4. Ecological Effects of Other Formulation Ingredients
The “inert” or “other” ingredients in the product formulation were not considered in the
ecological risk assessment conducted by EPA. As mentioned above, all inert ingredients in
pesticide products undergo scientific evaluation before approval for use by the EPA. The Agency
must have sufficient data to determine that the use of the product will not cause unreasonable
adverse effects to the environment. The inert ingredients in Clipper Herbicide have all been
approved for application on nonfood and food sites.
For the purpose of the review presented here, the risks of the other formulation ingredients to
aquatic non-target organisms were evaluated based on the consideration of toxicity information
and concentrations in the formulation. It was concluded that these compounds are of a nature
and/or present at levels in the product such that use of it as directed would not cause adverse
aquatic ecological effects.
The combined effect of multiple substances was assessed by using the concentration additions
approach. The combined effect of multiple compounds or substances is calculated by summation
of the concentration of each compound divided by an effect concentration for that compound.
This approach is considered to provide a conservative estimate of the mixture effect with
relatively small likelihood of underestimating effects due to interactions (Lydy et al., 2004;
Junghaus et al., 2006; Belden et al., 2007; Backhaus and Faust, 2012). The concentration
addition is commonly applied by the use of toxic units (TU). The TU is defined as the quotient
ci/ECxi which rescales the absolute concentrations of substances to individual potencies. The
combined effect is estimated by the summation of TUs. This approach was used in an
assessment of the combined effect of flumioxazin and its degradates. The assessment was based
1 Pesticide Inert Ingredients: http://www.epa.gov/opprd001/inerts/
MDAR/MassDEP 5 June 2013
on the AQUATOX-derived environmental concentrations and refined assessment of toxicity
endpoints of the degradate 482-HA based on ECOSAR predictions (see also Appendix 4 in
flumioxazin review). Only acute effects were evaluated here and therefore the APF and THPA
degradates were not considered. The toxicity endpoints for the inert ingredients were obtained
from the open literature and government review documents.
The results are shown in Appendix 2 and indicate that the combined effect to fish and algae is
dominated by the effect of flumioxazin, with very small contributions from effects of the other
ingredients. For invertebrates the contributions of other ingredient #4 (a surfactant) exceeds the
contribution of flumioxazin. If one applies the level-of-concern (LOC) thresholds as used in
ecological risk assessment by EPA, the LOC for acute high risk of 0.5 is not exceeded for fish
and invertebrates, but the LOC for endangered species of 0.05 is exceeded. The LOC for effects
to algae is exceeded due to high toxicity of flumioxazin.
The concentration addition approach is not recommended for assessment of chronic effects from
exposure from mixtures (Backhaus and Faust, 2012). The differences in environmental fate, such
as dissipation rates and partitioning behavior, also complicate the exposure assessment for longer
exposure times. A chronic ecorisk evaluation was conducted of the active ingredient
flumioxazin and its major degradates. Details of this risk assessment can be found in the
flumioxazin review document (Section 3). The refined assessment indicated that the projected
flumioxazin concentrations averaged over 21 days exceeded chronic LOC for fish, but not for
invertebrates. The projected concentrations of the three major degradates did not exceed LOCs
for aquatic organisms.