Sciencemadness Discussion Board

How carcinogenic is benzene really?

JefferyH - 13-7-2014 at 05:35

What is the consensus here? I have to work with some and no other reagent will do (no toluene, xylene, etc). Should I be wearing a ventilator mask? The room I work in has it's air totally replaced/cleaned/filtered once per minute.

I've heard differing opinions on this greatly. Some people say that it was only labeled carinogenic because it used to be found in drinks and drinking it could make you sick. Other people say inhaling the fumes can give you cancer. Other people say as long as you don't lather your skin with it you should be fine (based on the fact that people used to wash their hands with it? Yet many of them don't have cancer.)

The opinion I encounter most is that it only has the carcinogenic status because of the FDA and its past occurence in food (from decomposition of benzoic acid), and that it is no more carcinogenic than toluene or any other similar hydrocarbon. Though, I don't really know what "makes" it carcinogenic. Any solvent entering into the body is bad, but benzene is far more stable than something like Toluene or Xylene so I don't see how it could be more carcinogenic than those.

Edit: Yes I've read the threads here...but all opinions seem to differ.

http://www.sciencemadness.org/talk/viewthread.php?tid=29711
http://www.sciencemadness.org/talk/viewthread.php?tid=11925


One of those threads stated it was merely a matter of correlation, and that it was declared carcinogenic after a correlation study of people who had been exposed to it for 5-20+ years. There was also the list of known carcinogens which someone claimed Benzene was at the bottom..... so am I more likely to get cancer by inhaling second hand ciggarete fumes?

[Edited on 13-7-2014 by JefferyH]

woelen - 13-7-2014 at 09:16

Benzene is known to increase the risk of cancer, but this does not make it instant death in a bottle.

It is all a matter of doses and frequency of exposure. I look at it like smoking cigarettes. Each cigarette you smoke increases the risk of cancer somewhat, but if you smoke a few cigarettes in your life and then do not smoke again, the risk can be neglected. The same is true for working with benzene. If you use it for some experiments and these experiments are just something for a short period of time (e.g. a few days, and you only get a few whiffs per day), then I would not worry very much. If you expect to work with benzene on a day by day basis for a long time (months, years), then I certainly would try to avoid every exposure.

Dr.Bob - 13-7-2014 at 13:04

I know people that used it for years with no problem. As stated above, it is a minor carcinogen, so no worse than smoking one cigarette, and much less addictive. If you use it for a simple project, it is unlikely to create any great risk. Most chemicals are like that, asbestos, benzene, DCM, silica gel and others are all labelled as cancer suspect or carcinogen, but are much less dangerous that compounds which are known to cause mutations quickly, such as aminonapthelenes, alkyl iodides etc, N-mustards, and most older anti-cancer drugs. Some of those can cause issues with much smaller exposures over shorter times. But even those are not fast, many take years of use to create a risk.

Texium - 13-7-2014 at 20:11

Quote: Originally posted by Dr.Bob  
most older anti-cancer drugs. Some of those can cause issues with much smaller exposures over shorter times. But even those are not fast, many take years of use to create a risk.
There's some cruel irony in that...
Anti-cancer drug... may greatly increase risk of cancer.

Chemosynthesis - 14-7-2014 at 00:36

You might as well wear a respirator unless it impairs your ability to work. I know my current boss (pharmacology) freaks out about toluene (competitive inhibitor of benzene genotoxification), but when I worked in synthesis there were all kinds of open solvent drums just venting into the general labspace, for whatever that's worth....


Quote: Originally posted by zts16  
There's some cruel irony in that...
Anti-cancer drug... may greatly increase risk of cancer.

Not just the pharmaceutical treatments, either!

NexusDNA - 14-7-2014 at 09:13

Benzene is undoubtedly carcinogenic for prolonged exposure, but working with it in the lab with safety equipment is thought to be harmless. Here is a short documentary about the correlation between benzene and leukemia in China.

I believe you may have already seen it before, but research suggests that metabolites such as epoxides of benzene and phenol are responsible for the carcinogenic properties of these compounds. Here is a [rather inconclusive] study on rat liver DNA.

Manifest - 14-7-2014 at 10:03

Well think of it this way, alcohol is a carcinogen. When you stand around other people smoking you are breathing in carcinogens.
You have a greater chance of being killed in a road accident than developing cancer from short exposure to benzene.

Chemosynthesis - 14-7-2014 at 11:39

Quote: Originally posted by NexusDNA  
Here[/url] is a [rather inconclusive] study on rat liver DNA.


More recent review here as well: https://www.sciencemadness.org/whisper/viewthread.php?tid=29...

[Edited on 14-7-2014 by Chemosynthesis]

macckone - 15-7-2014 at 12:46

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3447593/

provides a comprehensive explanation of aplastic anemia and
leukemia. The recommended exposure on a 15 minute interval is
5 ppm (which is pretty darn low). You are much more likely to get
aplastic anemia than leukemia. Consistently high level exposure to
benzene will kill you from aplastic anemia well before you get
leukemia. As the article states the danger is linear. Meaning
that the longer you are exposed and the higher the level of exposure
the greater the risk.

Very few compounds are 'known carcinogens', many are 'suspected'.
The fact that benzene is a 'known carcinogen' should indicate it is
much more likely to cause cancer than other things.

But as others have stated the risk from occasional low level exposure
is minimal. Another consideration is your familial risk. If you have
family members with cancer, it may be advisable to further reduce
your risk by staying away from potential carcinogens.

Ascaridole - 15-7-2014 at 17:31

I don't think benzene is that dangerous. If you are careless and irresponsible yes it can be dangerous but so is aniline and may indicators. Be responsible and always use PPE.

Now dimethyl sulfate... that is some dangerous stuff...

unionised - 16-7-2014 at 13:00

Quote: Originally posted by macckone  


Very few compounds are 'known carcinogens', many are 'suspected'.
The fact that benzene is a 'known carcinogen' should indicate it is
much more likely to cause cancer than other things.

.

Or it means that benzene has been studied more carefully (possibly because it's widely used and a "prototype" aromatic chemical) or that it causes an obscure cancer that highlights the cause.

macckone - 17-7-2014 at 10:19

Quote: Originally posted by unionised  
Quote: Originally posted by macckone  


Very few compounds are 'known carcinogens', many are 'suspected'.
The fact that benzene is a 'known carcinogen' should indicate it is
much more likely to cause cancer than other things.

.

Or it means that benzene has been studied more carefully (possibly because it's widely used and a "prototype" aromatic chemical) or that it causes an obscure cancer that highlights the cause.


Here is the complete list on 'known carcinogens'.
http://ntp.niehs.nih.gov/ntp/roc/twelfth/listedsubstanceskno...

Benzene has been well studied but it does not cause an 'obscure'
cancer. The specific type of anemia it causes is fairly unique.
Benzene is pretty carcinogenic but as any cancer doc will tell you
there also has to be a genetic predisposition. Unfortunately
scientist no longer run experiments on humans so making definitive
links is harder for more recently studied chemicals.

Finding a substance is a suspected carcinogen usually uses rat or
tissue models. These can break badly. Saccharin for example which
is known to cause bladder cancer in rats but the mechanism leading
to tumor formation in rats does not occur in normal humans (not
saying it can't in abnormal humans).

unionised - 17-7-2014 at 10:47

I was pointing out that one of the reasons why a chemical might be a "known" rather than "suspected" carcinogen is that it causes an obscure cancer (for example oat cell carcinoma and Bis chloromethyl ether).
I didn't say that benzene caused an odd cancer.
However acute myeloid leukemia is relatively rare and strongly associated with benzene exposure.

I'm guessing you didn't really mean to say "Unfortunately scientist no longer run experiments on humans so making definitive links is harder for more recently studied chemicals."

Once a material is a strongly suspected carcinogen it is usually treated pretty much the same as a known carcinogen.
So there's not much incentive to do the additional research that would offer final "proof" of carcinogenicity

Ascaridole - 17-7-2014 at 19:46

Any chemical should always be treated as if hazardous. Especially in the case of home experimenters. Assuming a reagent that may not be normally toxic or carcinogenic as safe may be a fatal mistake.

Purity is most times unknown and what may be 98% acetone may very well contain 2% formaldehyde or any number of other unknown chemicals. All chemicals should be treated with respect and handled responsibly. Naturally certain chemical should be handled with more care depending of their inherent hazards but treating acetone as GRAS (generally regarded as safe) is a bad practice.

At my lab even if a chemical is of known purity from a reliable source I always tell my workers to treat it as if the impurities could be hazardous. Always better to be safe than filling out an EH&S report for an accident.

Pyro - 18-7-2014 at 16:54

according to the wiki page in benzene if you work an entire life at 40h per week with an exposure of 1ppm of benzene in the air, you will have a 0,5% bigger chance of getting leukemia. (thats +-83200 hours of exposure, assuming a working life is 40 years (20-60))
so our few hours experimenting with benzene should hardly be a problem