10 Chemicals You Really SHOULD Be Scared Of

From one deadly plant to another, this time the castor oil plant. Many of us are vaguely aware of castor oil. It used to be, and actually still is, used as a medicine. It's quite a good laxative, and some people swear that it induces labour, although there's no good evidence for its effectiveness.

A dose of castor oil, with its unpleasant oily, petroleum jelly-like taste, used to be used as a punishment for children. There are still references to the practice in older films and books. For example, there's a classic episode of Tom and Jerry in which Tom is forced to swallow a spoonful of the stuff. Doctors began to recommend against the practice in the early 20th century; using medicine as a punishment being all very well until you need the child to actually swallow a life-saving treatment.

Clearly, castor oil can't be that deadly, so why bring it up? Because it comes from the seeds of the castor oil plant, and the only reason it's safe is that heat is applied during the extraction process. The poison, ricin, is actually a protein. Like all proteins, it denatures when it's heated, which renders it inactive.

Take away that heating process, and we're looking at something very nasty indeed. A dose of purified ricin powder the size of a few grains of table salt can kill an adult human, and you don't even have to swallow it. If the dust comes into contact with your eyes, or worse still, you inhale it, you're still in big trouble. It prevents cells from making proteins, a process that is essential for life but, unlike some of the other compounds we've met so far, this one works slowly. Symptoms of swallowing ricin can take 2-5 days to appear, and include vomiting, diarrhoea, difficulty swallowing. Inhalation causes different problems, including coughing and fever. Either way, the ultimate outcome is death from organ failure.

There are some antidotes and treatments for ricin, although the antidotes haven't been tested in humans. Treatment usually involves intravenous fluids and airway support, and hoping that the patient recovers. Even so, survivors often have long-term organ damage.

There is a vaccine for ricin poisoning, but it's only effective for relatively short periods of time, so is only really useful for people who have good reason to think they might be exposed.