Allison Tracy is a Chemicals Policy Fellow. Richard Denison, Ph.D., is a Senior Scientist.

For millennia people have contemplated the question “who am I?”  But how about the even more fundamental question, “what am I”?  The human body is made up of about 10 trillion cells that form our tissues and organs.  But did you know that the human gut is the home to microbes that comprise 10 times more – that is, 100 trillion – cells?  And that, while the human genome contains about 23,000 genes, there are some 3 million genes in the microbes living in the human gut?  Obviously, this complicates things.  It arguably means we could be considered to be more microbe than human!

These numbers should tip us off to the importance of what is known as our “microbiome.”  New science is shedding light on the central function of the microbiome as a mediator between external agents to which we’re exposed and the impacts of those exposures.  Recent studies show, for example, that as chemicals pass through the gastrointestinal tract, they undergo major changes in bioavailability (i.e., how easily they are taken up into our bodies) and in their toxicity.  Recognition of the role of the microbiome is shifting the playing field for toxicology in fundamental ways.   Read More »