Date: Mon, 11 Oct 2010 10:30:37 EDT
Reply-To: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
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From: ACTSNYC**At_Symbol_Here**CS.COM
Subject: Re: Science Education & Safety

Paul,  Oh my.  How I wish you were in NYC and we could meet at our neighborhood hangout for coffee.  Those are wonderful questions but they take time to answer.  I teach toxicology and risk assessment to lay people in art, theater, and science as part of my OSHA/EPA training courses.

The only thing I'll go into in this post, however, is your quest for a list of teratogens.  The fact is, very few chemicals have been tested sufficiently to even know if they cause birth defects or not. The reason we know ethyl alcohol is a teratogen is that thousands of pregnant women were involuntary lab rats. 

Two studies in a major Toronto hospital now indicate that exposure to any solvent during pregnancy is a risk factor for birth defects.  More importantly, follow up of the "normal" children at ages 3 to 9 years of age born to solvent-exposed mothers showed higher rates of hyperactivity, learning deficits, and the like. That makes sense because all solvents are neurotoxins, that is, they affect the brain and can get us high.  Glue sniffers have effectively demonstrated that.  There were even three deaths one year from sniffing White Out!

So once a woman is pregnant, she shouldn't be exposed to anything for which there isn't a minimum daily requirement!   And yet, she can work with highly toxic substances if the ventilation and protective equipment are proper.  The secret is that: no one was ever harmed by a chemical to which they were not exposed.

I have no problem with using toxic chemicals if you really have lab hoods that function at or above the ACGIH requirements, gloves that specifically resist the particular chemicals that are being used (see the manufacturer's permeation data), goggles and other PPE, and, most important, if there is the supervision and enforcement in the lab to insure that every precaution is being followed.

The same for carcinogens.  You can't avoid them.  And many of the chemicals we use are probably carcinogens that just have never been studied.  Even phenolphthalein, used as a laxative since the late 1800s, was untested until the 1990s when it was found to be one of the most potent carcinogens ever studied!  It caused cancer in the animals at the doses that people take. 

How many more phenolphthaleins are there?  Who knows.  Of the 70,000 chemicals estimated to be in use in commerce, only about 900 have been evaluated for their carcinogenic potential.  But if you use the chemistry lab both for teaching chemical principles and teaching people how to practice proper precautions, there won't be any problem.

So I'm against looking for chemicals that you think are without risk if the plan is to use them without all the protective gear.  First, you absolutely don't know which of those "safe" chemicals used for decades will turn out to be teratogens or carcinogens in future studies.  Second, the protective gear should be used with all the chemicals so students become comfortable and practiced at using it. 

After all, we don't practice fire drills with real fires.  We practice when there is no fire so we will know exactly what to do when one starts.



In a message dated 10/11/2010 5:47:27 AM Eastern Daylight Time, pharriso**At_Symbol_Here**UNIVMAIL.CIS.MCMASTER.CA writes:


I have an undergrad. lab experiment that uses dichloromethane to extract caffeine, but hadn't thought of changing the solvent.  This interesting discussion raises the question of whether there is a "safety series" of solvents, much like the elutropic series.  What exactly is the problem with DCM?  Is it safer or more environmentally friendly (not necessarily the same thing) to replace 1 mL of one solvent with xx mL of another?  What about volatility?  Should David replace the hexane in his fries experiment with e.g. heptane, as we have done in the research lab?  Does price enter into the "value" of a solvent?

On another note, I have recently been involved in assessing chemicals around a pregnant student.  I googled "teratogen" and found many sites that quoted ethanol and dilantin and a few other prominent examples.  Does anyone know if there is a more complete list?

Lastly, I was surprised to find dilantin on the list, especially since we have another experiment in this class in which students make dilantin which has run for years uneventfully (ignorance is bliss).  Does anyone know what level of exposure to dilantin is required to exert an effect?  Should I worry about the (remote but not inconceivable) possibility that a student in this class is pregnant?  My feeling is that the chances of successful synthesis X pregnancy likelihood X likelihood of actually absorbing an adequate dose is pretty remote, when compared to e.g. alcohol exposure for students.  I can certainly warn students, but do not want mass hysteria.  I would appreciate any expertise.

I look forward to continuing to read the excellent posts to this list: keep up the great work!

Best wishes,


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