The Science and the Air are Unsettled

I came to Ocean Beach for the fresh air. "Fresh air? What fresh air? We're in Ocean Beach."
I was misinformed.----with apologies to Casablanca

Air quality monitors have consistently shown that a surprising section of San Francisco has harmful air pollution, according to EPA standards for particulate matter. [bold added]

The Chronicle’s analysis shows that the PM 2.5 levels of six sensors in the Outer Sunset located within two blocks of the shore all exceeded the annual average daily exposure standard of 12 micrograms per cubic meter set by the Environmental Protection Agency...The median PM 2.5 over the one-year period recorded by the three sensors closest to the shoreline was about 14 micrograms per cubic meter, compared with about 9 among sensors citywide, data showed.

The reasons are not the usual suspects: traffic, wildfire smoke, or inversion layers.

[Air quality scientist Michael] Flagg had noticed that the huge spikes in PM 2.5 readings from sensors along the Great Highway tended to coincide with certain meteorological conditions. “It would be when the surf and swells were well over 10 feet and the winds were either light or slightly onshore,” he said.

That led him to suspect that a phenomenon called sea spray aerosol — tiny particles from the ocean that scatter into the air — could be playing a part in the high PM 2.5 levels.

It's always refreshing to encounter a scientist like Michael Flagg who, in seeking to solve a puzzle, doesn't try to bend the facts to fit a theory but constructs hypotheses to fit the facts.