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Effect of exposure time on the acute toxicities of permethrin, fenitrothion, carbaryl and carbofuran to mosquito larvae
Author(s) -
Parsons J. T.,
Surgeoner G. A.
Publication year - 1991
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620100913
Subject(s) - permethrin , fenitrothion , carbaryl , carbofuran , toxicology , acute toxicity , toxicity , pesticide , chemistry , biology , organic chemistry , agronomy
Static toxicity tests were used to assess the acute toxicity to third‐instar Aedes aegypti (L.) to short‐term exposures of five insecticides (technical permethrin, microencapsulated permethrin, fenitrothion, carbaryl, and carbofuran). Larvae were exposed to each insecticide for times of 0.25, 0.5, 1, 2, 4, 8, or 24 h, then transferred to clean water and reared to the adult stage. Technical permethrin was most toxic to Aedes aegypti , followed by fenitrothion, microencapsulated permethrin, carbofuran, and carbaryl (24 h LC50 values, based on survival to the adult stage, were 0.45, 3.1, 21.6, 90.0, and 510.0 μg/L, respectively). Acute toxicity increased with increasing exposure time to all five insecticides. However, the relationship between exposure time and acute toxicity differed among insecticides. The increase in acute toxicity was greater over short than over long exposures for technical permethrin, carbaryl, and carbofuran (LC50 values decreased 11.2 to 22.4‐fold over a 0.5‐ to 4‐h exposure, and 2.6‐ to 5.2‐fold over a 4‐ to 24‐h exposure). The opposite was true for microencapsulated permethrin (LC50 values decreased 3.6‐fold over a 0.5‐ to 4‐h exposure, and 6.2‐fold over a 4‐ to 24‐h exposure). Acute toxicity to fenitrothion increased proportionately with increasing exposure time. Some larvae recovered from immobilization following short (0.5‐ to 4‐h) exposures to technical permethrin, microencapsulated permethrin, carbaryl, and carbofuran (EC50 values based on immobilization immediately after exposure terminated were 0 to 15 times lower than corresponding LC50 values). However, ability to recover decreased with increasing exposure time such that no recovery from immobilization occurred after 8 or 24 h exposure. Larvae did not recover from immobilization following exposure to fenitrothion. These results indicate the need for a postexposure observational period to fully assess acute toxicity following exposure to insecticides.