Evolution of Intelligence (05:54)

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Using IQ tests of conscripts joining the Scandinavian armed forces, anthropologist Edward Dutton found that IQs were increasing until the mid-1990s. They have been decreasing throughout the world, while autism and behavioral disorders are on the rise.

Peter Pharoah's Study (04:20)

Research has found a connection between decreased cognitive function and thyroid disfunction. Pharoah explains his study on a tribe in Papua New Guinea regarding thyroids, iodine, and cretinism.

Iodine Deficiency (05:03)

Iodine is necessary for the creation of thyroid hormones and brain development during pregnancy. The World Health Organization has found iodine deficiency in 50 countries. In the 1970s, Dr. Francesco Vermiglio found that a slight iodine deficiency leads to a minor decrease in cognitive function.

Endocrine Disruptors (05:03)

Many manufactured chemicals in our environment are similar to iodine and disrupt thyroid hormones. Endocrine disruptors can be found in trace amounts and are linked to decreased IQ if the mother is exposed during pregnancy.

Flame Retardants (05:53)

Endocrine disruptors can be found in many household items that are flame retardant. In the 1970s, over 50 million American children were exposed to the tris chemical, which can change DNA. Though flame retardants were banned, strong lobbying has led to a resurgence.

Need for Flame Retardants (04:51)

Scientists found that most flame retardants did little to stop the spread of fire but did discover there were links to reduced IQ and health problems.

Pesticides (07:55)

Many pesticides include endocrine disruptors and chemicals that affect the nervous system. Researchers tested the effects on brain development for unborn children of farm workers in California and found a link to autism

Chemical Exposure (03:48)

Exposure to organophosphates from pesticides is the same for children in farming areas and cities. They led to a similar decrease in IQ. Researchers found they caused a change in brain structure.

Newborns and Chemicals (03:38)

Babies born in the U.S. have 100 measurable chemicals in their bloodstreams. Scientist Barbara Demeneix wants to develop a test to identify thyroid disrupting chemicals.

Decreased IQ (08:21)

Chemical companies have argued the cost of more regulation would be too great. Economics calculated the societal cost of IQ loss. Researchers have argued the need for regulation before the European Union.

Credits: Brains in Danger (00:42)

Credits: Brains in Danger