We live in a world of dangers seen and unseen, dangers to ourselves, our family, our children, and our children not yet born. On one side of the coin is the fact that if you spend all your time worrying about dangers, sooner or later you will be immobilized. On the other side of the coin is the fact that some dangers can be eliminated, and if we don't do something about those dangers, when the misery happens who will we be able to blame but ourselves?
On the front page of today's New York Times (Sunday, August 23, 2009) there begins a series called "Toxic Waters" -- about contamination of local water supplies and effects on people. This first article is about the pesticide atrazine. It's a long article, with details about concentrations, about arguments, about the Environmental Protection Agency (EPA), and so on. Everyone should read it. And if you do read it, and it doesn't make the hairs on the back of your neck stand up, maybe you ought to sit and think about it awhile.
For the past several years, my life had been entangled with the problem of the effects of toxic environmental chemicals on the development of the fetal brain -- and the effects on later behavior and intelligence. My entanglement resulted in a book that will be out in a few weeks: More Than Genes: What Science Can Tell Us About Toxic Chemicals, Development, and the Risk to Our Children (Oxford University Press. October, 2009.) My guess is that more than one head will pop up to call me a fear-monger. My response is the fear is necessary.
It's a sticky subject, especially for old people like myself. Let me tell you a secret about old people. When old people walk through the halls of a children's hospital, they walk while they cry inside. I've asked many old people about this, and so far the answer is always the same -- they cry inside. They stop and smile at the kids, wave to them, make a funny face -- but inside the old people are crying. That's the way it is.
The question for all of us is how much of what we see in the halls of a children's hospital is preventable. The basic question for toxicologists and pediatricians (and for the EPA) is whether there is indeed such a thing as a "safe" concentration of a toxic substance for an embryo or fetus. My own view, and the view of many scientists, is that for chemicals already known to be toxic the most scientifically sensible answer is no, there is no "safe" concentration for the developing embryo or fetus.
It's an enormous problem, and the public has the right and the need to at least know about the problem. The fact that toxic chemicals in the environment can have tragic effects on human fetal development is well known to scientists, and for some time now the concerns of scientists have been leaking into the media. Here are some examples:
By the early 1990s, it was already obvious to researchers that ethyl alcohol in the prenatal environment can cause prenatal damage. Measurable concentrations of maternal blood alcohol produce the recognizable clinical entity of fetal alcohol spectrum disorder (FASD). But on biological grounds, even minute immeasurable quantities of ethyl alcohol are expected to cause subtle effects on the developing nervous system, especially during the earlier stages of embryonic formation. These effects might involve damage other than FASD or its most severe form, fetal alcohol syndrome (FAS) -- subtle damage not yet clinically recognized. There is, in other words, no apparent safety threshold for ethyl alcohol consumption, and no apparent safe period after conception.
In 2002, a news article in the journal Science highlighted low birth weight as a predictor of adult chronic disease, the article pointing out that epidemiological studies of such correlations have been accumulating since the 1980s. Birth-weight is merely a crude measure of the rate of fetal development. Are there subtle behavioral effects of lower than average birth weight that have not yet been tested in children and adults? We already have some evidence that birth-weight is correlated with childhood and adult intelligence quotient (IQ) and various behavior patterns.
In 2004, a review of the impact of environmental toxic chemicals on childhood health pointed out that in Europe the prenatal environment is at risk of contamination by 15,000 synthetic chemicals, nearly all developed over the past 50 years, and that worldwide between 50,000 and 100,000 chemicals are being produced commercially. The review emphasized that end-organ vulnerability may be greatest in the fetus, and that for some chemicals the toxic effects seen in childhood are the result of continuous exposure beginning with conception.
In 2005, a review pointed out that exposure to infection or nutritional deprivation during early fetal development may elevate the risk of later onset of schizophrenia. Lead exposure has also been established as a risk factor for schizophrenia, the lead correlations suggesting environmental chemicals as a new class of schizophrenia risk factors that are still inadequately investigated.
In February 2008, 200 researchers who had met the year before in Norway announced that embryos and fetuses are more vulnerable than previously thought to chemical pollutants that can cause disease or disability, and that embryos and fetuses are vulnerable even to extremely small doses that do not harm adults.
We cannot hide the reality of the impact of the environment on fetal development. The above examples are only a hint of what is available in the scientific and medical literature about the effects of environmental toxic chemicals on fetal development and later childhood and adult disease.
There are problems and there are problems, and some problems are certainly not as important as other problems. But in the halls of any children's hospital anywhere, the only question that seems important is clear: How much of this is preventable?
[All comments are welcome, but if you're commenting as a professional, please give your real name and affiliation.]