The thick fog stretched for more than 400 miles, covering more than twenty counties, turning the area into a scene resembling a science fiction movie.
What initially appeared to be ordinary fog quickly revealed its danger when residents began reporting strange health symptoms. Gerald Debralanta, a resident of Tracy, was among the first to notice the connection, as he and his family suffered from a severe cough and congestion that lasted for more than a week. "We've kept the children's inhalers close by and are trying to keep them indoors as much as possible," Debralanta said, sharing videos showing his car covered in a strange white film—not just water droplets, but a dust-like substance that clung to surfaces.
Debralanta's case was not unique. Dozens of testimonies from residents suffering from similar symptoms spread across social media, especially on TikTok. One complained that he had been coughing for three weeks without responding to any treatment, while a mother complained of her children's eczema worsening, and others of frequent headaches and chest pains they had never experienced before.
But experts explain that the fog itself isn't the direct culprit. Radiation fog, also known as Tull fog, is a natural phenomenon that forms when the ground cools rapidly after sunset. The real danger lies in what accompanies this phenomenon: a temperature inversion. In this inversion, a layer of warm air acts as a blanket, trapping the cooler air and fog beneath, along with all the pollutants emitted from the Earth's surface.
Beneath this invisible veil, car exhaust, factory fumes, stove smoke, and farm dust accumulate, forming a toxic mixture that hangs in the air breathed by residents. These fine particles, scientifically known as PM2.5, penetrate deep into the lungs and even the bloodstream, causing severe respiratory irritation, exacerbating conditions like asthma, and increasing emergency room visits.
The danger isn't limited to health; dense fog turns roads into death traps. The history of California's Central Valley is replete with tragic stories of mass traffic accidents caused by poor visibility. In November 2007, fog caused a horrific pileup involving 108 vehicles and closed Interstate 99 for more than 12 hours.
In January of this year, a traffic jam of 40 cars resulted in the death of two drivers and injuries to nine others. Locals describe driving in this fog as "one of the most terrifying experiences on earth."
Despite this bleak picture, there is a glimmer of hope: long-term data shows that the number of days with heavy smog has decreased significantly compared to three or four decades ago. Researchers at the University of California, Berkeley, attribute this decline to the effectiveness of the state's stricter clean air laws, which have reduced the amount of particulate matter needed for smog to form.
As for the current crisis, residents are anxiously awaiting a strong weather system expected in mid-December, hoping it will mix the atmosphere and clear the thermal inversion. But until then, the inhabitants of California's central valley remain trapped under a blanket of fog that not only obscures visibility but also traps everything that threatens their health and safety—a stark reminder of how a natural phenomenon can be transformed into a serious hazard by human intervention in the environment.
