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In a recent paper published by PloS Medicine, three US researchers Bruce P. Lanphear, Charles V. Vorhees, David C. Bellinger, insist on the importance of toxicity testing of pesticides and industrial chemicals. The paper indicates that “Epidemics of overt toxicity following widespread environmental contamination from commercial toxins heralded the discovery of children’s enhanced vulnerability to lead, methyl mercury, polychlorinated biphenyls (PCBs), and tobacco. Over the past three decades, researchers have found that remarkably low-level exposures to these toxins are linked with less overt symptoms of toxicity -intellectual impairments, behavioral problems, spontaneous abortions, or preterm births. Moreover, there is emerging evidence that decrements in intellectual abilities and low birth weight linked with lead or tobacco are, for a given increment of exposure, greater at lower levels than those found at higher levels.”
“The consequences of exposure to many other chemicals or mixtures of chemicals, such as insecticides -chemicals oftentimes specifically designed to be toxic- are largely unknown. Many of these chemicals or their metabolites are routinely found in the blood and body fluids of pregnant women and children.”
“The developing fetus and young child is particularly vulnerable to certain environmental toxins. Critical neurodevelopmental processes occur in the human central nervous system during fetal development and in the first three years of life. These processes include cortical functional differentiation, synaptogenesis, myelination, and programmed apoptosis”.
“Children's exposure to environmental toxins is insidious. Environmental toxins covertly enter a child's body transplacentally during fetal development or by direct ingestion of house dust, soil, and breastmilk and other dietary sources during early childhood. Our ability to directly measure the actual levels of environmental chemicals in human tissues and body fluids using biologic markers (biomarkers) enables scientists to more effectively link exposures to environmental toxins with disability or disease.
Despite our increased knowledge of the toxicity of environmental chemicals, testing for developmental neurotoxicity (DNT) and reproductive toxicity is rarely done. DNT testing uses animal experiments to provide information on the potential functional and morphologic toxicity to the fetal nervous system that results from the mother's exposure to toxins during pregnancy and lactation. Paradoxically, DNT testing of a chemical is seldom requested, and then typically requested only if there is pre-existing evidence that it is neurotoxic.
The paper concludes: “In contrast with the EU’s proposed REACH program, which would require industry to conduct more tests or analyses to demonstrate that high-production chemicals will not cause harm to fetuses or children, the Bush administration has argued -in unison with the American Chemistry Council -that such regulations would harm industry. It is time to acknowledge that the existing requirements for toxicity testing and regulations are inadequate to safeguard pregnant women and children. Until a formal regulatory system is developed to effectively screen and identify new and existing chemicals that are toxic to pregnant women and children, we are left to await the next epidemic to warn us about an environmental disaster”.
Source: PloS Medicine, March 2005.
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