Hydrochloric acid [factsheet]

HYDROCHLORIC ACID

Please Note: The main source of information for this fact sheet is EPA's Integrated Risk Information System (IRIS), which contains information on inhalation chronic toxicity of hydrochloric acid and the RfC. Other secondary sources include the Hazardous Substances Data Bank (HSDB), a database of summaries of peer-reviewed literature, and the Registry of Toxic Effects of Chemical Substances (RTECS), a database of toxic effects that are not peer reviewed.

Environmental/Occupational Exposure

* Occupational exposure to hydrochloric acid may occur via inhalation or dermal contact during its production and use. (1,2)

Assessing Personal Exposure

* No information was located regarding the measurement of personal exposure to hydrochloric acid.

Health Hazard Information

Acute Effects:

* Hydrochloric acid is corrosive to the eyes, skin, and mucous membranes. Acute (short-term) inhalation exposure may cause coughing, hoarseness, inflammation and ulceration of the respiratory tract, chest pain, and pulmonary edema in humans. Acute oral exposure may cause corrosion of the mucous membranes, esophagus, and stomach, with nausea, vomiting, and diarrhea reported. Dermal contact may produce severe burns, ulceration, and scarring. (1-4)

* Pulmonary irritation, lesions of the upper respiratory tract, and laryngeal and pulmonary edema have been reported in rodents acutely exposed by inhalation. (1,4)

* Acute animal tests, such as the LC₅₀ and LD₅₀ tests in rats, mice, and rabbits, have demonstrated hydrochloric acid to have moderate to high acute toxicity from inhalation and moderate acute toxicity from oral exposure. (3)

Chronic Effects (Noncancer):

* Chronic (long-term) occupational exposure to hydrochloric acid has been reported to cause gastritis, chronic bronchitis, dermatitis, and photosensitization in workers. Prolonged exposure to low concentrations may also cause dental discoloration and erosion. (1-4)

* Chronic inhalation exposure caused hyperplasia of the nasal mucosa, larynx, and trachea in rats. (4)

* The RfC for hydrochloric acid is 0.007 mg/m³ based on hyperplasia of the nasal mucosa, larynx, and trachea in rats. (4)

* EPA has low confidence in the study on which the RfC was based since it used only one dose and had limited toxicological measurements; low confidence in the database because the database does not provide any additional chronic or reproductive studies; and, consequently, low confidence in the RfC. (4)

* EPA has not established an RfD for hydrochloric acid. (4)

* EPA'sOffice of Air Quality Planning and Standards, for a hazard ranking under Section 112(g) of the Clean Air Act Amendments, has evaluated hydrochloric acid for chronic toxicity and has given it a composite score of 11 (scores range from 1 to 100, with 100 being the most toxic). These scores are nonlinear and are the product of two ratings: a rating based on the minimal-effect-dose and a rating based on the type of effect. (6)

Reproductive/Developmental Effects:

* No information is available on the reproductive or developmental effects of hydrochloric acid in humans.

* In rats exposed to hydrochloric acid by inhalation, severe dyspnea, cyanosis, and altered estrus cycles have been reported in dams, and increased fetal mortality and decreased fetal weight have been reported in the offspring. (4)

Cancer Risk:

* No information is available on the carcinogenic effects of hydrochloric acid in humans.

* In one study, no carcinogenic response was observed in rats exposed via inhalation. (1)

* EPA has not classified hydrochloric acid with respect to potential carcinogenicity. (4)

Physical Properties

* Hydrogen chloride is a common synonym for hydrochloric acid. (4)

* The chemical formula for hydrochloric acid is HCl, and its molecular weight is 36.47 g/mol. (1,3)

* Hydrochloric acid occurs as a colorless, nonflammable aqueous solution or gas. (1,3,4)

* Hydrochloric acid has an irritating, pungent odor, with an odor threshold of about 7 mg/m³. (1)

Uses

* Hydrochloric acid is used in the production of chlorides, for refining ore in the production of tin and tantalum, for pickling and cleaning of metal products, in electroplating, in removing scale from boilers, for the neutralization of basic systems, as a laboratory reagent, as a catalyst and solvent in organic syntheses, in the manufacture of fertilizers and dyes, for hydrolyzing starch and proteins in the preparation of various food products, and in the textile and rubber industries. (1-4)

Health Data from Inhalation Exposure

Concentration (mg/m³)	Health numbers^a	Regulatory, advisory numbers^b	Reference
10,000.0
_ _ _ _ 1,000.0	* LC₅₀ (rats) (4,655 mg/m³) * LC₅₀ (mice) (1,651 mg/m³)		5 5
_ _ _ _ 100.0
_ _ _ _ 10.0	* LOAEL (rats)^c (15 mg/m³)		4
_ _ _ _ 1.0		* ACGIH TLV, NIOSH REL, MSHA standard and OSHA PEL (7 mg/m³)	5
_ _ _ _ 0.1
_ _ _ _ 0.01
_ _ _ _ 0.001	* RfC = 0.007 mg/m³		4

ACGIH TLVCAmerican Conference of Governmental and Industrial Hygienists' threshold limit value expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effect.

LC₅₀ (Lethal Concentration₅₀)CA calculated concentration of a chemical in air to which exposure for a specific length of time is expected to cause death in 50% of a defined experimental animal population.

LOAELCLowest-observed-adverse-effect level.

MSHACMine Safety and Health Administration.

NIOSH RELCNational Institute of Occupational Safety and Health's recommended exposure limit; NIOSH-recommended exposure limit for an 8- or 10-h time-weighted-average exposure and/or ceiling.

OSHA PELCOccupational Safety and Health Administration's permissible exposure limit expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effect averaged over a normal 8-h workday or a 40-h workweek.

(continued)

RfCCReference concentration.

^a Health numbers are toxicological numbers from animal testing or risk assessment values developed by EPA.

^b Regulatory numbers are values that have been incorporated in Government regulations, while advisory numbers are nonregulatory values provided by the Government or other groups as advice.

^c This LOAEL is from the critical study used as the basis for the EPA RfC.

References

1. U.S. Department of Health and Human Services. Hazardous Substances Data Bank (HSDB, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.

2. M. Sittig. Handbook of Toxic and Hazardous Chemicals and Carcinogens. 2nd ed. Noyes Publications, Park Ridge, NJ. 1985.

3. The Merck Index. An Encyclopedia of Chemicals, Drugs, and Biologicals. 11th ed. Ed. S. Budavari. Merck and Co. Inc., Rahway, NJ. 1989.

4. U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS) on Hydrogen Chloride. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1993.

5. U.S. Department of Health and Human Services. Registry of Toxic Effects of Chemical Substances (RTECS, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.

6. U.S. Environmental Protection Agency. Technical Background Document to Support Rulemaking Pursuant to the Clean Air ActCSection 112(g). Ranking of Pollutants with Respect to Hazard to Human Health. EPAB450/3-92-010. Emissions Standards Division, Office of Air Quality Planning and Standards, Research Triangle Park, NC. 1994.