| Simple recipe for detecting contaminants in water |
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| Tuesday, 22 April 2008 | |
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Soak a piece of tissue paper untreated water. Place some lettuce seeds and incubate them at room temperature for four to five days. Compare the length of roots and those obtained from seeds sown in normal rainfall and drinking water free of toxic products: Here is a simple recipe for assessing the toxicity of drinking water.
If the water contains relatively little toxic substances, the seeds will grow normally, researcher at the Institute National de Recherche sur les eaux (NWRI) of Environment Canada, Burlington (Ontario). But if the level of toxicity of the water is high, it is unlikely that seed grow, the roots are formed or that the germination occurs. We can expect all kinds of reactions depending on the type and concentration of chemicals in water. The bioassays of this kind have been the subject of a workshop on analyzing the water quality organized by the International Development Research Centre (IDRC) in Cornwall (Ontario) last winter. Scientists from Canada and South have had the opportunity to evaluate new methods of water analysis and the possibility of their use in developing countries. A real danger According to the presence of toxic substances in drinking water sources is in some countries, a problem more serious than microbiological contamination of water by bacteria or viruses. Exposure to chemicals such as pesticides, herbicides and heavy metals present a real danger to health; these pollutants can cause dizziness, blurred vision or even seriously damage the nervous system. Even if they can have easy access, most developing countries have neither the time nor the means to use the current tests. It may cost between 5 000 and $ 10 000 (an amount that far exceeds the per capita income in many countries) to analyze water samples in order to detect the presence of 50 different chemicals. However, a package of 250 grams of lettuce seeds (enough to make 50 000 to 100 000 tests) costs about $ 50 Cdn. Unlike the usual tests that measure the concentration of chemicals in water, these tests indicate if water is contaminated by a toxic substance or more and determine the effects of these contaminants. The tests are designed to be used together. They are not testing the most sophisticated or more that are sensitive, but they react as well as the more expensive tests found in commerce, said Barney Dutka. Everyone can detect the presence of a substance in particular, it is better to use them all together. The bioassays do not react similarly all the same chemicals. The interest IDRC for bioassays is born of a project in Chile. We arrived here in early 1990, have taken samples at various locations, reduced water and sediment in Canada and made the bioassays. Each sample contained toxic substances and a good number of these chemicals were pesticides, said Dutka. A workshop on water analysis In 1996, IDRC invited to a workshop he organized in Ottawa scientists from Canada and South to assess various tests to measure the degree of toxicity of drinking water and choose those most suitable for developing countries . We have retained a battery of tests based on their simplicity, low cost and the possibility of their use in the Third World. In addition to the tests using seeds of lettuce and onions, participants were tested other methods involving microscopic worms, shellfish and freshwater polyps. Gathered seven months later in Cornwall, researchers from Argentina, Chile, Colombia, Costa Rica, India, Mexico, Turkey and Ukraine have learned how to perform various bioassays. Then they returned, bearing crops and supplies necessary to carry out the tests in their own laboratories. They are currently on a comparative study, sponsored by IDRC and coordinated by the NWRI. During the next year, each will receive six samples of water unidentified containing toxic substances, and they will do the analysis using the bioassays. The NWRI then determine the effectiveness of different tests in each laboratory and will review the results depending on each substance or toxic chemicals in combination with each other. Projects for schoolchildren This study will be followed by trials in which researchers will analyze samples of water from local sources. IDRC also invite school children worldwide to take part in scientific projects designed for them. Linked by the Internet, researchers and students will compare notes on the status of water on a global scale. According to Gilles Forget, principal scientist at IDRC, the benefits of these tests are not limited to the progress of work in the laboratory. They can encourage local authorities to take control of protecting their environment, he says. Test results will not only determine if the water is safe to drink, they can help communities advocate for the fight against pollution and lead them to adopt more sustainable farming practices. |
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| Last Updated ( Monday, 30 June 2008 ) |
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