So they want us to " take precautions to protect their health" by "walking or biking" in the polluted air?

Yes, because when you don't fire up a gas-powered motor vehicle, you are removing pollutants from the air. Even if you drive, if you carpool, two people in one vehicle generate basically half as much air pollution as two people driving in separate vehicles.

Or let's say you put 100 people in an electric light rail train versus having one hundred people driving their own gas-powered automobiles.

Having people do other behaviors can influence the outcome of the situation.

Do you require additional explanation?

If you look at the air pollution forecast, dangerous pollution levels are only forecasted for the East Bay and far South Bay. Pollution created on the peninsula quickly blows inland and doesn't affect peninsula residents. Walking and biking on the peninsula remains safe and helps with health problems in East Bay and South Bay. You do want your neighbors to be healthy, right??

I love how people have bought into thinking that 10 million acre forest fires started by lightning have no effect on the environment, but a sigle backyard barbecue will destroy the planet! My propaganda is working!