Chronic exposure to imidacloprid, clothianidin, and thiamethoxam mixtures and toxicity in Chironomus dilutus

Widespread agricultural use of neonicotinoid insecticides has resulted in frequent detection of mixtures of these compounds in global surface waters. Recent evidence suggests that neonicotinoid mixtures can elicit synergistic toxicity in aquatic insects under acute exposure conditions, however this has not been validated for longer exposures more commonly encountered in the environment. Therefore, we aimed to characterize the chronic (28-day) toxicity of imidacloprid, clothianidin, and thiamethoxam mixtures under different doses and mixture ratios to determine if the assumption of synergistic toxicity would hold under more environmentally realistic exposure settings. The sensitive aquatic insect Chironomus dilutus was used as a representative test species, and successful emergence was used as a chronic endpoint. Applying the MIXTOX modeling approach, predictive parametric models were fitted using single-compound toxicity data and statistically compared to observed toxicity in subsequent mixture tests. Imidacloprid-clothianidin, clothianidin-thiamethoxam and imidacloprid-clothianidin-thiamethoxam mixtures did not significantly deviate from concentration-additive toxicity. However, the cumulative toxicity of the imidacloprid-thiamethoxam mixture deviated from the concentration-additive reference model, displaying dose-ratio dependent synergism and resulting in up to a 10% greater reduction in emergence from that predicted by concentration addition. Furthermore, exposure to select neonicotinoid mixtures above 1.0 toxic unit tended to shift sex-ratios toward more male-dominated populations. Results indicate that, similar to acute exposures, the general assumption of joint additivity cannot adequately describe chronic cumulative toxicity of all neonicotinoid mixtures. Indeed, our observations of weak synergism and sex-ratio shifts elicited by some mixture combinations should be considered in water quality guideline development and environmental risk assessment practices for neonicotinoid insecticides, and explored in further investigations of the effects of neonicotinoid mixtures on aquatic communities.

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Metadata Record Information

File Identifier
9df7eb6a-54c7-47d8-84d8-dbf3e623c436 XML
Date Stamp
2021-05-12T06:05:16
Metadata language

eng; CAN
Character set
UTF8
Hierarchy Level
Dataset
Author
  Government of Canada; Environment and Climate Change Canada - Environment and Climate Change Canada ( Public inquiries centre )
Fontaine Building 12th floor, 200 Sacré-Coeur Blvd , Gatineau , Quebec , K1A 0H3 ,
1-800-668-6767
https://www.canada.ca/en/environment-climate-change.html
 

Data identification

Date (Publication)
2018-03-21
Date (Creation)
2017-11-04
Status
On going
Metadata language

eng; CAN
Character set
UTF8
Topic category
  • Farming
  • Environment
  • Inland waters
Maintenance and Update Frequency
As needed
Spatial representation type
Text, table
Collaborator
  Government of Canada; Environment and Climate Change Canada; Water Science and Technology - Headley, John ( Senior Research Scientist )
11 Innovation Blvd , Saskatoon , Saskatchewan , S7N 3H5 , Canada

Keywords

Theme

  • MITOX

  • Observation/Measurement

  • Neonicotinoids

  • insecticide

Government of Canada Core Subject Thesaurus

  • Insecticides

ECCC Information Category EN

  • Nature and Biodiversity - Contaminants

Business Functions

  • Monitor / Assess Substance and Waste Levels in Air, Water, Soil, Biota

  • Assess Toxicity, Manage and Monitor for Environmental Presence of Hazardous Substances and Waste

Geography

  • Prairie - Saskatchewan (SK)

external.theme.EC_Branch

  • Science and Technology Branch

external.theme.EC_Directorate

  • Water Science and Technology

external.theme.EC_Program_PAA

  • 1.2.1. Water Quality and Aquatic Ecosystems Health

external.theme.GC_Security_Level

  • Unclassified
 
Use Limitation

Open Government Licence - Canada ( http://open.canada.ca/en/open-government-licence-canada )

Access Constraints
License
Use Constraints
License
Begin Date
2018-03-02

Extent

N
S
E
W
thumbnail


 
 

Ref. system Reference Systems

Reference system identifier
EPSG / 4326 /
 

Distribution

Distribution Formats

Distribution format
  • CSV ( unkown )

 
Distributor
  Government of Canada; Environment and Climate Change Canada - Environment and Climate Change Canada ( Public inquiries centre )
Fontaine Building 12th floor, 200 Sacré-Coeur Blvd , Gatineau , Quebec , K1A 0H3 ,
1-800-668-6767
https://www.canada.ca/en/environment-climate-change.html
 
 

Overviews

N
S
E
W
thumbnail


Keywords

MITOX Neonicotinoids Observation/Measurement insecticide
Business Functions
Assess Toxicity, Manage and Monitor for Environmental Presence of Hazardous Substances and Waste Monitor / Assess Substance and Waste Levels in Air, Water, Soil, Biota
ECCC Information Category EN
Nature and Biodiversity - Contaminants
Government of Canada Core Subject Thesaurus
Insecticides
external.theme.EC_Branch
Science and Technology Branch
external.theme.EC_Directorate
Water Science and Technology
external.theme.EC_Program_PAA
1.2.1. Water Quality and Aquatic Ecosystems Health
external.theme.GC_Security_Level
Unclassified

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