Researchers have found that childhood lead exposure can lead to a decrease in IQ over time as well as a lower occupational standing.
The study gathered 565 individuals who had grown up during the years when lead gasoline was prevalent. These individuals are participants of a life-long study and have undergone cognitive skills assessments since birth. They were born in New Zealand in 1972 and 1973, a time in which New Zealand had the highest lead gasoline consumption in the world. At age 11, researchers tested the participants' blood samples for lead.
The findings showed that exposure to higher levels of lead meant a greater loss of IQ. For every 5 microgram increase of lead in the blood, the participants lost 1.5 IQ points.
In the 1920s, tetra-ethyl-lead was added to gasoline and used to boost engine power. Automobiles then released lead as elemental lead and lead oxides. These particulates settled in the soil, which then held on to the particulates. Children were became prone to inhaling dust or swallowing small amounts of soil containing lead particulates, leading to lead exposure. The lead can then accumulate in the children's blood.
New Zealand phased lead gasoline out between the 1970s and the 1990s, but many countries, particularly Asian ones, still use lead gasoline.
Unfortunately, lead is a neurotoxin and thus can significantly damage both developing and mature nerve tissues. Neurotoxins can also impact neural communitcation. Things like snake venom and nerve agents for chemical warfare are neurotoxic.
Participants who had over 10 micrograms of lead per deciliter of blood had an IQ 4.25 points lower than that of their peers at age 38. More tellingly, these individuals even lost IQ points compared to their childhood IQ. At age 11, the participants had an average of 10.99 micrograms of lead per deciliter of their blood. None of the participants, in fact, had safe blood lead levels as children.
The participants had a lower socio-economic status than that of their peers who did not have high levels of blood lead. As 38-year-old adults, the particpants also had a lower social and occupational standing than that of their parents. As their IQ went down, so did their social mobility. The loss of IQ thus has a part to play in the loss of socio-economic status. The findings show that high lead exposure can have a lifelong impact on those it affects.
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