Diazinon aquatic organisms

Lowest tested diazinon concentrations that in medium produced significant nonlethal biological effects to aquatic organisms... 

Table 16.2 Acute Toxicity of Diazinon to Aquatic Organisms (All values...

Table 16.2 (continued) Acute Toxicity of Diazinon to Aquatic Organisms (All values shown are in micrograms of diazinon [active ingredients] per liter of medium fatal to 50% in 96 h.)... 

Table 16.7 Lowest Tested Diazinon Concentrations in Medium that Produced Significant Nonlethal Biological Effects to Aquatic Organisms...

Menconi, M. and C. Cox. 1994. Hazard Assessment of the Insecticide Diazinon to Aquatic Organisms in the Sacramento-San Joaquin River System. Calif. Dept. Fish Game, Environ. Serv. Div., Admin. Rep. 94-2. 

Diazinon released to water from both point and nonpoint sources may be emitted to the atmosphere by volatilization, sorbed to soils and sediments, or accumulated in aquatic organisms. While evaporation may not be expected to be significant based upon the Henry s law constant (see Table 3-2), volatilization of diazinon can be an important transport process. Sanders and Seiber (1983) reported that 17% of the diazinon added to a model pond volatilized in 24 hours. Diazinon released to water also may be adsorbed moderately by soils and sediments based on its organic carbon partition coefficient (K00) values measured in soil (Sharom et al. 1980a). Because this pesticide is only moderately adsorbed by some soils, leaching into groundwater can occur. 

Food Chain Bioaccumulation. Diazinon has an estimated low bioconcentration potential (BCF=77) (Kenaga 1980) in aquatic organisms, which is generally confirmed by measured BCF values obtained from laboratory studies with fish and other aquatic invertebrates (El Arab et al. 1990 Keizer et al. 1991 Sancho et al. 1993 Tsuda et al. 1989, 1995). Further information on measured BCF values for additional edible fish and shellfish would be helpful, as would information on tissue residues of diazinon and its major degradation products in edible species. No information was found on studies associated with plant uptake, but diazinon is rarely detected above EPA tolerance limits (Hundley et al. 1988). Bioaccumulation in aquatic food chains does not appear to be important, and no further information on biomagnification is required. 

Aquatic organisms were impacted by diazinon water concentrations between 0.3 and 1.2 jig/L effects included lowered emergence and elevated drift of stream insects (0.3ttg/L), reduced fecundity of marine minnows (0.47 ixg/L), accumulations in freshwater teleosts (0.55 p,g/L), and daphnid immobilization (1.0p.g/L) and death (1.2p,g/L). These comparatively low levels are of concern because transient peak water concentrations of 4.0-200.0 ttg diazinon/L have been recorded near diazinon sheep-dipping sites in England, and 36.8 ttg/L in the Sacramento-San Joaquin River, California. For protection of sensitive aquatic organisms, a water diazinon level should not exceed 0.08 p-g/L. This value represents a safety factor of about 4 over the lowest recorded adverse effect level of 0.3 pg/L. For protection of freshwater aquatic life, an average 4-day concentration of 0.04 pg diazinon/L is recommended, provided that this value is... 

For protection of sensitive aquatic organisms, diazinon concentrations in water should not exceed 0.08 xg/L however, more data are needed on the effects of fluctuating and intermittent chronic exposures of diazinon on reproduction of fish and aquatic invertebrates. Granular formulations of diazinon seem to he... 

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