Ecology Center

Prenatal exposure to extraordinary low levels of dioxin can reduce motivation in rats to perform in behavioral experiments. The researchers exposed pregnant rats to a single low dose of dioxin. A few months after birth, the female offspring were then used in behavioral experiments. Dioxin exposure had a large and significant impact on the rats’ performance. Exposed rats did not work as hard as the control rats.

The fact that dioxin had clear, adverse effects at such a low level confirms that standard toxicity testing is wholly inadequate as a means of protecting people against contamination risks. Of greatest importance is the levels at which these impacts are detected in rats are comparable to background levels in people around the world!

Source: Markowski, VP, G Zareba, S Stern, C Cox and B Weiss. Altered Operant Responding for Motor Reinforcement and the Determination of Benchmark Doses Following Perinatal Exposure to Low Level 2,3,7,8-Tetrachlorodibenzo-p-dioxin. Environmental Health Perspectives 2001 109:621-627.

IQ Deficits Linked With Lead Levels in Blood Lower Than "Acceptable" Values

Many more children may be suffering from the harmful effects of lead than were previously thought. Lead is toxic at concentrations in the blood that were previously thought to be harmless, according to a new study by a physician at Children’s Hospital Medical Center of Cincinnati.

According to this study, children who have blood lead concentrations lower than the current acceptable level demonstrate IQ declines as blood lead levels increase. "Not only is there an adverse affect below currently acceptable levels, but the decline in IQ for each microgram per deciliter increase in blood lead is greater at lower levels," says Dr. Lanphear, the study’s main author. The lowest blood lead concentration associated with adverse effects has not yet been defined.

Before 1970, the acceptable blood lead standard was 6 times what the standard is today. Since then, levels considered acceptable declined several times, before reaching the current 10 micrograms per deciliter standard. This study shows that the current standard may need to be revised and lowered to prevent problems in children from lead poisoning such as lowered intelligence, behavioral problems and diminished school performance.

Source: Lanphear BP, Dietrich K, Auinger P, Cox C. Cognitive deficits associated with blood lead concentrations <10 microg/dL in US children and adolescents. Public Health Rep 2000 Nov-Dec;115(6):521-9

Scientists Link Bayer’s Baygon to Child Leukemia

Scientists in Scotland have linked infant leukemia to commonly used pesticides in Europe. The study showed that pregnant women who were exposed to a substance from the same family of chemicals were 10 times more likely to have a baby who developed the deadly disease than mothers who were not exposed.

The results of the study found an association between exposure to one chemical in the carbamate family, Baygon, and infants with leukemia. This family of chemicals is used to kill a variety of pests including aphids, cabbage root fly, vine weevils, codling moths, earwigs, and mosquitoes.

Experts believe the findings could offer at least a partial explanation for a series of childhood leukemia clusters in various parts of the UK. Although the causes of leukemia are very complex, the results of this study urge using caution around pesticides containing chemicals from the carbamate family.

Source: Alexander FE, Patheal SL, Biondi A et al. Trans-placental chemical exposure and risk of infant leukemia with MLL gene fusion. Cancer Res 2001 Mar 15;61(6):2542-6

Puberty and DDT

DDT, a chemical that has been banned in the US for 30 years, may be causing children to reach puberty early in countries that still use the pesticide to control malaria.

Researchers in Belgium found that some immigrant children with "precocious puberty" (early sexual development) had high levels of a chemical derivative of DDT in their blood. This chemical, called DDE, mimics the effects of the hormone estrogen, which is important in controlling sexual development.

The researchers suggest that children living in the developing countries do not normally suffer from early puberty because they tend to be undernourished, and this slows down their development. The early puberty has not been noticed until they reach the west, where they are provided with adequate nourishment. However, even if the effect on puberty is masked while living in the developing countries, their reproductive systems could still be harmed from these chemicals in their environment.

Source: Krstevska-Konstantinova M, Charlier C, Craen M et al. Sexual precocity after immigration from developing countries to Belgium: evidence of previous exposure to organochlorine pesticides. Human Reproduction 2001 May;16(5):1020-6

DDT Linked to Premature Births

In a recent study examining a possible association between pre-term births and a product of the breakdown of DDT, called DDE, researchers tested previously stored serum samples from women who were pregnant between 1959 and 1966, when DDT was still used in the US.

They demonstrated a powerful association between DDE levels in mothers’ serum and the likelihood of premature birth. The higher the level of DDE, a pre-term birth was more likely. They also showed that high concentrations of DDE was linked to the baby’s size. Babies were more likely to be small for their gestational age when born to mothers with higher DDE levels.

Source: Longnecker, MP, MA Klebanoff, H Zhou, and JW Brock. Association between maternal serum concentration of the DDT metabolite DDE and pre-term and small-for-gestational-age babies at birth. The Lancet 2001 358: 110-114.

Heather Rohrer is an Ecology Center intern.

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