Small Doses Matter

By Philip J. Landrigan, MD, MSc, FAAP Icahn School of Medicine at Mount Sinai

More than 100,000 new chemicals have been invented in the past 50 years. Many have become widely disseminated in the environment, and the Centers for Disease Control and Prevention (CDC) surveys document that low-levels of several hundred man-made chemicals can now be found in the bodies of nearly all Americans, even in our youngest children. Children are exquisitely sensitive to these chemicals.

Over the summer, two events have drawn our attention to the impacts of low-level chemical exposures on children’s health. First was the story in the New York Times and other national news outlets reporting that measurable levels of the plastic chemical, phthalate, has been detected in mass-produced macaroni and cheese products. Phthalates are toxic chemicals that can injure children’s developing brains and cause reproductive problems. Yet, spokespersons for the processed food industry assured the world that the levels of phthalates present in their products were too small to cause concern.

The second event was the death on July 18 of Dr. Herbert Needleman. Dr. Needleman, a pediatrician and child psychiatrist, conducted landmark studies of childhood lead poisoning using analyses of lead levels in discarded baby teeth. He documented that low-level lead exposures — even exposures at levels widely considered “safe” — were actually causing permanent damage to children’s brains. He showed that children exposed to lead can have reduced IQ scores, short attention spans, and difficulties in controlling their behavior. These injuries occur even when there are no obvious symptoms of lead poisoning.

Dr. Needleman’s findings were attacked by the lead industry as “worthless” and “emotional.” But they have stood the test of time and today, almost 40 years after publication of his landmark study in the New England Journal of Medicine, hundreds of studies have confirmed that even very low levels of lead can interfere with brain development in young children and cause lifelong damage. The CDC and the World Health Organization now state that no level of lead is safe. Federal rules restrict lead in gasoline, paint, children’s products, plumbing, water and food can solder. As a result, there has since been a 94% decline in the number of American children with elevated blood lead levels. We have come a long way.

But even as blood lead levels were going down, new chemicals have entered the market, fouled the environment, and entered children’s bodies. These toxic chemicals include the phthalates found in macaroni and cheese, new classes of insecticides, brominated flame retardants, and components of air pollution. In the last three years, seven published studies have found that early-life exposures to phthalates are linked to lower intelligence, memory problems, attention deficit disorder, aggression, impulsivity and other behavioral problems in children. Twenty-one additional studies have found evidence for reproductive injury in children exposed to phthalates — lower levels of testosterone, abnormalities in the structure of the male reproductive organs in baby boys, and earlier onset of puberty. The food that we Americans eat and the products that we use every day were the sources of this exposure.

What can we learn from the story of Herb Needleman and lead? And what does the lead story teach us about low-level exposures to phthalates?

The first lesson is that low levels of exposure that cause no harm to adults can have profound effects on young children. This is especially true for chemicals that damage the developing brain. In 1993, I chaired a Committee at the National Academy of Sciences that examined the effects of pesticide chemicals on children’s health. Our Committee concluded that, “children are not little adults.” Children are more heavily exposed to toxic chemicals pound-for-pound of body weight than adults because they eat more food, drink more water and breathe more air. And on top of that, brain development in young children is rapid, complex and all too easily disrupted. As every parent knows, children are very vulnerable.

The second lesson is that cumulative harm can result from multiple low-level exposures — small doses add up. Responsible corporations need to respond to this lesson. They take action to reduce their contributions to children’s exposures rather than lobbying government to ignore scientific findings or claiming to the public that their products cause no harm.

And the third lesson is that the world, and especially the children in it, need the protection of more visionary and courageous leaders like Herb Needleman. My grandchildren have a better chance at life because of Herb’s research. It will be a tribute to Herb Needleman to identify and reduce exposures to phthalates and the other toxic chemicals that are still harming babies’ brains. Our children deserve no less. Small doses matter.