Adverse Effects
Chlorodifluoromethane (Freon 22)
CAS No. 75-45-6

 
 

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ACTIVITY: Insecticide, Fungicide, Propellant, EPA List 2 Inert (Halogenated organic)
Structure:

Adverse Effects:
Body Weight Decrease
Brain
Cancer:
limited evidence, fibrosarcomas
Cholesterol
CNS

Endocrine: Adrenal
Endocrine: Pituitary
Eye -
Microphthalmia and Anophthalmia
Heart
Kidney
Liver
Lung
Mutagenic (Eye)
Salivary Glands
Spinal Cord
Tremors

Environmental

Chlorodifluoromethane is produced extensively for use in refrigeration and air conditioning; significant quantities are subsequently released into the atmosphere, resulting in widespread, low-level human exposure. Occupational exposure to chlorodifluoromethane occurs during its production and use.
Ref: IARC 1986.
http://www.fluorideaction.org/pesticides/chlorodifluoromethane.iarc.htm


Animal Data - INHALATION: 4 hour, LC50, rat: 220,000 ppm.

The compound is a skin irritant and a slight eye irritant, but is not a skin sensitizer in animals. Effects from single high exposures include central nervous system depression, anesthesia, rapid breathing, lung congestion and microscopic liver changes. Cardiac sensitization occurred in dogs at 50,000 ppm or greater from the action of exogenous epinephrine... Long-term exposures to 50,000 ppm (v/v) of vapors produced organ weight increases and a decrease in body weight gain... In chronic inhalation studies, "FREON" 22, at a concentration o 50,000 ppm (v/v), produced a small, but statistically significant increase of late-occurring tumors involving salivary glands in male rats, but not female rats or male or female mice...

"FREON" 22 was mutagenic in some strains of bacteria in bacterial cell cultures, but not mammalian cell cultures or animals. It did not cause heritable genetic damage in mammals.

A slight, but significant increase in developmental toxicity was observed at high concentrations (50,000 ppm) of "FREON" 22, a concentration which also produced toxic effects in the adult animal. Based on these findings, and other negative developmental studies, "FREON" 22 is not considered a unique hazard to the conceptus. Studies of the effects of "FREON" 22 on male reproductive performance have been negative. Specific studies to evaluate the effect on female reproductive performance have not been conducted...

Ref: Material Safety Data Sheet for Freon 22. DuPont. 1996.

 

Body Weight Decrease (click on for all fluorinated pesticides)

Long-term exposures to 50,000 ppm (v/v) of vapors produced organ weight increases and a decrease in body weight gain...
Ref: Material Safety Data Sheet for Freon 22. DuPont. 1996.
http://www.fluoridealert.org/pesticides/chlorodifluoromethane.msds.pdf

The Registry of Toxic Effects of Chemical Substances
Methane, chlorodifluoro - RTECS #: PA6390000
NIOSH - National Institute for Occupational Safety and Health
ROUTE/ ORGANISM DOSE EFFECT REFERENCE
oral rat lowest published toxic dose: 2,457 mg/kg/26 week- intermittent

Brain and Coverings: Other degenerative changes

Blood: Changes in other cell count (unspecified)

Nutritional and Gross Metabolic: Weight loss or decreased weight gain

Gigiena i Sanitariya. For English translation, see HYSAAV. (V/O Mezhdunarodnaya Kniga, 113095 Moscow, USSR). V 48(8): 69,1983.

Brain  (click on for all fluorinated pesticides)

The Registry of Toxic Effects of Chemical Substances
Methane, chlorodifluoro - RTECS #: PA6390000
NIOSH - National Institute for Occupational Safety and Health
ROUTE/ ORGANISM DOSE EFFECT REFERENCE
inhalation mouse lowest published toxic concentration: 50 gm/m3/6 hour/43 week- intermittent Brain and Coverings: Other degenerative changes

Spinal Cord: Other degenerative changes

Behavioral: Alteration of classical conditioning

Trudy Leningradskogo Sanitarno-Gigienicheskogo Meditsinskogo Instituta. (Leningrad, Russia).
V 75: 231,1963.

oral rat lowest published toxic dose: 2,457 mg/kg/26 week- intermittent

Brain and Coverings: Other degenerative changes

Blood: Changes in other cell count (unspecified)

Nutritional and Gross Metabolic: Weight loss or decreased weight gain

Gigiena i Sanitariya. For English translation, see HYSAAV. (V/O Mezhdunarodnaya Kniga, 113095 Moscow, USSR). V 48(8): 69,1983.

Reports on fatalities of chlorofluorocarbons usually involve chlorotrifluoroethane, trichlorofluoromethane, dichlorodifluoromethane or chlorodifluoromethane, where analysis was done using packed column gas chromatography. In this case a death was caused by an azeotropic mixture of chlorodifluoromethane & chloropentafluoroethane, a combination that has not previously been reported in the forensic literature. This report details the analysis using mass selective detection employing capillary gas chromatography columns currently used in many toxicology laboratories. Postmortem toxicology revealed blood concns of chlorodifluoromethane & chloropentafluoroethane of 71 mg/L & 0.30 mg/L, respectively. Brain, liver, & lung concns of chlorodifluoromethane were (mg/kg) 2.8, 4.4, and 1.6, respectively. Brain, liver, & lung concns of chloropentafluoroethane were (mg/kg) 0.80, 0.80, & 0.11, respectively. The victim's blood contained 5.5 mg/L caffeine. Lidocaine, used in resuscitation attempts, was also present in the victim's blood. No other alkali-extractable drugs or volatile alcohols were detected in the victim's blood. The cause of death was acute respiratory arrest due to chlorofluorocarbon inhalation.
Ref: Fitzgerald RL et al; J Forensic Sci 38 (2): 477-483 (1993); cited in the TOXNET profile from the Hazardous Substances Data Bank.
http://www.fluoridealert.org/pesticides/chlorodifluoromethan.toxnet.htm

Cancer (click on for all fluorinated pesticides)

Experimental data. Chlorodifluoromethane was tested for carcinogenicity in one experiment in rats by oral administration by gavage and in experiments in rats and mice by inhalation exposure. No increase in tumour incidence was observed in rats after oral administration. The inhalation study in mice was inconclusive for males, and negative results were obtained for females. In the inhalation study in rats, males receiving the high dose had increased incidences of fibrosarcomas and Zymbal-gland tumours; negative results were obtained for female rats...
Evaluation:
There is limited evidence for the carcinogenicity of chlorodifluoromethane to experimental animals.
Ref: 5. Summary of Data Reported and Evaluation. International Agency for Research on Cancer IARC. 1986

http://www.fluorideaction.org/pesticides/chlorodifluoromethane.iarc.htm

Cholesterol (click on for all fluorinated pesticides)

Lee and Suzuki (1981) exposed groups of 16 male Sprague-Dawley rats to 0 or 50,000 ppm HCFC-22 for 5 hours/day, 7 days/week for 8 weeks (duration- adjusted concentrations = 0 or 36,800 mg/cu.m, respectively). Six rats/group were sacrificed at 8 weeks, and the rest were used in a fertility study (discussed below). The only exposure-related effects noted were a slight decrease in prostate weight (without accompanying histopathological changes), an increase in plasma cholesterol, and decreases in plasma glucose and triglycerides. The toxicological significance of these changes is not clear because functional studies on adrenal or hepatic function were not undertaken, and there were no histopathological changes in these organs. Nevertheless, a LOEL of 50,000 ppm [LOEL(HEC) = 36,800 mg/cu.m] can be estimated from this study.
Ref: US EPA IRIS (Integrated Risk Information System).
http://www.fluoridealert.org/pesticides/chlorodifluoromethane.iris.htm

CNS (click on for all fluorinated pesticides)

The substance may cause effects on the cardiovascular system and central nervous system, resulting in cardiac disorders and central nervous system depression.
Ref: ICSC: 0049. March 2002. International Programme on Chemical Safety (IPCS).
http://www.inchem.org/documents/icsc/icsc/eics0049.htm

Potential Health Effects - Inhalation of high concentrations of vapor is harmful and may cause heart irregularities, unconsciousness or death. .. Human Health Effects: Higher exposures may lead to temporary alteration of the heart's electrical activity with irregular pulse, palpitations, or inadequate circulation. Fatality may occur from gross overexposure. Individuals with preexisting diseases of the central nervous or cardiovascular system may have increased susceptibility to the toxicity of excessive exposures.
Animal Data - INHALATION: 4 hour, LC50, rat: 220,000 ppm. The compound is a skin irritant and a slight eye irritant, but is not a skin sensitizer in animals. Effects from single high exposures include central nervous system depression, anesthesia, rapid breathing, lung congestion and microscopic liver changes...
Ref: Material Safety Data Sheet for Freon 22. DuPont. 1996.
http://www.fluoridealert.org/pesticides/chlorodifluoromethane.msds.pdf
.

Endocrine: Adrenal and Pituitary (click on for all fluorinated pesticides)

Increased kidney, adrenal and pituitary weights... The female rats in the 50,000-ppm group exhibited a statistically significant increase in liver (absolute and relative), kidney (absolute), adrenal (absolute), and pituitary (absolute, at interim sacrifice--pituitaries were not weighed at terminal sacrifice) weights. No nonneoplastic histopathological changes attributable to exposure to HCFC-22 were observed. The liver weight effect was not considered adverse because it did not exceed a 10% weight change and there was no histopathology observed. Based on effects on kidney, adrenal, and pituitary weight, a NOAEL of 10,000 ppm [NOAEL(HEC) = 5260 mg/cu.m] and a LOAEL of 50,000 ppm [LOAEL(HEC) = 26,300 mg/cu.m] can be estimated.
Ref: US EPA IRIS for Chlorodifluoromethane.
http://www.fluoridealert.org/pesticides/chlorodifluoromethane.iris.htm

Eye - Microphthalmia and Anophthalmia (click on for all fluorinated pesticides)

Chlorodifluoromethane (FC-22) was evaluated for embyotoxicity and teratogenicity in groups of 40 pregnant Charles River rats exposed to the test substance by inhalation at concentrations of 0, 0.05, 0.10, and 2.00% on days 6-15 of gestation. No clinical signs of toxicity were observed in maternal animals. The number of implantations, early and late resorptions, and number of live fetuses per litter were unaffected. There was a sporadic appearance of major malformations of the eye in all test groups. The increased incidence of eye defects was not statistically significant. Authors believe that the test substance may have interacted with the genetic make-up of affected fetuses and caused the increased expressivity of a mutant gene. The authors considered the test substance to be a mutagen under the conditions of this study.
Ref: 1992 - INITIAL SUBMISSION: EMBRYOTOXIC AND TERATOGENIC STUDIES IN RATS WITH INHALED CHLORODIFLUOROMETHANE WITH COVER LETTER DATED 06-15-92 AND ATTACHMENTS. HASKELL LABORATORY. Report Nos. NTIS/OTS0540606 and EPA/OTS; Doc #88-920004258.

Chlorodifluoromethane causes malformations of the eyes of fetal rats, but has no reproductive effect in male rats and does not cause prenatal toxicity in rabbits following exposure by inhalation.
Ref: 5. Summary of Data Reported and Evaluation. International Agency for Research on Cancer IARC. 1986

http://www.fluorideaction.org/pesticides/chlorodifluoromethane.iarc.htm

Palmer et al. (1978a) conducted a large developmental study in an attempt to elucidate the role of CFC-22 exposure in the eye lesion seen in the previous studies (see Culik et al., 1977, and Culik and Crowe, 1978, in the Additional Studies/Comments section). In this study, an experimental design was used in which 34 control pregnant rats were used, and 22/group were exposed to 100, 1000, or 50,000 ppm of CFC-22 (354, 3,540, or 176,800 mg/cu.m, respectively) for 6 hours/day on gestation days 6-15. This protocol was repeated 19 times so that more than 6000 control fetuses and 4000 fetuses from each exposed group were thoroughly examined for the eye defect... The eye abnormalities (small or missing eye) were noted again in all exposure groups, but statistical significance for these effects was achieved only in the 50,000-ppm group. The combined incidences of microphthalmia and anophthalmia were 3/607, 5/393, 3/390, and 10/383 in the control, 100, 1000, and 50,000-ppm groups, respectively. Additional data on the control incidence of the eye effects during 10 years after the Palmer et al. (1978a) study was conducted are presented in European Chemical Industry Ecology and Toxicology Center (ECETOC) (1989). The data were analyzed in blocks of 19 studies, and the control incidence in the first six blocks was similar to the controls in the Palmer study, while in later studies, the control incidence increased (0.4-2.4% in the last four blocks) and, in one experiment, was similar to the incidence found in the high-dose group in the Palmer study (2.6%). The incidence of the eye abnormality in the high-concentration group in the Palmer et al. (1978a) study is significantly increased compared with the overall controls in the studies conducted in the 10-year period after the study (ECETOC, 1989), adding strength to the interpretation that this is an adverse, treatment-related effect. This study identifies a LOAEL for maternal weight, fetal weight, and fetal abnormalities at 50,000 ppm. The LOAEL(HEC) is 176,800 mg/cu.m for the fetal effects (no duration adjustment is applied) and 44,200 mg/cu.m for the maternal toxicity (exposure is adjusted for duration).
Ref: US EPA IRIS for Chlorodifluoromethane.
http://www.fluoridealert.org/pesticides/chlorodifluoromethane.iris.htm

Teratogenicity was evaluated in 4 groups of 19 pregnant CD female rats receiving Arcton 22 via inhalation at concentration levels of 0, 100, 1,000 and 50,000 ppm for 6 hours per day on gestation days 6 through 15. There were no treatment-related effects in appearance, behavior, mortality, or pregnancy rate. At 50,000 ppm maternal weight gain was slightly lower than the control. There were no effects on body weight at 100 or 1,000 ppm. In all test groups litter size, post-implantation loss, litter wight, and mean fetal weight were similar to the control. At 50,000, there was an increased incidence of anophthalmic fetuses.
Ref: 1989 -  EFFECT OF ACRTON 22 ON PREGNANT RATS: RELATIONSHIP TO ANOPHTHALMIA AND MICROPHTHALMIA WITH ATTACHMENTS AND COVER LETTER DATED 07-05-89. Report Nos. NTIS/OTS0520413 and EPA/OTS; Doc #87-890000011

Anophthalmic definition: Absence of an eye(s).  It can be a congenital (born without) or an acquired condition (surgically removed).
Heart (click on for all fluorinated pesticides)

The substance may cause effects on the cardiovascular system and central nervous system, resulting in cardiac disorders and central nervous system depression.
Ref: ICSC: 0049. March 2002. International Programme on Chemical Safety (IPCS).
http://www.inchem.org/documents/icsc/icsc/eics0049.htm

Potential Health Effects - Inhalation of high concentrations of vapor is harmful and may cause heart irregularities, unconsciousness or death. .. Human Health Effects: Higher exposures may lead to temporary alteration of the heart's electrical activity with irregular pulse, palpitations, or inadequate circulation. Fatality may occur from gross overexposure. Individuals with preexisting diseases of the central nervous or cardiovascular system may have increased susceptibility to the toxicity of excessive exposures.
Ref: Material Safety Data Sheet for Freon 22. DuPont. 1996.
http://www.fluoridealert.org/pesticides/Chlorodifluoromethane.MSDS.pdf

PubMed abstract: Case report of a plumber's fatal work accident. Investigations on the causes of death made at post mortem showed that the worker had absorbed a large quantity of freon 22 (chlorodifluoromethane) which is known to be a narcotic agent and capable of inducing cardiac arrhythmia. It is believed freon inhalation was the cause of loss of consciousness with consequent death from drowning in the water issuing from the pipes. It is concluded that preventive measures need to be reinforced by adequate information to the workforce on the risks connected to this type of gas.
Ref: Med Lav 1992 Jul-Aug;83(4):361-4. [Sudden death caused by freon 22?]. [Article in Italian]; by M Dal Grande et al.

PubMed Abstract: After exposure to decomposed chlorodifluoromethane (freon-22), a 65-year-old man developed respiratory symptoms such as cough, blood-stained sputum, and increasing dyspnea. Three weeks later, his family doctor diagnosed infectious bronchitis. Another week later he died due to myocardial infarction. The discussion focuses on an inflammatory process caused by the inhalation of decomposed freon and its possible association with myocardial infarction.
Ref: Scand J Work Environ Health 2002 Jun;28(3):205-7, Inhalation of decomposed chlorodifluoromethane (freon-22) and myocardial infarction; by
Sjogren B, Gunnare S, Sandler H.

Kidney (click on for all fluorinated pesticides)

Increased kidney, adrenal and pituitary weights... The female rats in the 50,000-ppm group exhibited a statistically significant increase in liver (absolute and relative), kidney (absolute), adrenal (absolute), and pituitary (absolute, at interim sacrifice--pituitaries were not weighed at terminal sacrifice) weights. No nonneoplastic histopathological changes attributable to exposure to HCFC-22 were observed. The liver weight effect was not considered adverse because it did not exceed a 10% weight change and there was no histopathology observed. Based on effects on kidney, adrenal, and pituitary weight, a NOAEL of 10,000 ppm [NOAEL(HEC) = 5260 mg/cu.m] and a LOAEL of 50,000 ppm [LOAEL(HEC) = 26,300 mg/cu.m] can be estimated.
Ref: US EPA IRIS for Chlorodifluoromethane.

http://www.fluoridealert.org/pesticides/chlorodifluoromethane.iris.htm

Liver (click on for all fluorinated pesticides)

Animal Data - INHALATION: 4 hour, LC50, rat: 220,000 ppm. The compound is a skin irritant and a slight eye irritant, but is not a skin sensitizer in animals. Effects from single high exposures include central nervous system depression, anesthesia, rapid breathing, lung congestion and microscopic liver changes...
Ref: Material Safety Data Sheet for Freon 22. DuPont. 1996.

Lung (click on for all fluorinated pesticides)

Animal Data - INHALATION: 4 hour, LC50, rat: 220,000 ppm. The compound is a skin irritant and a slight eye irritant, but is not a skin sensitizer in animals. Effects from single high exposures include central nervous system depression, anesthesia, rapid breathing, lung congestion and microscopic liver changes...
Ref: Material Safety Data Sheet for Freon 22. DuPont. 1996.

Mutagenic (click on for all fluorinated pesticides)

Chlorodifluoromethane (FC-22) was evaluated for embyotoxicity and teratogenicity in groups of 40 pregnant Charles River rats exposed to the test substance by inhalation at concentrations of 0, 0.05, 0.10, and 2.00% on days 6-15 of gestation. No clinical signs of toxicity were observed in maternal animals. The number of implantations, early and late resorptions, and number of live fetuses per litter were unaffected. There was a sporadic appearance of major malformations of the eye in all test groups. The increased incidence of eye defects was not statistically significant. Authors believe that the test substance may have interacted with the genetic make-up of affected fetuses and caused the increased expressivity of a mutant gene. The authors considered the test substance to be a mutagen under the conditions of this study.
Ref: 1992 - INITIAL SUBMISSION: EMBRYOTOXIC AND TERATOGENIC STUDIES IN RATS WITH INHALED CHLORODIFLUOROMETHANE WITH COVER LETTER DATED 06-15-92 AND ATTACHMENTS. HASKELL LABORATORY. Report Nos. NTIS/OTS0540606 and EPA/OTS; Doc #88-920004258.

Teratogenicity was evaluated in 4 groups of 19 pregnant CD female rats receiving Arcton 22 via inhalation at concentration levels of 0, 100, 1,000 and 50,000 ppm for 6 hours per day on gestation days 6 through 15. There were no treatment-related effects in appearance, behavior, mortality, or pregnancy rate. At 50,000 ppm maternal weight gain was slightly lower than the control. There were no effects on body weight at 100 or 1,000 ppm. In all test groups litter size, post-implantation loss, litter wight, and mean fetal weight were similar to the control. At 50,000, there was an increased incidence of anophthalmic fetuses.
Ref: 1989 -  EFFECT OF ACRTON 22 ON PREGNANT RATS: RELATIONSHIP TO ANOPHTHALMIA AND MICROPHTHALMIA WITH ATTACHMENTS AND COVER LETTER DATED 07-05-89. Report Nos. NTIS/OTS0520413 and EPA/OTS; Doc #87-890000011

Anophthalmic definition: Absence of an eye(s).  It can be a congenital (born without) or an acquired condition (surgically removed).

Salivary Glands (click on for all fluorinated pesticides)

-- Groups of 80 male and 80 female Alderley Park Wistar-derived rats (age unspecified) were exposed by inhalation to 0 (2 groups), 1000, 10,000 or 50,000 ppm (0, 3540, 35,400 or 177,000 mg/cu m) chlorodifluoromethane (CFC 22; purity >99.8%) for 5 hr/day, on 5 days/wk for up to 118 (females) or 131 (males) wk, by which time approx 80% of animals had died. Body-wt gain was reduced in high-dose males up to wk 80. Treatment did not affect number of animals with benign tumors. Among males, the proportions of animals with malignant tumors were higher in treated groups (controls, 16/80 & 18/80; low-dose, 27/80; mid-dose, 22/80; high-dose, 33/80), due primarily to increases in incidences of fibrosarcomas (controls, 5/80 & 7/80; low-dose, 8/80; mid-dose, 5/80; high-dose, 18/80). The numbers of animals in which such tumors involved the salivary glands were, 1, 0, 1, 0 & 7, respectively. The increase in the overall incidence of fibrosarcomas occurred between weeks 105 & 130. In addition, 4 high-dose males had Zymbal-gland tumors, whereas no such tumor was found in males of the other groups. No increased incidence of malignant tumors was observed in treated females. [IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Geneva: World Health Organization, International Agency for Research on Cancer,1972-PRESENT. (Multivolume work).,p. V41 242 (1986)]
-- TSCA Test Submissions: Oncogenicity was evaluated in male and female Alderley Park rats (80/sex/group) exposed to chlorodifluoromethane via inhalation at 0 (2 groups), 1000, 10,000 and 50,000 ppm for 5 hrs/day, 5 days/week for 27-30 months. The only reported finding of significance was an increase in the incidence of malignant neoplasms, due mainly to fibrosarcoma of the salivary gland in both sexes at 50,000 ppm. The incidence of these tumors was significant only after 25 months. This preliminary report did not contain information concerning the histopathological results of the study. [ICI Americas, Inc.; Chlorofluorocarbon 22 (CFC 22 - chlorodifluoromethane). (1981), EPA Document No. FYI-OTS-0481-0111, Fiche No. 0111-0 ]
Ref: TOXNET profile from Hazardous Substances Data Base for Chlorodifluoromethane.
http://www.fluoridealert.org/pesticides/chlorodifluoromethan.toxnet.htm

Spinal Cord (click on for all fluorinated pesticides)

mouse lowest published toxic concentration: 50 gm/m3/6 hour/43 week- intermittent Brain and Coverings: Other degenerative changes: Spinal Cord. Other degenerative changes. Behavioral: Alteration of classical conditioning. [Trudy Leningradskogo Sanitarno-Gigienicheskogo Meditsinskogo Instituta. (Leningrad, Russia) 75,231,1963]
Ref: NIOSH. Registry of Toxic Effects. July 2000.
http://www.fluoridealert.org/pesticides/chlorodifluoromethane.niosh.htm#TLSMA6

Tremors (click on for all fluorinated pesticides)

... GUINEA PIGS SHOWED DEFINITE NERVOUS SYSTEM RESPONSE TO CONCN OF 16% BY VOL IN AIR, OVER PERIOD OF 55 MIN. THEY SHOWED TREMORS & CONVULSIVE MOVEMENTS BUT RECOVERED ON REMOVAL. AT 40%, THEY SHOWED TREMORS & WERE HELPLESS OVER A PERIOD OF 2.5 HR BUT RECOVERED ... AT CONCN OF 58%, DEATH OCCURRED IN 8 MIN. [Patty, F. (ed.). Industrial Hygiene and Toxicology: Volume II: Toxicology. 2nd ed. New York: Interscience Publishers, 1963. 1324]
Ref: TOXNET profile from Hazardous Substances Data Base for CHLORODIFLUOROMETHANE

http://www.fluoridealert.org/pesticides/chlorodifluoromethan.toxnet.htm

Environmental (click on for all fluorinated pesticides)

"Dangerous for the ozone layer"
Ref: OBSERVATION LIST: examples of substances requiring particular attention second, revised edition, 1998. Issued by the Swedish National Chemicals Inspectorate in collaboration with the Swedish Environmental Protection Agency and the Swedish National Board of Occupational Safety and Health.
http://www.fluorideaction.org/pesticides/sweden.dangerous.subs.1998.pdf

Abstract: Chlorodifluoromethane (HCFC-22), the most widely used substitute for chlorofluorocarbons, is currently emitted into the atmosphere at a global rate of about 220,000 tyr-1. In this work, national emissions of HCFC-22 for the year 1990 are estimated using the calculated emissions of CFC-12 as a surrogate distribution function. The releases so calculated match the sp arse published data in most cases.
Ref: Estimated national releases to the atmosphere of chlorodifluoromethane (HCFC-22) during 1990; by Pauline M. Midgley and Archie McCulloch. Atmospheric Environment ; Volume 31, Issue 6 , March 1997, Pages 809-811.

 
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