Field of Science

Heresy about Ethidium Bromide

Recently I've received several copies of an email warning of the dangers of ethidium bromide (a chemical used to visualize DNA in agarose gels) and advertising a seminar about a safer alternative. The email originated from Invitrogen, the company that sells the alternative DNA stain ("SYBR safe"*) and is sponsoring the seminar. Here's the first two paragraphs of the email:
A real risk of lab science is accidental exposure to hazardous chemicals, especially ones that may be fatal if inhaled, harmful if swallowed or absorbed through skin, causing irritation to skin, eyes and the respiratory tract and causing heritable damage.

Ethidium bromide has just such characteristics and is frequently in use at many UBC labs. A safer alternative is available that is non-toxic, non-mutagenic and is not classified as cytotoxic waste when disposed. To alert the UBC res
earch community to this safer alternative called SYBRSafe Gel Stain, the Department of Health Safety and Environment and the UBC Sustainability Office are sponsoring a seminar presentation by Invitrogen on the product comparison and practical application of SYBRSafe.
This would be fine if ethidium bromide (EthBR) really was a serious hazard. But it's not. And it's actually less toxic than this alternative.

Ethidium (also called homidium) was developed as a treatment for trypanosomiasis (African sleeping sickness), and is still used in Africa where resistance to it is not a problem. The following quote is taken from the Encyclopedic Reference of Parasitology (2004): "...homidium is generally well tolerated at recommended dose and also at higher dose levels (no systemic toxicity)..." (source). The recommended dose for cattle is 1mg/kg body weight (up to 50mg/kg has been used in mice). Compare this with the 0.25 - 1 microgram/ml used in molecular biology (previous error corrected - thanks, anonymous commenter). A 50kg researcher would need to drink 50 liters of gel-staining solution to get even the non-toxic dose used in cattle.

Here's information from a materials safety data sheet (MSDS) provided by Fisher Scientific:
Ethidium Bromide: (inhalation, rat): 0.0118 - 0.1340 mg/L/6H. (oral,rat): 1503 mg/kg. sts determined to be toxic based on: LC50 (inhalation rat) 0.0472mg/L/1H * 100 (dilution rate)=approximately 4.72mg/L/1H.
Carcinogenicity:
CAS# 7732-18-5: Not listed by ACGIH, IARC, NTP, or CA Prop 65.
CAS# 1239-45-8: Not listed by ACGIH, IARC, NTP, or CA Prop 65.

Epidemiology: No information found
Teratogenicity: No information found
Reproductive Effects: No information found
Mutagenicity: Possible mutagenic effect in humans. The suspicion is based on proven damage to the genetic material in the somatic cells of man and animals and requires further clarification.
Neurotoxicity: No information found
Translating as best I can, half of mice given 1.5g /kg body weight will die, as will half of mice that spend 6 hours breathing air containing about 0.12mg EthBr dust/liter. There is no evidence of neurotoxicity or of birth defects or reduced fertility even at the high doses routinely used in cattle.

Despite the evidence, the "EthBR is very dangerous" meme has become dogma in molecular biology. This is because EthBR can increase the frequency of mutations, a topic on which most people are very irrational.

Ethidium is a flat molecule, just the right size to get in between the stacked base-pairs of double-stranded DNA. This, and its fluorescence, are what makes it a sensitive dye for detecting DNA. The presence of ethidium when DNA is being replicated can cause DNA polymerase to slip, creating short insertion or deletion mutations. Here's a 1999 reference. However there's no direct evidence that exposure to EthBr causes mutations, tumors or birth defects in any animal, and its routine use at high doses in cattle suggests that it doesn't.

Excessive concern about mutagenicity can make us overlook short-term toxic effects, and here EthBr is the safer dye. The reference above found that the SYBRsafe alternative was actually much more toxic than EthBr to the bacterial cells used in the mutagenicity tests. SYBRsafe was toxic at concentrations as low as 1 microgram/ml, whereas EthBr toxicity was not observed until 250micrograms/ml. The authors suggest that this is because living cells are much more permeable to SYBR green than to EthBr. But a MSDS for SYBR safe reports a LD50 for rats of >5g/kg, which is higher than that of EthBr (1.5g/kg). As both these LD50s are many orders of magnitude higher than the concentrations used in molecular biology, toxicity of gel staining solutions is trivial compared to the risks of of burns from melted agarose or slipping on spilled gel buffer.

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.

A final issue is cost, and here SYBR dyes may indeed be better, even though they cost a lot more per use than EthBr. This note compares the costs of different DNA stains used in agarose gels, and concludes that the new SYBR stains may save money because their greater sensitivity allows use of smaller amounts of the costly size standards. For example, this photo shows that SYBR gold can reveal bands containing as little as 100pg of DNA. (It also shows how big a problem fluorescent dust flecks can be when using SYBR stains.)

Despite the evidence of its safety, all the scientists I know continue to believe that EthBr is dangerous. It's not that we differ on how the evidence should be interpreted - they have never examined the evidence and see no point in doing so, even when I tell them that it contradicts their beliefs. I find this scary.

*I haven't been able to find out what SYBR safe is, nor the actual concentrations of the products on the market. It's all "proprietary information".

72 comments:

  1. I would add to your comments that it's important to remember that Cybr-Gold doesn't have the same toxicity profile as Cybr-Safe - I am not even sure to what extent the toxicity of Cybr-Gold has been tested. The same goes for the other Cybr-products.

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  2. I think you should post this on the LSI newsletter and let everyone knows that EthBR isn't that dangerous to use. I can still remember the "horrified/end of the world" look on the person's face(upstair) when I "almost" placed my gel in a container on a bench. It was as if I had done something horribly wrong...

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  3. So I shouldn't have been so frustrated when an undergrad spilled a bottle of EtBr? That's good to know. Now if I could only find out about all that EMS I handled.

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  4. Dear Rosie:

    A long time since grad school, hey? I have followed and enjoyed your work for a long time.

    I LOVE the EtBr story. You warned me about this in graduate school, as I recall---ticking off relative risks compared to EtBr.

    Do you mind if I send this around to people? I'll use a link so you get credit and all that. I just haven't seen this in one place before. You should consider what one of your commenter suggested and write an opinion piece on this subject?

    Best wishes...

    -Mark Martin

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  5. Your remarks are compelling, but what do you make of Invitrogen's claims?

    www.invitrogen.com/sybrsafe

    Deft marketing or scientifically justified?

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  6. Interesting, but main reason we use SYBR-safe in my laboratory is that it can be used in combination with blue light boxes, negating the need for UV boxes. Less damage to DNA samples and no risk of UV exposure to researchers.

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  7. Well this is encouraging news, especially after reading on wikipedia that the regular latex gloves I have been using in lab for the past year and a half don't protect against EthBr.

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  8. Here is the information to see the NTP data that caused the lastest RoC (Report on Carcinogens, 11th edition) to find "no additional testing"
    http://ntp-server.niehs.nih.gov/index.cfm?objectid=6DE15C4C-F1F6-975E-73A5D57B3D6FC3C3

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  9. This link will save you one step at the NTP site

    http://ntp.niehs.nih.gov/index.cfm?objectid=6F5EA06A-F1F6-975E-73079A5FE34F7E88

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  10. Propidium iodide, a related chemical, only stains the DNA in dead cells. I'd think it likely that ETBr doesn't get into living cells well either.

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  11. This comment has been removed by the author.

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  12. I just looked at the NTP report for EthBR, and one of the first characteristics under description is: "bitter-tasting dark red crystals from alcohol (Budavari, 1989)". We need to talk to this Budavari, and see if he/she is still alive, then we'll know. One assumes that there is a fair mass of EthBR in a crystal, and tasting it...blimey! Some sacrifices are made for science.

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  13. This comment has been removed by a blog administrator.

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  14. I was looking for information on possible carcinogenicity of ethidiumbromide for my master-thesis (environmental studies). So, thanks for the information

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  15. I FEEL REALLY STUPID. I LEFT MY BEAUTIFUL JOB, SOLD MY CAR, MOVED MY APARTMENT .... ALL BECAUSE I WANTED TO GET AWAY FROM THE EtBr. I TRIED TO RUN AWAY... I FELT THAT, IF I CAN DISTANCE MYSELF FROM THE THINGS I TOUCHED AFTER COMMING FROM LAB... I WOULD NOT DIE.

    I USED TO WASH MY HANDS FOR OVER 15 MINUTES (45 MINUTE ON ONE OCCATION WHEN A DROP OF TAE BUFFER SPLASHED ON MY ARM). EVEN AFTER ALL THIS WASHING, I NEVER FELT "CONTENT".

    READING THAT EtBr IS NOT REALLY TOXIC GIVES ME UNDESCRIBABLE AMOUNT OF JOY.

    BUT YET, THE FEAR INSIDE ME IS NOT YET GONE. EVEN AS THIS WRITE THIS COMMENT... I STILL AM SCARED DEEP INSIDE.

    BUT I HOPE THIS FINDING IS TRUE AND NO HARM IS DONE TO PEOPLE WORKING WITH EtBr. NO GENETIC DEFECTS...NO TERATOGENIC HAZARD.

    THANK YOU FOR THIS GREAT NEWS.

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  16. 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.

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  17. Please write this article a little bit longer and send it to Biotechniques. More people have to read it!
    thanks.

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  18. I have had problems with ethidium bromide hysteria in several labs. and been rebuked by junior "safety officers" for picking up my gels containing 0.5 micrograms/ml EB without gloves.
    I pointed out that Masai and Samburu give gram quantities to their cattle while continuing to drink their blood and milk.
    Also that EB binds to protein including my skin squames (which are dead) and are most unlikely to penetrate my skin.
    Also that I used to analyse commercial EB for use as a trypanocide for 4 years in the 1950's. I do not say it was good practice in retrospect but my hands were stained red for prolonged periods and I ate sandwiches daily.
    I am fit and well 50 years on.
    None of this would convince so I took one person to the first aid kit and showed him the acriflavine cream that was there to put on burns and cuts. Nothing would suffice to calm the safety guru.
    One last thing. There was until recently a safety website whose recommendation for handling sodium chloride included using gloves, a respirator, disposing of contaminated clothes and seeking medical help for spills. It did however recommend washing the offending chemical out of the eye with normal saline.

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  19. is there any methodology developed to remove the ethidium bromide from agarose gel and reuse the agarose?

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  20. Reverse the gel polarity

    or else just boil the gel and reuse it ( 1min on normal setting
    in a microwave)

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  21. Ethidium bromide induces mutations in cells and that is a fact. If there are not strong evidence that it is also a cancerogen it doesn't mean you should start drinking it with a coffee. I cannot understand that somebody who didn't present any experimental data about the safety of EtBr but only put together selected information gets such a positive response. I would suggest that Rosie Redfield and her bolivars should start administrating EtBr to themselves to proof who's right! Where is your common sense?

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  22. Why does she need to present experimental evidence, when there's already evidence out there, like people giving it to cows in significant quantities? That's just an extreme example, but it suffices to show the point. The paranoia about EtBr is over-blown. Just because something is a proven mutagen does not mean that in small quantities it is dangerous. That's a non-sequitar. It means it may be dangerous. But there can always be evidence to the contrary, which in this case there is. Furthermore, there is no direct evidence that it is actually dangerous.

    There are also quite a few theories (with evidence) regarding hormesis that very small quantities of otherwise harmful things -- like radiation, which is mutagenic -- can be beneficial. There is evidence to suggest this. The explanatory theory is that small doses cause DNA mutations, which induces the DNA repair mechanisms, which "over-compensate" and end up correcting the new errors as well as others.

    In fact, just about everything is hormetic. Vitamins normally healthy to you in moderate doses can prove lethal if given in extreme over-doses. (although the recommended daily values are extremely conservative, and there's much evidence to suggest that "megadoses" of various vitamins can be healthy, despite being 300-500% of recommended daily values).

    In any event, no-one's saying that you should start drinking 10mg/ml concentrations of EtBr like Orange Juice. But just maybe, you shouldn't be so paranoid about it.

    It is a common misconception that being "over-paranoid" or "overly cautious" isn't harmful. This is wrong. There is always opportunity cost, and who knows, maybe all the psychological stress people have over EtBr will shorten their lifespan much more than EtBr.

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  23. Hi, both of these molecules bind to DNA and it is this which prevents correct DNA replication (or RNA production) leading to mutations of DNA and damage to proteins. Obviously it is not always possible to, but I recommend evasion of contact with either.

    Since it is non-base specific, however, there is low chance of problems occurring in adult life.

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  24. Hello. I am working on tagging/staining nanoparticles so that when I put them in agarose gel electrophoresis I can see them move. I can't use ethidium bromide and was wondering if you had any suggestions for an alternative. Thanks!

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  25. Rosie, I remember you once throwing up your arms and asking "where's the data?!" with respect to EtBr toxicity. This has stuck with me and I've since found that even the Molecular Cloning manual simply indicates that the breakdown products of ethidium bromide are 'mildly mutagenic'. Yet so many labs treat it like radioactivity and even dedicate rooms for the handling and post-staining of gels.

    I read a note in "A field guide for
    THE DIAGNOSIS, TREATMENT AND PREVENTION OF AFRICAN ANIMAL TRYPANOSOMOSIS" that "Ethidium bromide is a widely used compound in molecular biology, where it is handled with stringent security precautions because it is highly mutagenic and therefore potentially carcinogenic. The same compound has been used extensively in the treatment of bovine trypanosomosis since the 1950s. (The author has commonly seen the kettle, used in the morning to prepare the solution of ethidium bromide in hot water, become the tea-pot in the afternoon.)"

    From one scientist to another, thank you for writing this article and dispelling the myth.

    EtBr use in labs seems somewhat analogous to the potential danger of religion: so few data supporting so much certainty and emotion.

    I agree with one of the other comments: this should be beefed up for Biotechniques.

    Josh Neufeld.

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  26. I was interested in the critical comment from an anonymous correspondent, implying that Rosie Redfield is being irresponsible in criticising the orthodoxy concerning ethidium. Ironically the author warns against drinking ethidium bromide with one's coffee. Has that author seen what doses of greater than 200 micromolar caffeine can do to mitotic eukaryotic cells? [Schlegel and Pardee,
    Science 232, 1264-1266 (1986)]. That concentration (~40mg/l) is not even a strong cup of coffee!

    It is obvious that many things might be toxic in the absence of a protective skin/ mucosal barrier and in the absence of a very efficient system for detoxifying all of the poisons that even nature throws at us. But we have these barriers.

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  27. I threw out two t shirts this week because i got buffer from the gel on it. I still think that its better to be safe than sorry. And yeah i wash my hands 1 billion times a day to the point where my skin gets very dry.

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  28. Finally, thank goodness! I've ben telling people about the uses of EthBr as a drug for treating trypansomosis for years now and I am continually met with the same horrified looks (often from people who routinely handle their gels with latex gloves mind you!).

    Personally, I am more afraid of the long-term effects of the pollution in the air we breath every day than almost any chemical in the lab!

    Thank you, Maria Trainer.

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  29. •Ethidium bromide (From http://en.wikipedia.org/wiki/Staining_(biology)#Common_biological_stains)

    Ethidium bromide intercalates and stains DNA, providing a fluorescent red-orange stain. Although it will not stain healthy cells, it can be used to identify cells that are in the final stages of apoptosis - such cells have much more permeable membranes. Consequently, ethidium bromide is often used as a marker for apoptosis in cells populations and to locate bands of DNA in gel electrophoresis. The stain may also be used in conjunction with acridine orange (AO) in viable cell counting. This EB/AO combined stain causes live cells to fluoresce green whilst apoptotic cells retain the distinctive red-orange fluorescence.
    [edit]

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  30. "The recommended dose for cattle is 1mg/kg body weight (up to 50mg/kg has been used in mice). Compare this with the 0.25 - 1 microgram/liter used in molecular biology. A 50kg researcher would need to drink 50,000 liters of gel-staining solution to get even the non-toxic dose used in cattle."

    Isn't the concentration used in gel staining typically 1 ug/mL, or 1 mg/L? For the 50kg researcher, "only" 50 liters of staining solution would be needed to get a veterinary bovine dose.

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  31. This comment has been removed by a blog administrator.

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  32. Brilliant brilliant brilliant and yes, as other people have said - please try to get someone to publish this as it is so very important. The reason I found this blog was because I was looking up EtBr due to paranoia and wondering what will become of my future children! Thank you so very much!
    Indie

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  33. Dear Rosie:

    I must thank you first. b/c i am an botany student doing my ph.D on molecular work. My tutor told that ethidium bromide is very dangerous. Even though i have not came in direct contact some times tearing of gloves occurs and I feel tense and i fear the total day that i may get something.
    I also feared that as i compleate my ph.d i may also get canceralong with my degree due to this chemical. Please publish this information as such all people who are working with this chemical feel relax and happy.

    maduri, India

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  34. Two years ago, I spilled some EthBr, in my hand and I did not wash it immediately. After few minutes I washed it. Since that day, I have become a paranoid person> thinking that I might develop a cancer. Actually this article helped me quite a lot to forget about. But still I am very worried. So, can some one please let me know, is their any chance of some one can develop a cancer due to EthBr. ?

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  35. i am a freshman coming from a lab in China.i am happy i have found and read it.do you have something new about EthBr or your latest investigation?if you have,could you tell me and send it to my E-mail:ouyang19860810@126.com?thank you for your article.

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  36. in our institute, most labs have been advised by the safety office to move from EtBr to SybrSafe. why? because they say it's safer and much easier to dispose.

    i've forwarded this to our risk management officer and lab manager. i'll try to echo what they have to say...

    thanks for the info!

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  37. Biochem Int. 1988 Aug;17(2):367-74. A simple quantitative method of estimation of cell-intactness based on ethidium bromide fluorescence. Dey CS, Majumder GC

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  38. I am a nephrologist in the UK, and I have just come across a patient who used EB for the Milk Marketting board to stain milk for bovine white blood cells. He used to make up large quantities of solution containing EB. He developed renal carcinoma in one kidney which was completely removed then a second primary in his other kidney three years later which was partially resected and now spread to his liver.

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    1. coincidence maybe. My Dad had Renal cancer and has never been near Ethidium Bromide!!!!

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  39. And how exactly have you established the causal relationship between ethidium bromide exposure and this person's recurring kidney cancer? Non-controlled experiments are often misleading.

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  40. Wouldn't this said patient have had to have drunk the solution for it to get anywhere near his kidneys?

    I'm not about to drink it, what most lab users are worried about is it getting into our cells via the skin.

    I see there being more chance that I'll get hereditary breast cancer than some skin cancer on my face beacause the tiny diluted droplet of stain solution that splashed onto my cheek somehow found it's way into my healthy skin cells!

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  41. I don't think anyone that is afraid of EtBr is thinking they are going to die from the initial dose.

    Just because they are treating cattle with it doesn't really mean much. Do you not think these cattle are butchered a few years down the road and eaten? Or do you think they are aloud to live 60 years more like humans? Your logic is retarded. But yeah all you idiots can expose yourself to a mutagen just because some idiot said they do it to cows.

    Oh hey I also heard about some guy who smoked a pack a day for 70 years. Lets all go do it!

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  42. I was only told that EtBr was 'toxic' from my supervisor when I was learning how to make agarose gels for PCR. I wasn't told about it being a mutagen or possible carcinogenic effects.

    Today, I spilled some EtBr on my hand (though I had gloves on). As well, my bangs got in my way(as the fume hood fan was on) when I was pouring the gel to the cassette, leaving my hair to be wet in the agarose gel containing like, what, 1ul EtBr/100mL buffer solution.

    As I got home, my friend told me that EtBr is rather a mutagen, and that a small amount can cause DNA mutation in my body and cause cancer. Of course I totally freaked out after that conversation with my friend. I ended up calling my hairdresser to book an appointment ASAP, shampoo-ed my hair three times, washed my hand a million times, etc.

    Even though I'm sure I was exposed to less than 5ul of EtBr, the fact that it is a 'mutagen' just made me to freak out.

    Thanks for the post, I feel relieved at least.

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  43. For more information please read information posted by the National Institute for Occupational Safety and HEalth (NIOSH), http://www.cdc.gov/niosh/rtecs/sf794eb0.html

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  44. There is no doubt that EtBr is a mutagen and carcinogen. The question is, why expose yourself to it when it's so easy to take percausion. The fact is that the effect - if cancer - take decades to develop. The husteria around it is there for a reason.

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  45. Thanks for an informative read, but also for linking to just the right article I needed as a reference for a paper... :)

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  46. Thanks for your great analysis! I'm going to use your findings and references. I'm glad to see I'm not alone. It is a prime example of ignorance by "experts" on a mass scale. Follow the data.

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  47. I think its stupid on the side of the author to undermine the potential of EtBr to be a health hazard for those working in the lab without proper gear (like nitrile gloves) and also to look at the waste disposal thing in such childish manner. Bloggers like these dont realize that its not just perfectly healthy adults working in the lab, there can be people who need a little higher protection like a pregnant member of staff. Also important to mention that the worst dis-service this article does is for the developing countries where health in labs is already a very tiny issue. Any how I dont have time to write more at present. As a biologist I would actually suggest one to use GelRed an impermeable dye ... instead of the Etbr or invitrogen product. Work Safe !

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  48. Basically, one should be careful with all these stains; whether or not they are stated to be safe and non-mutagenic. If they interact with DNA, they have some "potential" to do damage. But many are weaker binders under physiological salt conditions, and also are unlikely to enter live cells - let alone the nucleus (spoken as one who tries to target drugs to the DNA). So, if handled carefully, then it's unlikely they will cause lasting damage. Therefore, be careful, but don't overreact.
    Save your freaking out for acrylamide - now that is nasty, nasty stuff - and radioactivity.

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  49. I totally agree with this comment:
    "Anonymous said...

    I don't think anyone that is afraid of EtBr is thinking they are going to die from the initial dose.

    Just because they are treating cattle with it doesn't really mean much. Do you not think these cattle are butchered a few years down the road and eaten? Or do you think they are aloud to live 60 years more like humans? Your logic is retarded. But yeah all you idiots can expose yourself to a mutagen just because some idiot said they do it to cows.

    Oh hey I also heard about some guy who smoked a pack a day for 70 years. Lets all go do it!"

    Nobody tracks down whether cows are developing cancers many years after being treated with EtBr. Mutations will also accumulate, and may eventually give rise to problems with weaker DNA repair machineries in older cells.

    Besides, it is always safe to think conservatively, not only for healthy people, but also for individuals who are pregnant or have pre-exsiting health conditions.

    It is also not responsible to go from one extreme to another to claim that EtBr is not as dangerous because cows can tolerate it. Let's just face the truth: EtBr causes mutations, and EtBr does have the potential to cause problems down the road. It should always be handled with extra caution, especially compared to how you treat your coffee or sandwishes.

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  50. Well summed up and useful. I think people have to be careful with this, like any contentious issue. Your article is a useful indication that the science on EthBr is not complete. It is a mutagen - but we also have some non scientific indications that it is not harmful to living adults. This should be tested properly before being stated.

    As to the alternatives - I think that the claim that they are safe despite the same inadequate research is more dangerous than anything else. That SYBR products are cytotoxic is of great concern to me as it is marketed as safe and therefore used under flippant health regulations.

    People should be educated and sensible, research should be conducted before claims are made about of the danger or lack thereof in a chemical.

    You'd think scientists would appreciate this.

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  51. I agree it's scary because most people has an almost religious attitude towards EtBr.
    Meanwhile other dangerous products are overlooked (like xylene, for instance)

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  52. When I was researching the toxicity of EtBr for myself I ran across a clinical report of a suicide attempt. A female grad student tried to kill herself by injecting the lab's entire supply of EtBr into her vein. About half of it was estimated to have gone into the vein, the rest formed a large bump under the skin of her arm. It is hard to say how much this was, but it was said to be a couple of bottles worth of raw material.

    About 4 hours later the girl complained of abdominal cramps and confessed to her boyfriend that she was going to die from the injection. He rushed her to an ER where they kept her under observation overnight. The next day she went home. She had discolored urine and some cramping.

    EtBr is not very toxic.

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  53. Wow. While it is true that molecular biologists may use ethidum bromide at concentrations significantly below the LD50, that doesn't mean that lower concentrations are safe. The test animals developed serious health symptoms well before the LD50 was reached. This is why your safety officers are requiring all those pesky precautions.

    By the way, ethidium bromide is not just a suspected mutagen. Prolonged or repeated (i.e. chronic) exposure by any route (dermal, injestion, inhalation) can cause methemoglobinemia. And what can happen if you get an acute exposure via inhalation? Inhalation can cause methemoglobinemia, cyanosis, irregular heartbeat, nausea and vomiting. If exposure is severe, it can cause blood and CNS system effects, kidney damage, anemia, reticulocytosis, hematuria, chemical pneumonitis, pulmonary edema, coma and death (from Caledon Ethidium Bromide MSDS). This is why some manufacturers of ethidum bromide give it a health rating of 3 or 4 (toxic/poison). We use Gel Red in Water (not DMSO) instead of ethidium bromide. Really, is it that hard to wear nitrile gloves, a lab coat, eye protection, and clean up after yourselves??????

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  54. I can't believe how many people misunderstand this article. It's not saying that EthBr is atoxic and that you should handle it with your bare hand. It's saying that you should take precautions, but not freak out if you touch a gel with your hands or spill a drop on your skin. You won't get cancer and you won't turn into a mutant, just be more careful next time.

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  55. Rosie. There's a difference between toxicity and mutagenicity. SYBR is more toxic than EtBr, but EtBr is way more mutagenic than SYBR. As you need a considerable higher doasge for the cells to die than do mutate, the real risk here is mutagenicity. Also I'd rather prefer my exposed skin cells to die than to start mutate.

    Eric

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  56. Hi,
    Great article. I learnt that the evidence that EtBr goes through latex gloves is based on bad science. The gloves used in these experiments apparently had expired and had holes. At least this is what I was told during the education as genetic safety officer in Germany.
    On another note. EtBr is used to disrupt mitochondrial DNA replication in human cells, and can even lead to a complete loss of mitochondria DNA in cultured cells.

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  57. EtBr is used to generate cells devoid of mitochondrial DNA (quite a few references about that in NCBI). On the other hand, it is probably true that the toxicity of EtBr is overstated.

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  58. Helen Hunt please email me asap, I have a very important thing want to ask you about life and death. email junxie8@hotmail.com. Thank you very much.

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  59. somebody help. I accidently ingested some EB 1 year ago, now I have problems, hand feels so cold, and facical numb, weakness, please help. .

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    1. I am not sure if you read this blog anymore but i have been exposed myself and have problems with my extremeties... I am having some difficulty finding any information but I know that this is all real to me. If you have any words to help me out- it would be greatly appreciated. I hope you are doing better, if a diagnosis and treatment are helping. Thanks

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  60. Thanks first of all for helping to clear the air over EtBr! I am the Scientific Operations Manager and I have some paranoids here scared about EtBr, so I told them I'd ask around for further information.

    Does anyone know of any data regarding chronic, low-level exposure to EtBr, such as lab workers (potentially) inhaling steam from re-boiled agarose? Yeah, kinda specific question, I know...
    I could probably point to the number of scientists from the 70's onwards who have been exposed to trace levels of EtBr for a couple of decades (and are still alive and kicking), but then I'd probably have to get epidemiological data on their rates of mutagenic diseases, compared to a control group of scientists who weren't exposed, etc etc, blah blah blah.

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  61. @Mike S:

    Do you think they might be convinced by data on volatility of EthBr? I think it's not at all volatile, though I don't know where to find the data. You could do a simple experiment:

    Dissolve 0.1 mg of EthBr in 1 ml of water, and another 0.1 mg in 100 ml of water. Then boil the 100 ml down to 1 ml (in the fume hood, just in case), and compare the absorbances.

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  62. some very intersting new information about EtBr:
    1: EtBr was non-mutagenic in a subchronic carcinogenicity study in mice (these results support the NTP-data; in the same study tamoxifen and bromo-deoxyuridine induced mutations)
    source: http://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=2136

    2: EtBr is a topoisomerase I poison, just like some novel anticancer drugs.
    source:
    Gentry et. al (2010) The geometry of DNA supercoils modulates the
    DNA cleavage activity of human topoisomerase I

    3: IN VIVO EtBr induced mtDNA alterations are repaired by TERT
    source:
    Altschmied et al. (2009) Mitochondrial telomerase reverse transcriptase binds to and protects mitochondrial DNA and function from damage

    4: EtBr isn't even teratogenic in tstse flies
    source:
    Kibugu et al. (2010) Effects of Ethidium (homidium bromide) on female reproductive performance of laboratory-reared tsetse flies, Glossina morsitans morsitans Westwood (Diptera: Glossinidae)

    ReplyDelete
  63. We actually use GelGreen in place of EthBr and SYBR because
    - it is safer than SYBR (cannot penetrate cells)
    - Is very sensitive and stable, even for small fragments
    - Does not need a UV lamp so DNA is not damaged when cutting band for purification.

    you can find more info on Biotum web site (including tox experiments)
    Note that I am not affiliated to Biotum but I think it is worth a try for people who which to switch from EthBr.

    Franck.

    ReplyDelete
  64. Hi your blog is strangely relevant to a concern I’ve been having. I used to work in a lab that used ethidium bromide. And ever since I heard about its carcinogenic properties I just really didn’t want to go anywhere near it even though some other people in my lab used it. (to help justify my paranoia a family member of mine was recently diagnosed with cancer soo)

    I mean how toxic is it? I have not and probably will not handle it because it is not in my field, but I’m just afraid of exposure because lets say someone wearing a glove that has ethidium bromide on it touched my clothes or just like being around it in lab in general.

    ReplyDelete
  65. im a post grado in biochemistry and handled etbr for mol bio experiments with gloves.im worried thinking little dry etbr might hav touched my pens n i bought them home.if i touch the pen everyday does it come under prolonged exposure to etbr or mutagenicity depends on quantity of etbr, i hav a 3 monthLO n im scared thinking i touched different places of room after touching pen, im worried my LO may touch d same places as she grows, does this harm her, plz clarify ots a mums anguish

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  66. ''ethidium bromide showed high revertant frequencies in several frameshift indicator strains (averaging 68-fold higher than vehicle controls in TA98, 80-fold higher in TA1538'' if you think thats 'safe' by all means drink the stuff, win yourself a Darwin Award.

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  67. In my undergrad cell bio course, the lab had a table in the corner with signs informing students that they were not allowed to so much as touch or lean against it, because it had been set aside for ethidium bromide staining.

    ReplyDelete
  68. This is very informative. As the director of biohem. laboratories at a local university, I am printing this out and placing it where the EtBr purification equipment is now stored. NO MORE RUNNING LONG clean-ups with EtBr! As of Monday I am throwing out all those decon packets and placing this on the safe to vent to sewer list.

    Now, what to do with all the money we'll save. We may be able to sponsor another student research project with the amount that will not be spent of purification filters, decon reagents, etc. And a single pair of gloves! No need to double glove and then wash hands afterward--to much lab time wasted. We won't have to start cleaning up as early either.

    THANK YOU SO MUCH FOR THIS TIME AND MONEY SAVING INFORMATION! As I say, the solution to pollution is dilution! And once again I'm proven right. You made it so clear this is not the hazard the government makes it out to be. Thank you also on behalf of another student we'll be able to help with the cost savings!

    Mark Stahl

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  69. So you are saying I should not wear gloves when handling Ethidium Bromide? EtBR is a known mutagen. EtBR won't kill me tomorrow or next week, but over years of constant exposure, mutagens will add up and could multiply exponentially due to my cells constantly dividing.This is a stupid article and completely misleading. You are doing a disservice to your fellow scientists. If someone gets metastatic melanoma from following your idiotic advice, can they sue you??

    ReplyDelete
  70. Good, since I've spent years covering all the banisters, lifts and many of the doors in Aberdeen University's Zoology building, I can stop worrying about contaminating the rest of the non-gel running staff!

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