Aquatic phyto-toxicity of 23 pesticides applied at expected environmental concentrations

• Published in: Aquatic toxicology 1994, Vol.28 (3), p.275-292
• Main Authors: Peterson, Hans G., Boutin, Céline, Martin, Pamela A., Freemark, Kathryn E., Ruecker, Norma J., Moody, Mary J.
• Format: Article
• Language: English
• Subjects: adverse effects; Agronomy. Soil science and plant productions; Algae; Animal, plant and microbial ecology; Applied ecology; Bacillariophyta; Biological and medical sciences; carbaryl; carbofuran; Chlorophycota; Cyanobacteria; Duckweed; Ecotoxicology, biological effects of pollution; Expected Environmental Concentration; Fresh water environment; Freshwater; Fundamental and applied biological sciences. Psychology; herbicide residues; herbicides; Lemna minor; nontarget effects; nontarget organisms; Pesticide; pesticide residues; phytotoxicity; propiconazole; Soil and water pollution; Soil science; Toxicity
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/0166-445X(94)90038-8

Environment Canada uses an Expected Environmental Concentration (EEC) in evaluating the hazard of pesticides to nontarget aquatic organisms. This concentration is calculated by assuming an overspray of a 15 cm deep waterbody at the label application rate. The EEC of pesticides is then related to the EC50 (concentration causing a 50% reduction in a chosen toxicity endpoint) for a given aquatic test organism. At present, the use of an uncertainty factor is suggested in the literature if only a few species are tested because of important interspecific differences in pesticide sensitivity. The phytotoxicity of the EEC of 23 different pesticides to ten algae (24 h inhibition of 14C uptake) and one vascular plant (7-day growth inhibition) was determined in an effort to examine the question of interspecific sensitivity and its relation to the development of pesticide registration guidelines. Chemicals included five triazine herbicides (atrazine, cyanazine, hexazinone, metribuzin, and simazine), four sulfonylurea herbicides (chlorsulfuron, metsulfuron-methyl, ethametsulfuron-methyl, triasulfuron), two phenoxyalkane herbicides (2,4-D and MCPA), two pyridine herbicides (picloram and triclopyr), a substituted urea, an amine derivative, and an imidazolinone herbicide (tebuthiuron, glyphosate and imazethapyr, respectively), a bipyridylium (diquat), a hydroxybenxonitrile (bromoxynil), an aldehyde (acrolein) and an acetanilide (metolachlor) herbicide, as well as two carbamate insecticides (carbofuran and carbaryl) and a triazole derivative fungicide (propiconazole). Test organisms were selected based on ecological relevance and present use in test protocols. Organisms included green algae ( Scenedesmus quadricauda and Selenastrum capricornutum), diatoms ( Nitzschia sp. and Cyclotella meneghiana), cyanobacteria ( Microcystis aeruginosa, Oscillatoria sp., Pseudoanabaena sp., Anabaena inaequalis and Aphanizomenon flos-aquae) and a floating vascular plant, duckweed ( Lemna minor). The five triazine herbicides, acrolein and diquat inhibited the carbon uptake of all algae, diatoms and cyanobacteria by more than 50%. Two other pesticides, carbaryl and tebuthiuron, caused more than 50% inhibition in 90% of the algae tested. Nine of the 23 pesticides, five of which were triazine herbicides, were therefore highly phytotoxic to algae. Twelve pesticides inhibited growth of duckweed by more than 50%. Once again, all five of the triazine herbicides were among this group, as well as th