Explosions rocked at least two buses in the southwestern Chinese city of Kunming on Monday, local media report, killing at least two people and injuring another 14 as the country attempts to tighten security ahead of next month's Beijing Olympics.

Since undertaking market reforms in late 1970s, China has enjoyed an economic boom -- but the economic progress has also produced serious environmental damage and pollution problems. Margaret Warner reports on China's environmental woes and their impact on the run-up…

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