Exposure to Lead Gasoline as Child Linked to Lower Intelligence, Jobs as Adult: Study

New research highlights the long-term risks children face from lead exposure, finding that adults who were exposed to leaded gasoline in childhood were more likely to have reduced intelligence and lower job standing later in life.  

The study was published this week in the Journal of the American Medical Association, evaluating the long-term side effects for children who grew up in the 1970s in New Zealand, which had high levels of leaded gasoline at that time, By the time the children reached the age of 38, they no only had decreased IQ levels, but also were negatively affected economically.

During the 1920s, tetra-ethyl-lead was added to gas to increase octane ratings and boost engine power. However, the lead didn’t burn off and was emitted from tailpipes, accumulating in soil and released into the air.

Lead can accumulate in the bloodstream and the body, settling in the bones, teeth and  soft tissue. Many children don’t receive blood lead testing to help identify serious exposure. Leaded gas was eventually phased out in the U.S. and New Zealand by the mid-1990s. However, during the 70s and 80s, New Zealand had some of the highest gasoline lead levels in the world.

Researchers studied children from the 1972-1973 Dunedin Multidisciplinary Health and Development Study birth cohort. They took samples of children’s blood, testing for lead levels, and later observed participants to age 38.

Nearly 600 New Zealanders were observed for four decades. Researchers concluded lead exposure in childhood was significantly associated with lower cognitive function. It was also associated with lower socioeconomic status in adulthood.

In the new study, authors sampled participants’ blood at age 11. The average blood lead levels at that age was 10.99 mg/dL. Overall, 94 percent of children tested had blood levels higher than the limits set today, 5 micrograms per deciliter (mg/dL) of blood.

Children who had more than 10 mg/dL at age 11 experienced a decrease of 4.25 IQ points at age 38, compared to those who were not exposed to lead during childhood. Researchers noted that affected children also lost IQ points relative to their own childhood scores,

Researchers determined that, overall, the levels of lead affected children’s IQ scores, perceptual reasoning and verbal memory by age 38.

Each increase of 5 mg/dL of lead in the blood in childhood was associated with 1.61 point lower IQ score in adulthood. It was also associated with 2.07 point lower score in perceptual reasoning and 1.26 point lower score in working memory.

Each 5 mg/dL higher level of blood lead during childhood was also associated with 1.79 point lower score in socioeconomic status. Researchers noted increased levels of lead in the blood was linked to downward socioeconomic mobility, which they said could be partially due to cognitive decline from childhood.

No associations between childhood blood lead level and deficits in verbal comprehension and processing speed were noted.

Lead is a developmental neurotoxin and no safe levels of lead exposure exist for children. In January, the U.S. Centers for Disease Control & Prevention (CDC) began considering lowering the “safe level” or “level of concern” for lead in children’s blood, which may help to identify more children suffering from lead poisoning.

Lead poisoning for children is already known to increase the risk of nervous system injury, brain damage, seizures or convulsions, growth or mental retardation, coma and even death.

One of the more common causes of of lead poisoning is lead-based paint, which was banned in the United States in 1978 due to the risk of severe and permanent brain damage and developmental problems, particularly in children. However, a number of older homes still contain the toxic paint on the walls, and if it flakes or peals off, young children could ingest the paint chips or breathe dust that comes from the paint, resulting in lead poisoning.

The majority of those children are poor and live in older urban areas, mainly in the inner city. Most are minorities, meaning such exposures add to numerous problems already plaguing inner city black and Latino youths, such as poverty, high crime and poor schools.