What is 1,1,1-trichloroethane?

The organic compound 1,1,1-trichloroethane (chemical formula: C₂H₃Cl₃ or CH₃CCl₃), also known as methyl chloroform, is a chloroalkane. It is a colourless liquid with a sweet odour, once produced in large industrial quantities as a solvent. It is regulated under the Montreal Protocol as an ozone-depleting substance, and its use has largely been phased out worldwide.

What is 1,1,1-trichloroethane used for?

Historically, 1,1,1-trichloroethane was widely applied in:

• Industrial solvents – for dissolving substances such as paints, glues, and coatings.
• Degreasing – for cleaning and removing oils from manufactured metal parts.
• Household products – in spot cleaners, adhesives, aerosol sprays, and similar formulations.

Environmental Effects

• Most environmental release occurs to the air, where the chemical can persist for ~6 years.
• In the atmosphere, it can travel to the ozone layer, where sunlight breaks it down into by-products that deplete ozone.
• From landfills and hazardous waste sites, it can leach into soil and groundwater.
• In surface waters (lakes/rivers), it evaporates quickly into the air.
• In soil and groundwater, it can move as a gas and re-enter the air.
• Some microorganisms in soil and water can break it down.
• It does not bioaccumulate in plants or animals.

Sources and Routes of Exposure

Sources of Exposure

General population

• Inhalation of low levels present in ambient air.
• Ingestion of very small amounts in drinking water or some foods.
• Use of older consumer products (cleaners, adhesives, aerosols) that still contain the compound.
• Intentional abuse (“sniffing”) of household products to achieve psychoactive effects.

Occupational populations

• Workers involved in the manufacture of 1,1,1-trichloroethane for export.
• Workers are exposed during its use as a chemical intermediate in hydrofluorocarbon production.

Routes of Exposure

• Inhalation – the primary route for the general population, workers, and people near hazardous waste sites.
• Oral ingestion – possible via contaminated drinking water, soil, or food.
• Dermal contact – through use of contaminated consumer products or in workplaces where the chemical is handled.

Health Risks

Acute Effects

• Humans: Short-term inhalation exposure may cause low blood pressure, mild liver effects, and CNS depression. Symptoms include dizziness, nausea, vomiting, diarrhoea, lightheadedness, loss of coordination, ataxia, loss of consciousness, and reduced blood pressure. Severe cases may lead to cardiac arrhythmia or respiratory arrest due to CNS depression.
• Skin: Mildly irritating when applied to human skin.
• Animals: Neurological and liver effects have been observed following acute inhalation. Tests in rats, mice, rabbits, and guinea pigs show low acute toxicity via inhalation or ingestion and low-to-moderate toxicity from dermal exposure.

Chronic Effects

• Humans/Animals: Most studies show no adverse effects from chronic low-level exposure.
• Rodents: Some studies indicate liver damage and neurological effects from long-term inhalation exposure.
• Regulation: EPA has not set RfC or RfD values. CalEPA has set a chronic reference exposure level of 1 mg/m³, based on CNS effects in gerbils.

Reproductive/Developmental Effects

• Humans: Epidemiological studies show no link between exposure and pregnancy outcomes.
• Animals: No developmental or reproductive effects observed.

Cancer Risk

• Humans: No data available.
• Animals: Limited studies show no carcinogenicity from inhalation or oral exposure, but findings are considered inadequate due to study design limitations.
• EPA Classification: Group D — not classifiable as to human carcinogenicity.

Safety

First Aid Measures

• Eye Contact: Remove contact lenses. Flush with water for at least 15 minutes, keeping eyelids open. Do not apply ointments. Seek immediate medical attention.
• Skin Contact: Wash thoroughly with soap and water. Pay attention to skin folds and creases. Apply an emollient to irritated areas. Wash clothing before reuse. Seek medical attention if irritation persists.
• Serious Skin Contact: Clean with disinfectant soap, apply anti-bacterial cream, and seek medical attention.
• Inhalation: Move victim to fresh air and allow to rest. Seek immediate medical attention.
• Serious Inhalation: Evacuate to a safe area, loosen tight clothing, administer oxygen if needed. If not breathing, provide artificial respiration (mouth-to-mouth only if safe). Seek medical attention immediately.
• Ingestion: Do not induce vomiting. Loosen clothing. If the victim is not breathing, provide artificial respiration. Seek immediate medical attention.

Exposure Controls and Personal Protection

Engineering Controls

• Provide local exhaust ventilation to keep vapour levels below exposure limits.
• Ensure eyewash stations and safety showers are nearby.

Personal Protective Equipment (PPE)

Routine handling: 

• Splash goggles
• Lab coat
• Certified vapour respirator
• Gloves

In case of a large spill:

• Full protective suit, boots, splash goggles, gloves
• Vapour respirator
• Self-contained breathing apparatus (SCBA) to prevent inhalation

Regulation

United States

OSHA: The Occupational Safety & Health Administration has set the following Permissible Exposure Limit (PEL) for 1,1,1-trichloroethane:

General Industry: 29 CFR 1910.1000 Z-1 Table -- 350 ppm, 1900 mg/m3 TWA

Construction Industry: 29 CFR 1926.55 Appendix A -- 350 ppm, 1900 mg/m3 TWA

Maritime: 29 CFR 1915.1000 Table Z-Shipyards -- 350 ppm, 1900 mg/m3 TWA

ACGIH: The American Conference of Governmental Industrial Hygienists has set a Threshold Limit Value (TLV) for 1,1,1-trichloroethane of 350 ppm, 1910 mg/m3 TWA; 450 ppm, 2460 mg/m3 STEL; Appendix A4 - Not Classifiable as a Human Carcinogen

NIOSH: The National Institute for Occupational Safety and Health has set a Recommended Exposure Limit (REL) for 1,1,1-trichloroethane of 350 ppm, 1900 mg/m3 Ceiling (15 Minutes); Appendix C - Supplementary Exposure Limits (chloroethanes)

Australia

Safe Work Australia: Safe Work Australia has set an 8-hour Time Weighted Average (TWA) concentration of 100ppm or 555mg/m3 for 1,1,1-trichloroethane for a 40-hour work week. 

The short-term exposure limits are 200ppm or 1110mg/m3, which is the time-weighted average maximum airborne concentration of 1,1,1-trichloroethane calculated over a 15-minute period.