The challenge faced by pollution planners is literally to find ways to measure the particulate pollution from two-wheelers. As yet little has been done. One study done In the US finds that particulate emissions from two-stroke engines are rich in toxic volatile organic fraction, and particulates, says Michael Walsh, citing a study by James N Caroll and Jeff J White done for Yellowstone Park Foundation, a recreational centre in Montana in 1999. Worse, the particles are ultrafine - varying between 23-84 nanometres - posing a grave threat to public health. The size distribution is similar to that of diesel particulates, which are tiny and therefore go deep Into the human lungs.

Matthew Spears of the US Environment Protection Agency (USEPA) says measuring particulates from two-stroke engines is beset with hurdles. USEPA is evaluating changes to the two-stroke particulate measurements protocol. USEPA plans to study in-use two-wheelers in Thailand to develop this methodology further, says Jane Armstrong of the USEPA.

But Indian industry, which has still not even begun to measure these emissions, remains skeptical of the methods used to estimate particulates. Says N V Iyer, general manager, Bajaj Auto limited, "The challenge lies in generation of data using reliable test methods. Many investigators have employed methods used for testing particulate matter from diesel engines. A comprehensive project to address issues of testing standards must be conducted at an international or national level." This is a task for our scientists to explore this critical human health linkage. Is anyone listening in India?