Occupational exposure to fluorinated hydrocarbons during refrigeration repair work

Asthma onset after exposure to fluorinated hydrocarbons in the presence of combustion

Fluorinated hydrocarbons, which can thermally degrade into toxic hydrofluoric acid, are widely used as, for example, cooling agents in refrigerators and air conditioning systems and as medical aerosol propellants. Hydrofluoric acid is a known causative agent of irritant-induced asthma. We report on two patients with asthma initiation shortly after exposure to fluorinated hydrocarbon-based cooling agents while welding or smoking cigarettes in a confined space. Both cases developed respiratory symptoms and headache and later demonstrated nonspecific bronchial hyperresponsiveness. In follow-up, asthma was persistent and responded poorly to asthma medication. Exposure to the fluorinated hydrocarbons themselves is unlikely to have caused asthma due to their low toxicity. Instead, exposure to small amounts of hydrofluoric acid via the thermal degradation of the fluorinated hydrocarbons was considered the most likely cause of asthma onset. This is supported by the typical clinical picture of irritant-induced asthma and acute symptoms resembling hydrofluoric acid poisoning. When fluorinated hydrocarbons are used in the presence of combustion, thermal degradation may lead to the formation of hydrofluoric acid. In confined spaces, this exposure may induce asthma via irritation. Welding, smoking, and other sources of combustion in confined spaces may be a risk in workplaces and other places in which fluorinated hydrocarbons are used.

Non-positive autoimmune responses against CYP2E1 in refrigeration mechanics exposed to halogenated hydrocarbons

The aim of the study was to determine if occupational exposure to hydrofluorocarbons (HFC) and hydrochlorofluorocarbons (HCFC) generates autoimmune responses against CYP2E1. HFCs and HCFCs have replaced the chlorofluorocarbons (CFC) in e.g. refrigeration installations and air-conditioning systems. During the substitution period, refrigeration mechanics reported symptoms like asthma, influenza-like reactions, and joint troubles. These symptoms resemble those of chronic inflammatory diseases with an autoimmune component. Since exposure to structurally similar chemicals, e.g. halothane, has previously been associated with autoimmune responses and diseases, autoimmunity among the refrigeration mechanics might hypothetically explain the reported inflammatory symptoms. Serum from 44 Swedish men, occupationally exposed to halogenated hydrocarbons, was screened for antibodies against CYP2E1 with enzyme-linked immunosorbent assay. Thirty of the workers had asthma, joint problems or influenza-like symptoms whereas 14 of them had no such symptoms. They were all selected from a cohort of 280 refrigeration mechanics. Unexposed, healthy, Swedish men (n=35) constituted control group. The study was approved by the Ethics Committee at Karolinska Institutet. No increase in autoantibodies against CYP2E1 was detected among the occupationally exposed workers as compared to the unexposed controls. Further, there was no difference in antibody titer between the exposed workers with symptoms and the exposed, asymtomatic workers or the unexposed controls. The present study does not completely exclude a connection between exposure and effect but makes the relation less likely at these exposure levels.

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.