I know its October and so this story of black rain in Shenzen is well past its "sell by" date, but now that Al Gore is a Nobel Peace Prize winner (since the environment and peace have a clear connection, eh?), why not give it a reprise?
When I saw the story it shocked me, not so much because of the black rain (it is a sad state of affairs when black rain falling isn't something shocking, but such is China's environment), but that it happened in Shenzhen, while I've been living here, and yet I had no clue about it. It seems this problem occurred away from the city center, however Nanshan is still within the SEZ. This is really surprising because at least during my experience here over the last 6 months, environmental conditions in Shenzhen are better than almost all other large cities in China. I've heard horror stories about the situation outside the SEZ, where factories are abundant, but that is far from the case inside the SEZ.
Beyond that, though, even if it is a freak occurrence, the fact you have black rain falling should come as a huge shock and lead to massive changes instead of being covered up.