Wednesday, May 8, 2013


Preliminary comments on blogging mechanics.

Many of the people that I most want to see this blog are on LinkedIn.   There are no auto buttons for linking to LinkedIn on Google blog so I had to learn how to find and insert some HTML code into the blog template to make that happen.    It seemed to work fine except that the process chopped off the title of the blog and it somehow killed the link to my web site while inserting a link to another unrelated web site over the text “risk assessment”.   I am not sure how to fix this but until I can fix it I will be putting the title in the first line of any subsequent blog and somewhere in there I will have my web site and this blog site spelled out.


In order to understand the risk from a chemical to human health, one needs to understand its toxicity.   That is, WHAT happens when you become overexposed to it (e.g., it damages your kidneys or lungs or brain, etc).   Indeed, every substance (even oxygen) is toxic given a high enough exposure while some chemicals are toxic at very low doses (e.g., bis-chloromethylether).   Once you know the toxicity you need to understand the level of actual human exposure to that chemical.   The simple equation is:

Risk = The integrated product of Toxicity and Exposure

You cannot even start a risk assessment without some knowledge of the toxicity of the chemical. Many folks assume that the chemicals we are exposed to have been tested for toxicity.   The fact of the matter is that in the vast majority of cases they have not.   For the most part, except for pesticides and chemicals which have proven themselves dangerous because people become frankly sick or died from exposure to them (e.g., benzene), there has been relatively little testing of their toxic effects.   Indeed, 16 year ago the Environmental Defense Fund issued a ground breaking report:  Toxic Ignorance  -   

An excerpt from that document quotes even earlier work:  “In the early 1980s, the National Academy of Sciences’ National Research Council completed a four-year study and found that 78% of the chemicals in highest-volume commercial use had not had even "minimal" toxicity testing. Thirteen years later, there has been no significant improvement.”  Well now the clock is up to almost 30 years.

This turned out to be such a powerful message in 1997 that the EPA got involved and started the High Product Volume (HPV) challenge program in which companies would volunteer to test these chemicals.   From my perspective it is safe to say that this program has been evaluated by many as being not completely successful.   I am not familiar with the details but I do know that for most of the chemicals for which I go looking today for good toxicology data in order to make some decisions about the type of adverse health effect or its potency I come up empty.   There are literally tens of thousands of chemicals in our environment, mostly from the chemicals we as a society produce and use to make our life better.  The vast majority of these have no definitive or inadequate toxicity data on them.   

There are new attempts to fill this gap from a scientific (EPA ToxCast Screen) and a regulatory perspective (European REACh program) which I hope to discuss in a future blog.   In the meantime, I have an opinion relative to the title of this blog.   My sense is that the vast majority of chemicals that we use and are exposed to in our everyday lives are safe at the exposure levels that most of us encounter.  Thus, I do not think that we should be lying awake at night worrying about our exposures.   Having said this, please note that it is simply my opinion.   It is an opinion born of a professional lifetime working in this field; however it is important to realize that my opinion is NOT a risk assessment.    Also I am also almost certain that there are some (perhaps many) chemicals and some subpopulations of people whose exposures to those chemicals are dangerous but, at this point, they remain unevaluated and thus not controlled. I think most of this happens in the workplace but some may be happening in our homes.  Suffice it to say that without the data and subsequent risk assessments, the size of these subpopulations is unknown.  In short, a lot of regulatory/political and scientific work remains to be done to identify these situations and to protect these folks.  

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