MDAR/MassDEP 4 June 2013
Figure 1. Risk quotient (RQ) of four spray adjuvants based on adjuvant concentrations associated with
applications to a 1-foot deep water body. The adjuvant concentration was 1% v/v. The risk quotient was
calculated based on the 96-h LC50 values for rainbow trout as reported by Smith et al. (2004) and
USEPA (1994). The RQ values are compared with the Levels of Concern (LOC) for acute risk as
developed by US EPA (2011).
Smith et al. (2004) estimated water depth at which the 96-h LC50 value for juvenile trout would be
reached with an application volume of 20 gal/acre and labeled tank mix concentration (0.5 – 5%).
The authors determined the water depths at which LC50 for the exposed trout would be reached.
When used at the minimum recommended percentage of adjuvant in the tank mix the LC50 depth
was label recommended percentages of adjuvant in the tank mix, the LC50 depth for Agri-Dex would
remain concluded that Agri-Dex posed the lowest hazards to fish among the surfactants evaluated.
In the case of Clipper Herbicide, a high-end estimate of spray volume is 50 gal per acre. From the
graph depicted in Fig. 1 above, it can be concluded that at that spray volume, even the R-11
adjuvant with the highest toxicity would not reach or even approach the LOC for aquatic animals,
though it would exceed the LOC for endangered species. The LI700 adjuvant would not exceed
the LOC for aquatic animals, but would exceed the LOC for endangered species. The Hasten,
Agri-Dex and Cide-Kick adjuvants would not exceed the LOC for aquatic animals or endangered
0 20 40 60 80 100
Risk Quotient (RQ)
Application volume (gal/acre)
LOC Aquatic Animals
MDAR/MassDEP 5 June 2013
AMEC, 2009. Human Health and Ecological Effects Risk Assessment, Imazapyr Risk
Assessment Washington State. Prepared by AMEC Geomatrix, Inc., Lynwood, WA for
Washington State Department of Agriculture, Olympia, WA. Available at:
Curran, C. et al., 2003. Toxicity of Rodeo and Arsenal tank mixes to juvenile rainbow trout.
University of Washington, Seattle, WA, USA. Meeting Abstract for SETAC 24th Annual
Curran, C. A., J. M. Grassley, et al. (2004). “Toxicity of R-11® Surfactant to Juvenile Rainbow
Trout: Does Size Matter?” Bulletin of Environmental Contamination and Toxicology
Entrix, Inc. 2003. Ecological Risk Assessment of the Proposed Use of the Herbicide Imazapyr to
Control Invasive Cordgrass (Spartina spp.) in Estuarine Habitat of Washington State.
Prepared for Washington State Department of Agriculture, Project No. 3000901.
Pless, P. 2005. Use of Imazapyr Herbicide to Control Invasive Cordgrass (Spartina spp.) in the
San Francisco Estuary: Water Quality, Biological Resources, and Human Health and
Safety. Prepared for San Francisco Estuary Invasive Spartina Project. Prepared by Petra
Pless, D.Env. Leson & Associates, Berkeley, CA.
Smith, B.C. et al., 2004. Toxicity of four surfactants to juvenile rainbow trout: Implications
for use over water. Bull. Environ. Contam. Toxicol. 72:647-654.
USEPA, 1994. Reregistration Eligibility Decision: Limonene. Accessed at:
USEPA, 2011. Technical Overview of Ecological Risk Assessment. Accessed at:
MDAR/MassDEP 6 June 2013
MDAR/MassDEP 4 June 2013