Previously in the good news saga here and here. The story so far is that if such one-time air-pollution hellholes as Los Angeles (from the 1950s and 1960s) and Mexico City (from the 1980s and 1990s) can clean themselves up, there could be reason for hope in today's hellholes in China and elsewhere. Now, two more reasons for (modest) optimism.
Evidence from Bangladesh. A reader writes:
Interesting comments re urban pollution. Dacca is the most dramatic case I've seen. 10 years ago the city was choking on fumes - the improvement has been dramatic due to conversion to CNG [compressed natural gas] for all public transport, no diesel trucks in the city limit area, and subsidized conversion from petrol to cng for private car owners. stunning success.
Indeed, LA and California were richer in the 1950s and 60s than China is today, but the level of pollution control technology is immensely different. The key technological advance for automobiles -- the catalytic converter -- wasn't even put into production until the 1970s. Since that time, the advances in catalytic converter and engine technology have been so great that laboratories that test new vehicles often need to pre-clean the laboratory and engine-intake air because it is dirtier than what is coming out of the tailpipe!Again, no one who has thought about China's environmental problems can feel "good" about the situation. But an alternative to out and out fatalism and despair is always a plus.
Considering just the last two decades, the EPA standard for nitrogen oxide emissions (a smog precursor) from passenger cars in 1994 was 0.6 grams per mile. In 1999 it was reduced to 0.3 grams per mile. In 2004 it was reduced to 0.07 grams per mile. Each of these has been met without much trouble. And it will be dropping even lower in the future. Granted, China is not adopting the latest U.S. or European technology, but even technology from a few years ago is drastically cleaner than what L.A. had in the early days of the war on smog. And that doesn't even get into advances in battery technology, hybrids or diesel engines.
Evidence from the world of technology