isobutylene

H220: Extremely flammable gas [Danger Flammable gases]

P203, P210, P222, P280, P377, P381, and P403 (click each P-code to see the statement)

This chemical does not meet GHS hazard criteria for < 0.1% (1 of 1424) of reports.

H220 (99.9%): Extremely flammable gas [Danger Flammable gases]

H280 (74.2%): Contains gas under pressure; may explode if heated [Warning Gases under pressure]

P203, P210, P222, P280, P377, P381, P403, and P410+P403 (click each P-code to see the statement)

Aggregated GHS information provided per 1424 reports by companies from 20 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

Reported as not meeting GHS hazard criteria per 1 of 1424 reports by companies.

There are 19 notifications provided by 1423 of 1424 reports by companies with hazard statement code(s).

Information may vary between notifications depending on impurities, additives, and other factors. The percentage value in parenthesis indicates the notified classification ratio from companies that provide hazard codes. Only hazard codes with percentage values above 10% are shown. For more detailed information, please visit ECHA C&L website.

H280: Contains gas under pressure; may explode if heated [Warning Gases under pressure]

H336: May cause drowsiness or dizziness [Warning Specific target organ toxicity, single exposure; Narcotic effects]

P203, P210, P222, P261, P271, P280, P304+P340, P319, P377, P381, P403, P403+P233, P405, P410+P403, and P501 (click each P-code to see the statement)

Fresh air, rest. Artificial respiration may be needed. Refer for medical attention.

ON FROSTBITE: rinse with plenty of water, do NOT remove clothes. Refer for medical attention .

First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then refer for medical attention.

EYES: First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. IMMEDIATELY transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop.

SKIN: CAUTION: Exposure of skin to compressed gases may result in freezing of the skin. Treatment for frostbite may be necessary. Remove the victim from the source of contamination. IMMEDIATELY wash affected areas gently with COLD water (and soap, if necessary) while removing and isolating all contaminated clothing. Dry carefully with clean, soft towels. If symptoms such as inflammation or irritation develop, IMMEDIATELY call a physician or go to a hospital for treatment.

INHALATION: IMMEDIATELY leave the contaminated area; take deep breaths of fresh air. If symptoms (such as wheezing, coughing, shortness of breath, or burning in the mouth, throat, or chest) develop, call a physician and be prepared to transport the victim to a hospital. Provide proper respiratory protection to rescuers entering an unknown atmosphere. Whenever possible, Self-Contained Breathing Apparatus (SCBA) should be used; if not available, use a level of protection greater than or equal to that advised under Protective Clothing.

INGESTION: This compound is a gas, therefore inhalation is the first route of exposure. (NTP, 1992)

General First Aid:

· Call 911 or emergency medical service.

· Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination.

· Move victim to fresh air if it can be done safely.

· Administer oxygen if breathing is difficult.

· If victim is not breathing:

-- DO NOT perform mouth-to-mouth resuscitation; the victim may have ingested or inhaled the substance.

-- If equipped and pulse detected, wash face and mouth, then give artificial respiration using a proper respiratory medical device (bag-valve mask, pocket mask equipped with a one-way valve or other device).

-- If no pulse detected or no respiratory medical device available, provide continuous compressions. Conduct a pulse check every two minutes or monitor for any signs of spontaneous respirations.

· Remove and isolate contaminated clothing and shoes.

· For minor skin contact, avoid spreading material on unaffected skin.

· In case of contact with substance, remove immediately by flushing skin or eyes with running water for at least 20 minutes.

· For severe burns, immediate medical attention is required.

· Effects of exposure (inhalation, ingestion, or skin contact) to substance may be delayed.

· Keep victim calm and warm.

· Keep victim under observation.

· For further assistance, contact your local Poison Control Center.

· Note: Basic Life Support (BLS) and Advanced Life Support (ALS) should be done by trained professionals.

Specific First Aid:

· Clothing frozen to the skin should be thawed before being removed.

· In case of contact with liquefied gas, only medical personnel should attempt thawing frosted parts.

· In case of burns, immediately cool affected skin for as long as possible with cold water. Do not remove clothing if adhering to skin.

In Canada, an Emergency Response Assistance Plan (ERAP) may be required for this product. Please consult the shipping paper and/or the "ERAP" section.

Excerpt from ERG Guide 115 [Gases - Flammable (Including Refrigerated Liquids)]:

DO NOT EXTINGUISH A LEAKING GAS FIRE UNLESS LEAK CAN BE STOPPED. CAUTION: Hydrogen (UN1049), Deuterium (UN1957), Hydrogen, refrigerated liquid (UN1966) and Hydrogen and Methane mixture, compressed (UN2034) will burn with an invisible flame. Use an alternate method of detection (thermal camera, broom handle, etc.).

SMALL FIRE: Dry chemical or CO2.

LARGE FIRE: Water spray or fog. If it can be done safely, move undamaged containers away from the area around the fire. CAUTION: For LNG - Liquefied natural gas (UN1972) pool fires, DO NOT USE water. Use dry chemical or high-expansion foam.

FIRE INVOLVING TANKS: Fight fire from maximum distance or use unmanned master stream devices or monitor nozzles. Cool containers with flooding quantities of water until well after fire is out. Do not direct water at source of leak or safety devices; icing may occur. Withdraw immediately in case of rising sound from venting safety devices or discoloration of tank. ALWAYS stay away from tanks in direct contact with flames. For massive fire, use unmanned master stream devices or monitor nozzles; if this is impossible, withdraw from area and let fire burn. (ERG, 2024)

Shut off supply; if not possible and no risk to surroundings, let the fire burn itself out. In other cases extinguish with water spray, powder, carbon dioxide. In case of fire: keep drums, etc., cool by spraying with water. Combat fire from a sheltered position.

Suitable extinguishing media: Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.

Advice for firefighters: Wear self-contained breathing apparatus for firefighting if necessary.

Use water spray to cool unopened containers.

To fight fire, stop flow of gas.

· CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper not available or no answer, refer to appropriate telephone number listed on the inside back cover.

· Keep unauthorized personnel away.

· Stay upwind, uphill and/or upstream.

· Many gases are heavier than air and will spread along the ground and collect in low or confined areas (sewers, basements, tanks, etc.).

· ELIMINATE all ignition sources (no smoking, flares, sparks or flames) from immediate area.

· All equipment used when handling the product must be grounded.

· Do not touch or walk through spilled material.

· Stop leak if you can do it without risk.

· If possible, turn leaking containers so that gas escapes rather than liquid.

· Use water spray to reduce vapors or divert vapor cloud drift. Avoid allowing water runoff to contact spilled material.

· Do not direct water at spill or source of leak.

CAUTION: For LNG - Liquefied natural gas (UN1972), DO NOT apply water, regular or alcohol-resistant foam directly on spill. Use a high-expansion foam if available to reduce vapors.

· Prevent spreading of vapors through sewers, ventilation systems and confined areas.

· Isolate area until gas has dispersed.

CAUTION: When in contact with refrigerated/cryogenic liquids, many materials become brittle and are likely to break without warning.

Excerpt from ERG Guide 115 [Gases - Flammable (Including Refrigerated Liquids)]:

IMMEDIATE PRECAUTIONARY MEASURE: Isolate spill or leak area for at least 100 meters (330 feet) in all directions.

LARGE SPILL: Consider initial downwind evacuation for at least 800 meters (1/2 mile).

FIRE: If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 1600 meters (1 mile) in all directions; also, consider initial evacuation for 1600 meters (1 mile) in all directions. In fires involving Liquefied Petroleum Gases (LPG) (UN1075), Butane (UN1011), Butylene (UN1012), Isobutylene (UN1055), Propylene (UN1077), Isobutane (UN1969), and Propane (UN1978), also refer to the "BLEVE - Safety Precautions" section. (ERG, 2024)

Immediate precautionary measure

· Isolate spill or leak area for at least 100 meters (330 feet) in all directions.

Large Spill

· Consider initial downwind evacuation for at least 800 meters (1/2 mile).

· If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 1600 meters (1 mile) in all directions; also, consider initial evacuation for 1600 meters (1 mile) in all directions.

· In fires involving Liquefied Petroleum Gases (LPG) (UN1075), Butane (UN1011), Butylene (UN1012), Isobutylene (UN1055), Propylene (UN1077), Isobutane (UN1969), and Propane (UN1978), also refer to the "BLEVE - Safety Precautions" section.

Evacuate danger area! Consult an expert! Ventilation. Remove all ignition sources. Do NOT wash away into sewer. NEVER direct water jet on liquid. Personal protection: chemical protection suit including self-contained breathing apparatus.

ACCIDENTAL RELEASE MEASURES: Personal precautions, protective equipment and emergency procedures: Avoid breathing vapors, mist or gas. Ensure adequate ventilation. Remove all sources of ignition. Evacuate personnel to safe areas. Beware of vapors accumulating to form explosive concentrations. Vapors can accumulate in low areas. Environmental precautions: Prevent further leakage or spillage if safe to do so. Do not let product enter drains. Methods and materials for containment and cleaning up: Clean up promptly by sweeping or vacuum.

SRP: Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in air, soil or water; effects on animal, aquatic and plant life; and conformance with environmental and public health regulations. If it is possible or reasonable use an alternative chemical product with less inherent propensity for occupational harm/injury/toxicity or environmental contamination.

Product: Burn in a chemical incinerator equipped with an afterburner and scrubber but exert extra care in igniting as this material is highly flammable. Offer surplus and non-recyclable solutions to a licensed disposal company. Contact a licensed professional waste disposal service to dispose of this material. Contaminated packaging: Dispose of as unused product.

ACCIDENTAL RELEASE MEASURES: Personal precautions, protective equipment and emergency procedures: Avoid breathing vapors, mist or gas. Ensure adequate ventilation. Remove all sources of ignition. Evacuate personnel to safe areas. Beware of vapors accumulating to form explosive concentrations. Vapors can accumulate in low areas. Environmental precautions: Prevent further leakage or spillage if safe to do so. Do not let product enter drains.

Precautions for safe handling: Avoid inhalation of vapor or mist. Use explosion-proof equipment. Keep away from sources of ignition - No smoking. Take measures to prevent the build up of electrostatic charge.

Appropriate engineering controls: Handle in accordance with good industrial hygiene and safety practice. Wash hands before breaks and at the end of workday.

Gloves must be inspected prior to use. Use proper glove removal technique (without touching glove's outer surface) to avoid skin contact with this product. Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices. Wash and dry hands.

Excerpt from ERG Guide 115 [Gases - Flammable (Including Refrigerated Liquids)]:

ELIMINATE all ignition sources (no smoking, flares, sparks or flames) from immediate area. All equipment used when handling the product must be grounded. Do not touch or walk through spilled material. Stop leak if you can do it without risk. If possible, turn leaking containers so that gas escapes rather than liquid. Use water spray to reduce vapors or divert vapor cloud drift. Avoid allowing water runoff to contact spilled material. Do not direct water at spill or source of leak. CAUTION: For LNG - Liquefied natural gas (UN1972), DO NOT apply water, regular or alcohol-resistant foam directly on spill. Use a high-expansion foam if available to reduce vapors. Prevent spreading of vapors through sewers, ventilation systems and confined areas. Isolate area until gas has dispersed. CAUTION: When in contact with refrigerated/cryogenic liquids, many materials become brittle and are likely to break without warning. (ERG, 2024)

Fireproof. Separated from incompatible materials. See Chemical Dangers. Cool.

Keep container tightly closed in a dry and well-ventilated place.

· Wear positive pressure self-contained breathing apparatus (SCBA).

· Structural firefighters' protective clothing provides thermal protection but only limited chemical protection.

· Always wear thermal protective clothing when handling refrigerated/cryogenic liquids.

750 [ppm]

2000 [ppm]

12000 [ppm]

250.0 [ppm]

8 hr Time Weighted Avg (TWA): 250 ppm.

Peak Exposure Recommendation: Transient increases in workers' exposure levels may exceed 3 times the value of the TLV-TWA level for no more than 15 minutes at a time, on no more than 4 occasions spaced 1 hour apart during a workday, and under no circumstances should they exceed 5 times the value of the TLV-TWA level. In addition, the 8-hour TWA is not to be exceeded for an 8-hour work period.

A4: Not classifiable as a human carcinogen.

250 ppm as TWA; A4 (not classifiable as a human carcinogen)

· DO NOT EXTINGUISH A LEAKING GAS FIRE UNLESS LEAK CAN BE STOPPED.

CAUTION: Hydrogen (UN1049), Deuterium (UN1957), Hydrogen, refrigerated liquid (UN1966) and Hydrogen and Methane mixture, compressed (UN2034) will burn with an invisible flame. Use an alternate method of detection (thermal camera, broom handle, etc.)

Small Fire

· Dry chemical or CO2.

Large Fire

· Water spray or fog.

· If it can be done safely, move undamaged containers away from the area around the fire.

CAUTION: For LNG - Liquefied natural gas (UN1972) pool fires, DO NOT USE water. Use dry chemical or high-expansion foam.

Fire Involving Tanks

· Fight fire from maximum distance or use unmanned master stream devices or monitor nozzles.

· Cool containers with flooding quantities of water until well after fire is out.

· Do not direct water at source of leak or safety devices; icing may occur.

· Withdraw immediately in case of rising sound from venting safety devices or discoloration of tank.

· ALWAYS stay away from tanks in direct contact with flames.

· For massive fire, use unmanned master stream devices or monitor nozzles; if this is impossible, withdraw from area and let fire burn.

On loss of containment this substance can cause serious risk of suffocation when in confined areas.

Rapid evaporation of the liquid may cause frostbite. The substance may cause effects on the central nervous system. Exposure at high levels could cause unconsciousness.

Chemical gloves and eye protection; organic vapor canister or self-contained breathing apparatus. (USCG, 1999)

Eye/face protection: Face shield and safety glasses. Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).

Skin protection: Handle with gloves.

Body Protection: Impervious clothing. Flame retardant antistatic protective clothing. The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.

Respiratory protection: Where risk assessment shows air-purifying respirators are appropriate use a full-face respirator with multipurpose combination (US) or type AXBEK (EN 14387) respirator cartridges as a backup to engineering controls. If the respirator is the sole means of protection, use a full-face supplied air respirator. Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).

NO open flames, NO sparks and NO smoking. NO contact with oxidizing agents. Closed system, ventilation, explosion-proof electrical equipment and lighting. Prevent build-up of electrostatic charges (e.g., by grounding). Use non-sparking handtools.

Use closed system or ventilation.

Cold-insulating gloves.

Wear face shield or eye protection in combination with breathing protection.

Do not eat, drink, or smoke during work.

Isobutylene is a colorless gas with a faint petroleum-like odor. For transportation it may be stenched. It is shipped as a liquefied gas under its own vapor pressure. Contact with the liquid can cause frostbite. It is easily ignited. Its vapors are heavier than air and a flame can flash back to the source of leak very easily. The leak can either be a liquid or vapor leak. It can asphyxiate by the displacement of air. Under prolonged exposure to fire or heat the containers may rupture violently and rocket. It is used in the production of isooctane, a high octane aviation gasoline.

Gas Vapor; Liquid

Colorless liquid or gas with odor of coal gas; [Hawley] Compressed gas with an unpleasant odor; [MSDSonline] Boiling point = -6.9 deg C; [HSDB]

COLOURLESS COMPRESSED LIQUEFIED GAS WITH CHARACTERISTIC ODOUR.

Colorless gas

Colorless volatile liquid or easily liquefied gas

Coal gas odor

19.6 °F at 760 mmHg (NTP, 1992)

-6.9 °C @760 [mm Hg]

-220.5 °F (NTP, 1992)

-140.7 °C

-140.3 °C

-105 °F (NTP, 1992)

-80 °C (-112 °F) - closed cup

-105 °F (-76 °C)

-76.1 °C c.c.

Insoluble (NTP, 1992)

In water, 263 mg/L at 25 °C

Very soluble in ethanol and ether; soluble in benzene, sulfuric acid

Soluble in organic solvents

Solubility in water, g/100ml at 20 °C: 0.03

0.59 at 68 °F (USCG, 1999) - Less dense than water; will float

0.589 g/cu cm at 25 °C (p >1 atm)

Density: 0.6 at 20 °C

Relative density (water = 1): 0.59

0.6 @25 °C

1.9 (NTP, 1992) - Heavier than air; will sink (Relative to Air)

1.94 (Air = 1)

Relative vapor density (air = 1): 1.94

1 mmHg at -157.2 °F ; 5 mmHg at -141.7 °F (NTP, 1992)

2,308 mm Hg at 25 °C

Vapor pressure, kPa at 20 °C: 257

2308 [mm Hg] @25 °C

log Kow = 2.34

Henry's Law constant = 0.218 atm cu-m/mol at 25 °C

Stable under recommended storage conditions.

Volatile liquid or easily liquefied gas.

869 °F (USCG, 1999)

869 °F (465 °C)

Hazardous decomposition products formed under fire conditions: Carbon oxides

Highly flammable.

Hydrocarbons, Aliphatic Unsaturated

Polymerizable Compounds

Highly Flammable

Polymerizable

ISOBUTYLENE is incompatible with oxidizers. It polymerizes easily. It reacts easily with numerous materials, such as alkyl halides, halogens, concentrated sulfuric acid, hypochlorous acid, aluminum chloride, carbon monoxide and hydrogen with a cobalt catalyst. Polymerization is catalyzed by aluminum chloride and boron trifluoride. (NTP, 1992)

Incompatible materials: Strong oxidizing agents, strong acids, halogens.

Can react vigorously with oxidizing materials.

IDENTIFICATION AND USE: Isobutylene is an easily liquefied gas. It is used to produce diisobutylene, trimers, butyl rubber, and other polymers. It is also used to produce antioxidants for foods, packaging, food supplements, and for plastics. HUMAN STUDIES: Isobutene causes CNS depression at higher concentrations. There is a linear relationship between the degree of CNS depression and the cerebral concentrations. Isobutylene was not mutagenic when tested in the in vitro micronucleus test using human lymphocytes. ANIMAL STUDIES: Isobutene, at 30%, produces no CNS depression in mice, and excitement and CNS depression in 7 to 8 min at 40%, but immediate CNS depression in 2-2.25 min at 50%, or in 50-60 sec at 60 to 70%. Exposure to isobutene by inhalation for 2 years resulted in increased incidences and/or severities of nasal lesions including hyaline degeneration of the olfactory epithelium in mice and hyaline degeneration of the respiratory epithelium in male and female mice. There was no evidence of carcinogenic activity of isobutylene in male or female mice exposed to 500, 2,000, or 8,000 ppm 6 hours per day, 5 days per week, for 105 weeks. There was some evidence of carcinogenic activity of isobutene in male rats based on an increased incidence of follicular cell carcinoma of the thyroid gland. It was negative when tested for mutagenicity in Escherichia coli, the Ames Salmonella typhimurium assay, and a modified Salmonella assay, with and without metabolic activation. No increase in the frequency of micronucleated erythrocytes was seen in peripheral blood of male or female mice treated with isobutylene by inhalation for 14 weeks.

A4: Not classifiable as a human carcinogen.

Isobutene

TR-487: Toxicology and Carcinogenesis Studies of Isobutene (CASRN 115-11-7) in F344/N Rats and B6C3F1 Mice (Inhalation Studies) (1998 )

12/10/97

Some Evidence

No Evidence

Under the conditions of these 2-year inhalation studies, there was some evidence of carcinogenic activity of isobutene in male F344/N rats based on an increased incidence of follicular cell carcinoma of the thyroid gland. There was no evidence of carcinogenic activity of isobutene in female F344/N rats or male or female B6C3F1 mice exposed to 500, 2,000, or 8,000 ppm.

Exposure to isobutene by inhalation for 2 years resulted in increased incidences and/or severities of nasal lesions including hyaline degeneration of the olfactory epithelium in male and female rats and mice and hyaline degeneration of the respiratory epithelium in male and female mice.

The substance can be absorbed into the body by inhalation.

Dizziness. Drowsiness. Lethargy. Nausea. Unconsciousness. Vomiting.

ON CONTACT WITH LIQUID: FROSTBITE.

See Skin.

Neurotoxin - Acute solvent syndrome

Other Poison - Simple Asphyxiant

ACGIH Carcinogen - Not Classifiable.

LC50 (rat) = 620,000 mg/m3/4h

LC50 Mouse inhalation 415 mg/L/2 hr

LC50 Rat inhalation 620 mg/L/4 hr

LC50 Rat inhalation 620 g/cu m/4 hr

LC50 Mouse inhalation 415 g/cu m/2 hr

Gas-liquid chromatography was used to study brain hydrocarbon content in rats and mice inhaling mixtures of butane and isobutylene. There was summation of CNS depressant effects of butane and isobutylene toward potentiation rather than antagonism.

Immediate first aid: Ensure adequate decontamination has been carried out. If patient is not breathing, start artificial respiration, preferably with a demand-valve resuscitator, bag-valve-mask device, or pocket mask, as trained. Perform CPR if necessary. Immediately flush contaminated eyes with gently flowing water. Do not induce vomiting. If vomiting occurs, lean patient forward or place on left side (head-down position, if possible) to maintain an open airway and prevent aspiration. Keep patient quiet and maintain normal body temperature. Obtain medical attention. /Aliphatic hydrocarbons and related compounds/

Basic Treatment: Establish a patent airway (oropharyngeal or nasopharyngeal airway, if needed). Suction if necessary. Watch for signs of respiratory insufficiency and assist ventilations if necessary. Administer oxygen by nonrebreather mask at 10 to 15 L/min. Monitor for pulmonary edema and treat if necessary ... Anticipate seizures and treat as necessary ... For eye contamination, flush eyes immediately with water. Irrigate each eye continuously with with 0.9% saline (NS) during transport ... Do not use emetics. For ingestion, rinse mouth and administer 5 mL/kg up to 200 mL of water for dilution if the patient can swallow, has a strong gag reflex, and does not drool. Administer activated charcoal ... Treat frostbite with rapid rewarming techniques ... /Aliphatic hydrocarbons and related compounds/

Advanced treatment: Consider orotracheal or nasotracheal intubation for airway control in the patient who is unconscious, has severe pulmonary edema, or is in severe respiratory distress. Positive-pressure ventilation techniques with a bag-valve-mask device may be beneficial. Consider drug therapy for pulmonary edema ... . Monitor cardiac rhythm and treat arrhythmias as necessary ... . Start IV administration of D5W TKO /SRP: "To keep open", minimal flow rate/. Use 0.9% saline (NS) or lactated Ringer's (LR) if signs of hypovolemia are present. For hypotension with signs of hypovolemia, administer fluid cautiously. Watch for signs of fluid overload ... . Treat seizures with diazepam (Valium) or lorazepam (Ativan) ... . Use proparacaine hydrochloride to assist eye irrigation ... /Aliphatic hydrocarbons and related compounds/

/SIGNS AND SYMPTOMS/ Isobutene ... causes CNS depression at higher concentrations. There is a linear relationship between the degree of CNS depression and the cerebral concentrations.

/GENOTOXICITY/ 2-Methylpropene (isobutene), a gaseous compound widely used in chemical industries, is metabolized to the epoxide 2-methyl-1,2-epoxypropane. The parent compound has previously been shown to be non-mutagenic in a modified Ames test, whereas the epoxide metabolite gave a positive result. In this study, both compounds have been tested in the in vitro micronucleus test using human lymphocytes. Propylene oxide, a well known mutagenic compound, served as a positive control. It was found that 2-methylpropene had no mutagenic effect, whereas its epoxide induced a statistically significant dose-dependent increase in the number of micronuclei. The effect observed was comparable with that obtained for propylene oxide.

/LABORATORY ANIMALS: Acute Exposure/ Isobutene, at 30%, produces no CNS depression in mice, and excitement and CNS depression in 7 to 8 min at 40%, but immediate CNS depression in 2-2.25 min at 50%, or in 50-60 sec at 60 to 70%. The 2-hr LC50 in the mouse is 415 mg/L and the 4-hr LC50 in the rat is 620 mg/L.

/LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity/ Cardiac thrombosis, one of the causes of sudden death throughout the world, plays a principal role in several cardiovascular diseases, such as myocardial infarction and stroke in humans. Data from studies of induction of chemical thrombosis in rodents help to identify substances in our environment that may contribute to cardiac thrombosis. Results for more than 500 chemicals tested in rodents in 2-year bioassays have been published as Technical Reports of the National Toxicology Program (NTP) ... We evaluated atrial thrombosis induced by these chemical exposures and compared it to similarly induced lesions reported in the literature. Spontaneous rates of cardiac thrombosis were determined for control Fischer 344 rats and B6C3F1 mice: 0% in rats and mice in 90-day studies and, in 2-year studies, 0.7% in both genders of mice, 4% in male rats, and 1% in female rats. Incidences of atrial thrombosis were increased in high-dosed groups involving 13 compounds (incidence rate: 20-100%): 2-butoxyethanol, C.I. Direct Blue 15, bis(2-chloroethoxy)methane, diazoaminobenzene, diethanolamine, 3,3'-dimethoxybenzidine dihydrochloride, hexachloroethane, isobutene, methyleugenol, oxazepam, C.I. Pigment Red 23, C.I. Acid Red 114, and 4,4'-thiobis(6-t-butyl-m-cresol). The main localization of spontaneously occurring and chemically induced thromboses occurred in the left atrium. The literature survey suggested that chemical-induced atrial thrombosis might be closely related to myocardial injury, endothelial injury, circulatory stasis, hypercoagulability, and impaired atrial mechanical activity, such as atrial fibrillation, which could cause stasis of blood within the left atrial appendage, contributing to left atrial thrombosis ...

/GENOTOXICITY/ The mutagenic properties of 2-methylpropene (MP) and 2-methyl-1,2- epoxypropane (MEP) were investigated in the Salmonella assay. A simple exposure system, consisting of gastight tissue culture flasks, was used. This method has the advantage that the volatile test chemical is present during the entire incubation period and that several concentrations of the investigated compound can be tested on a single day. MP is not mutagenic in strains TA100, TA102 and TA1535, and in the latter strain not even in the presence of metabolizing S9 mix. MEP is mutagenic in all the strains tested, as demonstrated by a clear dose-response relationship. Strain TA1535 seems to be most sensitive to MEP compared with the other bacterial strains studied. For this strain, the mutagenic activity of MEP decreased significantly in the presence of S9 mix, compatible with the epoxide being inactivated by epoxide hydrolase and by glutathione S-transferase, as reported previously. From the present study it can be concluded that the parent compound MP is not mutagenic, but that its primary metabolite MEP is a mutagenic substance. However, very high concentrations are necessary to induce a mutagenic effect and the epoxide is efficiently detoxified by different liver enzymes.

/GENOTOXICITY/ Isobutene was negative when tested for mutagenicity in Escherichia coli, the Ames Salmonella typhimurium assay, and a modified Salmonella assay, with and without metabolic activation.

For more Non-Human Toxicity Excerpts (Complete) data for Isobutylene (6 total), please visit the HSDB record page.

The following link will take the user to the National Toxicology Program (NTP) Test Status of Agents Search page, which tabulates the results and current status of tests such as "Short-Term Toxicity Studies", "Long-term Carcinogenicity Studies", "Developmental Studies", "Genetic Toxicology Studies", etc., performed with this chemical. Testing status for isobutylene is available.[Available from, as of November 3, 2017: https://ntpsearch.niehs.nih.gov/?e=True&ContentType=Testing+Status]

Groups of 50 male and 50 female B6C3F1 mice were exposed to isobutene at concentrations of 0, 500, 2,000, or 8,000 ppm 6 hours per day, 5 days per week, for 105 weeks. Survival of exposed males and females was similar to that of the chamber controls. Mean body weights of exposed mice were generally similar to those of the chamber controls throughout the study except for female mice exposed to 2,000 or 8,000 ppm, which weighed slightly less than chamber controls from about week 52 until week 92. ... The incidences of hyaline degeneration of the respiratory epithelium in all groups of exposed males and females were significantly greater than those in the chamber control groups. The incidences of hyaline degeneration of the olfactory epithelium in 2,000 and 8,000 ppm mice were greater than those in the chamber controls. ... There was no evidence of carcinogenic activity of isobutene in male or female B6C3F mice exposed to 500, 2,000, or 8,000 ppm. Exposure to isobutene by inhalation for 2 years resulted in increased incidences and/or severities of nasal lesions including hyaline degeneration of the olfactory epithelium in mice and hyaline degeneration of the respiratory epithelium in male and female mice.

Groups of 50 male and 50 female F344/N rats were exposed to isobutene at concentrations of 0, 500, 2,000, or 8,000 ppm 6 hours per day, 5 days per week, for 105 weeks. Survival of exposed males and females was similar to that of the chamber controls. Mean body weights of exposed groups were generally similar to those of the chamber controls throughout the study ... The incidence of thyroid gland follicular cell carcinoma in male rats exposed to 8,000 ppm was increased compared to the chamber control group and exceeded the historical control range. The incidences of hyaline degeneration of the olfactory epithelium were marginally increased in exposed rats; however, the severities of hyaline degeneration increased with increasing exposure concentration in males and females. ... Under the conditions of these 2-year inhalation studies, there was some evidence of carcinogenic activity of isobutene in male F344/N rats based on an increased incidence of follicular cell carcinoma of the thyroid gland. There was no evidence of carcinogenic activity of isobutene in female F344/N rats ... Exposure to isobutene by inhalation for 2 years resulted in increased incidences and/or severities of nasal lesions including hyaline degeneration of the olfactory epithelium in male and female rats.

Groups of 10 male and 10 female F344/N rats and B6C3F1 mice were exposed to isobutene at concentrations of 0, 500, 1,000, 2,000, 4,000, or 8,000 ppm 6 hours per day, 5 days per week, for 14 weeks. Concentrations greater than 8,000 ppm isobutene were not used because of the danger of explosion. All rats and mice survived to the end of the study. The final mean body weights and body weight gains of all exposed groups were similar to those of the chamber controls. No exposure-related gross lesions were observed in male or female rats or mice at necropsy. Microscopically, minimal hypertrophy of goblet cells lining the nasopharyngeal duct in the most caudal nose section was observed in some rats in each exposed group of males and females.

Isobutene was not mutagenic in any of four strains of Salmonella typhimurium, with or without S9 metabolic activation, and no increase in the frequency of micronucleated erythrocytes was seen in peripheral blood of male or female mice treated with isobutene by inhalation for 14 weeks.

Isobutylene's production and use in the production of polymers, antioxidants and high octane aviation fuel may result in its release to the environment through various waste streams. It is also released to the environment from the exhaust of automobiles and other gasoline powered engines. If released to air, a vapor pressure of 2,308 mm Hg at 25 °C indicates isobutylene will exist solely as a gas in the ambient atmosphere. Gas-phase isobutylene will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals and ozone molecules with atmospheric half-lives of about 7.5 and 23 hours, respectively. Isobutylene does not absorb UV light at wavelengths >290 nm and, therefore, is not expected to be susceptible to direct photolysis by sunlight. If released to soil, isobutylene is expected to have very high mobility based upon an estimated Koc of 32. Volatilization from moist soil surfaces is expected to be an important fate process based upon a Henry's Law constant of 0.218 atm-cu m/mole. Isobutylene will volatilize from dry soil surfaces based upon its vapor pressure. Isobutylene was degraded to 1,2-epoxy butane by pure cultures of methanotrophic bacteria, suggesting biodegradation may occur at intefaces between aerobic and anaerobic conditions. If released into water, isobutylene is not expected to adsorb to suspended solids and sediment in the water column based upon the estimated Koc. Volatilization from water surfaces is expected to be an important fate process based upon this compound's Henry's Law constant. Estimated volatilization half-lives for a model river and model lake are 2 and 71 hours, respectively. An estimated BCF of 16 suggests the potential for bioconcentration in aquatic organisms is low. Occupational exposure to isobutylene may occur through inhalation and dermal contact with this compound at workplaces where isobutylene is produced or used. The general population may be exposed to isobutylene via inhalation of ambient air. (SRC)

Isobutylene is a component of petroleum and natural gas.

Isobutylene's production and use in the production of diisobutylene, trimers, butyl rubber, and other polymers, to produce antioxidants for foods, packaging, food supplements, and for plastics(1) as well as production of isooctane, high-octane aviation gasoline, polyisobutene resins, tert-butyl chloride, tert-butanol methacrylates; copolymer resins with butadiene, acrylonitrile and methyl-tert-butyl ether(2) may result in its release to the environment through various waste streams(SRC). It is also released to the environment from the exhaust of automobiles and other gas powered engines(3-5).

Isobutylene's production and use in the production of polymers, antioxidants and high octane aviation fuel may result in its release to the environment through various waste streams. It is also released to the environment from the exhaust of automobiles and other gasoline powered engines. If released to air, a vapor pressure of 2,308 mm Hg at 25 °C indicates isobutylene will exist solely as a gas in the ambient atmosphere. Gas-phase isobutylene will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals and ozone molecules with atmospheric half-lives of about 7.5 and 23 hours, respectively. Isobutylene does not absorb UV light at wavelengths >290 nm and, therefore, is not expected to be susceptible to direct photolysis by sunlight. If released to soil, isobutylene is expected to have very high mobility based upon an estimated Koc of 32. Volatilization from moist soil surfaces is expected to be an important fate process based upon a Henry's Law constant of 0.218 atm-cu m/mole. Isobutylene will volatilize from dry soil surfaces based upon its vapor pressure. Isobutylene was degraded to 1,2-epoxy butane by pure cultures of methanotrophic bacteria, suggesting biodegradation may occur at intefaces between aerobic and anaerobic conditions. If released into water, isobutylene is not expected to adsorb to suspended solids and sediment in the water column based upon the estimated Koc. Volatilization from water surfaces is expected to be an important fate process based upon this compound's Henry's Law constant. Estimated volatilization half-lives for a model river and model lake are 2 and 71 hours, respectively. An estimated BCF of 16 suggests the potential for bioconcentration in aquatic organisms is low. Occupational exposure to isobutylene may occur through inhalation and dermal contact with this compound at workplaces where isobutylene is produced or used. The general population may be exposed to isobutylene via inhalation of ambient air. (SRC)

Isobutylene is a component of petroleum and natural gas.

Isobutylene's production and use in the production of diisobutylene, trimers, butyl rubber, and other polymers, to produce antioxidants for foods, packaging, food supplements, and for plastics(1) as well as production of isooctane, high-octane aviation gasoline, polyisobutene resins, tert-butyl chloride, tert-butanol methacrylates; copolymer resins with butadiene, acrylonitrile and methyl-tert-butyl ether(2) may result in its release to the environment through various waste streams(SRC). It is also released to the environment from the exhaust of automobiles and other gas powered engines(3-5).

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 32(SRC), determined from a structure estimation method(2), indicates that isobutylene is expected to have very high mobility in soil(SRC). Volatilization of isobutylene from moist soil surfaces is expected to be an important fate process(SRC) given a Henry's Law constant of 0.218 atm-cu m/mole(3). Isobutylene is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 2,308 mm Hg at 25 °C(4). Isobutylene was degraded to 1,2-epoxy butane by pure cultures of methanotrophic bacteria(5), suggesting biodegradation may occur at intefaces between aerobic and anaerobic conditions in soil(SRC).

FIELD STUDY: Isobutylene was detected at 165 and 125 ppbv in 2 gas recovery wells at the Case Passerini landfill site in Florence, Italy. The concentration was <10 ppbv in cover soil samples at depths of 0, 30, 50 and 70 cm. Sampling was conducted during the summer dry season in July(1).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 32(SRC), determined from a structure estimation method(2), indicates that isobutylene is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(3) based upon a Henry's Law constant of 0.218 atm-cu m/mole(4). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 2 and 71 hours, respectively(SRC). According to a classification scheme(5), an estimated BCF of 16(SRC), from its log Kow of 2.34(6) and a regression-derived equation(2), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Isobutylene was degraded to 1,2-epoxy butane by pure cultures of methanotrophic bacteria(7), suggesting biodegradation may occur at intefaces between aerobic and anaerobic conditions in water(SRC).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), isobutylene, which has a vapor pressure of 2,308 mm Hg at 25 °C(2), is expected to exist solely as a gas in the ambient atmosphere. Gas-phase isobutylene is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 7.5 hours(SRC), calculated from its rate constant of 5.14X10-11 cu cm/molecule-sec at 25 °C(3). The rate constant for the gas-phase reaction of isobutylene with ozone has been measured as 1.2X10-17 cu cm/molecule-sec at 25 °C(4). This corresponds to an atmospheric half-life of about 23 hours at an atmospheric concentration of 7X10+11 ozone molecules per cu cm(4). Isobutylene does not absorb UV light at wavelengths >290 nm(5) and, therefore, is not expected to be susceptible to direct photolysis by sunlight(SRC).

PURE CULTURE: Isobutylene was degraded to 1,2-epoxy isobutene by pure cultures of methanotrophic bacteria. Rates of product formation were 0.82, 0.90 and 0.42 umol-hr/2.0 mg cell protein using Methylosinus trichlosporium, Methylococcus capsulatus and Methylobacterium organophilum, respectively(1).

The rate constant for the gas-phase reaction of isobutylene with photochemically-produced hydroxyl radicals has been measured as 5.14X10-11 cu cm/molecule-sec at 25 °C(1). This corresponds to an atmospheric half-life of about 7.5 hours at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). The rate constant for the gas-phase reaction of isobutylene with ozone has been measured as 1.2X10-17 cu cm/molecule-sec at 25 °C(2). This corresponds to an atmospheric half-life of about 23 hours at an atmospheric concentration of 7X10+11 ozone molecules per cu cm(2). Isobutylene is not expected to undergo hydrolysis in the environment due to the lack of hydrolyzable functional groups(3). Isobutylene does not absorb UV light at wavelengths >290 nm(2) and, therefore, is not expected to be susceptible to direct photolysis by sunlight(SRC).

An estimated BCF of 16 was calculated in fish for isobutylene(SRC), using a log Kow of 2.34(1) and a regression-derived equation(1). According to a classification scheme(2), this BCF suggests the potential for bioconcentration in aquatic organisms is low(SRC).

Using a structure estimation method based on molecular connectivity indices(1), the Koc of isobutylene can be estimated to be 32(SRC). According to a classification scheme(2), this estimated Koc value suggests that isobutylene is expected to have very high mobility in soil(SRC).

The Henry's Law constant for isobutylene is 0.218 atm-cu m/mole(1). This Henry's Law constant indicates that isobutylene is expected to volatilize rapidly from water surfaces(2). Based on this Henry's Law constant, the volatilization half-life from a model river (1 m deep, flowing 1 m/sec, wind velocity of 3 m/sec)(2) is estimated as 2 hours(SRC). The volatilization half-life from a model lake (1 m deep, flowing 0.05 m/sec, wind velocity of 0.5 m/sec)(2) is estimated as 71 hours(SRC). Isobutylene's Henry's Law constant indicates that volatilization from moist soil surfaces may occur(SRC). Isobutylene is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 2,308 mm Hg mm Hg(3).

Isobutylene was identified, not quantified, in the effluent of a plastic incineration plant in Japan(1).

URBAN/SUBURBAN: Isobutylene was detected in Los Angeles, CA at a concentration of 2.35 ug/cu m(1). Combined isomers of isobutylene and 1-butene were detected in Washington DC at a mean concentration of 0.67 ppb and a maximum concentration of 2.25 ppb in 1991(2). Isobutylene was identified, not quantified, in Chicago, IL, Raleigh, NC, Atlanta, GA and Budapest, Hungary(3). Combined isomers of isobutylene and 1-butene were detected in urban areas around Vienna, Austria at mean concentrations of 9.6 and 10.1 ppb at 2 different sampling locations(4). Isobutylene was detected at street levels in London, England at a mean concentration of 19 ppb(5). Isobutylene was detected in the atmosphere of London, England at concentrations of 132-1,506 parts per trillion at altitudes between 453 and 758 m(5). Isobutylene was detected at a mean concentration of 8.8 ppbC in urban air samples from a car park in Lancaster, England sampled June-July 1983(6). Butenes, including isobutylene, were detected at the following locations in Sweden: outdoor park (0.09 ug/cu m), city streets (0.7-7.7 ug/cu m) and a parking garage (7.7 ug/cu m)(7). Isobutylene was detected in Porto Alegre, Brazil at concentration range of 1-15 ug/cu m(8). The average concentration of isobutylene was 2.7 ppbv (range of 0.4-9.3in the atmosphere of Taipei metropolitan area, Taiwan, a region characterized by high passenger car and motor bike traffic and few major industrial sites(9).

SOURCE DOMINATED: Isobutylene has been identified, not quantified, in the exhaust of automobiles(1-3). Isobutylene was detected at a concentration of 60 and 28 ug/cu m in the emissions of automobiles(4). Isobutylene was detected at concentrations of 0.14 ppb (87 octane) and 0.13 ppb (89 octane) in automobile exhaust(5).

SOURCE DOMINATED: Isobutylene was detected in the Caldecott Tunnel, CA at a concentration of 0.058 g/L of August 1994 when vehicles were using low oxygenated gasoline and 0.089 g/l in October 1994 when vehicles were using high oxygenated gasoline(1). Combined isomers of isobutylene and 1-butene were detected in the Lincoln Tunnel, NY at a mean concentration of 344.9 ppb in 1970 and 89.1 ppb in 1982(2). Isobutylene concentrations of <5 mg HC/km were determined in the exhaust emissions from gasoline- and LPG-powered catalyst-equipped vehicles operating at the altitude of Mexico City in 1996(3). An average concentration of 758.8 ug/cu m (6 samples) was reported in the air at an ethanol and gasoline service station with 5 pumps in the Flamengo District, Rio de Janiero, Brazil, sampled on June 9, 2004(4).

SOURCE DOMINATED: Isobutylene sources to the atmosphere in Cairo, Egypt, June 1997(1).[Table#1717]

RURAL/REMOTE: Isobutylene was detected at a mean concentration of <0.5 ppbC in rural air samples and at 1.0 ppb in polluted rural air in northwest, England; sampling was conducted during May-June, 1983(1).

Isobutylene is released to the air from open burning of predominantly foliage, litter and herbaceous matter in typical fire-climax ecosystems in the United States(1).[Table#1719]

According to the 2016 TSCA Inventory Update Reporting data, 17 reporting facilities estimate the number of persons reasonably likely to be exposed during the manufacturing, processing, or use of isobutylene in the United States may be as low as 10 workers to less than 10,000 but unknown or unreasonably ascertainable as to how many workers per plant; the data may be greatly underestimated due to confidential business information (CBI) or unknown values(1).

NIOSH (NOES Survey 1981-1983) has statistically estimated that 7,002 workers (982 of these are female) are potentially exposed to isobutylene in the US(1). Occupational exposure to isobutylene may occur through inhalation and dermal contact with this compound at workplaces where isobutylene is produced or used(SRC). The general population may be exposed to isobutylene via inhalation of ambient air(SRC).

SRP: Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in air, soil or water; effects on animal, aquatic and plant life; and conformance with environmental and public health regulations. If it is possible or reasonable use an alternative chemical product with less inherent propensity for occupational harm/injury/toxicity or environmental contamination.

Product: Burn in a chemical incinerator equipped with an afterburner and scrubber but exert extra care in igniting as this material is highly flammable. Offer surplus and non-recyclable solutions to a licensed disposal company. Contact a licensed professional waste disposal service to dispose of this material. Contaminated packaging: Dispose of as unused product.

/GUIDE 115 GASES - FLAMMABLE (Including Refrigerated Liquids)/ Fire or Explosion: EXTREMELY FLAMMABLE. Will be easily ignited by heat, sparks or flames. Will form explosive mixtures with air. Vapors from liquefied gas are initially heavier than air and spread along ground. CAUTION: Hydrogen (UN1049), Deuterium (UN1957), Hydrogen, refrigerated liquid (UN1966) and Methane (UN1971) are lighter than air and will rise. Hydrogen and Deuterium fires are difficult to detect since they burn with an invisible flame. Use an alternate method of detection (thermal camera, broom handle, etc.) Vapors may travel to source of ignition and flash back. Cylinders exposed to fire may vent and release flammable gas through pressure relief devices. Containers may explode when heated. Ruptured cylinders may rocket.

/GUIDE 115 GASES - FLAMMABLE (Including Refrigerated Liquids)/ Health: Vapors may cause dizziness or asphyxiation without warning. Some may be irritating if inhaled at high concentrations. Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite. Fire may produce irritating and/or toxic gases.

/GUIDE 115 GASES - FLAMMABLE (Including Refrigerated Liquids)/ Public Safety: CALL Emergency Response Telephone Number on Shipping Paper first. If Shipping Paper not available or no answer, refer to appropriate telephone number listed on the inside back cover. As an immediate precautionary measure, isolate spill or leak area for at least 100 meters (330 feet) in all directions. Keep unauthorized personnel away. Stay upwind, uphill and/or upstream. Many gases are heavier than air and will spread along ground and collect in low or confined areas (sewers, basements, tanks).

/GUIDE 115 GASES - FLAMMABLE (Including Refrigerated Liquids)/ Protective Clothing: Wear positive pressure self-contained breathing apparatus (SCBA). Structural firefighters' protective clothing will only provide limited protection. Always wear thermal protective clothing when handling refrigerated/cryogenic liquids.

For more DOT Emergency Guidelines (Complete) data for Isobutylene (8 total), please visit the HSDB record page.

UN 1055; Isobutylene

IMO 2.1; Isobutylene

No person may /transport,/ offer or accept a hazardous material for transportation in commerce unless that person is registered in conformance ... and the hazardous material is properly classed, described, packaged, marked, labeled, and in condition for shipment as required or authorized by ... /the hazardous materials regulations (49 CFR 171-177)./

The International Air Transport Association (IATA) Dangerous Goods Regulations are published by the IATA Dangerous Goods Board pursuant to IATA Resolutions 618 and 619 and constitute a manual of industry carrier regulations to be followed by all IATA Member airlines when transporting hazardous materials. Isobutylene is included on the dangerous goods list.

The International Maritime Dangerous Goods Code lays down basic principles for transporting hazardous chemicals. Detailed recommendations for individual substances and a number of recommendations for good practice are included in the classes dealing with such substances. A general index of technical names has also been compiled. This index should always be consulted when attempting to locate the appropriate procedures to be used when shipping any substance or article. Isobutylene is included on the dangerous goods list.

Flammable Gas

Symbol: F+; R: 12; S: (2)-9-16-33; Note: C

UN Hazard Class: 2.1