Cited by 218Environmental Toxicology and EcotoxicologyPesticide and Herbicide Environmental StudiesAgricultural safety and regulations

Synergistic toxicity of atrazine and organophosphate insecticides contravenes the response addition mixture model

Pape-Lindstrom, Pamela A, Lydy, Michael J·1997·Environmental Toxicology and Chemistry

Abstract

A toxic unit (TU) approach was used to test the response addition model for mixtures of pesticides with differing modes of action. Atrazine was tested in binary and ternary combinations with the organochlorine insecticide methoxychlor and organophosphate insecticide methyl-parathion. Atrazine was also tested in binary combinations with additional organophosphates. The TU for atrazine was set slightly below its water solubility limits (TU = 20 ppm), which is well below its 96-h 50% effective concentration for the fourth instar of the midge, Chironomus tentans. In 96-h acute toxicity tests using C. tentans, atrazine was found to produce synergistic (greater than additive) toxicity in a binary mixture with methyl-parathion. Less than additive toxicity was found for the combination of atrazine with methoxychlor (likely due to the low TU assigned to atrazine). The ternary combination of atrazine + methyl-parathion + methoxychlor was found to be marginally synergistic. Results of toxicity tests with atrazine in binary combinations with other organophosphates indicate more than additive toxicity for all compounds except mevinophos. Possible hypotheses are presented in an attempt to explain the noted synergistic relationship between atrazine and various organophosphorous insecticides. These results suggest that the response addition model does not always accurately predict mixture toxicity for chemicals with differing modes of action.

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Crossref · 10.1002/etc.5620161130

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  • There is still scientific controversy about the safety of some currently permitted pesticides (e.g. organophosphorus compounds) even at levels below the MRL and complex mixtures of pesticides, as additive/synergistic effects of pesticide mixtures have been documented and safety testing of pesticide mixtures is currently not required.

    “There is still scientific controversy about the safety of some currently permitted pesticides (e.g. organophosphorus compounds) even at levels below the MRL and complex mixtures of pesticides, as additive/synergistic effects of pesticide mixtures have been documented and safety testing of pesticide mixtures is currently not required as part of the regulatory pesticide approval process( 58 – 60 ).”

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Authors
Pape-Lindstrom, P. A., & Lydy, M. J.
Affiliations
Wichita State University (US)
Corresponding author
Lydy, Michael J
Venue
Environmental Toxicology and Chemistry
Published
1997-11-01
Volume
16
Issue
11
Pages
2415-2420
ISSN
  • 0730-7268 (ISSN-L)
  • 1552-8618
OpenAlex
W2166679627
Cited by
218
References
39
Citations by year
2026: 1 · 2025: 3 · 2024: 3 · 2023: 2 · 2022: 4 · 2021: 5 · 2020: 4 · 2019: 4 · 2018: 9 · 2017: 15 · 2016: 6 · 2015: 10 · 2014: 9 · 2013: 13 · 2012: 13
FWCI
3.85
Type
journal article
Language
en
Open access
closed
Locations
  • Environmental Toxicology and Chemistry (publishedVersion)
  • Holmes Museum Of Anthropology (Wichita State University) (submittedVersion)
Topics
  • Physical Sciences › Environmental Science › Health, Toxicology and Mutagenesis › Environmental Toxicology and Ecotoxicology
  • Physical Sciences › Environmental Science › Pollution › Pesticide and Herbicide Environmental Studies
  • Life Sciences › Agricultural and Biological Sciences › Food Science › Agricultural safety and regulations
Keywords
atrazine, organophosphate insecticides, methyl parathion, methoxychlor, pesticide mixtures, synergistic toxicity, toxic units, Chironomus tentans, midges, acute toxicity, mixture toxicity prediction

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