Chloroethane

Chloroethane was first prepared by Basil Valentine in the 15th century by reacting ethanol with hydrochloric acid, and it was used as a general anesthetic in the late 19th century — including by Samuel White as an inhalation anesthetic in 1848. [1] Its extraordinarily low boiling point (12.3°C) means that when sprayed on skin, it evaporates instantly, cooling the skin surface to produce a topical numbing effect. This made it the spray of choice for topical anesthesia in minor dermatology procedures, sports injury assessment, and myofascial trigger point injection — the familiar 'freeze spray' used on athletic fields for decades. Industrially, chloroethane has been produced by the hydrochlorination of ethylene and used as a chemical intermediate (for ethyl cellulose), a blowing agent in polystyrene foam production, and historically as a refrigerant (designated R-160). [2] NTP carcinogenicity bioassays found clear evidence of uterine and hepatocellular tumors in female mice, and some evidence of carcinogenicity in male rats, supporting a probable carcinogen (Group B2) classification by EPA. The topical anesthetic use continued despite the carcinogen designation because dermal exposure is brief and the systemic absorption from topical freezing application is minimal. [3] Environmental releases are tracked from chemical manufacturing facilities, and chloroethane is a minor groundwater contaminant near some industrial sites.

Industrial workers manufacturing chloroethane or using it as a chemical intermediate are occupationally exposed by inhalation and skin contact. Medical and athletic training personnel who use ethyl chloride sprays frequently may have cumulative inhalation exposures. Persons who inhale chloroethane recreationally (it has been abused as an inhalant due to rapid CNS intoxication effects) face the highest acute exposures. The general public has negligible background exposure except from environmental releases near facilities.

The probable carcinogen classification based on rodent uterine and liver tumors is a concern for repeated occupational inhalation exposures. [2] Acute CNS effects from high concentrations include rapid intoxication, dizziness, and loss of consciousness — chloroethane is an inhalant of abuse with significant fatality risk from cardiac sensitization (sudden sniffing death syndrome). Like other halogenated hydrocarbons, it sensitizes the heart to epinephrine-induced arrhythmias. Prolonged or repeated inhalation at high concentrations can cause liver and kidney damage.

Industrial workers in ethyl chloride manufacturing and ethyl cellulose production face occupational exposures. Medical staff and athletic trainers who use ethyl chloride spray frequently are exposed to brief but regular inhalation doses. Young people abusing chloroethane as an inhalant are at highest risk for acute catastrophic outcomes.

1. Athletic trainers and medical personnel using ethyl chloride spray should use in well-ventilated areas and minimize their own inhalation during application. 2. Industrial workers require local exhaust ventilation and vapor monitoring. 3. Storage and use areas must be free of ignition sources — ethyl chloride is highly flammable (flashpoint -50°C). 4. Parents and educators should be aware that ethyl chloride sprays have been misused as inhalants. 5. The medical community should consider modern topical anesthetic alternatives (lidocaine gel, EMLA cream) that eliminate the inhalation hazard.