Effect of humic acids on toxicity of DDT and chlorpyrifos to freshwater and estuarine invertebrates.
The effects of dissolved humic acids (HAs) on the acute toxicities of the organophosphate pesticide chlorpyrifos and the organochlorine pesticide 4,4'-dichlorodiphenyltrichloroethane (DDT) were assessed by using freshwater crustaceans (Ceriodaphnia dubia) and saltwater crustaceans (Americamysis bahia). The effects of filtered Aldrich HAs (10-100 mg/L) on organism mortality were determined. Humic acids had no effect on mortality of A. bahia for either pesticide at a salinity of 20 parts per thousand, but greatly reduced the mortality of C. dubia for both pesticides in freshwater (0 parts per thousand). In the latter case, the effect was proportional to the HA concentration. The difference in toxicity mitigation as a function of salinity is believed to be due to conformational changes in the HA molecules, which impact pesticide-HA binding, rather than to organismal effects.
College of William and Mary, Virginia Institute of Marine Science, Gloucester Point, Virginia 23062-1346, USA. alkmist01@yahoo.com
Laurent C
LC
Mézin
Robert C
RC
Hale
D000818:Animals; D002244:Carbon / Q000032:analysis; D004390:Chlorpyrifos / Q000633:toxicity*; D003445:Crustacea / Q000187:drug effects* / Q000378:metabolism; D003634:DDT / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D005618:Fresh Water / Q000032:analysis; D006812:Humic Substances; D007928:Lethal Dose 50; D010575:Pesticides / Q000633:toxicity*; D012623:Seawater / Q000032:analysis; D018675:Toxicity Tests
D006812:Humic Substances; D010575:Pesticides; D002244:Carbon; D003634:DDT; D004390:Chlorpyrifos