Given Halloween is approaching I figured I would post about the scaries of science.
Today's edition:
Ethidium Bromide, EtBr.

If you've ever worked in a lab that does genotyping you've likely heard of it. You've also likely seen the bench space devoted just to it with hazard warning labels: BEWARE, CARCINOGENIC or some such. But how dangerous is it? I often wondered given that even as much as one tries, somehow it spreads throughout the lab like a virus. I can't imagine where it wouldn't be found if we brought in a UV light.

So that's when I decided to actually look it up and see just how bad is it and you know what? Turns out, it's not that dangerous!
Sure it makes all my bands show up nicely but what exactly is it?
Ethidium bromide is genotoxic, a frame-shift mutagen and teratogen.
It intercalates double stranded DNA (inserts itself between the strands), deforming the DNA and increasing chance of mutations (M.J. Waring, 1965). Because it's a fluorescent compound, when exposed to UV light it will fluoresce with an orange color. 

Since EtBr has been administered for treatment of African Sleeping Sickness in cattle you would think there would be a lot of increase in tumorigenesis... but there isn't! Appears that it is less genotoxic in animal systems compared to the in vitro tests performed. There is actually no evidence that direct exposure to EtBr has caused any tumors.

I'm not suggesting we should start gurgling with it. I'm just saying maybe we can tone it down on the EtBr disposal as incinerating anything that came in contact with it, putting it into activated charcoal, using hydrophosphorous acid or sodium nitrate are much more dangerous than it is itself.

Perhaps the largest real hazards associated with use of EthBr in molecular biology are the methods used to inactivate it. Some labs now incinerate all waste containing even a trace of EthBr, and others absorb it onto activated charcoal. Harsher methods involve use of bleach and sodium hydroxide, or hydrophosphorous acid and sodium nitrite, all much more dangerous than EthBr. - See more at: http://rrresearch.fieldofscience.com/2006/10/heresy-about-ethidium-bromide.html#sthash.yOLIpwZi.dpuf

bleach and sodium hydroxide, or hydrophosphorous acid and sodium nitrite, all much more dangerous than EthBr. - See more at: http://rrresearch.fieldofscience.com/2006/10/heresy-about-ethidium-bromide.html#sthash.yOLIpwZi.dpuf

Here is a great article on heresy about EtBr.