The minimal metabolism of inhaled 1,1,1,2-tetrafluoroethane to trifluoroacetic acid in man as determined by high sensitivity 19F nuclear magnetic resonance spectroscopy of urine samples

The development of environmentally acceptable fluorocarbons

Chlorofluorocarbons (CFCs) were introduced in the 1930s as the safe replacements for the toxic and flammable refrigerants being used at that time. Subsequently, hydrochlorofluorocarbons (HCFCs) were also developed. In addition to refrigerant applications, they were used as foam blowing agents, as solvents and as propellants for many aerosols. In the 1970s and 1980s, concern developed about their environmental impact, specifically on stratospheric ozone depletion. Industry began to consider acceptable replacements. In 1987, many of the governments of the world came together and drafted the Montreal Protocol, calling upon Industry to initially phase out production of the CFCs and later HCFCs. Within 4 months of the signing of the Montreal Protocol, the 15 global major producers joined together to form the Alternative Fluorocarbons Environmental Acceptability Study (AFEAS), which sponsored research into environmental effects and the Program for Alternative Fluorocarbons toxicity Testing, PAFT), which examined the toxicology of potential replacements for the CFCs and HCFCs. Nine replacements were identified by companies and, through this international cooperation; toxicology programs were designed, conducted, and evaluated without duplication of effort and testing; consequently these new products were introduced within less than 10 years. Indeed the Montreal Protocol has been recognized as the most appropriate international treaty to phase-down HFCs. In 2016 the Kigali Amendment to the Montreal Protocol set out a phase-down schedule for the consumption and production of HFCs. In order to reduce the consumption and emissions of high GWP HFCs. Recently lower GWP HFCs and very low GWP HFOs (hydrofluoroolefins and HCFOs (hydrochlorofluoroolefins) have been introduced into a range of applications. Summaries of the toxicology profiles of some of the original CFCs and HCFCs, the replacements and the new post-PAFT replacements are described. The chemicals in this review include CFC-11, CFC-12, CFC-113, CFC-114, HCFC 22, HCFC-123, HCFC-124, HCFC-141b, HCFC-142b, HCF-32, HFC-125, HFC-134a, HFC-143a, HFC-152a, HFC-245ea, HFC-245fa, HFO-1234yf, HFO-1234ze, and HCFO-1233zd.

Quantification of Aerosol Hydrofluoroalkane HFA-134a Elimination in the Exhaled Human Breath Following Inhaled Corticosteroids Administration

Inhaled corticosteroids (ICS) and β2-agonists are the primary pharmacotherapies of asthma management. However, suboptimal medication compliance is common in asthmatics and is associated with increased morbidity. We hypothesized that exhaled breath measurements of the aerosol used in the inhaled medications might prove useful as surrogate marker for asthma medication compliance. To explore this, 10 healthy controls were recruited and randomly assigned to ICS (Flovent HFA) or short acting bronchodilators (Proventil HFA). Both inhalers contain HFA-134a as aerosol propellant. Exhaled breath sampling and pulmonary function tests were performed prior to the inhaler medication dispersion, immediately after inhalation, then at 2, 4, 6, 8, 24, and 48 hours postadministration. At baseline, mean (SD) levels of HFA-134a in the breath were 252 (156) pptv. Immediately after inhalation, HFA-134a breath levels increased to 300 × 10(6) pptv and were still well above ambient levels 24 hours postadministration. The calculated ratio of forced expiratory volume in 1 second over forced vital capacity did not change over time following inhaler administration. This study demonstrates, for the first time, that breath HFA-134a levels can be used to assess inhaler medication compliance. It may also be used to evaluate how effectively the medicine is delivered.

Toxicokinetics of 1,1,1,2-tetrafluoroethane (HFC-134a) in male volunteers after experimental exposure

The aim of this study was to determine the uptake and disposition of inhaled 1,1,1,2-tetrafluoroethane (HFC-134a) in humans. Ten male volunteers were exposed to 500 ppm HFC-134a (2 h, 50 W exercise). The HFC-134a levels were monitored in blood, exhaled air and urine up to 19 h post-exposure. The concentration in blood increased rapidly, reaching a plateau of 9.4+/-1.9 microM (mean+/-S.D.) within 30 min, followed by a fast post-exposure decrease. HFC-134a in expired air decreased rapidly as well and in parallel with that in blood. The post-exposure urinary excretion was 0.002% of the inhaled amount, and the half-time was 58 min (pooled data). A physiologically based toxicokinetic (PBTK) model was developed for further analysis. Experimental and simulated time courses in blood and exhaled air agreed well in all 10 subjects. Further, the late decay in blood was consistent with a wash-out of HFC-134a from fat tissues, with a half-time of 114+/-21 min. The simulated relative uptake during exposure was 3.7+/-0.5%. No remarkable findings were observed in the electrocardiographic recordings. Fibrinogen in plasma increased 1 day after exposure, whereas no effects on C-reactive protein, serum amyloid A protein, D-dimer or uric acid were seen. Further studies are needed to investigate the possible inflammatory response.

An overview of environmental hazards and exposure risk of hydrofluorocarbons (HFCs)

Hydrofluorocarbons (HFCs) are being used as replacements for chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) that cause significantly stratospheric ozone depletion and global warming. HFCs under commercial uses as cleaning solvents in the electronic components, blowing agent in the foamed plastics, refrigerant in the air conditioning units and refrigerators, fire suppression agent in the fire protection, propellant in the metered dose inhalers (MDIs), and dry etching agent in the semiconductor manufacturing. Among these HFCs, 1,1,1,2-tetrafluoroethane (HFC-134a) is the most widely used one. From the environmental, ecological, and health points of view, it is urgent to mitigate and control the emissions of these HFCs from a diversity of commercial applications and industrial processes. This article aims to introduce these HFCs in commercial uses and environmental hazards (i.e., global warming, photochemical potential, flammability safety, environmental partition and ecotoxicity). Further, the updated data on the human toxicity, occupational exposure and health risk of these HFCs (esp., HFC-134a) are addressed in this review paper.

Fluorine-19 or phosphorus-31 NMR spectroscopy: A suitable analytical technique for quantitative in vitro metabolic studies of fluorinated or phosphorylated drugs

Fluorine-19 or phosphorus-31 NMR (19F NMR or 31P NMR) spectroscopy provides a highly specific tool for identification of fluorine- or phosphorus-containing drugs and their metabolites in biological media as well as a suitable analytical technique for their absolute quantification. This article focuses on the application of in vitro 19F or 31P NMR to the quantitative metabolic studies of some fluoropyrimidine or oxazaphosphorine drugs in clinical use. The first part presents an overview of the advantages (non-destructive and non-selective direct quantitative study of the biological matrices) and limitations (expensive cost of the spectrometers, limited mass or concentration sensitivity) of NMR spectroscopy. The second part deals with the criteria to be considered for successful quantification by NMR (uniform excitation over the entire spectral width of the spectrum, resonance signals properly characterised by taking into account T1 values and avoiding NOE enhancements, optimisation of the data processing, choice of a suitable standard reference). The third and fourth parts report some examples of quantification of 5-fluorouracil, its prodrug capecitabine, 5-fluorocytosine and their metabolites in bulk solutions (biofluids, tissue extracts, perfusates and culture media) and heterogeneous media (excised tissues and packed intact cells) as well as cyclophosphamide and ifosfamide in biofluids. These two parts emphasise the high potential of in vitro 19F or 31P NMR for absolute quantification, in a single run, of all the fluorine- or phosphorus-containing species in the matrices analysed. The limit of quantification in bulk solutions is 1-3 microM for 19F NMR and approximately 10 microM for 31P NMR. In heterogeneous media analysed with 19F NMR, it is 2-5 nmol in excised tissues and cell pellets.

Acute neurobehavioral effects in rats from exposure to HFC 134a or CFC 12

1,1,1,2-Tetrafluoroethane (HFC 134a), a chlorine-free hydrofluoroalkane, is internationally replacing billions of pounds of dichlorodifluoromethane (CFC 12) for coolant, refrigerant and aerosol propellant applications. The ALC50 for HFC 134a in rats is 567,000 ppm for 4 h; its potential for cardiac epinephrine sensitization in beagle dogs is acceptable (75,000 ppm); and its capacity to induce carcinogenicity or developmental disorders in animals is minimal. HFC 134a, with a serum half life estimated at 4-11 min, has been accepted for use as a propellant in metered-dose inhalant products, implying a low human toxicity risk from periodic brief exposures. There has been little published human or animal research evaluating possible neurobehavioral toxicity from longer HFC 134a exposures, as may be expected to occur in operational scenarios. In this study, male Wistar rats were exposed to various concentrations of HFC 134a or CFC 12 for up to 30 min while performing in either a rotarod/motorized running wheel apparatus or in an operant chamber The relative neurobehavioral toxicity of CFC 12 and its ozone-depleting substance replacement HFC 134a was assessed by comparing both gross motor system incapacitation and more subtle changes in ability to perform an operant discrimination task. It was shown that exposure to HFC 134a or CFC 12 concentrations from 40,000 to 470,000 ppm, for up to 30 min, induced neurobehavioral deficits in every subject, ranging from reduced operant efficiency to apparent anesthesia. For neurobehavioral endpoints examined in these experiments, HFC 134a inhalation was shown to induce deficits more rapidly, and at lower concentrations when compared to CFC 12 exposure.

Development of an 19F NMR method for the analysis of fluorinated acids in environmental water samples

This investigation was carried out to evaluate 19F NMR as an analytical tool for the measurement of trifluoroacetic acid (TFA) and other fluorinated acids in the aquatic environment. A method based upon strong anionic exchange (SAX) chromatography was also optimized for the concentration of the fluoro acids prior to NMR analysis. Extraction of the analyte from the SAX column was carried out directly in the NMR solvent in the presence of the strong organic base, DBU. The method allowed the analysis of the acid without any prior cleanup steps being involved. Optimal NMR sensitivity based upon T1 relaxation times was investigated for seven fluorinated compounds in four different NMR solvents. The use of the relaxation agent chromium acetylacetonate, Cr(acac)3, within these solvent systems was also evaluated. Results show that the optimal NMR solvent differs for each fluorinated analyte. Cr(acac)3 was shown to have pronounced effects on the limits of detection of the analyte. Generally, the optimal sensitivity condition appears to be methanol-d4/2M DBU in the presence of 4 mg/mL of Cr-(acac)3. The method was validated through spike and recovery for five fluoro acids from environmentally relevant waters. Results are presented for the analysis of TFA in Toronto rainwater, which ranged from < 16 to 850 ng/L. The NMR results were confirmed by GC-MS selected-ion monitoring of the fluoroanalide derivative.