What Did They Do?
Two separate studies published online last month, examined ADHD and hyperactive and impulsive behavior in children and then compared the results to PFC levels in the children's blood.
In the first study, Brooks Gump and colleagues assessed impulsive behavior using a common behavioral test called the DRL task. They examined 83 children from Oswego County, N.Y., aged from nine to 11 years old. They also measured six different PFC’s – PFOS, PFOA, PFHxS, PFNA, perfluorodecanoic acid (PFDA) and perfluorooctanesulfonamide (PFOSA) – in the children's blood. Lead and mercury were also analyzed because they can alter DRL performance.
During the task, children press the space bar on a computer keyboard in order to earn a reward of 25 cents. The first three presses are rewarded, but thereafter, the task requires the child to wait 20 seconds between presses in order to earn the reward. Each correct space bar press results in the word "CORRECT" flashing on the computer screen.
In a second study published online in Environmental Health Perspectives, researchers Cheryl Stein and David Savitz reviewed data from the C8 Health Project survey conducted between 2005 and 2006. The project examined more than 10,000 parents and their 5- to 18-year-old children who lived in West Virginia and Ohio near a DuPont plant that manufactures PFOA. The communities surrounding this plant are highly exposed to PFOA from their tap water and plant emissions.
The researchers measured the concentrations of PFOA, PFOS, PFHxS and PFNA in the children's blood. They asked the parents a series of questions, including whether their child had a learning disability or was diagnosed with ADHD or used ADHD medications like Ritalin.
In both studies, gender, income, education and other lifestyle factors were considered in the analysis.
What Did They Find?
The complimentary studies found associations between PFCs and behavioral disorders.
PFCs were detected in the blood of children from both studies. Overall, most tweens in the Gump et al. study had significant levels of multiple chemicals in their blood. All children had blood levels of PFOS, PFOA and PFHxS, and these three chemicals made up the majority of the total chemicals measured in the children.
These same three PFCs plus PFNA were found in the children participating in the C8 study. In this group, PFOA levels were the highest of the four measured compounds. Surprisingly, PFOA concentrations were not associated with ADHD in this group of children.
However, higher concentrations of PFHxS were associated with increased odds of ADHD. Odds is a measure of probability of an event occurring. When the probability of the event is low, then the odds will approximate the probability. Children with the highest exposure to PFHxS were 60 percent more likely to have ADHD and take ADHD medication. The other two PFCs were not strongly associated with ADHD. None of the PFCs were associated with report of a learning problem.
Gump et al. takes a slightly different research approach yet reports a similar finding. In their study, total and individual PFC levels were associated with impulsive behavior. Increasing blood levels of total PFCs were associated with earlier and more frequent responses on the DRL task, clearly seen during the last 15 minutes of a 20-minute testing session. Increases in premature responses also related to blood levels of five individual chemicals, including PFOS, PFNA, PFDA, PFHxS and PFOSA. However, the blood levels of the chemicals measured are highly correlated, making it difficult for researchers to tell which PFCs may have the most influence.
What Does It Mean?