Of China?s major cities, Beijing?s pollution problem is probably the worst, causing thousands of premature deaths every year. Its residents are fed up. The growing outrage has forced leaders to declare a ?war on pollution,? including the goal of slashing Beijing?s PM2.5? the concentration of the particles that pose the greatest risk to human health?by 25% by 2017. The Beijing municipal government will earmark nearly 1 trillion yuan (0 billion) to meet that target.