Second in Lab Muffin's Big 3 series is toluene. Part 1 - DBP
Toluene - TOLL-lew-een - MSDS
aka toluol, methylbenzene, phenylmethane
Where is it found? Nail polish, permanent markers, paint.
Why is it there? Toluene is a solvent - in other words, it dissolves up all the other bits in nail polish so you’re not putting chunky powder across your nails. It has a relatively high boiling point (BP = 111 °C) so the nail polish dries slower than if only ethyl acetate (BP = 77 °C), for instance, was used.
Is it toxic? LD50 = 636 mg kg-1 - don't drink it!
Although the two main solvents used - ethyl acetate and butyl acetate - are quite safe (although smelly!), toluene is less friendly. The strong smell of nail polish is actually the solvent (liquidy part) of nail polish entering your nose, and inhalation is the main route of exposure to toluene in nail polish (as long as you don't drink it!).
Like a lot of other solvents and the alcohol that you drink, toluene is a central nervous system depressant - it makes you drowsy, and slows down your breathing and heart rate. It can also cause confusion, slurring, headaches, dizziness and nausea - a lot like drinking too much! Luckily, like alcohol, it doesn't hang around the body for too long, and the effects stop once you go outside for some fresh air.
In the long term though, if you inhale it too often for a long period of time,toluene can cause damage to your lungs, liver, and kidneys. However, the amount used in nail polish is probably too small for this to be an issue.
It's also a possible teratogen, which means that you shouldn't expose yourself to large amounts of it when you're pregnant, as it might harm your unborn child. Again, this is more of an issue for people who inhale toluene as a recreational drug than those who are exposed to small amounts while painting their nails - however, if you're pregnant or planning to become pregnant soon, be cautious.
Toluene is sometimes classified as a possible carcinogen, although it hasn't been conclusively linked to cancer yet (see here for more info). On the other hand, the carcinogenic activity of benzene, a very similar molecule (cover the "antenna" on toluene and you have benzene), is well documented. What a difference that little line makes!
Lab Muffin's Verdict: It's the least scary of the Big 3. Don't huff nail polish, girls! And don't drink it.