The government's Air Quality Index shows "unhealthy" pollution levels in much of Southern California.

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An unofficial reading from the US embassy's air quality index recorded over 500 early in the morning, but changed to 168 as of 13:00 (05:00 GMT).

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Its report grades cities using, in part, the EPA's color-coded Air Quality Index, as well as its own weighting system that ranks the severity of pollution on a daily basis.

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The Environmental Protection Agency, together with other federal, state, local, and tribal agencies, developed AIRNow.gov, offering the public daily Air Quality Index forecasts and real-time Air Quality Index conditions for over 300 cities across the country as well as links to detailed state and local air quality cites.

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