Substance fact sheet
The background information page contains information and concepts that will be useful in understanding some of the issues surrounding the NPI. It is strongly recommended that you read this before reading the information presented below.
For an explanation of some of the terms used in this page, see the Glossary
| Substance name | Hydrochloric acid |
| CASR number | 7647-01-0 |
| Molecular formula | HCl |
| Synonyms | muriatic acid; chlorohydric acid; hydrochloride; spirits of salts; hydrogen chloride (acid); hydrogen chloride; hydrogen chloride gas only |
Physical and chemical properties Physical properties: Hydrochloric acid is a solution of hydrogen chloride in water. Hydrogen chloride occurs as either a colourless liquid with a an irritating, pungent odour, or a colourless to slightly yellow gas which can be shipped as a liquefied compressed gas; highly soluble in water. Melting Point (°C): -114.24 Boiling Point (°C): -85.06 Specific Gravity: 1.2 Vapour Density: 1.268 1 ppm = 1.49 mg/m3 Chemical properties: |
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Common uses It is used in the manufacture of phosphoric acid, chlorine dioxide, ammonium chloride, fertilisers, dyes, and artificial silk and pigments for paints. It is used as a refining ore in the production of tin and tantalum, as a lab reagent, and as a metal treating agent. It is used to remove scale and dust from boilers and heat exchange equipment, to clean membranes in desalination plants, to increase oil well output, to prepare synthetic rubber products by treating isoprene, and to clean and prepare other metals for coatings. It is used in the neutralisation of waste streams, the recovery of zinc from galvanised iron scrap, the production of chloride chemicals, the production of vinyl chloride from acetylene and alkyl chlorides from olefins, the manufacture of sodium glutamate and gelatine, the conversion of cornstarch to syrup, sugar refining, electroplating, soap refining, leather tanning, and the photographic, textile, brewing, and rubber industries. It is used to maintain pH balance in swimming pools, spas, etc. It is also used as a bactericide, a fungicide, and a virucide to disinfect bathrooms, kitchens and food preparation areas, and other areas in commercial and industrial buildings, in hospitals, in nursing homes, and in and around household dwellings. It is used in food processing as a starch modifier. |
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Sources of emissions Point sources Manufacturers of industrial inorganic chemicals; electric services companies; and manufacturers of guided missiles, space vehicles, and parts. Also, the combustion of fuels, refuse incineration, smelting of metal scrap, thermal decomposition of gases, and pyrolysis of wire insulation materials such as polyvinyl chloride, chlorinated acrylics, and retardant treated materials. It is also produced as a by-product in dehalogenation processes. Diffuse sources, and point sources included in aggregated emissions data From its use to maintain pH balance in swimming pools, spas, etc; and its use as a bactericide, a fungicide, and a virucide to disinfect bathrooms, kitchens and food preparation areas, and other areas in commercial and industrial buildings, in hospitals, in nursing homes, and in and around household dwellings. Natural sources In the gases evolved from volcanoes and related geothermal activity. It does not occur free in nature but is a component of the minerals halite, sylvite, and carnallite, and as chloride ion in seawater. Mobile sources Vehicle exhaust (from thermal decomposition processes). Consumer products which may contain Hydrochloric acid Disinfectants, other polishing preparations and related products, toilet bowl cleaners, and stain-removers for brickwork and paving. |
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Health effects How might I be exposed to Hydrochloric acid? Probable routes of human exposure to hydrochloric acid are inhalation and skin contact during any of the consumer uses of the chemical outlined above. By what pathways might Hydrochloric acid enter my body? Probable routes of human exposure to hydrochloric acid are skin contact and inhalation of hydrogen chloride gas. Relative health hazard On a health hazard spectrum of 0 - 3 Hydrochloric acid registers 1.5. A score of 3 represents a very high hazard to health, 2 represents a medium hazard and 1 is harmful to health. Factors that are taken into account to obtain this ranking include the extent of the material's toxic or poisonous nature and/or its lack of toxicity, and the evaluation of its tendency to cause, or not cause cancer and/or birth defects. It does not take into account exposure to the substance. Human exposure is reflected in the NPI rank given to this substance (see comparative data below). A substance that scores highly as a health hazard is arsenic at 2.3 and one of the lowest scores is ammonia at 1.0.  Health guidelines Worksafe Australia has set the exposure standard for hydrochloric acid (hydrogen chloride) to 5 ppm (7.5 milligram/m3 (TWA). Note: For some rapidly acting substances and irritants, averaging of airborne concentration over an eight hour period is inappropriate. These substances may induce acute effects after relatively brief exposure to high concentrations and so the exposure standard for these substances represents a maximum or peak concentration to which workers may be exposed. Irritant: concentration cut-off level: 1 % weight/weight Corrosive: concentration cut-off level: 5 % weight/weight See the Additional Information page for current health information. The Australian NOHSC National Exposure Standards Database link is probably the most useful source of information. Note that the emissions data in the NPI database is not directly comparable with these guidelines. What effect might Hydrochloric acid have on my health? Exposure to concentrated hydrochloric acid can cause circulatory collapse, which may lead to death; it can also cause death by asphyxia due to glottic oedema. Less concentrated solutions, can also cause conjunctivitis and corneal burns, inflammation and ulceration of the respiratory tract, dermatitis, skin burns, rhinitis, laryngitis, tracheitis, bronchitis, pulmonary oedema, dental erosion, hoarseness, a feeling of suffocation, nausea, vomiting, abdominal pain, diarrhoea, dehydration, convulsions, oliguria, hypotension, chills, shock, lethargy, stupor, permanent visual damage, cough, and choking. Ingestion or skin contact with hydrochloric acid can cause corrosion of mucous membranes of the mouth, throat, and oesophagus, with immediate pain and dysphagia; it can also cause gastric haemorrhage and intense thirst. |
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Environmental effects Environmental Fate Hydrogen chloride released into the atmosphere as a gas will undergo wet and dry deposition, and will be readily incorporated into cloud, rain, and fog water. It thus forms a component of acid rain. It also contributes to the processes that cause photochemical smog. Environmental Transport Hydrogen chloride is carried in the air. If released to soil, it will usually quickly react with alkaline and other buffering components, if present. It can be mobile in soil, however, and may contaminate groundwater. Relative hazard to the environment On an environmental spectrum of 0 - 3 Hydrochloric acid registers 0.7. A score of 3 represents a very high hazard to the environment and 0 a negligible hazard. Factors that are taken into account to obtain this ranking include the extent of the material's toxic or poisonous nature and/or its lack of toxicity, and the measure of its ability to remain active in the environment and whether it accumulates in living organisms. It does not take into exposure to the substance. Environmental exposure is reflected in the NPI rank for this substance (see comparative data below). A substance that scores highly as an environmental hazard is oxides of nitrogen at 3.0 and one of the lower scores is carbon monoxide at 0.8.  Environmental guidelines See the Additional Information page for current environmental guidelines. No national guidelines. What effect might Hydrochloric acid have on the environment? Hydrochloric acid has a high acute toxic effect on all forms of life. There is no information on long term effects. It will also accelerate the dissolution of many minerals, such as the carbonates (including limestone) and all aluminosilicates (such as clays and many igneous rocks). It thus contributes to the decay of limestone buildings, other structures such as bridges, and art works. It also contributes to the processes that cause photochemical smog. |
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Comparative data NPI Rank Approximately 400 substances were considered for inclusion on the NPI reporting list. A risk ranking was given based on health and environmental hazard identification and human and environmental exposure to the substance. Some substances were grouped together at the same rank with 208 ranks in total. Hydrochloric acid was ranked as 39 out of the 208 ranks. Total hazard score (human health + environmental criteria) = 2.2.  |
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Sources of information used in preparing this fact sheet
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