Unless you are about to eat an uncooked live lobster, the food on your plate would not normally make you fear for your safety.

And if someone - especially if it was the Government - told you something was safe to eat, the chances are you would not expect your brain to turn to sponge if you ate it.

Safe? Who knows

But in the fallout from Mad Cow disease, and especially amid fears that it might be linked with Creutzfeld-Jakob Disease in humans, nothing seems certain.

BSE is just one worry over the safety of food. A possible link between milk and Crohn's Disease, the scare over the E-coli outbreak in Scotland in 1997, and fears over salmonella in eggs have all hit the headlines in recent years.

One view

Speaking before an inquiry looking into the handling of BSE, the former Chief Medical Officer, Sir Kenneth Calman, said just because the Government had declared beef safe did not mean there was no risk from it.

He said: "The meaning of 'safe' is central . . . If you look at 'safe' in ordinary speech, we don't mean that a driver we describe as safe will never have an accident . . . In ordinary usage, safe doesn't necessarily mean 'no risk'."

Another view

That is one view. The Concise Oxford Dictionary, however, defines safe as: "free of danger or injury . . . not involving danger or risk". Which is, perhaps, another view.

Dot Churchill, of Wiltshire, whose son Stephen died of CJD in 1995, aged 19, is one of those who might take the other view. She said Sir Kenneth's comments in effect amounted to "safe" not necessarily meaning "safe".

Whether safe means 100% certainty of no risk whatsoever, or merely an acceptable risk that most people would be prepared to take, can be a crucial difference. But the definition depends on who you are talking to.

• Nothing is safe: A spokesman for the Association of British Insurers said "safe" was not a word that insurers tended to use - partly because it was so hard to define.

  He said: "We deal in terms of risk. If you were trying to think of something totally and utterly safe, as far as insurance is concerned, it would have to be something that will never ever happen. I can't think of anything in that category.

  "It's fairly safe you're not going to win the lottery, and that's one in 14 million. But you could tie yourself in knots coming to terms with this. It's all a matter of semantics."

• You can cut risks: A spokesman for the British Safety Council, which aims to cut accidents in industry, accepted that 100% safety was not going to be achieved.

  "You can reduce risks as much as possible, but to say something is completely safe is kind of ridiculous," he said.

• Things are safe if you use them properly: But a spokesman for the Royal Society for the Prevention of Accidents interpreted the concept of safety a bit more strictly.

  "People assume that, for instance, because something has a British Standard, it will be safe. But it is only safe for the things it's tested for. With fireworks, if people follow the instructions on the label, they will be safe, but of course if they misuse them they will be dangerous."

  Thus, he said people would be entitled to think food which was officially safe would not harm them, unless they choked on it or introduced germs into it.

So when is safe safe? It might be a bit risky to say.