Bakersfield's Air: The Valley's Invisible Geography

On winter mornings in Bakersfield, a layer of yellowish-gray air sits in the bowl of the valley below the surrounding mountains. It does not move. The air in the San Joaquin Valley sits differently than air elsewhere in California, and the reason is geography: the valley is open at its northern end near Sacramento but closed on three sides by mountain ranges to the east, south, and west that trap the air mass in the basin. What goes into the valley stays in the valley until the weather pattern changes enough to flush it out.

Bakersfield sits at the southern end of the San Joaquin Valley, at the worst position for air trapping. The diesel exhaust from the freight corridor along Highway Ninety-Nine, the dust from agricultural operations on hundreds of thousands of acres of tilled soil, the emissions from the Kern River Oil Field's steam injection operations, the smoke from prescribed burns in the surrounding forests and from wildfires in drought years, and the particulate matter that blows in from the Mojave Desert to the south all accumulate in this basin and are trapped by the same mountain barrier that makes Tejon Pass the main road route to Los Angeles.

Kern County has routinely been cited by the American Lung Association as having among the worst particle pollution in the United States. The specific pollutant that drives those rankings is PM two point five, microscopic particles small enough to penetrate deep into lung tissue. The health consequences for populations that live here long-term include elevated rates of asthma, chronic obstructive pulmonary disease, and cardiovascular disease.

The irony is that the oil economy that produces much of the pollution also produces much of the tax base that funds the public health infrastructure that monitors it. Kern County's air quality management district has worked to reduce emissions. Whether the reductions are adequate to the health burden that a century of heavy industry in a closed basin has produced is a question that the epidemiological literature has not resolved in the county's favor.

The air on a clear day here is genuinely beautiful. The Sierra Nevada to the east rises above the valley haze in the late afternoon light, and the view from the ridge roads into the basin shows you the whole system at once: the flat agricultural floor, the oil infrastructure, the freight lines, the mountain walls holding it all in. The geology that made this place productive is the same geology that makes it hard to breathe.