Ethidium bromide carcinogenicity?

R.G. Walters mbrgw at
Wed Apr 12 05:20:47 EST 1995

In article <D6wCG7.Iq6 at> sferguso at writes:
>In article <edbeaty-1104951801360001 at>,
>Ed Beaty <edbeaty at> wrote:
>>The question has come up in my lab again about the possible risk of
>>exposure to Ethidium bromide.  I've heard statments to the effect that
>>exposure is harmless; that it is used in Australia as a "sheep dip" to
>>kill parasites but that the sheep are unharmed; that smoking is a
>>hundredfold worse for you than exposure to EtBr.  What's the current
>>status of this argument?  Any information would be appreciated.
>>Thank you,
>>Edward Beaty
>Well, it's use as a sheep dip is news to me. However, I have a difficult
>time believing that EtBr is harmless. Even if there were no data to indicate
>that it is a mutagen, think about it. 

It is not used a sheep dip, but has been (and probably still is) used as
a treatment for certain parasites which infect sheep's eyes - in high
concentration.  My understanding is that it is only classed as "harmful"
because to re-rate it would prevent its agricultural use - ie the decision
has been political rather than on safety grounds.

I think the "lack of harm" is more related to a sheep's longevity (or
lack of it) rather than the toxicty of the chemical.

>Here's a molecule that intercalates into DNA and will induce a break in 
>that DNA if energized (e.g. with UV light). I can't think of a better 
>molecule to pick if you wanted to guess which ones are mutagenic. I don't
>need to see extensive epidemiological studies to figure out that a chemical 
>that disrupts and nicks DNA can't be a good thing.  

Too right.  

>Oh yeah, remind me not to eat or wear anything imported from Australia :)

It's not just Australia :-(

Robin Walters,                              Robert Hill Institute, Sheffield UK
Scientists for Labour                                    R.G.Walters at         mbrgw at

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