Tuesday, June 19, 2012

Autism and the Fathead Minnow

I saw an article recently that reminded me that at one time in my life, I wanted to be a limnologist.  I studied water chemistry and all of the little known plant and animal life in freshwater rivers and lakes.  At one point I was standing out on a frozen section of Lake Superior hand pumping 50 gallons of water through a plankton sampler.  The Fathead minnow (Pimephales promelas) was not a stranger to me.

In this experiment, the researchers were focused on the effect of medications in the water supply.  This phenomenon has been widely reported (1, 2, 3, 6).  The issue of whether exposure to low levels of pharmaceuticals in the water supply is controversial (4, 5).  The researchers used a gene expression study to show that a mixture of unmetabolized psychoactive pharmaceuticals (UPPs) can induce an Autism Spectrum Disorder-like gene expression profile in the fathead minnow.  In this case the UPPs used were  fluoxetine, venlafaxine, and carbamazepine used in concentrations that were about one order of magnitude greater than observed concentrations in drinking water, rivers and wastewater.  The greatest concentration in the water systems occurred in either wastewater treatment plant effluent or the water system downstream from the plant.  The authors conclude that their experiment shows that psychoactive drugs at low concentrations may be an environmental trigger for individuals susceptible to autism.

Reading this paper also reminded me of a paper I had read in Science several years ago on the production of fluorinated pharmaceuticals.  It is a little known fact that there are very few naturally occurring fluorinated molecules in biological systems.  Advances in organic chemistry made it possible to easily fluorinate molecules for medicinal purposes and several of the more well known medications like Prozac (fluoxetine) and Lipitor (atorvastatin) are members of that new class of molecules.

The solution to the problem is the same solution I was taught as a tree hugger over 30 years ago.  Keep potential pollutants out of the water supply.  No pharmaceuticals should be dumped into the water supply.  In the solid unused form they should be completely incinerated, hopefully in a plasma furnace.  Wastewater treatment needs to engineer new methods to remove both unmetabolized and metabolized pharmaceuticals from the wastewater effluent.  These are preliminary results that need widespread replication, but from an environmental perspective adding novel biologically active compounds to the environment and not expecting unintended consequences does not seem to be a very well thought out course of action to me.

George Dawson, MD, DFAPA

Thomas MA, Klaper RD (2012) Psychoactive Pharmaceuticals Induce Fish Gene Expression Profiles Associated with Human Idiopathic Autism. PLoS ONE7(6): e32917. doi:10.1371/journal.pone.0032917

Müller K, Faeh C, Diederich F. Fluorine in pharmaceuticals: looking beyond
intuition. Science. 2007 Sep 28;317(5846):1881-6. Review. PubMed PMID: 17901324.

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