Was that a long time ago? They used to use organic, and even chlorinated, solvents to extract the caffeine, but for the last 15-20 years, supercritical CO2 is used, and that leaves nothing of itself behind.
I was taking a course at the time when a classmate, a chemist from General Foods, told me that Coca-Cola and Pepsi were buying every gram of caffeine they could get out of the coffee.
From Here:
http://en.wikipedia.org/wiki/Methylene_chloride
I found this:
Methylene chloride's volatility and ability to dissolve a wide range of organic compounds makes it an ideal solvent for many chemical processes. It is mainly used as a paint stripper and a degreaser. In the food industry, it is used to decaffeinate coffee and to prepare extracts of hops and other flavorings. Its volatility has led to its use as an aerosol propellant and as a blowing agent for polyurethane foams. It is also used as a fumigant pesticide for stored strawberries and grains. However, concerns about its health effects have led to a search for alternatives to it in many of these applications.
It's only been in the last ten years or so that I have had this reaction - The most painful headaches imaginable.
I am not doubting what you say about the decaf process, I only know what decaf does to me.
Sounds like it's in beer too (hops) I don't drink beer so that's not a problem.