Earlier this week, I got a chance to fly in the cockpit of a small airplane up above California’s Central Valley (thanks to our pilot, Michael, and an awesome organization called Lighthawk).

My mission: to photograph fracking from above and to see what I could of the oil industry’s secret activities.

What I saw was pretty disappointing. Thick low-lying clouds of smog lay between our small craft and the fields below. Oil rigs and ag land were buried underneath layers of gray. A haze obscured the mountains and ruined any opportunity to capture images of how the Central Valley landscape was being shaped by oil extraction. When we landed — giving up all hopes of the fog lifting — I could barely even make out the runway.

But the picture couldn’t have been more clear. Let me explain.

The Central Valley suffers from poor air quality on a continual basis. Surrounded by mountains on three sides, the valley is home to various industrial activities (oil being one among many). Add industrial agriculture and the emissions from big-rig traffic driving through the valley on 1-5, and you come up with some of the worst pollution in the nation.

So, even though my hopes were dashed to get any stunning, wide-angle shots of California’s oil fields (in order to show where most of the fracking in the state is taking place), I did walk away with a deeper understanding of how polluted the air really is — and how it can affect your health for the worse.

The main beast is PM 2.5. Made up of tiny soot particles, chemicals, and debris, PM 2.5 buries into your lungs and can cause breathing problems, heart attacks, and even strokes. For those who have pre-existing health problems, such as asthma, days like that one spell out trouble.

The day that I was there, the San Joaquin Valley Air Pollution Control District’s real time monitoring website coded the air as “extremely unhealthy.” No wonder I came home feeling a bit out of it.