Answer: Benzene

There’s a long history of humanity using a compound for something only to discover, oftentimes years after the fact, that the compound isn’t so healthy for us to handle, burn, use on our bodies, or ingest. The history of coffee production is no exception to that rule as the first commercial decaffeination process relied on benzene. Yes, that benzene, the highly carcinogenic crude-oil derived hydrocarbon that is a critical precursor component in gasoline, styrene foam, and nylon production.

In 1903, German coffee merchant and inventor Ludwig Roselius developed the world’s first commercially viable coffee decaffeination process. This process, known as the Roselius Process, involved steaming green coffee beans with acidified water and then washing them with a solvent solution of benzene to remove the caffeine from the beans before the roasting process. Concerns over the use of benzene in the process eventually led to a phaseout and subsequent replacement with ethyl acetate (a low-toxicity and naturally occurring organic solvent derived from fruit) and dichloromethane.

Although it seems quite odd to a modern reader that anyone would wash their coffee beans in what is now used as a gasoline additive and hardly used elsewhere outside of industrial applications, benzene had a brief, but glamorous, life during parts of the 15th through early 20th centuries. People were unaware that it was a carcinogen, and it has a very sweet smell; as such, it was used in a wide variety of non-industrial ways like men’s aftershave, perfumes, and other distinctly bad-for-the-body applications.