Dose Doesn’t Always Make Poison

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Dr. Philip Landrigan

Sunday, March 22, 2009

It goes without saying that it is imperative to know the appropriate dose of any medication you need to take. Take too little and you may feel no relief; too much and you could become sicker.

In fact, it's actually quite marvelous that some things can be poisonous in large doses, but beneficial in small. Still, this rule does not always hold true.

For centuries, the basic tenet of toxicology has been "the dose makes the poison." Increasingly, scientists are finding "the timing makes the poison" - in other words, it's not just how much you are exposed to, but also when the exposure occurs. This new rule is especially important for fetuses who are uniquely susceptible to exquisitely small amounts due to their developing systems. In fact, many of these prenatal exposures leave the mother unscathed while causing injury to her fetus.

The growing brain appears to be the most sensitive, but scientists are also extremely concerned about the newest animal research suggesting that chemicals can alter gene expression. In essence, a single chemical exposure during a critical window of development can turn a gene on or off and subsequently predispose people to disease. Although the DNA is unchanged, isolated genetic alterations can be permanent, placing all subsequent generations at greater risk of diseases. Toxic exposures during these moments of heightened susceptibility can cause disease and disability in childhood and throughout life.

Though some chemicals connected to negative health or development impacts are now regulated in the United States, many remain unregulated Adverse health effects have been linked to chemicals at exposure levels commonly found in our everyday environments. Moreover, tests for developmental effects are not routinely required before a chemical is used in everyday products. So, we have an incredible gap in understanding because 80% of major chemicals in commerce have never been tested to see if they damage early development - the period of highest vulnerability.

What can you do to protect yourself and your children (whether you have kids now or are planning on having them in the future)? Prevent unnecessary exposures. Use the Health eHome to find out how.

Philip J. Landrigan, MD, MSc, a pediatrician, epidemiologist, and internationally recognized leader in public health and preventive medicine. He is currently the Ethel H. Wise Professor of Pediatrics, Chair of Community and Preventative Medicine, and Director of the Children's Environmental Health Center at the Mount Sinai School of Medicine.

The opinions expressed here are solely those of the author and not necessarily those of Healthy Child Healthy World.