Global lead

From Lead: A Global Health Problem by Timothy Taylor.

One of the major US public health victories in recent decades was to get the lead out of gasoline and paint, and also to (mostly) shift away from lead in pipes that carried water–such that when lead is detected in the water supply in places like Flint, Michigan, or Jackson, Mississippi, it’s rightfully a scandal, and typically linked to the use of badly outdated pipes. But dealing with sources of lead exposure around the world is very much a slow-motion work in progress. Rachel Silverman Bonnifield and Rory Todd discuss the issue in “Opportunities for the G7 to Address the Global Crisis of Lead Poisoning in the 21st Century: A Rapid Stocktaking Report” (Center for Global Development, 2023)/

They set the stage in this way (footnotes and references to figures omitted):

Lead poisoning is responsible for an estimated 900,000 deaths per year, more than from malaria (620,000) and nearly as many as from HIV/AIDS (954,000). It affects almost every system of the body, including the gastrointestinal tract, the kidneys, and the reproductive organs, but has particularly adverse effects on cardiovascular health. According to the World Health Organization (WHO), it is responsible for nearly half of all global deaths from known chemical exposures.

Despite this massive burden, the greater part of the harm caused by lead may come not through its effects on physical health, but its effect on neurological development in young children. The cognitive effects of lead poisoning on brain development are permanent, and most severe when lead exposure occurs between the prenatal period to the age of around 6 or 7. Even low-level lead exposure at this age has been conclusively shown to cause lifelong detriments to cognitive ability; though evidence is less definitive, there is also a very strong and compelling literature which links lead exposure to anti-social/violent behavior, attention deficits, and various mental disorders. An estimated 800 million children—nearly one in three globally, an estimated 99 percent of whom live in low- and middle-income countries (LMICs)—have blood lead levels (BLL) above 5 micrograms per deciliter (μg/dL), which the WHO uses as a threshold for recommending clinical intervention to mitigate neurotoxic effects. Effects on cognitive development have been demonstrated in BLLs significantly below this …

There is a significant literature on national IQs claiming that many countries of the world have average national IQs in 70s.  I have always been leery of these claims.  Part of it is simply the implication.  85 is considered barely functional in the US.  Even in underdeveloped agricultural economies, is 75 even feasible?  

Most of my reluctance is a matter of preference.  I view humanity as a whole and, while acknowleding some differences arising from evolved adaptation to local environments, am reluctant to believe that there is such a large real IQ differences between nations, regions, ethnicities and races.  Intellectually I know it is conceivable, I just don't want to lend it too much credence.  

I justify my reluctance in a couple of ways.  Even though there is quite a bit of research behind these numbers, whenever you are doing cross-cultural research, it can be quite challenging to accommodate language and culture differences.  In addition, between-country comparisons can be muddied by variance in education exposure and quality of education.

On the other hand . . . there is quite a bit of this research.  It can't be dismissed out of hand simply because you prefer it not to be true.

IQ cannot be "raised."  You are born with whatever potential you might have.  But the expression of IQ can be hampered.  Kids in a stable (material and emotional) environment with sufficient food and healthcare will express a higher percentage of their potential IQ than those who are not.  

It has appeared to me that consistent exposure to structured education in combination with strong safety nets that assure children dietary needs are sufficient might allow a higher expression of IQ of as much as 5-10 points.  This would account for some of the global gap in national IQs but it certainly wouldn't close it.

Taylor's blog post opens an additional avenue that might explain why the national IQ differences might in fact be real.  If a significant portion of your children are exposed to lead (or any other toxins or minerals which are neurological development impeding), then lower national IQs might be a reflection of environmental policies rather than native IQ.

Still not sure that diet, education, and clean environment close all of the gap but it would explain a healthy portion of it.