## MEMORANDUM

To: Margaret Sheppard ; U.S. EPA Cc Melissa Fiffer, Monica Shimamura, and Bella Maranion, U.S.EPA From: Neha Mukhi, Candace Prusiewicz, Reva Rubenstein , Ed Carr, Emily Herzog, and Mark Wagner ; ICF International Date: July 20 , 20 10 Re: Summary of HFO - 1234yf Breakdown Products and Impacts of Aldehydes (Deliverable under EPA Contract Number EP - W - 06 - 008 Task Order 0 38 , Task 0 1 ) On December 19, 2009, EPA received a comment on the proposed rule, Protection of the Stratospheric Ozone: New S

ubstitute in the Motor Vehicle Air Conditioning Sector under the Significant New Alternatives Policy (SNAP) Program (EPA -HQ - OAR- 2008 - 0664) , stating : A first analysis based on a slide presentation given at the Montreal Protocol Geneva meeting in July 2009 by the Scientific Assessment Panel shows possible reaction processes and suggests that given the high chemical reactivity of unsaturated HFCs the toxic impact of aldehydes would be higher than that of carbonic acids. 1 HFOs could thus harm the human nervous system. At the same time, given that all aldehydes formed as end products are water- soluble and will be leached from the atmosphere, the aldehydes formed as end products of HFOs will be environmental pollutants. In response to this comment, ICF has reviewed data on the atmospheric chemistry of HFO - 1234yf , HFC 152a, and HFC - 134a and their degradation products. This memorandum summarizes ICF’s analysis of the possible pathways for atmospheric degradation of HFO - 1234yf and the impacts of the aldehydes produce d as degradation products . Please contact Mark Wagner at 202 - 862 - 1155 with any questions or comments.

1 See page 17 of Newman et al. (2009). HCFCs and HFCs: An Update from the Scientific Assessment Panel., available from http://www.r744.com/files/news/HCFCs - HFCs - An -update - from- the - SAP.pdf- 1 -

ATMOSPHERIC DEGRADATION OF HFO - 1234yf Hydrofluoro carbons, HFC - 134a and HFC - 152a , and hydrofluoro o lefins such as HFO - 1234yf , undergo atmospheric degradati on reactions via numerous pathways including oxidation with chlorine ato ms and hydroxyl (OH) radicals ; interaction with OH radicals is the predominant degradation reaction. The chemical degradation pathway is complex and includes numerous radical species and short - lived intermediates. The most prevalent , s table , and toxicologically relevant to human health end-products are summarized and discussed here. The major atmospheric oxidation product of HFO - 1234yf is trifluoroacetyl fluoride ( C F 3 COF ) . For chlorine - ( Cl ) initiated oxidation reactions C F 3 COF is formed in approximately 92 % of the reactions along with 56% of the reactions forming formyl chloride (HCOCl), also formed are carbon monoxide ( CO ) , and peroxy radical reactions with NO to form NO 2 (shown as XO 2 ) . Other products are formed but are not carried in the assessment as they either become unreactive or are not important to the final reaction products of interest. The predominant Cl - initiated degradation products of HFO - 1 234yf are summarized in Reaction #1 assuming freely available nitrogen (N2 ) and oxygen (O 2 ). This reaction pathway is likely to be important in the marine environment where Cl is found in greater abundance. N 2 + O 2 CF 3 CF=CH 2 + Cl CF 3 COF + HCOCl + CO + XO 2 (Reaction #1) Hydroxyl mediated oxidation is considered the predominant degradation pathway of HFO - 1234yf (Luecken et al., 20 1 0) . C F 3 COF is formed in nearly all OH - initiated oxidation degradation of HFO 1234yf along with formaldehyde (HCHO) and hydroperoxy radicals (HO 2 ) and peroxy radical reactions with NO to form NO 2 (shown as XO 2 ) (Hurley et.al., 2007 ; Luecken et al., 20 10 ) . N 2 + O 2 CF 3 CF=CH 2 + OH CF 3 COF + HC HO + XO 2 + HO 2 (Reaction #2) CF 3 COF, the predominant atmospheric degradation product of HFO - 1234yf , is hydrolyzed to trifluoroacetic acid ( C F 3 COOH) in the hydrosphere ( Pap adimitriou et al., 200 8 ) . Due to the formation of peroxy radicals, the concentration of ground level ozone will also consequently increase (Luecken et al., 20 10 and Papadimitriou, et al., 2008). This ground level o zone reacts with propene in the atmosphere leading to the formation of acetaldehyde. Therefore, this secondary effect from the degradation of HFO - 1234yf will lead to a minor increase in the concentration of acetaldehyde. ATMOSPHERIC DEGRADATION OF HFC - 134 a AND HFC - 152 a Like HFO - 1234yf, the primary de gradation pathway of HFC - 134a is initiated with tropospheric hydroxyl radicals. However, HFC - 134a reacts less readily with OH than HF O - 1234yf reacts with OH . The presence of nitrogen oxides (NO x) in the atmosphere also influences the degradation products formed from HFC - 134 a . The major atmospheric oxidation product s of HF O - 134a are carbonyl fluoride ( COF 2 ) , CF 3 CO F , formyl fluoride ( HCOF ) , and HC O OH , as depicted in Reaction #3 (Kotamarthi et al., 1998) . C O F 2 is rapidly hydrolyzed in the presence of water to form HF (hydro gen fluoride) and CO 2 (carbon dioxide) . In addition, HCOF decomposes at room temperature to form HF and CO

. Because the reaction rate of HFC - 134a with hydroxyl radicals is slower than the reaction rate of HFO - 1234yf with hydroxyl radicals, it is estimated that HFC - 134a will produce s maller yields of CF 3 COOH

—7 to 21 percent

—from the hydrolysis of CF 3 COF (Wallington et al., 1996) .

CF 3 CH 2 F  COF 2 + CF 3 COF + HCOF + HCOOH (Reaction # 3 )- 2 -

HFC - 152a is oxidized in the atmosphere in a similar manner as HFC - 1 34 a and HFO - 1234yf . H owever the maj or end-product of HFC - 152a is chemically dissimilar. In the absence of NO x , HFC 152a is oxidized to predominantly form COF 2 for about 97% of the reactions. In about 3% of the reactions the presence of NO x , causes both C OF 2 and C F 3 COF to be formed ; the concentration of C F 3 COF increas es as the concentration of available NO increases . It ’s estimated that the bulk (> 75%) of HFC - 152a is atmospherically degraded to form COF 2 while approximately 25 % is converted to CF 3 COF (T aketani et al., 2005) . CH3 C HF 2  COF 2 + CF 3 COF (Reaction #4) Table 1 : Comparison of Atmospheric Degradation Products initiated by OH Compound HFC - 134a HFC - 152a HFO - 1234yf Form ula CF 3 CH 2 F CH 3 CHF 2 CF 3 CF=CH 2 IUPAC name 1,1,1,2 -tetrafluoroethane 1,1 - difluoroethane 2,3,3,3 - tetrafluoropropene Atmospheric lifetime 1 4.4 years 1.4 years 11 days k (OH + HFC or HFO) 3.37 x 10 - 15 (a) cm3 /molecule . sec 3.08 x 10 - 14 (b) cm3 /molecule . sec 1.05 x 10 - 12 exp ( - 35/T) (c) cm3 /molecule . sec Majo r atmospheric oxidation products initiated by OH CF 3 COF (trifluoroacetyl fluoride) COF 2 (carbonyl fluoride) HCOF (formyl fluoride ) CF 3 COF (trifluoroacetyl fluoride ) COF 2 (carbonyl fluoride) CF 3 COF (trifluoroacetyl fluoride) HCHO (formaldehyde) Hydroperoxyl radical (HO 2 ) NO 2 Further conversion of major atmospheric oxidation products COF 2 converted into CO 2 and HF within 1 - 2 weeks. CF 3 COF further hydrolyzed to CF 3 COOH (trifluoroacetic acid). HCOF decom

poses to HF and CO COF 2 converted into CO 2 and HF within 1 - 2 weeks. CF 3 COF further hydrolyzed to CF 3 COOH (trifluoroacetic acid). CF 3 COF further hydrolyzed to CF 3 COOH (trifluoroacetic acid).

Sources: (a) Franklin (1993); (b) Taketani et al. (2005); (c) Papadimitriou, et al. (2008). ALDEHYDES FROM HFO - 1234yf ARE NOT A CONCERN The primary atmospheric degradation products of HFO - 1234yf, HFC - 1 34 a, and HFC - 152 a are summarized in Table 1. Although the atmospheric degradation products of HFO - 1234yf, HFC - 134a , and HFC - 152a are similar and all include CF 3 COH , the quantities in which they are produced differ because HFO - 1234yf

, an unsaturated hydro fluorocarbon, reacts more rapidly with OH radicals compared with HFC - 134 a and HFC - 152a , saturated hydrofluoro carbons . The remaining paragraphs provide an overview of the physical and chemical properties of aldehydes, exposure levels of concern and related impacts, projected maximum increases in daily average concentrations of formaldehyde, and a discussion on why aldehydes formed due to atmospheric degradation of HFO - 1234yf are not a concern. Formaldehyde is an ubiquitous, colorless gas with a pungent, suffocating odor at room temperature; the odor threshold for formaldehyde is 0.83 ppm (830,000 ppt) . Acetaldehyde is a colorless liquid with an odor threshold of 0.21 ppm (21 0,000 ppt) . The major acute and chronic toxic effects associated with exposures to either aldehyde are eye, nose, and throat irritation and effects on the nasal cavity. Other effects seen from exposure to high levels of formaldehyde in humans are- 3 -

coughing, wheezing, chest pains, and bronchitis. Animal studies have reported effects on the nasal respiratory epithelium and lesions in the respiratory system from chronic inhalation exposure to formaldehyde and acetaldehyde . EPA has not established a Reference Concentration (RfC ) for formaldehyde . However, the Agency for Toxic Substances and Disease Registry (ATSDR) has established a chronic inhalation minimal risk level (MRL) of 0.0 03 ppm ( 3,000 ppt or 0.004 mg/m3 ) based on respiratory effects in humans. The MRL is an estimate of the average daily human exposure to a hazardous substance that is likely to be without appreciable risk of adverse non- cancer health effects over a specifie d duration of exposure. EPA considers formaldehyde to be a probable human carcinogen (cancer- causing agent) based on limited evidence in humans and sufficient evidence in laboratory animals and has ranked it in EPA's Group B1. 2 EPA has established a Reference Concentration (RfC) of 0.005 ppm ( 5,000 ppt or 0.009 mg/m3 ) for acetaldehyde. EPA considers acetaldehyde as a “probable human carcinogen" and IARC classifies it as "possib ly carcinogenic to humans" based on increased incidences of nasal tumors in animal studies . OSHA has established a PEL ( 8 hr TWA) of 200 ppm (2 x 10 8 ppt) for acetaldehyde . 3 Using an extended version of the carbon bond five chemical mechanism as developed by Luecken et al. (20 10 ) and incorporating the gaseous and aqueous chemistry of HFO - 1234yf and its products, EPA’s CMAQ model version 4.7 with a 36 x 36 -km grid resolution was used to estimate the difference between the existing daily average c oncentrations of formaldehyde and acetaldehyde in Houston and L os Angeles and the increase in concentrations from the introduction of HFO - 1234yf . Emission assumptions of HFO - 1234yf were based on the worst case scenario developed for ICF International’s Assessment of the Potential Impacts of HFO- 1234yf and the Associated Production of Trifluoroacetic Acid (TFA) on Aquatic Communities, Soil and Plants, and Local Air Quality (ICF International 2010) . The model provides the estimated change in daily average formaldehyde and acetaldehyde concentrations for each grid cell for both the Los Angeles and Houston regions. The value from the grid cell in each region with the greatest increase in concentration can then be selected . B ased on data for the last day of each month , the maximum increase in daily average concentrations of formaldehyde and acetaldehyde for each region are shown in Table 2. Table 2 : Maximum Increase in Daily Average Concentrations of Form aldehyde and Acetaldehyd e (ppt) Date Los Angeles Houston

Form aldehyde Acetaldehyde Form aldehyde Acetaldehyde Jan 31 1.96 0.07 0.09 0.01 Feb 28 0.41 0.01 0.03 0.05 Mar 31 4.42 0.47 0.14 0.02 Apr 30 8.64 0.36 0.44 0.04 May 31 7.02 1.15 0.13 0.02 Jun 30 3.39 0.23 0.30 0.03 Jul 31 2.40 0.09 0.25 0.03 Aug 31 1.51 0.10 0.09 0.01 Sep 30 6.06 0.24 0.22 0.02 Oct 31 0.57 0.01 0.17 0.01 Nov 30 0.30 0.02 0.06 <0.01 Dec 31 0.89 0.02 0.04 0.01 Average 3.13 0.23 0.16 0.02 Source: CMAQ model version 4.7 using chemistry developed b y Luecken et al. (2010)

2 http://www.epa.gov/ttn/atw/hlthef/formalde.html 3 http://www.epa.gov/chemfact/s_acetal.txt- 4 -

Itcan be conservatively assumed that the average of the maximum daily values on the last day of the month (see Table 2 ), for each modeled region , provide s an upper bound estimate of the annual average concentration increase for formaldehyde and acetaldehyde. As such, for Los Angeles and Houston, the formaldehyde concentration is expected to increase on average by no more than 3.13 ppt and 0.16 ppt, respectively. This increase is comparable to the estimated maximum annual average increase in formaldehyde concentrations of 1.1 ppt. reported by Kajihara et al. (2010) for the Kanto plain region in Japan from the atmospheric degradation of HFO - 1234yf. Further , these annual average increase s are well below the current annual average formaldehyde concentration for the United States , as determined at the county level across the US by the National Air Toxic Assessment (2002) , wh ere annual average formaldehyde concentrations range between 80 ppt (pristine) to 3, 300 ppt (New York, New York) . The National Air Toxic Assessment (2002) also determined the county level annual concentration for acetaldehyde, which ranges from 47 ppt to 3,100 ppt . This annual concentration is approximately three orders of magnitude higher than the projected annual average increase in acetaldehyde concentration for Los Angeles (0.23 ppt). Thus , changes in ambient formaldehyde and acetaldehyde concentrations from the introduction of HFO - 1234yf would be well below current background concentrations even in pristine environments. Finally, projected increases in formaldehyde concentrations in LA and Houston represent less than 0.1% and 0.005% of the MRL threshold concentration f or formaldehyde while the projected increases in acetaldehyde concentrations are less than 0. 005% of the RfC. As a result, increases in formaldehyde and acetaldehyde concentrations due to emissions of HFO - 1234yf are not expected to have an adverse effect on human health or the environment .- 5 -

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