People are increasingly worried about chemicals these days (even if they don't quite know what the word means), but most of that fear is unfounded. The ingredients in cosmetics and foods are actually pretty harmless on the whole, certainly in the quantities you usually meet them.
This is because we've had decades of extensive testing and health and safety regulations - the truly nasty stuff simply isn't allowed anymore. Even, sometimes, in fairly-obviously dangerous things like rat poison.
But the nasty stuff exists. Oh yes it does. You might be unlikely to come across it these days, but it's still out there. Locked away. (Or not.)
So, come with me as I take you on a tour of 10 chemicals you really SHOULD be scared of...
10. Potassium Cyanide
I know a chemistry teacher who's fond of telling his classes: "If you smell almonds in a chemistry lab, send someone in ahead of you."
Potassium cyanide, the salt of hydrogen cyanide gas, has a colourful history. It is, of course, much beloved of murder mystery writers. Agatha Christie was fond of killing her characters off with it, perhaps most famously in the eponymous Sparkling Cyanide. There are good reasons for selecting it as a murder weapon.
Cyanide kills by preventing enzymes in our cells from working properly, with the result that the cells can't produce ATP for energy, and so die. The heart and central nervous system are particularly affected, causing seizure and cardiac arrest. This process is irreversible and extremely fast. A tiny dose of potassium cyanide can kill an adult in under a minute, hence its infamous use in suicide pills by members of military and espionage organisations.
Why did people have this sort of thing knocking around within easy reach? It actually had several 'household' uses. For starters, it's an effective insecticide. In Sparkling Cyanide, we're told it was being used to get rid of wasps nests. There were good reasons for people to have potassium cyanide in their home, even if they weren't serial poisoners.
As poisons go, it is a good one. It's very fast-acting, and unless cyanide residue is found on or near the victim, it may never be discovered. Until recently, it could only be detected in the body with specialised tests, and then for up to two days after death, so unless the forensics team got going moving extremely quickly, and had some idea what to look for, the poisoner might well get away with it.
There have been so many deaths attributed to cyanide that Wikipedia has a whole page devoted to cyanide poisoning. It's been implicated in many suspected suicides, perhaps most famously, the mathematician Alan Turing. Cyanide murders aren't just historical curiosities: on 6th January 2016, Indonesian Wayan Mirna Salihin died in hospital after drinking a cyanide-laced coffee, thought to have been given to her by her 'friend' Jessica Wongso.
So if you smell bitter almonds (not unlike the smell of Amaretto liqueur ), you might have good reason to be cautious. Except, it turns out that the ability to smell the almond-y smell of cyanide is genetic, so maybe you'll never know... until it's too late...
Kat Day is a science blogger, writer and teacher living in Oxfordshire in the U.K. Her award-winning blog is called The Chronicle Flask, and she has also written articles for Sense About Science, Things We Don't Know and Nature Chemistry. When she's not writing or teaching she is usually trying to keep on top of important parenting skills such as negotiation, conflict resolution and always having the right coloured cup.