CHAPTER 2-74: FREONS AND HALONS

INTRODUCTION

Freons (fluorocarbons and chlorofluorocarbons [CFCs]) historically have been widely used as aerosol propellants, in refrigeration units, in the manufacture of plastics, in foam blowing, metal and electronics cleaning, mobile air conditioning, and sterilization. Although the use of CFCs is being phased out to avoid further depletion of stratospheric ozone, freons remain in older refrigeration and air conditioning systems, and illicit importation of freons occurs. Most freons are gases at room temperature, but some are liquids (freons 11, 21, 113, and 114) and may be ingested. Specialized fire extinguishers contain closely related compounds known as halons, which contain bromine, fluorine, and chlorine. HCFCs (Hydrochlorofluorocarbons) and HFCs (hydrofluorocarbons) are being used as transitional refrigerants because they break down more easily in the atmosphere than CFCs.

MECHANISM OF TOXICITY

1. Freons are mild CNS depressants and asphyxiants that displace oxygen from the ambient environment. Freons are well absorbed by inhalation or ingestion and are usually rapidly excreted in the breath within 15–60 minutes.

2. Like chlorinated hydrocarbons, freons may potentiate cardiac arrhythmias by sensitizing the myocardium to the effects of catecholamines.

3. Direct freezing of the skin, with frostbite, may occur if the skin is exposed to rapidly expanding gas as it escapes from a pressurized tank.

4. Freons and halons are mild irritants and may produce more potent irritant gases and vapors (eg, phosgene, hydrochloric acid, hydrofluoric acid, and carbonyl fluoride) when heated to high temperatures, as may happen in a fire or if a refrigeration line is cut by a welding torch or electric arc.

5. Some agents are hepatotoxic after large acute or chronic exposure.

TOXIC DOSE

1. Inhalation. The toxic air level is quite variable, depending on the specific agent (see Table IV–4). Freon 21 (dichlorofluoromethane; TLV, 10 ppm [42 mg/m³]) is much more toxic than freon 12 (TLV, 2,000 ppm). In general, anesthetic or CNS-depressant doses require fairly large air concentrations, which can also displace oxygen, leading to asphyxia. The air level of dichloromonofluoromethane considered immediately dangerous to life or health (IDLH) is 5,000 ppm. Other TLV and IDLH values can be found in Table IV–4.

2. Ingestion. The toxic dose by ingestion is not known.

CLINICAL PRESENTATION

1. Skin or mucous membrane exposure can cause pharyngeal, ocular, and nasal irritation. Dysesthesia of the tongue is commonly reported. Frostbite may occur after contact with rapidly expanding compressed gas. Chronic exposure may result in skin defatting and erythema.

2. Respiratory effects can include cough, dyspnea, bronchospasm, hypoxemia, and pneumonitis.

3. Systemic effects of moderate exposure include dizziness, headache, nausea and vomiting, confusion, impaired speech, tinnitus, ataxia, and incoordination. More severe intoxication may result in coma or respiratory arrest. Ventricular arrhythmias may occur even with moderate exposures. A number of deaths, presumably caused by ventricular fibrillation, have been reported after freon abuse by "sniffing" or "huffing" freon products from plastic bags or air ...