From the news release, he said, it appeared that "what we have is an estimate of theoretical risk based on conditions which don't exist in reality."

Some women are also concerned about what he called the "theoretical risk" that frequent mammographies could cause cancer.

Notes issued by central banks had a theoretical risk when they were backed by gold and silver.

This is a theoretical risk, and such weapons have not been used by terrorists.

"The fact that it happened is not a total surprise, but our research shows that it's not just a theoretical risk."

There is, at least, a theoretical risk that email sent over the internet may be intercepted.

Recent work, using real-world numbers, indicate that the actual risk is probably less than half the theoretical risk.

Evidence indicates that these theoretical risks might not be major problems.

Dutch health officials, he added, considered mad cow disease, "at the maximum, a theoretical risk of a very small nature for the human blood supply."

And it is still not known how one animal passes the disease to another, much less if humans face more than a theoretical risk.