NIOSH Pocket Guide to Chemical Hazards

Chromic acid and chromates

CAS 1333-82-0 (CrO3)

CrO3 (acid)

RTECS GB6650000 (CrO3)
Synonyms & Trade Names
Chromic acid (CrO3): Chromic anhydride, Chromic oxide, Chromium(VI) oxide (1:3), Chromium trioxide
Synonyms of chromates (i.e., chromium(VI) compounds) such as zinc chromate vary depending upon the specific compound.
DOT ID & Guide
1755 154 (acid solution)
1463 141 (acid, solid)


NIOSH REL (as Cr): Ca TWA 0.001 mg/m3 See Appendix A See Appendix C
OSHA PEL (as CrO3): C 0.1 mg/m3 See Appendix C
IDLH Ca [15 mg/m3 {as Cr(VI)}] See: 1333820 Conversion
Physical Description
CrO3: Dark-red, odorless flakes or powder. [Note: Often used in an aqueous solution (H2CrO4).]
MW: 100.0
BP: 482°F (Decomposes)
MLT: 387°F (Decomposes)
Sol: 63%
VP: Very low

Sp.Gr: 2.70 (CrO3)
Fl.P: NA

CrO3: Noncombustible Solid, but will accelerate the burning of combustible materials.
Incompatibilities & Reactivities
Combustible, organic, or other readily oxidizable materials (paper, wood, sulfur, aluminum, plastics, etc.); corrosive to metals
Measurement Methods
NIOSH 7600, 7604, 7605, 7703, 9101; OSHA ID103, ID215, W4001
See: NMAM or OSHA Methods
Personal Protection & Sanitation (See protection)
Skin: Prevent skin contact
Eyes: Prevent eye contact
Wash skin: When contaminated
Remove: When wet or contaminated
Change: Daily
Provide: Eyewash, Quick drench
First Aid (See procedures)
Eye: Irrigate immediately
Skin: Soap flush immediately
Breathing: Respiratory support
Swallow: Medical attention immediately
Important additional information about respirator selection
Respirator Recommendations NIOSH
At concentrations above the NIOSH REL, or where there is no REL, at any detectable concentration:
(APF = 10,000) Any self-contained breathing apparatus that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode
(APF = 10,000) Any supplied-air respirator that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode in combination with an auxiliary self-contained positive-pressure breathing apparatus
(APF = 50) Any air-purifying, full-facepiece respirator with an N100, R100, or P100 filter. Click here for information on selection of N, R, or P filters./Any appropriate escape-type, self-contained breathing apparatus
Exposure Routes inhalation, ingestion, skin and/or eye contact
Symptoms Irritation respiratory system; nasal septum perforation; liver, kidney damage; leukocytosis (increased blood leukocytes), leukopenia (reduced blood leukocytes), eosinophilia; eye injury, conjunctivitis; skin ulcer, sensitization dermatitis; [potential occupational carcinogen]
Target Organs Blood, respiratory system, liver, kidneys, eyes, skin

Cancer Site [lung cancer]
See also: INTRODUCTION   See ICSC CARD: 1194   See MEDICAL TESTS: 0051