Lead and Delinquency

by Robin Mosman

In 1979, Dr. Herbert Needleman et al reported in the New England Journal of Medicine that evidence existed of a lead behaviour learning triad, after 2,146 school children's shed teeth were examined.

The study by Boston's Children's Hospital Medical Center and Harvard Medical School concluded that "the impaired function of children with high lead levels, demonstrated in the neuropsychologic laboratory, mirrored by disordered classroom behaviour, appears to be an adverse effect of exposure to lead".

Behaviours common to the higher lead children were:

• Distractibility

• lacking in persistence

• Constantly dependent and clinging

• Impulsiveness

• Easily become frustrated

• Daydreaming

• Fail to follow simple directions

• Fail to follow sequence of directions

The lead levels found to affect the school children's behaviour were below the levels usually considered to be toxic - in 1979 in the USA the safe standard was 30 µg/dL (micrograms of lead per decilitre of blood).

A follow-up study by Needleman et al (1990) reported that the educational success of a group of young adults was significantly linked with the amount of lead in the teeth they shed as small children. In this study, tooth lead levels above 20 ppm (parts per million) were associated with a seven-fold risk of not graduating from high school, a six-fold risk of having a reading disability, deficits in vocabulary, problems with attention and fine motor co-ordination, greater absenteeism and lower school class ranking.

Although tooth lead levels do not correspond in any simple way to blood lead levels, the available preschool blood lead levels of the more highly exposed children averaged 35 µg/dL.

In his book, "Diet, Crime and Delinquency", published the year after the Needleman study in 1980, Alexander Schauss takes this information further to make a link between lead and delinquency.

Data from the Clinical Ecology Treatment Program of the San Luis Obispo County Juvenile Probation Department in California showed that among 20 medically and educationally screened juvenile delinquents, 70 percent were found to be learning disabled and 60 percent had tooth lead levels above 11 parts per million (ppm). Virtually all of the learning disabled clients had tooth lead levels ranging from 11 ppm to 35 ppm.

Increased tooth (in this case circumpulpal dentine) lead levels (>16 ppm) have also been linked to higher rates of learning disabilities in a recent Danish study (Lyngbye et al., 1990).

Schauss states "The bottom line is that the learning-disordered and behavioural- disordered child is less receptive to the usual social sanctions and rewards of our society and, therefore, develops an increased susceptibility for criminal behaviour".

"Lead, Behaviour and Criminality" (paper) CDC "Preventing Lead Poisoning in Young Children - A statement by the Centers for Disease Control (US)". Oct. 1991

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