Two Environmental Articles: Deformed Frogs & Dioxin In Old Soil

April 28, 1998

The following research articles appear in Environmental Science & Technology, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society. The recent finding of abnormal frogs in many different states and Canada spanned a wide range of amphibians and was not limited to species, geography or climate, according to James J. La Clair of The Scripps Research Institute in La Jolla, Calif. In a new report in the April 14 Web edition of Environmental Science & Technology, La Clair and colleague John Bantle offer an explanation for these findings by examining the effects of pesticide degradation in the early amphibian development.

La Clair's group found that S-methoprene, an insect growth regulator that was introduced in the late 1970s to control fleas and mosquitos, posed little risk to the development of amphibians. However, when exposed to sunlight, water and microorganisms, La Clair found that S-methoprene breaks up into other products that dramatically alter embryo development. By adding minute amounts of these degradation products to developing embryos of the African clawed frog, Xenospus laevis, the Scripps group found that the embryo developed into a juvenile with deformations similar to those found in nature.

La Clair emphasizes that the current procedure of assessing the risk posed by pesticides by examining only the host pesticide must be changed to include the relationship between amphibian development and the degradation products that form under natural conditions.

Chlorinated Dioxins Found In Century-Old Soil Sample

The discovery by K. C. Jones and his colleagues at Lancaster University in Lancaster, U.K., of a previously unopened bottle of soil collected in 1881 from an agricultural experimental station northwest of London has allowed a scientific look back before the modern chemical industry existed. Jones was particularly interested in polychlorinated dibenzo-para-dioxins and furans (PCDD/Fs), which today are released into the atmosphere in ultratrace amounts from various combustion sources or as unwanted byproducts in various chlorinated chemical formulations.

Because the PCDD/Fs may be a threat to human health, many industrialized countries have attempted to locate the PCDD/F sources in order to take reduction measures, Jones says. But there is no agreement on whether the key sources have been found, or even if there were PCDD/Fs in the environment before chloro aromatics were made synthetically, according to Jones.

Using scrupulous care to avoid contaminating this century-old soil sample by exposure to modern air, the Lancaster group reports in the April 28 Web edition of Environmental Science & Technology that the PCDD/Fs were indeed present in the U. K. in the late 1800s, long before the development of the chlorine industry. "This is not surprising," Jones maintains, "given the reliance on coal and wood combustion for energy at that time, and the widespread smelting of metals."

The data collected by Jones provides an historical baseline level for comparison of other samples. Jones says that for many decades the soil has acted as a "sink" for accumulating PCDD/Fs in the atmosphere, but that atmospheric PCDD/Fs have clearly declined in recent years.

A nonprofit organization with a membership of more than 155,000 chemists and chemical engineers, the American Chemical Society publishes scientific journals, convenes major research conferences, and provides educational, science policy and career programs in chemistry. Its main offices are in Washington, D.C., and Columbus, Ohio.
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American Chemical Society

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