The US started hearing about a substance that could be used to track the movements of any person who touches, or walks across, a contaminated surface. in 1963. It wasn’t until 1984 that they got a sample of the stuff.
A defecting agent revealed that powder containing both luminol and a substance called nitrophenyl pentadien (NPPD) had been applied to doorknobs, the floor mats of cars, and other surfaces that Americans living in Moscow had touched. They would then track or smear the substance over every surface they subsequently touched.
The revelation caused a scandal, not so much because of the tracking, but because of the potential health hazards of what came to be known as “spy dust.” The dust was tested to see whether it was a carcinogen or a mutagen. Scientists decided that the substance was safe for external use at low levels.
Technically, the substance probably wasn’t used in dust form. A 2004 study synthesized spy dust and used it to trace the movements of both a car and a human. The researchers conducting the study dissolved the dust in methanol and sprayed it on surfaces instead of sprinkling it. Once it had been picked up by bare hands, the wheels of a car, or cotton gloves, they tested suspected areas for exposure to NPPD or luminol. The multiple chemicals in spy dust allowed them to test multiple ways for exposure:
“The color examination was a two-steps process: first was the addition of 1 mL of a 0.1% naphthoresorcinol methanol solution to the methanol extracts of a methanol-contained cotton swab used to smear some surfaces of the suspect, and second, the addition of 1 mL of concentrated hydrochloric acid, which turned the solution dark red. The gamma max of the colored solution was 510 nm, measured by ultraviolet-vis spectroscopy. Detection limits for three methods were determined: a visual method (detection limit 100 ng/3 mL), an ultraviolet-visible spectrometric method (detection limit 10 ng/3 mL), and a selected-ion-monitoring gas chromatographic/mass spectrometric method (detection limit 300 pg/injection).”
The study concluded that spy dust is a “useful shadowing pursuit.” So, if someone wants to know where you were, you might be smearing spy dust over your keyboard right now.