Assessment of risks to listed species from the use of atrazine in the USA: a perspective.

Atrazine is a triazine herbicide used predominantly on corn, sorghum, and sugarcane in the US. Its use potentially overlaps with the ranges of listed (threatened and endangered) species. In response to registration review in the context of the Endangered Species Act, we evaluated potential direct and indirect impacts of atrazine on listed species and designated critical habitats.

Derivation of combined species sensitivity distributions for acute toxicity of pyrethroids to aquatic animals.

The aquatic toxicity profiles of synthetic pyrethroid insecticides are remarkably similar, and results for a large number of species can be combined across compounds in Species Sensitivity Distributions (SSDs). Normalizing acute toxicity values (median lethal concentrations, LC50s) for each species and each pyrethroid to the LC50 of the same pyrethroid to the freshwater amphipod Hyalella azteca (the most sensitive species to all pyrethroids tested) enabled expression of LC50s as Hyalella equivalents that can be pooled across pyrethroids. The resulting normalized LC50s (geometric means for each species across pyrethroids) were analyzed using SSDs.

Data quality scoring system for microcosm and mesocosm studies used to derive a level of concern for atrazine.

The US Environmental Protection Agency (USEPA) has historically used different methods to derive an aquatic level of concern (LoC) for atrazine, though all have generally relied on an expanding set of mesocosm and microcosm ("cosm") studies for calibration. The database of results from ecological effects studies with atrazine in cosms now includes 108 data points from 39 studies and forms the basis for assessing atrazine's potential to impact aquatic plant communities. Inclusion of the appropriate cosm studies and accurate interpretation of each data point-delineated as binary scores of "effect" (effect score 1) or "no effect" (effect score 0) of a specific atrazine exposure profile on plant communities in a single study-is critical to USEPA's approach to determining the LoC.

Risks to aquatic organisms from use of chlorpyrifos in the United States.

The risk of chlorpyrifos (CPY) to aquatic organisms in surface water of North America was assessed using measured concentrations in surface waters and modeling of exposures to provide daily concentrations that better characterize peak exposures.Ecological effects were compared with results of standard laboratory toxicity tests with single species as well as microcosm and mesocosm studies comprised of complex aquatic communities. The upper 90th centile 96-h concentrations(annual maxima) of chlorpyrifos in small streams in agricultural watersheds in Michigan and Georgia were estimated to be :-:;0.

Exposures of aquatic organisms to the organophosphorus insecticide, chlorpyrifos resulting from use in the United States.

Concentrations of CPY in surface waters are an integral determinant of risk to aquatic organisms. CPY has been measured in surface waters of the U.S.

Properties and uses of chlorpyrifos in the United States.

Physical properties and use data provide the basis for estimating environmental exposures to chlorpyrifos (CPY) and for assessing its risks. The vapor pressure ofCPY is low, solubility in water is <1 mg L-1, and its log Kow is 5. Chlorpyrifos has short to moderate persistence in the environment as a result of several dissipation pathways that may proceed concurrently.

The relative sensitivity of macrophyte and algal species to herbicides and fungicides: an analysis using species sensitivity distributions.

Lemna spp. are the standard test species representing aquatic macrophytes in the current risk assessment schemes for herbicides and plant growth regulators in the European Union and North America. At a Society of Environmental Toxicology and Chemistry (SETAC) 2008 workshop on Aquatic Macrophyte Risk Assessment for Pesticides (AMRAP), a Species Sensitivity Distribution (SSD) working group was formed to address uncertainties about the sensitivity of Lemna spp.

Comparative aquatic toxicity of the pyrethroid insecticide lambda-cyhalothrin and its resolved isomer gamma-cyhalothrin.

In this review we compare the sensitivity of a range of aquatic invertebrate and fish species to gamma-cyhalothrin (GCH), the insecticidally active enantiomer of the synthetic pyrethroid lambda-cyhalothrin (LCH), in single-species laboratory tests and outdoor multi-species ecosystem tests. Species sensitivity distribution curves for GCH gave median HC(5) values of 0.47 ng/L for invertebrates, and 23.

Effects analysis of time-varying or repeated exposures in aquatic ecological risk assessment of agrochemicals.

Exposure to agrochemicals in the aquatic environment often occurs as time-varying or repeated pulses. Time-varying exposures may occur due to runoff events and spray drift associated with precipitation and application events. Hydrologic dilution, dispersion, and degradation also produce pulsed exposures.