted in the UK, Babu said that CNG buses emit marginally higher ultra-fine particles than the diesel buses.

A 2003 Suep study of 10 CNG converted vehicles showed that emissions contained 7 to 12 percent Carbon Monoxide against tolerable levels of 4 percent, as well as 450 to 1472 PPM (parts per million) of Hydrocarbon against approved levels of 180 PPM.

Though there is no device for measuring the level of ultra-fine particles emitted from CNG driven vehicles, the high level of Carbon Monoxide (CO) and Hydrocarbon (HC) in vehicular emission is indicative of high levels of ultra-fine particle emission, Babu said.

Ultra-fine particles generated from CNG at high combustion temperatures, as well as fine particles from diesel combustion cause lung cancer, he said, adding that Carbon Monoxide is poisonous to human health, while Hydrocarbon increases cancer risk and causes eye irritation.

Citing information from the Bangladesh Atomic Energy Commission, the Suep general secretary said that motor vehicles, soil and road dusts contribute considerably to the composition of pollutants in Dhaka's air.

Motor vehicles are responsible for 40.2 percent of course particles and 38.2 percent of fine particles in the air. Soil dust is responsible for 43 percent of course particles and 10.2 percent of fine particles, while road dust and metal smelter contribute 19.4 and 9.96 percent respectively of fine particles.

Babu said that the government must ensure that imported CNG vehicles have integrally designed with their engines a Regenerating Catalytic Trap (CRT), a mechanical device that filters and absorbs emitted particles. The government must also ensure that engine conversion to CNG is strictly performed in compliance with approved standards, he said.

He urged immediate government steps to measure the level of nanoparticles emission from CNG vehicles, as well as stringent measures against unscrupulous CNG converters.

Suep president advocate Mollah Mohammad Mokbul Hossain and vice-president Golam Kibria Chowdhury were also present at the conference.