The first commercially successful decaffeination method was invented around 1905, by German coffee merchant Ludwig Roselius. According to Atlas Obscura, one bit of lore about the origins of decaf claims that Roselius received a shipment of coffee beans that was soaked in seawater. Instead of tossing the beans, Roselius decided to process and test them. He found that the coffee had been stripped of its caffeine content but still basically tasted like coffee, albeit a bit salty.
Roselius then figured out he could use benzene — a chemical that, at the time, was also used in paint strippers and aftershave — as a solvent to remove caffeine from coffee beans. His company, Kaffee HAG, was the first to produce instant decaf coffee. The coffee was sold as "Sanka" in the United States by General Foods, and was a mid-20th-century staple — and occasional punchline. (In the 1982 movie "Fast Times at Ridgemont High," a biology teacher pleads with his students, "I'm a little slow today. I just switched to Sanka, so have a heart.")
Is decaf coffee bad for you?
Like all coffee, decaffeinated coffee is safe for consumption and can be part of a healthy diet.
If you are wondering whether the decaffeination process itself is safe, the answer is yes. All four methods are safe, and once the caffeine is removed (well, at least 97% of it), the beans are washed, steamed, and roasted at temperatures that evaporate the liquids used in decaffeination.
The U.S. Food and Drug Administration has set a rigorous standard to ensure that any minute traces of solvents used to decaffeinate coffee are safe. FDA measures these traces in “parts per million.” After decaffeination, coffee can contain no more than 10 parts per million of, for example, methylene chloride -- that’s one one-thousandth of a percent.
Special Thanks to the NCAUSA for the great information