When talking about Sassafras, one of the seeming best pieces I found was from a home brewing forum.
Sassafras is Not Nearly as Dangerous as You Would Think, rriterson, 2010
This page contains the following:
“Let’s say that I drink 1 of my own rootbeers per day. In order to have a 50% chance of cancer, I’d have to have 3.85g of safrole per root beer. Since my batches are 5 gallons (~50 beers), that would mean I’d have to get 192.5g of safrole out of the sassafras I seep. I start with 16oz (1lb) of sassafras root. Well, 1lb is actually only 453g. 192.5g/453g is 42%.”
So this guy is using about 90g of Sassafras per gallon of Root Beer and feels it is a relatively safe amount, if he is getting a (very generous) 42% yield of Sassafras Oil per gram of sassafras root.
Old recipes call for 8-10 drops of Sassafras Oil per 5 gallon batch. I don’t know what the conversion is between Sassafras Oil drops and grams, but some things I’ve found indicate between 40-90 drops per gram for liquids. Castor Oil is said to be around 44 drops per gram. If Sassafras Oil is similar in weight, by rmitterson’s math, you would need to be using basically 3.85 times 44, or 169 drops of Sassafras Oil, per glass of Root Beer for a “50% chance of cancer”.
When I weighed out the amounts of herbs and barks in my Root Beer recipe, I found I was using about 4-6 grams of dried Sassafras Root Bark per gallon.
A pound of Sassafras sounds like a lot, but the yield of sassafras oil from my 4-6g of dried Sassafras Root per gallon, (most things I’ve read indicate the yield of Sassafras Oil from Sassafras Root Bark is 6-9% by weight when steam distilled,) isn’t going to be anywhere near significant in a simple heat infusion in water. Sassafras Oil isn’t even soluble in Water (Alcohol is another matter)!
So, mostly, I have to say I don’t feel that worried about Sassafras in my Root Beer recipe, at least compared to other potentially cancer risk elements in my life history or current environment.