Document Detail

Individual and mixture toxicity of three pesticides; atrazine, chlorpyrifos, and chlorothalonil to the marine phytoplankton species Dunaliella tertiolecta.
MedLine Citation:
PMID:  12929712     Owner:  NLM     Status:  MEDLINE    
This study analyzed the toxicity of three pesticides (the herbicide atrazine, the insecticide chlorpyrifos and the fungicide chlorothalonil) individually, and in two mixtures (atrazine and chlorpyrifos; atrazine and chlorothalonil) to the marine phytoplankton species Dunaliella tertiolecta (Chlorophyta). A standard 96 h static algal bioassay was used to determine pesticide effects on the population growth rate of D. tertiolecta. Mixture toxicity was assessed using the additive index approach. Atrazine and chlorothalonil concentrations > or = 25 microg/L and 33.3 microg/L, respectively, caused significant decreases in D. tertiolecta population growth rate. At much higher concentrations (> or = 400 microg/L) chlorpyrifos also elicited a significant effect on D. tertiolecta population growth rate, but toxicity would not be expected at typical environmental concentrations. The population growth rate EC50 values determined for D. tertiolecta were 64 microg/L for chlorothalonil, 69 microg/L for atrazine, and 769 microg/L for chlorpyrifos. Atrazine and chlorpyrifos in mixture displayed additive toxicity, whereas atrazine and chlorothalonil in mixture had a synergistic effect. The toxicity of atrazine and chlorothalonil combined was approximately 2 times greater than that of the individual chemicals. Therefore, decreases in phytoplankton populations resulting from pesticide exposure could occur at lower than expected concentrations in aquatic systems where atrazine and chlorothalonil are present in mixture. Detrimental effects on phytoplankton population growth rate could impact nutrient cycling rates and food availability to higher trophic levels. Characterizing the toxicity of chemical mixtures likely to be encountered in the environment may benefit the pesticide registration and regulation process.
Marie E DeLorenzo; Lorimar Serrano
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Journal of environmental science and health. Part. B, Pesticides, food contaminants, and agricultural wastes     Volume:  38     ISSN:  0360-1234     ISO Abbreviation:  J Environ Sci Health B     Publication Date:  2003 Sep 
Date Detail:
Created Date:  2003-08-21     Completed Date:  2003-12-23     Revised Date:  2009-07-21    
Medline Journal Info:
Nlm Unique ID:  7607167     Medline TA:  J Environ Sci Health B     Country:  United States    
Other Details:
Languages:  eng     Pagination:  529-38     Citation Subset:  IM    
Center for Coastal Environmental Health and Biomolecular Research, US Department of Commerce/NOAA, National Ocean Service, Charleston, South Carolina 29412, USA.
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MeSH Terms
Atrazine / toxicity
Biological Assay
Chlorpyrifos / toxicity
Dose-Response Relationship, Drug
Drug Combinations
Drug Synergism
Fungicides, Industrial / toxicity*
Herbicides / toxicity*
Insecticides / toxicity*
Lethal Dose 50
Nitriles / toxicity
Phytoplankton / drug effects,  growth & development*
Population Density
Water Pollutants, Chemical / toxicity*
Reg. No./Substance:
0/Drug Combinations; 0/Fungicides, Industrial; 0/Herbicides; 0/Insecticides; 0/Nitriles; 0/Water Pollutants, Chemical; 1897-45-6/tetrachloroisophthalonitrile; 1912-24-9/Atrazine; 2921-88-2/Chlorpyrifos

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