August 13, 2002
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Neuroendocrinology Letters incl. Psychoneuroimmunology & Chronobiology

including Psychoneuroimmunology, Neuro
Reproductive Medicine, Chronobiology
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ISSN 0172–780X


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Scheduled for publication in October issue,
Vol.23 No. 5, 2002

DDT in human milk and mental capacities in
children at school age:
An additional view on PISA 2000

(Günter Dörner & Andreas Plagemann)

The results of the PISA International and National studies on mental capacities of school children worldwide in 2000 are a matter of intensive debates, especially concerning a surprisingly bad outcome in various Western countries with a high socioeconomic status, e.g. Germany. Mainly, different school and preschool systems are held responsible for it, interacting with family matters of course. However, mental capacities are in general not only a result of learning possibilities but of learning capabilities, a so far rarely considered aspect with regard to PISA.
Dichlorodiphenyl trichloroethane (DDT) is a chlorinated phenyl derivative and was worldwide used as a pesticide. Interestingly, there are some indications for negative long-term effects on mental capacities of chlorinated phenyl compounds, observed in animal experiments and human studies.

Therefore, we aimed to investigate a possible lasting impact of DDT exposure in early (neonatal) life on mental capacities in school age. Statistical relationships were evaluated by correlation and regression analysis between total DDT concentrations in human breast milk in the birth years of 1984/85 and PISA 2000 results on mental capacities in 15-year-old pupils worldwide as well as percentages of backward school children in Germany in 1994/95. DDT concentrations were extrapolated in the best possible way from available publications on worldwide DDT levels. Thereby, estimations were possible for eleven international countries out of three continents as well as fourteen Federal States of Germany which participated in PISA 2000.
Thus, comparing the mental capacities of 15-year-old school children with population based total DDT levels in human breast milk in eleven international countries (PISA International), an inverse correlation was found, even under consideration (adjustment) of the socioeconomic status (see Figure 1).

Furthermore, a significant inverse relationship could be observed between the mental capacities of pupils born in 1984/85 and the total DDT concentrations in ten international countries (PISA International) plus fourteen Federal States of Germany (PISA National). Finally, a significant relationship was found between the total DDT contents in human milk in 1984/85 and the percentages of backward school children in evaluated German Federal States in 1994/95. In conclusion, these observations speak for a dose-dependent deleterious impact of DDT exposure in early life on mental health and mental capacities in later life.

As DDT is a hormonally active substance, it is noteworthy that hormones are important organizers of the brain, recognized by our group since the 1970s. Obviously, these chemical messengers are capable of "programming" fundamental processes of life dose-dependently during critical developmental periods. In view of extensive studies, mental disorders and important diseases of reproduction, metabolism, information processing and immune responsiveness may therefore be preventable, at least in part, by avoiding abnormal hormone concentrations during critical developmental periods of the organism. It should also be mentioned that total DDT concentrations in human breast milk are an indirect indicator of the offspring's exposure not only in early postnatal life but also in prenatal life.

In summary, our data -in association with additional experimental and epidemiological findings- suggest that DDT exposure in early life may lead to harmful effects on brain development and, therefore, mental capacities in later life. Thus, a neuroendocrine prophylaxis -as recommended by our group for many years- during critical developmental periods appears to be most important not only for primary preventive medicine but also for "preventive pedagogics". The validity of these theses should be re-tested in future PISA studies.

Fig. 1. Linear regression plots for DDT concentrations in human breast milk (log-transformed) in the years of birth (1984/85) vs mean mental capacities in school children according to PISA International 2000.

Scheduled for publication in October
Vol. 23 No.5, 2002
Neuroendocrinology Letters

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