Half of U.S. Population Lost IQ Points Due to Leaded Gasoline Exposure: Study

Exposure to leaded gasoline has reportedly caused half of the American population born before 1980 to collectively lose more than 824 million IQ points, according to new research.

In findings published this month in the medical journal Proceedings of the National Academy of Sciences, researchers indicate that lead exposure during childhood resulted in 2 to 7 IQ points lost per person, with more than 50% of the U.S. residents having high levels of lead in the blood. Another 17% had very high levels, and roughly 1% of the American population had extremely high levels from leaded gasoline exposure during childhood.

Increasing evidence suggests that exposure to lead during childhood, at any level, can lead to long-term damage and side effects, including cognitive impairment, seizures, brain damage, injury to the nervous system and death.

While lead paint poisoning has been a concern in many communities for decades, with banned lead-based paint often pealing from the walls of many older homes that have not been properly maintained and causing severe injuries for children who ingested the paint chips, researchers in this new study indicate that a primary source of lead exposure for many Americans came from inhaling exhaust from leaded gasoline.

Researchers from Duke University and Florida State University conducted a cross-sectional study using blood-lead level data from National Health and Nutrition Examination Survey (NHANES), a representative sample of US children ages 1 to 5, from 1976-1980 and 2015-2016. They compared that with population estimates from the US Census, the Human Mortality Database, and the United Nations, as well as leaded gasoline consumption data.

Despite efforts to protect children from lead exposure, first beginning in the late 80s and in 1996 when leaded gasoline was finally banned, hundreds of millions of Americans were exposed to enough lead to lead to cognitive decline, resulting in reduced IQ.

More than 170 million Americans still alive today were exposed to high levels of lead during early childhood. Several million were exposed to more than five times the current reference level, which is 3.5 micrograms per deciliter of blood.

The researchers indicate that in 2015, more than 170 million people had levels of lead above 5 µg/dL in their early childhood. Furthermore, 54 million Americans had lead levels above 15 µg/dL and 4.5 million had levels well above 30 µg/dL during early childhood.

Levels of lead in the blood were greater than 5 µg/dL among nearly all people born in the US between 1951 to 1980. Comparably, lead levels were considerably lower than 5 µg/dL among those born since 2001.

Using that data, researchers estimated lead is responsible for the loss of more than 824 million IQ points as of 2015. The average IQ loss was 2.6 per person, but for some born in the 60s and 70s, IQ loss was up to 6 and 7 points.

Losing a few IQ points may not be a significant concern for many people. However, for members of the population who may be closer to cognitive impairment or experiencing cognitive decline from other conditions, a few points can be a significant factor. Research indicates exposure to lead during childhood can reduce the brain’s structural integrity later in life.

Researchers said the exposure to lead was primarily from inhaling exhaust from leaded gasoline. There are other sources of exposure to lead as well, such as lead-based paint, manufacturing sources, and water from leaded pipes, as was seen in the recent Flint water lead poisoning crisis.