Risk assessment for selected xenobiotics by bioassay methods with higher plants |
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Authors: | Petra Günther Wilfried Pestemer |
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Institution: | (1) Federal Biological Research Centre, Weed Research Institute, Messeweg 11-12, D-3300 Braunschweig, Federal Republic of Germany |
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Abstract: | Different bioassays with higher plants were approved for use in a bioassay procedure for testing of xenobiotics according
to the German Chemicals Act. Selected environmental pollutants (atrazine, cadmium chloride, 2,6-dichlorobenzonitrile, pentachlorophenol,
potassium dichromate, thiourea), all from a list of reference chemicals, were tested with these methods. Dose-response curves
for growth of oats and turnips were evaluated in soil and vermiculite (nonsorptive substrate), and availability to plants
was calculated by comparing the EC50 values for one chemical in both substrates. The most active chemical was atrazine, followed by 2,6-dichlorobenzonitrile,
pentachlorophenol, potassium dichromate, cadmium chloride, and thiourea. The least available compound to plants was pentachlorophenol,
tested with turnips (Brassica rapa var.rapa). The strongest inhibition of germination, demonstrated in an in vitro assay with garden cress (Lepidium sativum), was found with 2,6-dichlorobenzonitrile, the lowest with atrazine. The effect of an extended exposure of the plants to
the chemicals was evaluated in a long-term bioassay with oats (Avena sativa) in hydroponic culture. Several dose-response curves during the growing period were derived. It was found that the EC50 values for atrazine and thiourea decreased markedly during the first four weeks; thereafter the changes were much smaller.
As an overall conclusion, a bioassay procedure is proposed that can be included in the graduated plan recommended by the German
Chemicals Act. |
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Keywords: | Xenobiotics Risk assessment Bioassay Higher plants |
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