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May 1994
Immediately Dangerous to Life or Health Concentrations (IDLH)

CAS number: 118–52–5

NIOSH REL: 0.2 mg/m3 TWA, 0.4 mg/m3 STEL

Current OSHA PEL: 0.2 mg/m3 TWA

1989 OSHA PEL: 0.2 mg/m3 TWA, 0.4 mg/m3 STEL

1993-1994 ACGIH TLV: 0.2 mg/m3 TWA, 0.4 mg/m3 STEL

Description of Substance: White powder with a chlorine-like odor.

LEL:. . Unknown

Original (SCP) IDLH*: Unknown [*Note: “Effective” IDLH = 5 mg/m3 — see discussion below.]

Basis for original (SCP) IDLH: Very little data are available on which to base an IDLH for 1,3-dichloro-5,5-dimethylhydantoin. For this draft technical standard, therefore, the respirators have been selected on the basis of the assigned protection factor afforded by each device up to 25 × the OSHA PEL of 0.2 mg/m3 (i.e., 5 mg/m3); only the “most protective” respirators are permitted for use in concentrations exceeding 5 mg/m3.

Short-term exposure guidelines: None developed


Lethal concentration data:

Species Reference LC50 LCLo Time Adjusted 0.5-hrLC (CF) Derivedvalue
Rat Glyco 1981 —– 20,000 mg/m3 1 hr 25,000 mg/m3 (1.25) 2,500 mg/m3


Lethal dose data:

Species Reference Route LD50(mg/kg) LDLo(mg/kg) Adjusted LD Derived value

G. pig

Kay 1961/1962Korolev et al. 1982

Korolev et al. 1982







3,794 mg/m310,640 mg/m3

9,450 mg/m3

379 mg/m31,064 mg/m3

945 mg/m3


Human data: None relevant for use in determining the revised IDLH.

Revised IDLH: 5 mg/m3Basis for revised IDLH: Based on health considerations and acute oral toxicity data in animals [Kay 1961/62; Korolev et al. 1982], a value of about 500 mg/m3 would have been appropriate for 1,3-dichloro-5,5-dimethylhydantoin. However, the revised IDLH for 1,3-dichloro-5,5-dimethylhydantoin is 5 mg/m3 based on being 25 times the NIOSH REL and OSHA PEL of 0.2 mg/m3 (25 is an assigned protection factor for respirators and was used during the Standards Completion Program for deciding when the “most protective” respirators should be used for 1,3-dichloro-5,5-dimethylhydantoin).



1. Chrostek WJ, Cromer JW [1975]. Health hazard evaluation report HHE 73-160-206, Glyco Chemicals, Inc., Williamsport, PA. Cincinnati, OH: National Institute for Occupational Safety and Health, Division of Surveillance, Hazard Evaluations, and Field Studies.

2. Glyco Chemicals [1981]. 1,3-Dichloro-5,5-dimethyl-2,4-imidazolidinedione. In: TSCA 8(e) Submission to the U.S. Environmental Protection Agency (8EHQ-0281-0382). Williamsport,PA: Glyco® Chemicals, Inc.

3. Kay JH [1961/1962]. Unpublished technical reports. Northbrook, IL: Industrial Bio-Test Laboratories. (August 28, 1961; May 1, 1962).

4. Korolev AA, Vasilenko VE, et al. [1982]. Hygienic standard of dichloantine and the product of its transforation with dimethylhydantoin in water. Gig Sanit 47(6):76-78 (in Russian).