Web Date: August 11, 2011
Perfluorochemicals Linked With Impulsivity
Children’s exposure to a growing list of industrial chemicals, including certain pesticides and phthalates, has been linked to development of attention deficit hyperactivity disorder (ADHD). Now evidence suggests that perfluorinated chemicals (PFCs) boost ADHD risks by making children prone to impulsive behavior (Environ. Sci. Technol., DOI: 10.1021/es103712g).
Used since the 1950s to make Teflon and many other stain- and water-repellent products, PFCs are now global contaminants. Scientists had already associated elevated PFCs with neurological problems, such as delayed gross motor development. A study published in December found tantalizing links between blood PFC levels and diagnoses of ADHD (Environ. Health Perspect., DOI: 10.1289/ehp.1001898). Brooks Gump, a psychologist at Syracuse University, wanted to go one step further: He and his colleagues were interested in how the chemicals might affect impulsivity, a core ADHD feature. Impulsivity has cascading effects on so-called “executive functions,” such as planning, verbal regulation, and motor control. ADHD is a complex and multi-faceted diagnosis, Gump notes, that results from deficits in executive functioning. By identifying any influence that PFCs have on impulsivity, Gump hoped to connect the dots between chemical exposure, nervous system effects, and processes leading to ADHD.
In the study, Gump’s team asked 83 children ranging from nine to 11 years old to learn and play a computer game without any outside instruction. The game had only one rule: Players must wait at least 20 seconds after pressing a keyboard’s space bar before doing it again. Patient children received a 25-cent reward for each time they hit the space key; more impulsive children who pressed the bar too fast received no reward. “This test measures a child’s ability to put the brakes on responding,” explains Gump. “And measures of response inhibition are directly related to impulsivity.”
The researchers also measured PFC levels in the children’s blood using high-performance liquid chromatography/electrospray tandem mass spectrometry. They found that as blood levels went up, the children waited less between button presses. According to Gump, the results hint that PFC levels influence impulsivity. But he cautions that cause and effect are unclear: Children who are more impulsive to begin with may spend more time licking and chewing commercial products, giving them higher exposure to PFCs. “We need to figure out what direction this association goes in,” Gump says, “because if PFCs really do influence impulsivity, then this is an important public health finding.” He noted that every child in the study had PFCs in their blood.
Margie Peden-Adams, a toxicologist at the University of Nevada, Las Vegas, commented that Gump’s results were compelling and agreed that teasing out causation is an important next step. She thinks that the next step would be a prospective study that starts by measuring PFC levels in cord and mothers’ blood. “Then we can follow these kids over time, find out who develops ADHD, and link that back to blood measures in kids that go all the way back to prenatal exposure,” she says.
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