Methanethiol

H220: Extremely flammable gas [Danger Flammable gases]

H331: Toxic if inhaled [Danger Acute toxicity, inhalation]

H400: Very toxic to aquatic life [Warning Hazardous to the aquatic environment, acute hazard]

H410: Very toxic to aquatic life with long lasting effects [Warning Hazardous to the aquatic environment, long-term hazard]

P203, P210, P222, P261, P271, P273, P280, P304+P340, P316, P321, P377, P381, P391, P403, P403+P233, P405, and P501 (click each P-code to see the statement)

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

H280 (33.7%): Contains gas under pressure; may explode if heated [Warning Gases under pressure]

H331 (100%): Toxic if inhaled [Danger Acute toxicity, inhalation]

H400 (99.2%): Very toxic to aquatic life [Warning Hazardous to the aquatic environment, acute hazard]

H410 (100%): Very toxic to aquatic life with long lasting effects [Warning Hazardous to the aquatic environment, long-term hazard]

P203, P210, P222, P261, P271, P273, P280, P304+P340, P316, P321, P377, P381, P391, P403, P403+P233, P405, P410+P403, and P501 (click each P-code to see the statement)

Aggregated GHS information provided per 1379 reports by companies from 14 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

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]

H315: Causes skin irritation [Warning Skin corrosion/irritation]

H319: Causes serious eye irritation [Warning Serious eye damage/eye irritation]

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

H370: Causes damage to organs [Danger Specific target organ toxicity, single exposure]

H372: Causes damage to organs through prolonged or repeated exposure [Danger Specific target organ toxicity, repeated exposure]

P203, P210, P222, P260, P261, P264, P264+P265, P270, P271, P280, P302+P352, P304+P340, P305+P351+P338, P308+P316, P316, P319, P321, P332+P317, P337+P317, P362+P364, P377, P381, P403, P403+P233, P405, P410+P403, and P501 (click each P-code to see the statement)

P203, P210, P222, P260, P261, P264, P264+P265, P270, P271, P280, P304+P340, P305+P351+P338, P308+P316, P316, P319, P321, P337+P317, 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.

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

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

Warning: Effects may be delayed. Caution is advised.

Signs and Symptoms of Acute Methyl Mercaptan Exposure: Signs and symptoms of acute exposure to methyl mercaptan may include fever, cough, shortness of breath, a feeling of tightness and burning in the chest, pulmonary edema, respiratory distress, respiratory paralysis, and respiratory failure/collapse. Headache, loss of the sense of smell, dizziness, staggering gait, and heightened emotions may occur. Memory loss, damage to the central and peripheral nervous systems, tremor, convulsions, and coma may also occur. Gastrointestinal symptoms include difficulty swallowing, redness of the tongue and pharynx, nausea, vomiting, abdominal pain, and diarrhea. Urinary disturbances may also be found. Methyl mercaptan may irritate the eyes and mucous membranes.

Emergency Life-Support Procedures: Acute exposure to methyl mercaptan may require decontamination and life support for the victims. Emergency personnel should wear protective clothing appropriate to the type and degree of contamination. Air-purifying or supplied-air respiratory equipment should also be worn, as necessary. Rescue vehicles should carry supplies such as plastic sheeting and disposable plastic bags to assist in preventing spread of contamination.

Inhalation Exposure:

1. Move victims to fresh air. Emergency personnel should avoid self-exposure to methyl mercaptan.

2. Evaluate vital signs including pulse and respiratory rate, and note any trauma. If no pulse is detected, provide CPR. If not breathing, provide artificial respiration. If breathing is labored, administer oxygen or other respiratory support.

3. Obtain authorization and/or further instructions from the local hospital for administration of an antidote or performance of other invasive procedures.

4. RUSH to a health care facility.

Dermal/Eye Exposure:

1. Remove victims from exposure. Emergency personnel should avoid self- exposure to methyl mercaptan.

3. Remove contaminated clothing as soon as possible.

4. If eye exposure has occurred, eyes must be flushed with lukewarm water for at least 15 minutes.

5. Wash exposed skin areas THOROUGHLY with soap and water.

6. Obtain authorization and/or further instructions from the local hospital for administration of an antidote or performance of other invasive procedures.

7. RUSH to a health care facility.

Ingestion Exposure:

1. Evaluate vital signs including pulse and respiratory rate, and note any trauma. If no pulse is detected, provide CPR. If not breathing, provide artificial respiration. If breathing is labored, administer oxygen or other respiratory support.

2. Obtain authorization and/or further instructions from the local hospital for administration of an antidote or performance of other invasive procedures.

3. Vomiting may be induced with syrup of Ipecac. If elapsed time since ingestion of methyl mercaptan is unknown or suspected to be greater than 30 minutes, do not induce vomiting and proceed to Step

4. Ipecac should not be administered to children under 6 months of age.Warning: Ingestion of methyl mercaptan may result in sudden onset of seizures or loss of consciousness. Syrup of Ipecac should be administered only if victims are alert, have an active gag-reflex, and show no signs of impending seizure or coma. If ANY uncertainty exists, proceed to Step

4.The following dosages of Ipecac are recommended: children up to 1 year old, 10 mL (1/3 oz); children 1 to 12 years old, 15 mL (1/2 oz); adults, 30 mL (1 oz). Ambulate (walk) the victims and give large quantities of water. If vomiting has not occurred after 15 minutes, Ipecac may be readministered. Continue to ambulate and give water to the victims. If vomiting has not occurred within 15 minutes after second administration of Ipecac, administer activated charcoal.

4. Activated charcoal may be administered if victims are conscious and alert. Use 15 to 30 g (1/2 to 1 oz) for children, 50 to 100 g (1-3/4 to 3-1/2 oz) for adults, with 125 to 250 mL (1/2 to 1 cup) of water.

5. Promote excretion by administering a saline cathartic or sorbitol to conscious and alert victims. Children require 15 to 30 g (1/2 to 1 oz) of cathartic; 50 to 100 g (1-3/4 to 3-1/2 oz) is recommended for adults.

6. RUSH to a health care facility. (EPA, 1998)

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.

Keep unnecessary people away; isolate hazard area and deny entry. Stay upwind; keep out of low areas. Ventilate closed spaces before entering them. Wear positive pressure breathing apparatus and special protective clothing. Evacuate area endangered by gas. Isolate for 1/2 mile in all directions if tank car or truck is involved in fire.

Small fires: let burn unless leak can be stopped immediately. Large fires: water spray, fog, or foam. Move container from fire area if you can do so without risk. Stay away from ends of tanks. Withdraw immediately in case of rising sound from venting safety device or any discoloration of tank due to fire. Cool container with water using unmanned device until well after fire is out. Isolate area until gas has dispersed. Preferably let fire burn, stop gas flow. Fires may be extinguished with dry chemical, foam, or carbon dioxide. (EPA, 1998)

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

Stop flow of gas before extinguishing fire. Use water spray to control fire by preventing its spread and absorbing some of its heat.

Preferably let fire burn, stop gas flow. Fires may be extinguished with dry chemical, foam, or carbon dioxide. Water may be ineffective.

To fight fire: Alcohol foam, carbon dioxide, dry chemical.

Flashback along vapor trail may occur.

· 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.).

· Ventilate closed spaces before entering, but only if properly trained and equipped.

· 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.

· 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.

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

· Prevent entry into waterways, sewers, basements or confined areas.

· Isolate area until gas has dispersed.

· Consider igniting spill or leak to eliminate toxic gas concerns.

Excerpt from ERG Guide 117 [Gases - Toxic - Flammable (Extreme Hazard)]:

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

SPILL: See ERG Table 1 - Initial Isolation and Protective Action Distances on the UN/NA 1064 datasheet.

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. (ERG, 2024)

Immediate precautionary measure

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

· See Table 1 - Initial Isolation and Protective Action Distances.

· 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.

Small spill:

- ISOLATE in all directions: 30 m (100 ft)

Large spill:

- ISOLATE in all directions: 200 m (600 ft)

- PROTECT people from downwind during DAY time: 0.1 km (0.1 mi)

- PROTECT people from downwind during NIGHT time: 0.3 km (0.2 mi)

- PROTECT people from downwind during DAY time: 1.3 km (0.8 mi)

- PROTECT people from downwind during NIGHT time: 3.9 km (2.4 mi)

Evacuate danger area! Consult an expert! Personal protection: self-contained breathing apparatus. Ventilation. Do NOT let this chemical enter the environment.

Stop or control the leak, if this can be done with undue risk. Use water spray to cool and disperse vapors, protect personnel, and dilute spills to form nonflammable mixtures. Control runoff and isolate discharged material for proper disposal.

Spills of thiols can be neutralized with a household bleach solution and flushed with an abundant flow of water. /Thiols/

A variety of methods and procedures, and also patents, are available with methods to absorb odors in scrubbers, by use of catalytic oxidizers or combined scrubber systems with oxidizing agents such as ozone or peroxides. /methyl mercaptans/

If methyl mercaptan is spilled or leaked, the following steps should be taken: 1. If methyl mercaptan is in the gaseous form, stop the flow of gas. If the source of the leak is a cylinder and the leak cannot be stopped in place, remove the leaking cylinder to a safe place in the open air and repair the leak or allow the cylinder to empty. 2. Remove all ignition sources. 3. Ventilate area of spill or leak. 4. For small quantities of liquids containing methyl mercaptan, absorb on paper towels and place in an appropriate container. Place towels in a safe place such as a fume hood for evaporation. Allow sufficient time for evaporation of the vapors so that the hood duct work is free from methyl mercaptan vapors. Burn the paper in a suitable location away from combustible material. 5. Large quantities of liquids containing methyl mercaptan may be absorbed in vermiculite, dry sand, earth, or a similar material and placed in an appropriate container. Methyl mercaptan should not be allowed to enter a confined space such as a sewer because of the possibility of an explosion. 6. Liquids containing methyl mercaptan may be collected by vacuuming with an appropriate system. If a vacuum system is used, there should be no sources of ignition in the vicinity of the spill, and flashback prevention devices should be provided.

Generators of waste (equal to or greater than 100 kg/mo) containing this contaminant, EPA hazardous waste number U153, must conform with USEPA regulations in storage, transportation, treatment and disposal of waste.

SRP: Wastewater from contaminant suppression, cleaning of protective clothing/equipment, or contaminated sites should be contained and evaluated for subject chemical or decomposition product concentrations. Concentrations shall be lower than applicable environmental discharge or disposal criteria. Alternatively, pretreatment and/or discharge to a permitted wastewater treatment facility is acceptable only after review by the governing authority and assurance that "pass through" violations will not occur. Due consideration shall be given to remediation worker exposure (inhalation, dermal and ingestion) as well as fate during treatment, transfer and disposal. If it is not practicable to manage the chemical in this fashion, it must be evaluated in accordance with EPA 40 CFR Part 261, specifically Subpart B, in order to determine the appropriate local, state and federal requirements for disposal.

Methyl mercaptan is a waste chemical stream constituent that may be subjected to ultimate disposal by controlled incineration, followed by effective scrubbing of the effluent gas.

A potential candidate for fluidized bed incineration at a temperature range of 450 to 980 °C and residence times of seconds for liquids and gases, and longer for solids. A potential candidate for rotary kiln incineration at a temperature range of 820 to 1,600 °C and residence times of seconds for liquids and gases, and hours for solids.

Excerpt from ERG Guide 117 [Gases - Toxic - Flammable (Extreme Hazard)]:

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. 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. If possible, turn leaking containers so that gas escapes rather than liquid. Prevent entry into waterways, sewers, basements or confined areas. Isolate area until gas has dispersed. Consider igniting spill or leak to eliminate toxic gas concerns. (ERG, 2024)

Fireproof. Separated from strong oxidants and acids. Cool. Store in an area without drain or sewer access.

Separate from oxidizing materials. Store in a cool, dry, well-ventilated location.

Store in a cool place.

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

· Wear chemical protective clothing that is specifically recommended by the manufacturer when there is NO RISK OF FIRE.

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

TIH (Toxic Inhalation Hazard) - Term used to describe gases and volatile liquids that are toxic when inhaled. Some are TIH materials themselves, e.g., chlorine, and some release TIH gases when spilled in water, e.g., chlorosilanes. [ERG 2016].

0.5 [ppm]

AEGL 1: Notable discomfort, irritation, or certain asymptomatic non-sensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure (Unit: ppm)

AEGL 2: Irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape (Unit: ppm)

AEGL 3: Life-threatening health effects or death (Unit: ppm)

NR = Not Recommended due to insufficient data Level of Odor Awareness is 1.9 ppb

AEGLs Status: Final

0.0050 [ppm]

23 [ppm]

68 [ppm]

0.5 ppm (1 mg/m³) [15 minutes]

C 0.5 ppm (1 mg/m3) [15-minute]

0.5 ppm (1 mg/m³) [Construction and Maritime Industries only]

10 ppm (20 mg/m³) [General Industry only]

C 10 ppm (20 mg/m3) See Appendix G

150 ppm (NIOSH, 2024)

150.0 [ppm]

Excerpts from Documentation for IDLHs: Human data: Students accidentally exposed to about 4 ppm for several hours experienced headaches and nausea [Clayton and Clayton 1981]. Some investigators have reported that the toxicity of methyl mercaptan is similar to hydrogen sulfide while others report the toxicity to be somewhat less than hydrogen sulfide [DeRekowski 1893; Frankel 1921].

See: 74931

8 hr Time Weighted Avg (TWA): 0.5 ppm.

Excursion Limit Recommendation: Excursions in worker exposure levels may exceed 3 times the TLV-TWA for no more than a total of 30 minutes during a work day, and under no circumstances should they exceed 5 times the TLV-TWA, provided that the TLV-TWA is not exceeded.

0.5 ppm as TWA.

0.5 ppm [2003]

1.0 mg/m

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

Small Fire

· Dry chemical, CO2, water spray or regular foam.

Large Fire

· Water spray, fog or regular foam.

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

· Damaged cylinders should be handled only by specialists.

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.

Methyl mercaptan appears as a colorless low-boiling liquid that is denser than water. Very toxic by inhalation. Can be absorbed through the skin. Has a sharp odor, but the sense of smell cannot be relied upon to warn of the presence of vapors at low concentrations. Rate of onset: Immediate Persistence: Minutes to hours Odor threshold: 0.002 ppm Source/use/other hazard: From decayed organic matter - pulp mills, oil refineries; highly flammable; liquid burns/frostbite.

Colorless gas with a disagreeable odor like garlic or rotten cabbage; Note: A liquid below 43 degrees F. Shipped as a liquefied compressed gas; [NIOSH]

COLOURLESS GAS WITH CHARACTERISTIC ODOUR.

clear liquid (at <6 °CC) or colourless gas with odour of rotten cabbage or garlic

Colorless gas with a disagreeable odor like garlic or rotten cabbage.

Colorless gas with a disagreeable odor like garlic or rotten cabbage. [Note: A liquid below 43 °F. Shipped as a liquefied compressed gas.]

Water-white liquid when below boiling point, or colorless gas

Odor of rotten cabbage

Powerful, unpleasant odor

Disagreeable odor like garlic

Pungent, decayed cabbage.

Unpleasant cabbage taste

42.7 °F at 760 mmHg (EPA, 1998)

5.95 °C at 760 mm Hg

6.10 to 6.20 °C. @ 727.00 mm Hg

5.9-6.0 °C

5.9 °C @760 [mm Hg]

-189.4 °F (EPA, 1998)

-189.4 °F

0 °F (EPA, 1998)

< -17.78 °Celsius, open cup

0 °F (Open cup) /Liquid/

0 °F (LESS THAN -18 °C) (OPEN CUP)

Flammable gas

NA (Gas) (oc) 0 °F (Liquid)

2 % (NIOSH, 2024)

Soluble in alcohol and ether; slightly soluble in chloroform

Soluble in petroleum naptha

In water, 15,400 mg/L at 25 °C

Very soluble in alcohol or in ether; soluble in water (23.3 g/L at 20 °C)

15.4 mg/mL at 25 °C

Solubility in water, g/100ml at 20 °C: 2.3

2.4 g/100 ml water; soluble in alcohol, ether, organic solvents

(in ethanol)

0.892 at 42.8 °F (USCG, 1999) - Less dense than water; will float

0.9600 at 25 °C/4 °C

Relative density (water = 1): 0.9

0.862-0.894 (gas); 1.032-1.040 (liquid)

0.90 at 42.8 °F

0.8665 @ 20°C

Highly flammable. Reacts with water, steam or acids to produce toxic, flammable vapors [Lewis].

Sulfides, Organic

Highly Flammable

Water-Reactive

METHYL MERCAPTAN is a reducing agent--can react vigorously with oxidizing agents. Dangerous fire or explosion hazard when exposed to heat, flame, sparks or strong oxidizing agents (e.g., calcium hypochlorite). When heating to decomposition emits highly toxic fumes of oxides of sulfur [Lewis, 3rd ed., 1993, p. 862]. Violent reaction with mercury(II) oxide [Klason P., Ber., 1887, 20, p. 3410].

Can react dangerously with strong oxidizing agents and mercury (II) oxide.

Strong oxidizers, bleaches, copper, aluminum, nickel-copper alloys.

Violent reaction with mercury (II) oxide.

Reacts with water, steam, or acids to produce toxic and flammable vapors.

Strong oxidizers, bleaches, copper, aluminum, nickel-copper alloys

CDC-ATSDR Toxicological Profile

The substance can be absorbed into the body by inhalation.

inhalation, skin and/or eye contact (liquid)

Cough. Sore throat. Dizziness. Headache. Nausea. Vomiting. Unconsciousness.

ON CONTACT WITH LIQUID: FROSTBITE.

Redness. Pain.

irritation eyes, skin, respiratory system; narcosis; cyanosis; convulsions; liquid: frostbite

Hematological (Blood Forming), Neurological (Nervous System)

Eyes, skin, respiratory system, central nervous system, blood

Occupational hepatotoxin - Secondary hepatotoxins: the potential for toxic effect in the occupational setting is based on cases of poisoning by human ingestion or animal experimentation.

Methemoglobinemia - The presence of increased methemoglobin in the blood; the compound is classified as secondary toxic effect

Other Poison - Chemical Asphyxiant

Toxic Pneumonitis - Inflammation of the lungs induced by inhalation of metal fumes or toxic gases and vapors.

Methyl Mercaptan

PDF Document

LC50 (rat) = 675 ppm

LD50 Mouse oral 61 mg/kg

LC50 Mouse inhalation 1,664 ppm/4 hr

LC50 Mouse inhalation 6,530 ug/cu m/2 hr

LC50 Rat inhalation 675 ppm

LC50 Sprague Dawley rat (male/female) inhalation 643-709 ppm (4-hr exposure; 14-day observation period)

Epigallocatechin gallate (EGCg), the main antimicrobial tea catechin, has been reported to inhibit growth and virulence factors of oral pathogens in vitro. Although the mechanism is unclear, the potential of EGCg in reducing halitosis caused by volatile sulfur compounds (VSCs) has been suggested. This study tested the hypothesis that EGCg reduces VSCs by suppressing mgl, the gene encoding L-methionine-alpha-deamino-gamma-mercaptomethane-lyase, responsible for methyl mercaptan (CH3SH) production by oral anaerobes. In this study, the effect of EGCg on in vitro growth, CH3SH production, and mgl gene expression in P. gingivalis W83 was investigated. EGCg inhibited growth of P. gingivalis W83 (MIC = 97.5 ug/mL) and was bactericidal (MBC = 187.5 ug/mL). At sub-MIC levels, EGCg inhibited CH3SH production, and mgl mRNA and protein expression (p < 0.05). /The authors/ conclude that EGCg may represent a natural and alternative agent to the antimicrobial chemicals currently available for halitosis control.

...The doses of ip injected ammonium acetate or sodium octanoate needed to induce hepatic coma (coma following acute necrosis of the liver) were greatly reduced when /rats/ were exposed to methyl mercaptan at 1,200 ppm within 1 minute after injection. /It was/ suggested that methyl mercaptan exposure may intensify the toxic effects of ammonia and fatty acids in human hepatic failure.

Methanethiol is associated with hepatic failure in humans and the synergistic action of methanethiol, ammonia and octanoate is sufficient to account for the coma of experimental hepatic necrosis. ...

Interactions between mercaptans, including methyl mercaptan, and ammonium acetate or sodium octanoate in the induction of coma in rats has been reported. ...Human exposure to methyl mercaptan in conjunction with hepatotoxins may result in exacerbated liver damage and/or neurotoxicity. There is a possibility of these multiple exposures in the workplace and in the vicinity of hazardous waste sites.

... Ammonia and fatty acids accentuated respiratory paralysis and coma due to exposure to methanethiol.

Immediate first aid: Ensure that 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 as 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. /Sulfur 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 if necessary ... . For eye contamination, flush eyes immediately with water. Irrigate each eye continuously 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 ... . Cover skin burns with dry sterile dressings after decontamination ... . /Sulfur 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 ... . Consider administering a beta agonist such as albuterol for severe bronchospasms ... . Monitor cardiac rhythm and treat arrhythmias if necessary ... . Start IV administration of D5W /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. Consider vasopressors if patient is hypotensive with a normal fluid volume. Watch for signs of fluid overload ... . Treat seizures with diazepam or lorazepam ... . Use proparacaine hydrochloride to assist eye irrigation ... . /Sulfur and related compounds/

Prior to placing a worker in a job with a potential for exposure to methyl mercaptan, the physician should evaluate and document the worker's baseline health status with thorough medical, environmental, and occupational histories, a physical examination, and physiologic and laboratory tests appropriate for the anticipated occupational risk. These should concentrate on the function and integrity of the nervous and respiratory systems. Medical surveillance for respiratory disease should be conducted by using the principles and methods recommended by NIOSH and the American Thoracic Society (ATS). A preplacement medical evaluation is recommended in order to detect and assess preexisting or concurrent conditions which may be aggravated or result in increased risk when a worker is exposed to methyl mercaptan at or below the NIOSH REL. The examining physician should consider the probable frequency, intensity, and duration of exposure, as well as the nature and degree of the condition, in placing such a worker. Such conditions, which should not be regarded as absolute contraindications to job placement, include chronic diseases of the respiratory system.

/SIGNS AND SYMPTOMS/ Occupational exposure to methyl mercaptan may induce headache, nausea, vomiting, eye irritation, chest tightness and wheezing, dizziness, diplopia and a productive cough.

/SIGNS AND SYMPTOMS/ Low-level signs and symptoms of exposure to methyl mercaptan have been eye and mucous membrane irritation, dizziness, staggering gait, nausea and vomiting. Respiratory tract irritation has led to pulmonary edema and hepatic and renal damage.

/SIGNS AND SYMPTOMS/ Clinical signs following acute exposure included initial hyperactivity, tachypnea, cyanosis, muscular weakness, convulsions, respiratory depression, /CNS depression/, skeletal muscular paralysis, and paralysis of the respiratory musculature.../and dose-related/ inflammation in the nasal mucosa and lungs.

/SIGNS AND SYMPTOMS/ Chief signs and symptoms are eye and mucous membrane irritation, headache, dizziness, staggering gait, nausea, and vomiting, and more or less pronounced paralysis of the locomotor muscles and respiration.

For more Human Toxicity Excerpts (Complete) data for METHYL MERCAPTAN (31 total), please visit the HSDB record page.

/LABORATORY ANIMALS: Acute Exposure/ /Rats were/ exposed to various concentrations of methyl mercaptan for 4 hours. No deaths occurred after inhalation of 400 ppm; however, all rats exposed at 700 ppm died. An LC50 of 675 ppm was determined. By way of comparison, an LC50 of 444 ppm was determined for hydrogen sulfide.

/LABORATORY ANIMALS: Acute Exposure/ ... When rats were injected with 40-120 umol methanethiol a range of responses was obtained which varied between normal consciousness and coma. The minimum blood concentration of methanethiol associated with coma (200 nmol/mL) was at least 10-fold greater than in patients with hepatic encephalopathy but brain concentrations were similar in comatose rats and those which remained awake. Blood methanethiol concentrations were similar in control and germ free rats and did not rise in cirrhotics or controls after ingestion of 2 g methionine. It is concluded that while methanethiol may accumulate in hepatic coma, it is unlikely to be of major pathogenetic importance. Endogenous mercaptans are unlikely to originate from bacterial metabolism in the gut.

/LABORATORY ANIMALS: Acute Exposure/ In normal rats in a coma induced by NH4+ alone or by methanethiol alone, the brain and blood levels of ammonia or methanethiol are much higher than those observed in rats in experimental hepatic coma. When various smaller dosage combinations of NH4+, methanethiol, and octanoic acid were injected simultaneously, coma occurred at lower brain and blood concentrations of ammonia and methanethiol. Brain ammonia and methanethiol concentrations in normal rats receiving 0.75 mmol NH4+ plus 0.15 mmol octanoic acid plus 18 umol methanethiol were comparable with those observed in 24 rats in hepatic coma after fulminant hepatic failure caused by acute massive ischemic liver necrosis. The normal rats became comatose. In these rats and in the rats in hepatic coma, the ammonia level in the brain was increased threefold and the methanethiol level in the brain was increased fivefold. Because these levels of ammonia and methanethiol were sufficient to induce coma in normal rats, they should also have been sufficient to induce coma in rats with damaged livers. Therefore, the accumulation of ammonia and methanethiol in the central nervous system after the acute massive ischemic necrosis may have been sufficient to account for the coma that ensued, without the involvement of other factors.

/LABORATORY ANIMALS: Acute Exposure/ Two studies that investigated the neurological effects of ip administration of methyl mercaptan have been located. An injection equivalent to 4.8 mg/kg was sufficient to induce coma in 100% of treated rats in 2-4 minutes. In germ-free rats administered methyl mercaptan at 9.6-28.8 mg/kg, 200 nmol/mL was the minimum blood concentration associated with coma. It is interesting to note that this level was much higher than the blood level of 0.5 nmol/mL in comatose rats reported ... in inhalation studies.

For more Non-Human Toxicity Excerpts (Complete) data for METHYL MERCAPTAN (15 total), please visit the HSDB record page.

LC50; Species: Salmonides; Concentration: 0.55-0.9 mg/L /Conditions of bioassay not specified/

/AQUATIC SPECIES/ Fish are highly sensitive to methyl mercaptan. ... The no-effect level is 0.5 ppm and the minimum lethal concentration is 0.9 ppm for the coastal cutthroat trout and king and silver salmon. Methyl mercaptan was lethal at 1 ppm to white bass, yellow perch, large- and smallmouth bass, bluegills, and rock bass.

/AQUATIC SPECIES/ King salmon (Oncorhynchus tschawytscha) (10 fish) were exposed for 120 hours in static cylindrical glass jugs of 18 L capacity. The LC100 was 0.9 mg/L and the LC0 was 0.5 mg/L. The LC100 was 1.75 mg/L and the LC0 was 0.9 mg/L in similarly exposed silver salmon (Oncorhynchus kisutch) and the LC100 was 1.2 mg/L with an LC0 of 0.7 mg/L in coastal cutthroat trout (Salmo clarki).

The substance is very toxic to aquatic organisms. It is strongly advised not to let the chemical enter into the environment.

Methyl mercaptan's production and use in chemical synthesis and as an odorant in natural gas may result in its release to the environment through various waste streams. Potential industrial emission sources include wood pulp, petroleum-processing, and sewage treatment plants. Methyl mercaptan is also generated in salt marshes, soils, freshwater algae, and decomposing algal mats. A major source of methyl mercaptan is the microbial degradation of methionine. If released to air, a vapor pressure of 1,510 mm Hg at 25 °C indicates methyl mercaptan will exist as a gas above its normal boiling point of 5.95 °C. Gas-phase methyl mercaptan will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 11.7 hours. In the night-time atmosphere, methyl mercaptan will react with nitrate radicals with a half-life of about 1 hour. Methyl mercaptan absorbs UV light at 290 nm suggesting that it may be susceptible to direct photolysis by sunlight. If released to soil, methyl mercaptan is expected to have high mobility based upon an estimated Koc of 13. However, gaseous methyl mercaptan adsorbs to dry and moist soil surfaces. Volatilization from moist soil surfaces is expected to be an important fate process based upon an estimated Henry's Law constant of 3.12X10-3 atm-cu m/mole. Methyl mercaptan may volatilize from dry soil surfaces based upon its vapor pressure. The importance of volatilization from soil surfaces may be attenuated by gas-phase adsorption to soil. Under anaerobic conditions in soils, dimerization of methyl mercaptan to dimethyl disulfide will occur. If released into water, methyl mercaptan is not expected to adsorb to suspended solids and sediment based upon the estimated Koc. Volatilization from water surfaces is expected to be an important fate process based upon this compound's estimated Henry's Law constant. Estimated volatilization half-lives for a model river and model lake are 0.8 hours and 2.8 days, respectively. An estimated BCF of 3 suggests the potential for bioconcentration in aquatic organisms is low. Hydrolysis is not expected to be an important environmental fate process since this compound lacks functional groups that hydrolyze under environmental conditions. Methyl mercaptan is produced under anaerobic conditions (e.g. in salt marshes) by sulfate-reducing and methane-producing bacteria from methionine, or reversibly formed from dimethyl sulfide and dimethyl disulfide. Ultimately, methyl mercaptan may be mineralized to methane, carbon dioxide, and hydrogen sulfide. When incubated in anaerobic lake sediment for 4 hrs, methyl mercaptan was rapidly mineralized. Occupational exposure to methyl mercaptan may occur through inhalation and dermal contact with this compound at workplaces where methyl mercaptan is produced or used. Workers will primarily be exposed to methyl mercaptan via inhalation in work settings such as pulp mills and oil refineries or water treatment works. Monitoring data indicate that the general population may be exposed to methyl mercaptan via inhalation of ambient air and ingestion of some foods. (SRC)

Natural sources of methyl mercaptan include vegetation, animal wastes, microbial degradation, and natural gas(1-4). Methyl mercaptan is generated in salt marshes, soils, freshwater algae, and decomposing algal mats(5). A major source of methyl mercaptan is the microbial degradation of methionine(5). Methyl mercaptan has been isolated from the roots of Raphanus sativas and traces of the chemical are found in some leaves and foods(4). Natural gas contaminated with methyl mercaptan (sour gas) found in west Texas contains sufficient amounts of methyl mercaptan that commercial quantities may be extracted from this gas(4).

Methyl mercaptan's production and use in chemical synthesis for jet fuels, pesticides, fungicides, and methionine(1) and as an odorant in natural gas(2-5) may result in its release to the environment through various waste streams(SRC). Potential industrial emission sources include wood pulp, oil shale, petroleum-processing plants, starch manufacturing, rendering plants, and sewage treatment plants(2-7).

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 13(SRC), determined from a structure estimation method(2), indicates that methyl mercaptan is expected to have very high mobility in soil(SRC). Gaseous methyl mercaptan has been observed to partition to soils(3). For example, when gaseous methyl mercaptan was passed over six air-dried and moist (50% field capacity) soils, 2.4-32.1 mg/g and 2.2-21.4 mg/g of methyl mercaptan rapidly adsorbed to the dry and moist soils, respectively(3). It was suggested that adsorption to soil surfaces might be an environmental sink for gaseous methyl mercaptan(3). Volatilization of methyl mercaptan from moist soil surfaces is expected to be an important fate process(SRC) given an estimated Henry's Law constant of 0.0031 atm-cu m/mole(SRC), based upon its vapor pressure, 1,510 mm Hg at 25 °C(4), and water solubility, 15,400 mg/L(5). Methyl mercaptan is expected to volatilize rapidly from dry soil surfaces based upon its vapor pressure and because it is a gas a temperatures above 6 °C(SRC). However, the importance of volatilization from soil surfaces may be attenuated by gas-phase adsorption to soil surfaces(SRC). Methyl mercaptan is produced under anaerobic conditions (e.g., in salt marshes) by a variety of organisms and is often liberated during the decay of sulfur-containing organic matter(6). It may be formed by sulfate-reducing and methane-producing bacteria from methionine, or reversibly formed from dimethyl sulfide and dimethyl disulfide(6). Ultimately, methyl mercaptan may be mineralized to methane, carbon dioxide, and hydrogen sulfide(6). The oxidation and consequent dimerization of methyl mercaptan to dimethyl disulfide occurs for soils supplemented with methionine and its sulfoxide, and sulfone or S-methyl cysteine(7). This results in part from the formation of methyl mercaptan and subsequent dimerization to dimethyl disulfide(7).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 13(SRC), determined from a structure estimation method(2) indicates that methyl mercaptan is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(3) based upon an estimated Henry's Law constant of 0.0031 atm-cu m/mole(SRC) derived from its vapor pressure, 1,510 mm Hg(4), and water solubility, 15,400 mg/L(5). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 0.8 hours and 2.8 days, respectively(SRC). According to a classification scheme(6), an estimated BCF of 3(SRC), from its estimated log Kow of 0.78(2) and a regression-derived equation(2), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Methyl mercaptan is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions(3). Methyl mercaptan is produced under anaerobic conditions (e.g. in salt marshes) by a variety of organisms and is often liberated during the decay of sulfur-containing organic matter(7). It may be formed by sulfate-reducing and methane-producing bacteria from methionine, or reversibly formed from dimethyl sulfide and dimethyldisulfide(7). Ultimately, methyl mercaptan may be mineralized to methane, carbon dioxide, and hydrogen sulfide(7). When incubated in anaerobic lake sediment from Lake Mendota, WI for 4 hr, methyl mercaptan was rapidly mineralized(8).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), methyl mercaptan, which has a vapor pressure of 1510 mm Hg at 25 °C(2) is expected to exist solely as a vapor/gas in the ambient atmosphere. Methyl mercaptan has a normal boiling point of 5.95 °C(2), so at temperatures above 5.95 °C, methyl mercaptan will exist as a gas in the atmosphere(SRC). Gas-phase methyl mercaptan 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 11.7 hours(SRC), calculated from its rate constant of 3.29X10-11 cu cm/molecule-sec at 25 °C(3). The half-life for the reaction of methyl mercaptan with ozone in the atmosphere has been reported to be 140 hr(4). The rate constant for the gas-phase reaction of methyl mercaptan with nitrate radicals that exist in the night-time atmosphere ranged from 8.1X10-13 to 12.2X10-13 cu cm/molecule-sec(5); this corresponds to an average atmospheric half-life of about 1 hour(SRC) at an atmospheric concentration of 2.4X10+8 nitrate radicals per cu cm(5). The UV spectrum of methyl mercaptan shows a log epsilon of 0.7 at 290 nm(6) suggesting that methyl mercaptan may be susceptible to direct photolysis by sunlight(SRC).

AEROBIC: Aerobic degradation of methyl mercaptan is insignificant compared to anaerobic degradation(1).

ANAEROBIC: Methyl mercaptan is produced by a variety of organisms and is often liberated during the decay of sulfur-containing organic matter under anoxic conditions(1). Methyl mercapatan appears to be produced ubiquitously by a majority of heterotrophic bacteria by enzymatic sulfide-dependant thiol methyltransferase activity(2). It may be formed by sulfate-reducing and methane-producing bacteria from methionine, or reversibly formed from dimethyl sulfide and dimethyldisulfide(1). Ultimately, methyl mercaptan may be mineralized to methane, carbon dioxide, and hydrogen sulfide(1). When incubated in anaerobic lake sediment from Lake Mendota, WI for 4 hr, methyl mercaptan was rapidly mineralized(3). Addition of methyl mercaptan to sediment slurries from seven chemically different anoxic aquatic environments stimulated methane production without any noticeable lag(1). These sediments included two estuarine salt marshes, a freshwater lake, and two hypersaline alkaline lakes(1). For the one sediment in which rate information was presented, biodegradation was completed within a week(1). Methyl mercaptan is produced anaerobically from dimethylsulfide (and 3-methiolpropionate) in salt marshes(2). The oxidation and consequent dimerization of methyl mercaptan to dimethyldisulfide occurs for soils supplemented with methionine and its sulfoxide, and sulfone or S-methylcysteine(2). This results in part from the formation of methyl mercaptan and subsequent dimerization to dimethyldisulfide(2).

The rate constant for the vapor-phase reaction of methyl mercaptan with photochemically-produced hydroxyl radicals is 3.29X10-11 cu cm/molecule-sec at 25 °C(1). This corresponds to an atmospheric half-life of about 11.7 hours at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). Kinetic evidence suggests that the hydroxyl radical adds to the sulfur atom, forming an adduct, or complex with the mercaptan(2,3); sulfur dioxide (SO2) is a major product of this reaction(4). The half-life for the reaction with ozone in the atmosphere has been reported to be 140 hr(5); no rate constant was available(SRC). The rate constant for the vapor-phase reaction of methyl mercaptan with nitrate radicals that exist in the night-time atmosphere ranged from 8.1X10-13 to 12.2X10-13 cu cm/molecule-sec(6). This corresponds to an average atmospheric half-life of about 1 hour(SRC) at an atmospheric concentration of 2.4X10+8 nitrate radicals per cu cm(6). The reaction products include formaldehyde, sulfur dioxide, methyl nitrate as well as particulate methane sulfonic acid and inorganic sulfate(7). Methyl mercaptan is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions(8). The UV spectrum of methyl mercaptan shows a log epsilon of 0.7 at 290 nm(9) suggesting that methyl mercaptan may be susceptible to direct photolysis by sunlight(SRC).

An estimated BCF of 3 was calculated in fish for methyl mercaptan(SRC), using an estimated log Kow of 0.78(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 methyl mercaptan can be estimated to be 13(SRC). According to a classification scheme(2), this estimated Koc value suggests that methyl mercaptan is expected to have very high mobility in soil. Gaseous methyl mercaptan has been observed to partition to soils(3). For example, when gaseous methyl mercaptan was passed over six air-dried and moist (50% field capacity) soils, 2.4-32.1 mg/g and 2.2-21.4 mg/g of methyl mercaptan rapidly adsorbed to the dry and moist soils, respectively(3). Neither the capacity or rate of sorption was correlated to soil pH, organic matter content, or clay content; sterile controls ruled out the involvement of microorganisms(3); it was suggested that adsorption to soil surfaces might be an environmental sink for gaseous methyl mercaptan(3).

The Henry's Law constant for methyl mercaptan is estimated as 0.0031 atm-cu m/mole(SRC) derived from its vapor pressure, 1,510 mm Hg(1), and water solubility, 15,400 mg/L(2). This Henry's Law constant indicates that methyl mercaptan is expected to volatilize rapidly from water surfaces(3). 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)(3) is estimated as 0.8 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)(3) is estimated as 2.8 days(SRC). Methyl mercaptan's Henry's Law constant indicates that volatilization from moist soil surfaces is expected to occur(SRC). Methyl mercaptan is expected to volatilize rapidly from dry soil surfaces based upon its vapor pressure and because it is a gas a temperatures above 6 °C(SRC). However, gaseous methyl mercaptan gas has been found to strongly adsorb to moist and dry soil surfaces suggesting that adsorption might be an environmental sink for methyl mercaptan(4). Therefore, the importance of volatilization from soil surfaces may be attenuated by adsorption(SRC).

SURFACE WATER: The concentration of methyl mercaptan in sea water and salt water marshes were reported to range from 14-19 ng/L and 48-144 ng/L, respectively(1). Methyl mercaptan was qualitatively detected in the mid-city flood waters of New Orleans following Hurricane Katrina(2).

The concentration of methyl mercaptan 1 km offshore from the effluent of a pulp mill in Japan was approximately 10 ppb(1).

In a comprehensive survey of wastewater from 4,000 industrial and publicly owned treatment works sponsored by the Effluent Guidelines Division of the USEPA, methyl mercaptan was identified in discharges of the following industries: timber products (frequency, 1%; mean concentration, 14 ppb), organics and plastics (frequency, 2%; mean concentration, 364 ppb), textile mills (frequency, 1%; mean concentration, 40 ppb), pulp and paper (frequency, 1%; mean concentration, 187 ppb), pharmaceuticals (frequency, 1%; mean concentration, 43 ppb) synfuels (frequency, 1%; mean concentration, 47 ppb), and publicly owned treatment works (frequency, 45%; mean concentration, 52 ppb)(1). Methyl mercaptan has been identified in the off-gas from shale oil retorting in Rio Blanco and Paraho, Colorado(2). Methyl mercaptan, at a concentration of 128 ppb, was found in the effluent of a community septic tank near Tacoma, WA; however, it was not found in the influent(3). Methyl mercaptan was found in both the influent and effluent of wastewater treatment plants receiving municipal wastes and waste from a viscose plant and a french fried potato plant(4). Wastewater from the viscose plant was rich in sulfate and the residence time in the distribution system was sufficient to deplete the water of oxygen, thereby creating anaerobic conditions(4). Effluent gases from a sulfate-cellulose mill were reported to contain 94 ppm methyl mercaptan(5). The concentration of methyl mercaptan in leachate from 3 hazardous waste sites in Germany ranged from not detected to 600 ug/L(6). A survey of about 2,950 industrial facilities in North Carolina reported fugitive and stack emissions of methyl mercaptan totaling 239,594 pounds/year(7).

Estimation of average methyl mercaptan emission from a saline marsh in Cox Landing, NC was 6.56 g sulfur/sq m/year(1). Contrary to expectations, volatile sulfur compounds emitted from tidal marsh soil increased as the soil moisture decreased from saturated to field capacity(2). Further decrease in the moisture content of the soil decreased sulfur emissions(2). The flux of methyl mercaptan from a salt marsh in Long Island, NY was 1.92 g S/sq m/year(3). In 2000-2002 monitoring of a biogas production facility in Sweden, methyl mercaptan concentrations in the VOC biogas ranged from 10-750 ppbv, but the dropped to <1 to 5 ppbv after upgrading the cleaning and scrubbing process(4).

URBAN/SUBURBAN: Methyl mercaptan was detected in ambient air at 4 ppb (8.2 ug/cu m) in Japan(1). Methyl mercaptan was detected at a primary school in Japan at 2.8 ppb (5.7 ug/cu m)(1).

Methyl mercaptan has been identified as a volatile flavor compound in roasted filberts(1). It is also a volatile component of Beaufort cheese, a Gruyere type cheese manufactured in a limited area of the French Alps(2).

Trace amounts of methyl mercaptan are present in the roots and leaves of some plants(1).

According to the 2006 TSCA Inventory Update Reporting data, the number of persons reasonably likely to be exposed in the industrial manufacturing, processing, and use of methyl mercaptan is 1000 or greater; the data may be greatly underestimated(1).

NIOSH (NOES Survey 1981-1983) has statistically estimated that 6,192 workers (380 of these are female) are potentially exposed to methyl mercaptan in the US(1). Occupational exposure to methyl mercaptan may occur through inhalation with this compound at workplaces where methyl mercaptan is produced or used(SRC). Workers will primarily be exposed to methyl mercaptan in industries such as pulp mills, oil refineries, or water treatment works(SRC). However, since methyl mercaptan has a extremely unpleasant odor and its odor threshold in air is 1.6 ppb(2), it is unlikely that workers would tolerate exposure to concentrations above the odor threshold for a substantial time(3). Monitoring data indicate that the general population may be exposed to methyl mercaptan via inhalation of ambient air and ingestion of some foods(SRC).

methylmercaptan ... is believed to be present in urine after eating asparagus (spears and tips), causing its peculiar odor.

Methyl mercaptan appears in urine within an hour after eating asparagus(1).

Generators of waste (equal to or greater than 100 kg/mo) containing this contaminant, EPA hazardous waste number U153, must conform with USEPA regulations in storage, transportation, treatment and disposal of waste.

SRP: Wastewater from contaminant suppression, cleaning of protective clothing/equipment, or contaminated sites should be contained and evaluated for subject chemical or decomposition product concentrations. Concentrations shall be lower than applicable environmental discharge or disposal criteria. Alternatively, pretreatment and/or discharge to a permitted wastewater treatment facility is acceptable only after review by the governing authority and assurance that "pass through" violations will not occur. Due consideration shall be given to remediation worker exposure (inhalation, dermal and ingestion) as well as fate during treatment, transfer and disposal. If it is not practicable to manage the chemical in this fashion, it must be evaluated in accordance with EPA 40 CFR Part 261, specifically Subpart B, in order to determine the appropriate local, state and federal requirements for disposal.

Methyl mercaptan is a waste chemical stream constituent that may be subjected to ultimate disposal by controlled incineration, followed by effective scrubbing of the effluent gas.

A potential candidate for fluidized bed incineration at a temperature range of 450 to 980 °C and residence times of seconds for liquids and gases, and longer for solids. A potential candidate for rotary kiln incineration at a temperature range of 820 to 1,600 °C and residence times of seconds for liquids and gases, and hours for solids.

If ... THERE IS NO FIRE, go directly to the Table of Initial Isolation and Protective Action Distances /(see table below)/ ... to obtain initial isolation and protective action distances. IF THERE IS A FIRE, or IF A FIRE IS INVOLVED, go directly to the appropriate guide /(see guide(s) below)/ and use the evacuation information shown under PUBLIC SAFETY. /Methyl mercaptan/

Table: Table of Initial Isolation and Protective Action Distances for Methyl mercaptan [Table#2190]

/GUIDE 117: GASES - TOXIC - FLAMMABLE (EXTREME HAZARD)/ Health: TOXIC; Extremely Hazardous. May be fatal if inhaled or absorbed through skin. Initial odor may be irritating or foul and may deaden your sense of smell. Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control may cause pollution.

/GUIDE 117: GASES - TOXIC - FLAMMABLE (EXTREME HAZARD)/ Fire or Explosion: These materials are extremely flammable. May form explosive mixtures with air. May be ignited by heat, sparks or flames. Vapors from liquefied gas are initially heavier than air and spread along ground. Vapors may travel to source of ignition and flash back. Runoff may create fire or explosion hazard. Cylinders exposed to fire may vent and release toxic and flammable gas through pressure relief devices. Containers may explode when heated. Ruptured cylinders may rocket.

/GUIDE 117: GASES - TOXIC - FLAMMABLE (EXTREME HAZARD)/ Public Safety: CALL Emergency Response Telephone Number ... . 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. Many gases are heavier than air and will spread along ground and collect in low or confined areas (sewers, basements, tanks). Keep out of low areas. Ventilate closed spaces before entering.

For more DOT Emergency Guidelines (Complete) data for METHYL MERCAPTAN (9 total), please visit the HSDB record page.

UN 1064; Methyl Mercaptan

IMO 2.3; Methyl Mercaptan

49 055 20; Methyl mercaptan

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.

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.

Poison Gas Flammable Gas

Marine pollutant.

Symbol: F+, T, N; R: 12-23-50/53; S: (2)-16-25-60-61

UN Hazard Class: 2.3; UN Subsidiary Risks: 2.1