Little Things Matter: Shifting IQs down a notch | Pesticide Action Network
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Little Things Matter: Shifting IQs down a notch

Emily Marquez's picture

We know that certain environmental contaminants are linked to decreases in children's intelligence quotient (IQ). A recently released seven-minute video, titled "Little Things Matter," explains what scientists know about this association — and why it's important.

Three types of environmental contaminants were discussed in the video. All three have been linked to falling IQs, and all three have been found in the bodies of the U.S. population — both children and adults — by the Centers for Disease Control (CDC). One of the three is a group of commonly used pesticides.

Scroll down to see the video in full. Released at a Canadian environmental health meeting last month, it was co-produced and narrated by Bruce Lanphear, M.D., M.P.H., a pediatrician who does research on fetal and early childhood exposures to environmental neurotoxins at Simon Fraser University in British Columbia, Canada. It gained immediate attention via social media and beyond.

The brain-harming culprits

The group of pesticides highlighted in the video is organophosphate (OP) pesticides, which are used as insecticides. If you follow our work here at PAN, you know we've talked a lot about the health harms of OPs.

We're pressing hard for a full phaseout of the OP insecticide chlorpyrifos, which was banned for home uses more than a decade ago due to known harms to children's developing nervous systems. Scientists know much more about these harms today, but millions of pounds are still applied in agricultural fields every year.

Another batch of brain-harming chemicals Dr. Lanphear highlights is a class of flame retardants known as PBDEs (polybrominated diphenyl ethers). Used in a number of products such as furniture foam and textiles, PBDEs are widespread in our environment and (like the other two contaminants) can be found in house dust. One PBDE is deca bromo diphenyl ether, a flame retardant currently under review for listing under the Stockholm Convention on Persistent Organic Pollutants.

Scientists are learning more all the time about how certain chemicals can harm children's developing brains.

And finally there is lead, a known nerve poison. Much is already known about the harmful effects of lead on children's intelligence. The Centers for Disease Control states that "No safe blood lead level in children has been identified... effects of lead exposure cannot be corrected."

From 1976 to 1990, the amount of lead used in gasoline decreased by 99.8% after EPA put policies in place to phase down the use of lead additive in gasoline. An analysis comparing National Health and Nutrition Examination Survey (NHANES) data from 1976 and 1990 found that the mean blood level of lead in children 1-5 years old decreased by 72%. Policies matter.

National "body burden" data from the CDC shows that all three groups of chemicals are found in children's bodies today. And as Dr. Lanphear makes clear, scientists are learning more all the time about how certain chemicals in our environment impact developing brains, and what this means to all of us.

A shift down the IQ continuum

Epidemiological studies for all three of these contaminants show an association between each individual contaminant or contaminant class and a drop in IQ. Maternal exposure to OPs has been associated with a 5-point drop in IQ when maternal blood levels rise from 10 to 75 parts per billion (ppb). This is a very small amount. One ppb is equivalent to two tablespoons of sugar in an Olympic-sized swimming pool.

Levels of lead in children's blood at 100 ppb are associated with a 6-point decrease in IQ. And yes, these levels in children's blood have been observed in the "real world." As lead exposure increases, a couple more points are lost from children's IQs.

But what if we project for neurodevelopmental effects of widespread exposure on an entire population? That scale makes many impacts seem dreadfully risky — and poses a situation that to me seems totally unacceptable. As Dr. Lanphear states in the video, by allowing kids to be exposed to toxins (or to chemicals of unknown toxicity), we are "unwittingly using our children as part of a massive experiment."

The video demonstrates that decreasing IQs by a few points on a population-wide scale results in differences of several million children having their IQs shifted towards the "challenged" end of the IQ distribution — which also means a corresponding decrease in the number of children who are assessed as "gifted."

What do falling IQs cost?

Can we put a dollar value on the loss of an IQ point? Economists have actually assigned monetary value to changes in full-scale IQ (FSIQ). Harvard neuroepidemiologist David Bellinger explored this idea in a recent review:

 “In estimating the economic benefits of reducing children’s lead exposure, Grosse et al. (2002) estimated that each FSIQ point lost reduces future work productivity by 1.76–2.38%, regardless of an individual’s initial FSIQ, a monetary loss placed by Gould (2009) at $17,815 in discounted lifetime earnings.”

This on top of the unquantifiable: the loss of human potential.

So where’s the ray of hope? The use of all of these chemicals is something we can change, and scientists and public health experts are now leading the charge. Leaded gasoline use has been severely restricted in most industrialized countries. We could reduce the use of (or take off the market!) environmental contaminants that have been linked with decreasing children’s IQs. The costs of using some of these chemicals are paid by an entire population of developing children.

That's too high a price to pay.


Emily Marquez
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Emily Marquez is PAN's Staff Scientist. She is a biologist with a background in endocrine disruption and environmental toxicology in reptiles. In addition to supporting scientific research for PAN’s campaigns, Emily trains community members in using PAN’s Drift Catcher to monitor for pesticide drift. Follow @EmilyAtPan