Davida Herzl, Aclima's boss, says they have revealed pollution highs on days when San Francisco's transit workers went on strike and the city's inhabitants were forced to use their cars.
For example, let's say a group of television writers demand higher pay. Their employers refuse. So, the writers go on strike. Then television actors join the strike.
We start today keeping an eye on ports in the United States, as longshore workers who run East and Gulf Coast ports from Maine to Texas could go on strike.
We've been told now that universities will go on strike this week and that the country's biggest trade union is also planning to tell its workers to down tools from tomorrow.