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Drop The Social Agenda

May 5, 2014 | A version of this story appeared in Volume 92, Issue 18

“The Crimes of Lead” reviewed interesting statistics, hypotheses, and facts about the effects of lead on the brain (C&EN, Feb. 3, page 27). However, the presentation of the material with a central theme of crime is unfortunate. Much better would have been an overall review of studies of cognitive impairment by lead, with the crime connection included but not dominant.

A social-cause bias is evident from the article’s use of the phrase “act out” instead of “misbehave” and the insertion of a quote suggesting that reevaluation of crime policies is in order. I do not dispute the possibility that lead toxicity contributes to aggressive behavior, and it seems clear we should strive toward low-lead environments for many reasons, but C&EN should not promote social agendas by making cases for related hypotheses of causality.

John C. Thompson
Coatesville, Pa.

The Article About lead tries to prove that low-level environmental lead exposure results in criminal brain activity. As demonstrated in the article, misinformation, disinformation, and media hype exist concerning very low level exposures to lead. I was one of 60 international lead experts invited to the Environmental Protection Agency’s airborne criteria document committee meetings in the early 1980s.

It’s important to note that all humans around the world are exposed to low levels of thousands of chemical agents—including lead—found in water, air, soil, food, and so on, all of which are well below any threshold of adverse effects but toxic at high exposure concentrations.

Blood lead levels—including the earlier safety standard of 40 µg per deciliter—are a measure of recent exposures, not clinical toxicity. Adverse health effects such as blood enzyme inhibition, colic, encephalopathy, and death are necessary findings. But insignificant IQ changes claimed by Herbert Needleman et al. at the 1980 committee meetings are not. R. A. Kehoe, a pioneering lead expert, reported toxicity in adults and children with blood lead levels at 80 µg/dL and above.

It is important to identify levels, conditions, and especially the form of lead to which a person is exposed. Insoluble lead compounds are often not absorbed into the body and are excreted without any adverse effects. Tetraethyl lead, a very toxic form of lead, causes rats to fight (“boxing rats”) and has been shown as lead deposits in rats’ brains. Toxic exposures in experimental studies in animals have erroneously been assumed relevant to humans at low-level exposures without any evidence of toxicity.

Environmental lead is ubiquitous around the world and results in low levels of lead in human tissues. I reported on lead in tissues of normal cadavers from the Cincinnati area and compared those lead levels with studies from England and Japan. Cadaver studies from Manchester, England, show normal tissue lead concentrations at two to four times the concentrations seen in my Cincinnati cadaver studies. Similar studies done in Japan showed normal tissue lead levels five times or more higher than in the Cincinnati bodies.

Environmental lead concentrations in England and Japan were much higher than in the U.S., contradicting the assertions by Needleman et al. that very low levels of blood lead cause mental problems in children or adults.

Stanley B. Gross
Burke, Va.


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