Single Versus Combined Lethal Effects of Three Agricultural Insecticides on Larvae of the Freshwater Insect Chironomus dilutus

Pesticides are currently regulated individually but are present in aquatic systems as mixtures of toxicants. In this study, the lethal effects of three agricultural insecticides—chlorpyrifos, imidacloprid and dimethoate—on Chironomus dilutus larvae were examined. Ninety-six–hour static bioassays wer...

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Bibliographic Details
Published in:Archives of environmental contamination and toxicology 2012-10, Vol.63 (3), p.378-390
Main Authors: LeBlanc, Heidi M. K., Culp, Joseph M., Baird, Donald J., Alexander, Alexa C., Cessna, Allan J.
Format: Article
Language:English
Subjects:
Additives
Agriculture
Agronomy. Soil science and plant productions
Animal, plant and microbial ecology
Animals
Applied ecology
Bioassays
Biological and medical sciences
Chemicals
Chironomidae
Chlorpyrifos
Chlorpyrifos - toxicity
Dilution
Dimethoate - toxicity
Earth and Environmental Science
Ecotoxicology
Ecotoxicology, biological effects of pollution
Environment
Environmental Chemistry
Environmental Health
Fresh Water
Fundamental and applied biological sciences. Psychology
General agroecology
General agroecology. Agricultural and farming systems. Agricultural development. Rural area planning. Landscaping
General agronomy. Plant production
General aspects
Generalities. Agricultural and farming systems. Agricultural development
Imidacloprid
Imidazoles - toxicity
Indicator organisms
Insecticides
Insecticides - toxicity
Investigations
Laboratories
Larvae
Mathematical models
Monitoring/Environmental Analysis
Neonicotinoids
Nitro Compounds - toxicity
Pesticides
Pollution
Risk Assessment
Soil Science & Conservation
Studies
Toxicity
Toxicology
Water Pollutants, Chemical - toxicity
Water pollution
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Summary:Pesticides are currently regulated individually but are present in aquatic systems as mixtures of toxicants. In this study, the lethal effects of three agricultural insecticides—chlorpyrifos, imidacloprid and dimethoate—on Chironomus dilutus larvae were examined. Ninety-six–hour static bioassays were performed using single, binary, and ternary toxicant mixtures. The effects of the binary mixtures were investigated using the MIXTOX model to determine if the mixtures behaved additively, synergistically, or antagonistically. Dimethoate was much less toxic than chlorpyrifos or imidacloprid. Chlorpyrifos and dimethoate were not additive in mixture despite their common mode of action (MOA) and resulted in opposing effects (synergism and antagonism, respectively) when combined with imidacloprid. Synergism was observed in the ternary mixture. These results suggest that current mixture models based on MOA alone may not always be adequate in describing mixture effects, as in the current situation of mixtures with relatively few components. Other factors, such as water solubility, secondary MOA, and mechanisms of toxicity, should also be considered in future investigations of multichemical-mixture effects.
ISSN:0090-4341
1432-0703
DOI:10.1007/s00244-012-9777-0