White big cloud in agar gel electrophoresis - (Apr/16/2012 )
True that our exposure is over a longer term than that of cattle administered EtBr prophylactically, but I also think it would be safe to assume that if cattle have no higher incidence of cancer at the massive doses they received (comparative to our incidental exposures), that the risk to us is equally negligible.
(I didn't do this calculation, rather read it on the blog of someone discussing this very issue)
"A 50kg researcher would need to drink 50,000 liters of gel-staining solution to get even the non-toxic dose used in cattle."
Interestingly, some of the new dyes purported to be "safer" than EtBr actually have higher toxicities in mouse studies than EtBr.
No harm in continuing to take precautions though 
The problem I have encountered is that, after I point out the massive doses given to cattle, someone will come back and say "Ah, but what do they know about long-term, very low level doses?" , which is crazy talk to my mind . High-level doses do not have an acute toxicity, nor a long-term cancer-risk factor, so the body can handle EtBr. How do they think that the body can't process ultra-low levels? I mean, what route of entry do these people envisage? The BP of ethidium is over 200C, so there won't be any in the steam that can be generated, thus no aerosol problem. You could drink it or inject it, I suppose, but that's what they did to the cattle, and as has already been pointed out, neither the cattle, nor their offspring, nor the herdsmen who lived with and on the cattle developed cancers. What we need is an epidemiological study of cancer rates across 30 to 40 years in molecular biologists vs scientists who do not use EtBr. Any volunteers?
Sometimes I think I work in a sheltered workshop for intellectually gifted people...
Well my idea on this is: It's a lab and I work carefully with chemicals...
EtBr diffuses through usual Latex gloves in a few seconds, and can be absorbed through the skin and aerosols don't need 200°C, but these tiny droplets are in steam of boiling water (to avoid this you boil the agarose without EtBr, because you're careful)...if a hood is really necessary then is surely arguable, but often prescribed.
EtBr has effects on animals (LD50 mice: 110 mg/kg with hypodermic injection; rats: 1503 mg/kg oral), the liver processes it and the metabolites are mutagen (too or alone). Here's a extensive webpage on studies about EtBr.
And I wonder if anybody ever checked all the treated cattle for tumours, I don't think so...anyway the effects on other species are a hint only and no proof that it's more or less toxic, teratogen or mutagen to humans. So I'm careful and avoid unnecessary contact.
According to a paper quoted in wikipedia it also acts as topoisomerase I poison similar to some anticancer drugs. Anyway do I want to take an anticancer drug? No.
I'm not hysteric about it (I work with EtBr almost every day), but careful and sceptic in both directions.
hobglobin on Thu Apr 19 17:06:15 2012 said:
Well my idea on this is: It's a lab and I work carefully with chemicals...
EtBr diffuses through usual Latex gloves in a few seconds, and can be absorbed through the skin and aerosols don't need 200°C, but these tiny droplets are in steam of boiling water (to avoid this you boil the agarose without EtBr, because you're careful)...if a hood is really necessary then is surely arguable, but often prescribed.
EtBr has effects on animals (LD50 mice: 110 mg/kg with hypodermic injection; rats: 1503 mg/kg oral), the liver processes it and the metabolites are mutagen (too or alone). Here's a extensive webpage on studies about EtBr.
And I wonder if anybody ever checked all the treated cattle for tumours, I don't think so...anyway the effects on other species are a hint only and no proof that it's more or less toxic, teratogen or mutagen to humans. So I'm careful and avoid unnecessary contact.
According to a paper quoted in wikipedia it also acts as topoisomerase I poison similar to some anticancer drugs. Anyway do I want to take an anticancer drug? No.
I'm not hysteric about it (I work with EtBr almost every day), but careful and sceptic in both directions.
You are right.
But what I "dislike" is that EthBr. "gets a lot of attention" and people freak out whenever something goes "wrong" with EthBr and at the same time they use other chemicals (often more dangerous or as dangerous as EthBr.) without any precautions. Or often they think that EthBr is soo bad that the alternatives must be 100% safe and (figure of speach), they could drink it and they drop their gaurd and start contamination the entire lab with this alternative.
The reaction of that supervisor is classical and shows how people dont think enough.. The gels themself contain EthBr etc.. as mentioned before.