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Chemical Sampling Information (CSI)
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General Description

Synonyms: 2-Mercaptoimidazoline; 4,5-Dihydroimidazole-2(3H)-thione; ETU; NA-22; Pennac CRA; Warecure C; 2-Imidazolidinethione; 1,3-Ethylene-2-thiourea; N,N-Ethylenethiourea; ETU; 2-Imidazolidine-2-thione

OSHA IMIS Code Number: 1159

Chemical Abstracts Service (CAS) Registry Number: 96-45-7

NIOSH Registry of Toxic Effects of Chemical Substances (RTECS) Identification Number: NI9625000

NIOSH Pocket Guide to Chemical Hazards, Ethylene Thiourea: chemical description, physical properties, potentially hazardous incompatibilities, and more

Exposure Limits

National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL): Use encapsulated form. Appendix A - NIOSH Potential Occupational Carcinogens

Health Factors

Carcinogenic Classification:

Environmental Protection Agency (EPA): Group B2, probable human carcinogen

International Agency for Research on Cancer (IARC): Group 3, not classifiable as to its carcinogenicity to humans [121 KB PDF, 45 pages]

National Toxicology Program (NTP): Reasonably anticipated to be a human carcinogen [116 KB PDF, 3 pages]

Potential Symptoms: Irritation of eyes; in animals: thickening of the skin; goiter; teratogenic effects; [potential occupational carcinogen].

Health Effects: Irritation-Eye, Nose, Throat, Skin---Moderate (HE15)

Affected Organs: Eyes, skin, thyroid, reproductive system


  1. Ethylene thiourea is an OSHA Select Carcinogen. Reclassification by the IARC of this chemical from Group 2B (possibly carcinogenic to humans) to Group 3 has remained controversial.
  2. EPA's oral reference dose (daily oral exposure likely to be without an appreciable risk of deleterious effects during a lifetime) is 0.00008 mg/kg/day.
  3. Based upon animal studies showing thyroid and/or liver tumors and alteration of thyroid function, a safe drinking water concentration of ethylene thiourea, as an environmental decomposition product (and urinary metabolite) of some agricultural fungicides, was proposed in 1988 to be 3 ppb.
  4. Measurement of urinary ethylene thiourea has been used as a marker for exposure of farmers in France to ethylene bisdithiocarbamate fungicides. Thyroid function or other potential health effects of exposure were not studied in these farmers.
  5. Evidence that ethylene thiourea has an effect like the antithyroid drug propylthiouracil, causing a low thyroxine level and a high TSH level in blood, was reported in a rubber manufacturing worker in the UK.
  6. Possible symptoms of exposure higher than that causing respiratory irritation include sweating, thirst, nausea, increased heart rate and blood pressure, and pulmonary edema (Pohanish, 2002).

Date Last Revised: 10/19/2005

Literature Basis:

  • NIOSH Pocket Guide to Chemical Hazards: Ethylene Thiourea.
  • International Chemical Safety Cards (WHO/IPCS/ILO): 2-Mercaptoimidazoline.
  • EPA Air Toxics Website: Ethylene Thiourea. U.S. Environmental Protection Agency Technology Transfer Network.
  • No Author: Ethylene Thiourea [116 KB PDF, 3 pages]. Report on Carcinogens (latest edition); U.S. Department of Health and Human Services, Public Health Service, National Toxicology Program.
  • El Balkhi, S., Sandouk, P. and Galliot-Guilley, M.: Determination of ethylene thiourea in urine by HPLC-DAD. J. Anal. Toxicol. 29(4): 229-233, 2005.
  • Frakes, R.A.: Drinking water guideline for ethylene thiourea, a metabolite of ethylene bisdithiocarbamate fungicides. Regul. Toxicol. Pharmacol. 8(2): 207-218, 1988.
  • Huff, J.: IARC monographs, industry influence, and upgrading, downgrading, and under-grading chemicals: a personal point of view. International Agency for Research on Cancer. Int. J. Occup. Environ. Health 8(3): 249-270, 2002.
  • Pohanish, R.P. (editor): Ethylene Thiourea. In, Sittig's Handbook of Toxic and Hazardous Chemicals and Carcinogens, Fourth Ed., Vol. 1. Norwich, NY: Noyes Publications, William Andrew Publishing, 2002, pp. 1102-1104.
  • Smith, D.M.: Ethylene thiourea: thyroid function in two groups of exposed workers. Br. J. Ind. Med. 41(3): 362-366, 1984.
Monitoring Methods used by OSHA

Primary Laboratory Sampling/Analytical Method (SLC1):

  • sampling media: Two Glass Fiber Filter (37 mm) in series. Sampled open face with filters separated by spacer.
    analytical solvent: Water
    maximum volume: 480 Liters
    maximum flow rate: 2.0 L/min
    current analytical method: High Performance Liquid Chromatography; HPLC/UV
    method reference: OSHA Analytical Method (OSHA 95)
    method classification: Fully Validated

Bulk Method:

  • Limit the amount of bulk submitted to one gram or one mL.

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