From: Ginger Moser/RTP/USEPA/US

To: Tim Benner/DC/USEPA/US@EPA

Date: 03/29/2010 08:26 AM

Subject: Re: Possible impact on wetlands - comments needed

Hi Tim

Below, I have copied Glen Thursby's review of the TFA information. In my naive reading, it appears that 

he agrees that the risk of TFA is minimal, which I believe was the original conclusion. Hopefully this will 

address the concerns that OAR had?

From Glen:

I looked over the information you sent relative to TFA—with particular emphasis on the aquatic 

plant toxicity data (my area of expertise). The data I evaluated were those summarize in the 

document entitled, Revised Draft Assessment of the Potential Impacts of HFO-1234yf and the 

Associated Production of TFA on Aquatic Communities and Local Air Quality, prepared by ICF 

International. As I mentioned earlier my comments are restricted to the aquatic toxicity test data. 

I do not have the expertise to evaluate the environmental fate information presented. I briefly 

reviewed the following papers that are the source of the aquatic plant data in that report:

Benesch, et al. 2002. Investigation of Effects of Trifluoroacetate on Vernal Pool Ecosystems. 

Environmental Toxicology and Chemistry. 21(3):640-647. 

Berends et al. 1999. Toxicity of Trifluoroacetate to Aquatic Organisms. Environmental 

Toxicology and Chemistry. 18(5):1053-1059. 

Boutonnet, et al 1999. Environmental Risk Assessment of Trifluoroacetic Acid. Human and 

Ecological Risk Assessment: An International Journal. 5(1):59 -124.

Hanson, ML and Solomon, KR. 2004a. Haloacetic acids in the aquatic environment. Part I: 

Macrophyte Toxicity. Environmental Pollution 130:371-383.

Hanson, ML and Solomon, KR. 2004b. Haloacetic acids in the aquatic environment. Part II: 

Ecological Risk Assessment. Environmental Pollution 130:385-401.

One general comment. The data from Berends et al. (1999) are reported in mg NaTFA/L and 

those from Hanson and Solomon (2004a) and Benesh et al. (2002) in mg TFA/L. The ICF report 

authors might want to consider normalizing all of the data to TFA. TFA is approximately 83% of 

the molecular weight of NaTFA.

The number of aquatic plant species for which data are available in the Boutonnet et al. (1999) 

report and the one by Hanson and Solomon (2004a) is greater than the number of values 

typically available to assess the effects of toxic compounds on this community. In brief, the 

methods used were standard methods and generally appropriate for the type of testing 

performed. The data reported in the risk assessment by Boutonnet et al. (1999) were published 

in more detail in Berends et al. (1999). It is this latter paper that contains the data for the most 

sensitive alga tested, Selenastrum capricornutum (currently known as Pseudokirchneriella 

subcapitata (Korshikov) F. Hindák—the use of Raphidocelis subcapitata did not last long). The 

EC50 for this species was reported as 4.8 mg.L NaTFA (ca. 4 mg/L TFA) and the NOEC was 

0.12 mg/L NaTFA (0.1 mg/L TFA). Although these values are substantially lower that those 

reported for the other 10 algal species, this range in sensitivity among algae is not uncommon. 

In a risk characterization for pesticides registration the initial evaluation relative to aquatic plants 
would consist of taking the lowest EC50 (4 mg/L in this case) and dividing that into the expected 

environmental concentration. The level of concern for this ratio is 1. Any ratio greater than 1 

would be cause for greater scrutiny. Based on some of the summary information presented I 

would expect that the ratio in this case would be several orders of magnitude less than 1. I’ve 

overly simplified this, but you get the idea.

The data presented by Hanson and Solomon (2004a) are for three species of aquatic vascular 

plants, Lemna gibba, Myriophyllum spicatum and Myriophyllum sibiricum. The authors present 

effects concentrations for several different endpoints for each species. The lowest EC50s for 

each were 618, 222 and 341 mg/L TFA, respectively. It interesting to note that the EC50 for L. 

gibba using frond number from Berends et al. (913 mg/L) was very similar to that calculated by 

Hanson and Solomon (884 mg/L) for this same endpoint (the EC50 from Berends et al. was 

corrected for TFA only). In the European Union initial risks to aquatic vascular plants are 

evaluated by dividing the EC50 from a standard test using Lemna (usually L. gibba) by 10. This 

is generally considered to result in a threshold concentration protective of aquatic vascular 

plants. In the case of TFA this would be ca. 90 mg/L. 

Benesh, et al. (2002) evaluated the potential toxic effect of TFA to species common in vernal

pools (dry in summer). They studied the effects on microbial communities as well as on 

germination and growth or several wetland plant species. The following summary is from their 

abstract.

Microbial respiration for three vernal pool soils and an agricultural soil was not affected 

by TFA exposures (0, 10, 100, 1,000, and 10,000 mg/L), and degradation of TFA by 

microbial communities was not observed in soils incubated for three months. 

Trifluoroacetate accumulated in foliar tissue of wetland plant species as a function of 

root exposure concentration (100 and 1,000 mg/L TFA), and accumulation was found to 

stabilize or decrease after the second or third month of exposure. Seeds accumulated 

TFA as a function of root exposure concentration; however, germination success was 

not affected. No adverse physiological responses, including general plant health and 

photosynthetic and conductance rates, were observed for root exposures at the TFA 

concentrations used in this study. Based on the soils and plant species used in this 

study, predicted TFA concentrations will not adversely affect the development of soil 

microbial communities and vernal pool plant species.

Finally, Hanson and Solomon (2004b) summarized the risks to freshwater aquatic plants of 

several different haloacetic acids (HAA) of which TFA was one. Their main conclusions are 

summarized below from their paper.

Haloacetic acids at current environmental concentrations do not pose a threat to these 

aquatic plants in European, Canadian or African freshwater systems as concluded 

through the use of both deterministic and probabilistic methods of ecological risk 

assessment. Several orders of magnitude separate effects concentrations from 

exposure concentrations for these HAAs. Even mixtures of HAAs do not appear to pose 

a significant risk to these plants. Myriophyllum spp. and L. gibba are not exceptionally 

sensitive to HAA toxicity. Most effect measures are in the mg/l range and some 

endpoints, especially pigments, do not exhibit effects until the g/l range. Current 

concentrations of HAAs in the environment rarely exceed the ng/l range. The 

degradation products of HAAs are carbon dioxide and halide ions and in themselves do 

not pose a risk to these plants.
I hope this brief summary helps. I am sorry that I could not help relative to the environmental 

fate questions. 

Ginger

_____________________________

Virginia C. Moser, Ph.D., D.A.B.T.

Acting Regulatory Support Coordinator

Research Planning and Coordination Staff

Toxicity Assessment Division (MD B105-04)

US Environmental Protection Agency

Research Triangle Park, NC 27711

(919) 541-5075