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Seeing Red in Molecular Biology Labs

January 1, 2012 - 11:08 -- Mark Benedict

Quick question: For those of you who work in a recombinant DNA lab, what is the most hazardous chemical that you use on a daily basis? To put it another way, what chemical do you ALWAYS wear gloves to handle? Probably the same one that I do, but risk perception and reality aren’t always the same thing.


When it comes to genetic control of mosquitoes, risks are a hot topic, so it’s useful to consider the answer to this question.


 A scientist does well to question some pronouncements. An attitude of second-guessing agreed-upon fact is an admirable – even essential – characteristic. The attitude that “Science is the belief in the ignorance of experts.” (Richard Feynman) won’t buy you points if you insist on shoving that attitude in the face of your graduate committee, but it has served the advancement of science quite well. Healthy skepticism is particularly called for when one hears wailing and gnashing over an area that can be extremely subjective: risk.


I was reminded of this recently when I was ferreting through various combs and gel trays in an unfamiliar lab. One of the denizens warned me that there was ethidium bromide all over the place and that I should wear gloves. Thanks for the information. I did. It was the second time I’d been warned about this in as many years, although the level of excitement in the first case was much more memorable (moving a power supply appeared to be an imminent cause of birth defects and cancer).


I noticed there was a highlighted sign on the wall above the gel area that in yellow-high-lighted text declared EtBr “estremamente tossico.“ You don’t have to know Italian to get an idea of what that means. Similar excited warnings followed down the hazard list so that when I got to the end, I was convinced that after standing the vicinity that I may as well check into a cancer therapy center. Or, more accurately, I was convinced that whoever had written it was convinced of this and  I should be too.


My skepticism about EtBr risk didn’t arise simply out of my general dour nature (though I can be justly described as having one). Years before, I had read an assessment of EtBr describing the commonly perceived risks as unjustified by the science. But hey: times change. Science moves forward, and maybe EtBr really has been found to be “estremamente tossico.”


The recent caution stimulated me to investigate the facts behind panic about EtBr  risk. How could the same risk perception exist in so many labs if there were nothing to it? Once again, I started digging around to find evidence that merits panic. A good place to start is a Material Safety Data Sheet, this one for 100% EtBr.


"Potential Acute Health Effects: 

Hazardous in case of ingestion. Slightly hazardous in case of skin contact (irritant), of eye contact (irritant), of inhalation. CARCINOGENIC EFFECTS: Not available. MUTAGENIC EFFECTS: Not available. TERATOGENIC EFFECTS: Not available. DEVELOPMENTAL TOXICITY: Not available."


 That doesn't sound so bad, but maybe this means that those effects simply haven't been investigated.


Wikipedia isn't the final word, but it contains an informative entry for EtBr. After reading that and thisI saw no huge red flags. (EtBr is used as anti-parasitic drug? Well, that doesn’t carry much weight with me since some very nasty chemicals are used as drugs, but extremely toxic?) Mutagenicity, toxicity, teratogenicity: on no count do I find evidence that the excitement around perceived risk matches the data. (If you’re skeptical -and I do hope you are,- do your own research and let us know what you find. And please try to report your findings in the context of other common chemicals if possible e.g. sodium hypochlorite.)


Risk perception is passed down around the world, from supervisors to employees, from faculty to students. Sadly, it’s even promulgated and reinforced by biosafety “authorities.” Unfortunately, in the lab, as in the field, over- and under-estimating risk creates hazard. A good example is the emotional trauma suffered by this person who commented on a similar blog:

"Once a few drop of EthBR(10mg/ml) splashed on the skin of my chest. Though I washed immediately, I am scared to death. After 7 years of exposure, I am still alive. But I often think I will develop some skin cancer, breast cancer or lung cancer. This paper may give me a peace of mind."

When it comes to the use of genetic control against mosquitoes, risks are real, just as they are in molecular biology labs, but they must be kept in perspective. We as scientists have a responsibility to get it right and to help those with whom we interact to understand as well.

Hang on! This just in: 

“MUTAGENIC EFFECTS: Mutagenic for mammalian somatic cells. Mutagenic for bacteria and/or yeast.”
Oh wait. That’s for table salt.


Submitted by Guest (not verified) on


There are too many scare notices and claims of toxicity and carcinogenicity in the press and some journals. I encounter people who have no idea about risk and benefit of chemicals or the dose rate that can be harmful or lethal. Alcohol and tobacco can be added to salt as a possible/probable cause of mutagenicity, sometimes at very low doses. Even too much ingested water can kill one.