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Registry of Toxic Effects of Chemical Substances (RTECS)

Methanethiol

RTECS #

PB4375000

CAS #

74-93-1

Updated

September 2013

Molecular Weight

48.11

Molecular Formula

CH4S

Synonyms

Mercaptan methylique (French)
Mercaptomethane
Methaanthiol (Dutch)
Methanethiol (OSHA)
Methanthiol (German)
Methvtiolo (Italian)
Methyl mercaptan
Methyl mercaptan (ACGIH:OSHA)
Methylmercaptaan (Dutch)
Metilmercaptano (Italian)
RCRA waste number U153
Thiomethanol
Thiomethyl alcohol

Mutation Data and Reference

System TestRoute/Organism/TissueDoseReference
sex chromosome loss and nondisjunctioninhalation/Drosophila melanogaster99 pph/6M-continuousENVRAL 7,286,1974

Acute Toxicity Data and References

Route/OrganismDoseEffectReference
inhalation/mouse lethal concentration (50 percent kill): 6530 µg/m3/2HGTPZAB 16(6),46,1972
inhalation/rat lethal concentration (50 percent kill): 675 ppmLung, Thorax, or Respiration: Other changes

Gastrointestinal: Hypermotility, diarrhea

Kidney, Ureter, and Bladder: Urine volume increased
LacHB# 09JUN1978
inhalation/rat lethal concentration (50 percent kill): 643 ppm/4HHPV297 -,-,2001
inhalation/rat lethal concentration (50 percent kill): 1428 ppm/1HBehavioral: Ataxia

Lung, Thorax, or Respiration: Dyspnea
HPV297 -,-,2001
inhalation/rat lowest published toxic concentration: 700 ppm/30MBehavioral: Somnolence (general depressed activity)HPV297 -,-,2001
inhalation/rat lowest published toxic concentration: 1500 ppm/30MBehavioral: Somnolence (general depressed activity)

Behavioral: Tremor
HPV297 -,-,2001
inhalation/rat Lowest published lethal concentration: 10000 ppm/30MBehavioral: Somnolence (general depressed activity)

Behavioral: Convulsions or effect on seizure threshold

Lung, Thorax, or Respiration: Acute pulmonary edema
HPV297 -,-,2001
unreported route/mammal (species unspecified) lethal dose (50 percent kill): 60670 µg/kgGTPZAB 16(6),46,1972

Other Multiple Dose Data and References

Route/OrganismDoseEffectReference
inhalation/rat lowest published toxic concentration: 17 ppm/7H/13W- intermittentEndocrine: Changes in adrenal weight

Endocrine: Changes in spleen weight

Blood: Changes in serum composition (e.g. TP, bilirubin, cholesterol)
JTEHD6 8,71,1981
inhalation/rat lowest published toxic concentration: 100 ppm/6H/3D- intermittentBehavioral: Excitement

Lung, Thorax, or Respiration: Fibrosis, focal (pneumoconiosis)

Nutritional and Gross Metabolic: Other changes
NTIS** OTS0571484
inhalation/rat lowest published toxic concentration: 57 ppm/12W- intermittentLiver: Other changes

Nutritional and Gross Metabolic: Weight loss or decreased weight gain

Biochemical: Enzyme inhibition, induction, or change in blood or tissue levels: Dehydrogenases
HPV297 -,-,2001

Reviews

OrganizationStandardReference
American Conference of Governmental Industrial Hygienists (ACGIH)Threshold Limit Value-time-weighted average 0.5 ppmDTLVS* TLV/BEI,2013

Standards and Regulations

OrganizationStandardReference
Mine Safety and Health Administration (MSHA) STANDARD-airtime-weighted average 0.5 ppm (1 mg/m3)DTLVS* 3,167,1971
Occupational Exposure Limit IN ARGENTINA, BULGARIA, COLOMBIA, JORDAN check ACGIH TLV;
Occupational Exposure Limit IN SINGAPORE, VIETNAM check ACGIH TLV
Occupational Exposure Limit-AUSTRALIAtime-weighted average 0.5 ppm (0.98 mg/m3), JUL2008
Occupational Exposure Limit-AUSTRIAMAK-TMW 0.5 ppm (1 mg/m3);KZW 0.5 ppm (1 mg/m3), 2007
Occupational Exposure Limit-BELGIUMtime-weighted average 0.5 ppm (0.99 mg/m3), MAR2002
Occupational Exposure Limit-DENMARKtime-weighted average 0.5 ppm (1 mg/m3), MAY2011
Occupational Exposure Limit-FINLANDtime-weighted average 0.5 ppm (1 mg/m3), short term exposure limit 1.5 ppm (3 mg/m3), NOV2011
Occupational Exposure Limit-FRANCEVME 0.5 ppm (1 mg/m3), FEB2006
Occupational Exposure Limit-GERMANYMAK 0.5 ppm (1 mg/m3), 2011
Occupational Exposure Limit-HUNGARYtime-weighted average 1 mg/m3, short term exposure limit 1 mg/m3, SEP2000
Occupational Exposure Limit-ICELANDtime-weighted average 0.5 ppm (1 mg/m3), NOV2011
Occupational Exposure Limit-KOREAtime-weighted average 0.5 ppm (1 mg/m3), 2006
Occupational Exposure Limit-MEXICOtime-weighted average 0.5 ppm (1 mg/m3), 2004
Occupational Exposure Limit-NEW ZEALANDtime-weighted average 0.5 ppm (0.98 mg/m3), JAN2002
Occupational Exposure Limit-NORWAYtime-weighted average 0.5 ppm (1 mg/m3), JAN1999
Occupational Exposure Limit-PERUtime-weighted average 0,5 ppm (1 mg/m3), JUL2005
Occupational Exposure Limit-POLANDMAC(time-weighted average) 1 mg/m3, MAC(short term exposure limit) 2 mg/m3, JAN1999
Occupational Exposure Limit-RUSSIAshort term exposure limit 0.8 mg/m3, JUN2003
Occupational Exposure Limit-SWEDENtime-weighted average 1 ppm, JUN2005
Occupational Exposure Limit-SWITZERLANDMAK-week 0.5 ppm (1 mg/m3), KZG-week 1 ppm (2 mg/m3), JAN2011
Occupational Exposure Limit-THAILANDtime-weighted average 10 ppm (20 mg/m3), JAN1993
Occupational Exposure Limit-THE NETHERLANDSMAC-TGG 1 mg/m3, 2003
Occupational Exposure Limit-THE PHILIPPINEStime-weighted average 10 ppm (20 mg/m3), JAN1993
Occupational Exposure Limit-TURKEYtime-weighted average 10 ppm (20 mg/m3), JAN1993
Occupational Exposure Limit-UNITED KINGDOMtime-weighted average 0.5 ppm (1 mg/m3), OCT2007
Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (Construction)8H time-weighted average 0.5 ppm (1 mg/m3)CFRGBR 29,1926.55,1994
Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (Federal Contractors)ceiling concentration 10 ppm (20 mg/m3)CFRGBR 41,50-204.50,1994
Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (General Industry)ceiling concentration 10 ppm (20 mg/m3)CFRGBR 29,1910.1000,1994
Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (Shipyards)8H time-weighted average 0.5 ppm (1 mg/m3)CFRGBR 29,1915.1000,1993

NIOSH Documentation and Surveillance

OrganizationStandardReference
National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Level TO METHANETHIOL-airceiling concentration 0.5 ppm/15MNIOSH* DHHS #92-100,1992
National Occupational Exposure Survey 1983Hazard Code 45850; Number of Industries 7; Total Number of Facilities 147; Number of Occupations 25; Total Number of Employees Exposed 6192; Total Number of Female Employees Exposed 380
National Occupational Hazard Survey 1974Hazard Code 45850; Number of Industries 1; Total Number of Facilities 11; Number of Occupations 3; Total Number of Employees Exposed 357

Status in Federal Agencies

OrganizationReference
ATSDR TOXICOLOGY PROFILE (NTIS** PB/93/110799/AS)
EPA TSCA Section 8(b) CHEMICAL INVENTORY
EPA TSCA Section 8(d) unpublished health/safety studies
EPA TSCA TEST SUBMISSION (TSCATS) DATA BASE, JANUARY 2001
NIOSH Analytical Method, 1994: Mercaptans, 2542
On EPA IRIS database
OSHA ANALYTICAL METHOD #26
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