ResearchMWatch as currently proposed, may not be sensitive enough to detect agents that act directly on thyroid hormone synthesis. (Environ. Toxicol. Chem. 2002, 21, 590−597)
Low concentrations of perchlorate may pose a threat to normal development and growth in natural amphibian populations, suggests new Genetic variations determine evidence from Texas Tech scientists. In laboratory experiments, Wanda susceptibility to organoGoleman and colleagues exposed phosphate effects African clawed frogs, Xenopus laevis, to ammonium perchlorate concentraResearch by British scientists suggests tions equal to, or less than, concenthat some farmers may have a genetic trations found in surface waters from predisposition to the adverse health contaminated sites. At high conceneffects associated with exposure to trations, perchlorate is known to inorganophosphates present in sheep hibit amphibian metamorphosis, but dip. its effects at low concentrations have Nicola Cherry and colleagues from not been previously described. the University of Manchester, United Fertilized frog eggs were exposed Kingdom, examined the DNA of 175 to perchlorate for 70 days, which infarmers who believed their ill health cluded the period of metamorphosis. was due to exposure to sheep dip. In The researchers found that exposure addition, they examined the DNA to ammonium perchlorate inhibited from 234 seemingly healthy sheepmetamorphosis in a concentrationdipping farmers. dependent manner, as evident from effects on forelimb emergence, tail resorption, and hindlimb growth. At 5-ppb exposure, the emergence of front legs was delayed. The development of front legs is controlled by thyroid hormones and marks the beginning of metamorphosis in X. laevis and other frog species. At 18-ppb exposure, rear hindlimb growth was reduced, and tail resorption was inhibited. Tail reSome farmersare more susceptible than othersto the sorption signals the end of toxic effectsoforganophosphatesin sheep dip. metamorphosis. At levels greater than 145 ppb, the frogs did not develop front legs. Farmers who reported poor health The researchers also exposed tadwere nearly twice as likely than the poles to ammonium perchlorate healthy farmers to have specific alusing the 14-day test recommended terations in the gene regulating by the U.S. EPA’s Endocrine Disruptor paraoxonase, an enzyme found in Screening and Testing Advisory blood. Paraoxonase is responsible for Committee (EDSTAC) to screen for breaking down the active metabolite endocrine-disrupting effects on thyof diazinon, an organophosphate roid hormones. Concentrations that often used in sheep dip chemicals in produced an adverse effect in the 70the United Kingdom. Those farmers day tests failed to produce an adverse with variations in the enzyme-regueffect in the 14-day test. As a result, lating gene were less able to break EDSTAC’s frog metamorphosis assay, down organophosphates.
“The results provide support for those who believe that repeated exposure to organophosphates may cause chronic ill health. Sheep dippers in the United Kingdom are one important group, but there are many others worldwide who are exposed to these chemicals and whose health may be affected as a result,” Cherry says. (Lancet 2002, 359, 763–764)
Trawling damages cold-water coral reefs Modern fishing equipment that is dragged along the seabed has severely damaged coral reefs in the northeast Atlantic, report a team of British, French, and Norwegian researchers. Because deep-water trawling destroys patches of coral and flattens the seafloor, damaging or wiping out delicate species that live there, legislation to create conservation areas to protect deep-water habitats and the fish they support is urgently needed, they say. Although coral reefs are primarily associated with warm, well-lit waters off tropical coasts, the researchers describe these reefs in the cold, grey Atlantic as “spectacular”. They are 4500years-old and lie 200–1300 m down along the edge of the European continental shelf. The researchers, led by Jason Hall-Spencer of the University of Glasgow’s Marine Biological Station in Millport, United Kingdom, analyzed commercial fish caught off Ireland and Scotland by two trawlers using otter boards—large metal plates on either side of the net mouth, which plough across the seabed. The nets contained a range of reef creatures, including sponges and pieces of broken coral up to one square meter in size. This is the first time scientists have examined trawler catches from these reef areas. The team also investigated two Norwegian reefs using a remotely opPHOTODISC
Perchlorate-contaminated sites could trouble frogs
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erated submersible vehicle. Only one had been intensively trawled. The trawled reef was littered with coral rubble, and otter boards had left trenches 5–10 cm deep. There was no sign of damage to the untrawled reef. (Proc. R. Soc. London, Ser. B 2002, 269, 507–511)
CH4 emissions, the consequences of increased UV radiation levels should be considered, say the researchers. (Geophys. Res. Lett. 2002, 29 (4), 10.1029/2001GL014295)
Greenhouse gases contribute to slower ozone layer recovery
In the largest study of its kind yet undertaken, Canadian and U.S. scientists have found that there is a statistically significant relationship between long-term exposure to fine particulate matter and lung cancer. The findings provide the strongest evidence yet linking lung cancer to air pollution in metropolitan areas, say the researchers. What makes this study so important is the sheer size of the human population studied—the risks to and health status of 500,000 adults were linked with pollution data from metropolitan areas across the United States. The study also is significant for the long time period over which exposed populations were followed
Fine particles—A cancer connection?
The researchers say that the results indicate that long-term exposure to combustion-generated fine particles, such as those that are found in coalfired power plant and vehicle emissions, is an important environmental risk factor for cardiopulmonary and lung cancer mortality. Although the potential effects of factors not accounted for cannot be excluded, the investigators note, the association between fine particles and lung cancer mortality is found even after taking into account a person’s smoking cigarettes, BMI (body mass index), diet, occupational exposure, other individual risk factors, and regional and other spatial differences. (JAMA 2002, 287, 1132–1141)
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Although halogen levels are declining in the stratosphere, the ozone layer will not recover to pre-1980 levels during this century, predicts a new model developed by researchers in Australia. Increases in atmospheric nitrous oxide (N2O) and decreases in methane (CH4) emissions are to blame. The results have implications UV-B alters arctic microbial for global warming mitigation strategies because both compounds are activity important greenhouse gases. Researchers in the Swedish Lapland Although reducing N2O emissions have found that subarctic soil miwould benefit both ozone recovery crobes are highly sensitive to UV-B and climate change, reducing CH4 and CO2 levels. Previously, it was emissions may contribute to stratosthought that only CO2 would have an pheric ozone depletion. effect. The new chemical transport David Johnson and colleagues model, developed by Ian Plumb at the University of Sheffield, the and colleagues at the CommonMacaulay Land Use Research wealth Scientific and Industrial Institute, and the University of Research Organisation (CSIRO) Wales, all in the United Kingdom, Telecommunication and Industconducted a five-year experiment rial Physics, calculates northern with researchers from the Abisko midlatitude stratospheric ozone Scientific Research Station in the levels from 2000 to 2100 for variSwedish Lapland. They exposed a ous scenarios provided by the plot of land near the research staIntergovernmental Panel on Clition to enhanced UV-B radiation, mate Change. Over the next 50 both with and without increased years, the model predicts that CO2 concentrations. Scientistshave found a link betw een fine particulate ozone levels will partially recover, After five years of exposure to matterin air,from sourcessuch asautomobile exhaust, UV-B radiation, the soil microbes but during the second half of the century, they will decline because and lung cancer. had significantly lower carbon to of increases in stratospheric NOx. nitrogen ratios, regardless of the Increases in atmospheric N2O levels (more than 16 years) and the extent CO2 levels. However, when the milead to increases in stratospheric of the exposure data analyzed, incrobes were exposed to enhanced NOx. Sources of N2O include cultivatcluding gaseous copollutant data and CO2 concentrations and UV-B radiaed soils, which contribute the most PM2.5 (particles
