A dense fog across the U.S. has sparked conspiracy theories reminiscent of the 1950 "Operation Sea Spray," when the U.S. Navy secretly tested biowarfare by releasing bacteria over San Francisco, causing illness and one death. Recent reports of unusual fog with "chemical-like" smells and respiratory symptoms have fueled fears of a government experiment. However, experts attribute these phenomena to natural winter fog mixed with pollutants, which can trap odors and cause respiratory irritation. The National Weather Service and atmospheric scientists explain that this fog, though appearing unusual in light or video, aligns with known meteorological patterns and does not indicate biowarfare.