The Environmental Protection Agency just tightened standards for tiny, pervasive soot particles from construction sites, smokestacks, tailpipes, wildfires and other sources.
Why it matters: This form of air pollution is dangerous. It's linked to asthma, irregular heartbeats, bronchitis, even premature death in people with heart or lung disease, per the EPA.
Heavy rainfall and mountain snow from a "dangerous" atmospheric river slamming Southern California that brought a rare "high risk" of potentially deadly flooding in Los Angeles County this week is set to linger until at least Thursday.
The big picture: The storm that rapidly intensified Sunday off California's coast has resulted in at least four deaths and disrupted travel across the state. City of Los Angeles crews have responded to 383 mudslides, and there have been multiple road closures and water rescues across the state due to flooding.
