Smog in China now a national security threat as low visibility creates need to find new technology Vehicles are shown under heavy smog in Beijing. SMOG is becoming not just a health issue in China - it is also a national security threat. The South China Morning Post reports that last month visibility in Harbin was so bad that visibility was at just 3 metres. Experts are concerned that terrorists may choose smoggy days to launch attacks. Kong Zilong, a senior project engineer with Shenzhen Yichengan Technology, said the security devices that could function in heavy smogs had yet to be invented. Even infrared imaging is useless because the smog is so thick the particles are blocking light completely. "According to our experience, as the visibility drops below three metres, even the best camera cannot see beyond a dozen metres," he said. The National Natural Science Foundation of China funded two teams to come up with a solution. Chinese women cycling through polluted smog over Tiananmen Square in Beijing. Professor Yang Aiping, an expert in digital imaging with the School of Electronic Information Engineering of Tianjin University and leader of the civilian team, said the answer was going to be hard to find. Most studies in other countries are to do with fog. In China, most people think that fog and smog can be dealt by the same method. Our preliminary research shows that the smog particles are quite different from the small water droplets of fog in terms of optical properties," she said. We need to heavily revise, if not completely rewrite, algorithms in some mathematical models. We also need to do lots of computer simulation and extensive field tests. The military team is led by professor Bi Duyan of the Air Force Engineering University of the People's Liberation Army in Xian , Shaanxi province. Bi could not be reached for comment on the research. Professor Zhang Li, an image processing expert with the department of electronic engineering of Tsinghua University, said the researchers might have to think out of the box because while microwaves or electromagnetic waves could travel through smog easily and bounce back if they hit an object. "On the smoggiest days, we may need to use radar to ensure security in some sensitive areas," he said. A woman wearing a mask uses her mobile phone in the smog in Harbin, northeast China's Heilongjiang province. China's financial hub Shanghai experiences heavy smog a week after the capital Beijing reported the worst air pollution ever measured there. Sarah Sheffer reports.