Phosphinic Acid

This chemical does not meet GHS hazard criteria for 1.5% (16 of 1039) of reports.

H290 (35.4%): May be corrosive to metals [Warning Corrosive to Metals]

H314 (98.5%): Causes severe skin burns and eye damage [Danger Skin corrosion/irritation]

H318 (82.7%): Causes serious eye damage [Danger Serious eye damage/eye irritation]

P234, P260, P264, P264+P265, P280, P301+P330+P331, P302+P361+P354, P304+P340, P305+P354+P338, P316, P317, P321, P363, P390, P405, P406, and P501 (click each P-code to see the statement)

Aggregated GHS information provided per 1039 reports by companies from 13 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

Reported as not meeting GHS hazard criteria per 16 of 1039 reports by companies.

There are 12 notifications provided by 1023 of 1039 reports by companies with hazard statement code(s).

Information may vary between notifications depending on impurities, additives, and other factors. The percentage value in parenthesis indicates the notified classification ratio from companies that provide hazard codes. Only hazard codes with percentage values above 10% are shown. For more detailed information, please visit ECHA C&L website.

H314: Causes severe skin burns and eye damage [Danger Skin corrosion/irritation]

H318: Causes serious eye damage [Danger Serious eye damage/eye irritation]

P260, P264, P264+P265, P280, P301+P330+P331, P302+P361+P354, P304+P340, P305+P354+P338, P316, P317, P321, P363, P405, and P501 (click each P-code to see the statement)

Excerpt from ERG Guide 154 [Substances - Toxic and/or Corrosive (Non-Combustible)]:

Refer to the "General First Aid" section. Specific First Aid: For corrosives, in case of contact, immediately flush skin or eyes with running water for at least 30 minutes. Additional flushing may be required. (ERG, 2024)

Excerpt from ERG Guide 154 [Substances - Toxic and/or Corrosive (Non-Combustible)]:

SMALL FIRE: Dry chemical, CO2 or water spray.

LARGE FIRE: Dry chemical, CO2, alcohol-resistant foam or water spray. If it can be done safely, move undamaged containers away from the area around the fire. Dike runoff from fire control for later disposal.

FIRE INVOLVING TANKS, RAIL TANK CARS OR HIGHWAY TANKS: Fight fire from maximum distance or use unmanned master stream devices or monitor nozzles. Do not get water inside containers. Cool containers with flooding quantities of water until well after fire is out. Withdraw immediately in case of rising sound from venting safety devices or discoloration of tank. ALWAYS stay away from tanks in direct contact with flames. (ERG, 2024)

Suitable extinguishing media: Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide. /Hypophosphorous acid solution/

Advice for firefighters: Wear self-contained breathing apparatus for firefighting if necessary. /Hypophosphorous acid solution/

If material on fire or involved in fire: Use water in flooding quantities as fog. Use "alcohol" foam, dry chemical or carbon dioxide.

Excerpt from ERG Guide 154 [Substances - Toxic and/or Corrosive (Non-Combustible)]:

IMMEDIATE PRECAUTIONARY MEASURE: Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters (75 feet) for solids.

SPILL: Increase the immediate precautionary measure distance, in the downwind direction, as necessary.

FIRE: If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions. (ERG, 2024)

ACCIDENTAL RELEASE MEASURES: Personal precautions, protective equipment and emergency procedures: Use personal protective equipment. Avoid breathing vapors, mist or gas. Ensure adequate ventilation. Evacuate personnel to safe areas. Environmental precautions: Do not let product enter drains. Methods and materials for containment and cleaning up: Soak up with inert absorbent material and dispose of as hazardous waste. Keep in suitable, closed containers for disposal. /Hypophosphorous acid solution/

Environmental considerations - Land spill: Dig a pit, pond, lagoon, holding area to contain liquid or solid material. Dike surface flow using soil, sand bags, foamed polyurethane, or foamed concrete. Absorb bulk liquid with fly ash, cement powder, or commercial sorbents.

Environmental considerations - Water spill: Use natural barriers or oil control booms to limit spill travel. Use natural deep water pockets, excavated lagoons, or sand bag barriers to trap material at bottom. Add ferric chloride (FeCl3). Use mechanical dredges or lifts to remove immobilized masses of pollutants and precipitates.

Environmental considerations - Air spill: Apply water spray or mist to knock down vapors. Disperse vapors using fans or blowers.

SRP: Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in air, soil or water; effects on animal, aquatic and plant life; and conformance with environmental and public health regulations. If it is possible or reasonable use an alternative chemical product with less inherent propensity for occupational harm/injury/toxicity or environmental contamination.

Product: Offer surplus and non-recyclable solutions to a licensed disposal company. Contact a licensed professional waste disposal service to dispose of this material. Dissolve or mix the material with a combustible solvent and burn in a chemical incinerator equipped with an afterburner and scrubber; Contaminated packaging: Dispose of as unused product. /Hypophosphorous acid solution/

ACCIDENTAL RELEASE MEASURES: Personal precautions, protective equipment and emergency procedures: Use personal protective equipment. Avoid breathing vapors, mist or gas. Ensure adequate ventilation. Evacuate personnel to safe areas. Environmental precautions: Do not let product enter drains. /Hypophosphorous acid solution/

Precautions for safe handling: Avoid inhalation of vapor or mist. /Hypophosphorous acid solution/

Appropriate engineering controls: Handle in accordance with good industrial hygiene and safety practice. Wash hands before breaks and at the end of workday. /Hypophosphorous acid solution/

Gloves must be inspected prior to use. Use proper glove removal technique (without touching glove's outer surface) to avoid skin contact with this product. Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices. Wash and dry hands. /Hypophosphorous acid solution/

For more Preventive Measures (Complete) data for Hypophosphorous acid (6 total), please visit the HSDB record page.

Excerpt from ERG Guide 154 [Substances - Toxic and/or Corrosive (Non-Combustible)]:

ELIMINATE all ignition sources (no smoking, flares, sparks or flames) from immediate area. Do not touch damaged containers or spilled material unless wearing appropriate protective clothing. Stop leak if you can do it without risk. Prevent entry into waterways, sewers, basements or confined areas. Absorb or cover with dry earth, sand or other non-combustible material and transfer to containers. DO NOT GET WATER INSIDE CONTAINERS. (ERG, 2024)

Keep container tightly closed in a dry and well-ventilated place. Containers which are opened must be carefully resealed and kept upright to prevent leakage. /Hypophosphorous acid solution/

1.2 [mg/m3]

13 [mg/m3]

79 [mg/m3]

Excerpt from ERG Guide 154 [Substances - Toxic and/or Corrosive (Non-Combustible)]:

Wear positive pressure self-contained breathing apparatus (SCBA). Wear chemical protective clothing that is specifically recommended by the manufacturer when there is NO RISK OF FIRE. Structural firefighters' protective clothing provides thermal protection but only limited chemical protection. (ERG, 2024)

Eye/face protection: Tightly fitting safety goggles. Faceshield (8-inch minimum). Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU). /Hypophosphorous acid solution/

Skin protection: Handle with gloves. /Hypophosphorous acid solution/

Body Protection: Complete suit protecting against chemicals. The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace. /Hypophosphorous acid solution/

Respiratory protection: Where risk assessment shows air-purifying respirators are appropriate use a full-face respirator with multipurpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls. If the respirator is the sole means of protection, use a full-face supplied air respirator. Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU). /Hypophosphorous acid solution/

Hypophosphorous acid appears as colorless oily liquid or deliquescent crystals with a sour odor. Density 1.439 g / cm3. Melting point 26.5 °C. Inhalation of vapors irritates or burns the respiratory tract. Liquid and vapors may irritate or burn eyes and skin.

Deliquescent solid (from the water-free acid); Supercools to colorless odorless liquid; mp = 26.5 deg C; [Merck Index] Colorless odorless solution; [MSDSonline]

Hygroscopic crystals or colorless oily liquid

Water free acid forms deliquescent crystals; supercools to a colorless oily liquid

Decomposes upon heating >133 °C

130 °C @760 [mm Hg]

Miscible with water

Miscible with alcohol

Marketed in aqueous solutions of varying concentrations, 50% (density 1.274), 30-32% (density 1.13), 10% (density 1.04)

1.439 @25 °C

0.00323 mmg Hg at 25 °C (effusion method: vapor pressure balance)

Stable under recommended storage conditions. /Hypophosphorous acid solution/

Hazardous decomposition products formed under fire conditions - Oxides of phosphorus. /Hypophosphorous acid solution/

Dec by heat into /phosphoric acid/ and spontaneously flammable /phosphine/.

When heated to decomposition it emits toxic fumes of /phosphorous oxides/.

58.4 mN/m (60% aqueous solution)

pH = 0.71 at 37 °C (100 g/L solution)

pKa = 2.27 at 22 °C (OECD Guideline 112 - Dissociation Constants in Water)

Decomposed by heat into H3PO4 and spontaneously flammable PH3. Oxidized by hot H2SO4, SO2 and S formed. Powerful reducing agent.

A strong monobasic acid and reducing agent sold in solution.

Disproportionates upon heating >133 °C to generate phosphoric and phosphonic acids, hydrogen, and phosphine.

Standard heat of formation for crystalline H3PO2 is 604.6 kJ/mol (144.5 kcal/mol)

Toxic Gases & Vapors -> Acids, Inorganic

FCS -> FDA Cumulative Estimated Daily Intake (CEDI)

Deliquescent. Water soluble.

Reducing Agents, Strong

Acids, Weak

Strong Reducing Agent

HYPOPHOSPHOROUS ACID decomposes when heated into phosphoric acid and spontaneously flammable phosphine. Is oxidized by sulfuric acid with release of sulfur dioxide and sulfur. Reacts explosively with mercury(II) oxide [Mellor, 1940, Vol. 4, 778]. Reacts violently with mercury(II) nitrate [Mellor, 1940, Vol. 4, 993]. Neutralizes bases in exothermic reactions.

Incompatible materials: Strong oxidizing agents, strong bases. /Hypophosphorous acid solution/

Powerful reducing agent.

Oxidized by hot /sulfuric acid/; /Sulfur dioxide and sulfur/ formed.

Reaction with mercury(II) oxide is explosive. Violent reaction with mercury(II) nitrate.

Fire and explosion risk in contact with oxidizing agents.

IDENTIFICATION AND USE: Hypophosphorous acid is used in preparation of hypophosphites, and in electroplating baths. HUMAN STUDIES: Hypophosphorous acid solution (50%) was corrosive in a standardized and quantitative in vitro corrosivity test. ANIMAL STUDIES: There are no data available.

Dermatotoxin - Skin burns.

Toxic Pneumonitis - Inflammation of the lungs induced by inhalation of metal fumes or toxic gases and vapors.

/SRP:/ Immediate first aid: Ensure that adequate decontamination has been carried out. If patient is not breathing, start artificial respiration, preferably with a demand-valve resuscitator, bag-valve-mask device, or pocket mask, as trained. Perform CPR as necessary. Immediately flush contaminated eyes with gently flowing water. Do not induce vomiting. If vomiting occurs, lean patient forward or place on left side (head-down position, if possible) to maintain an open airway and prevent aspiration. Keep patient quiet and maintain normal body temperature. Obtain medical attention. /Phosphine and Related Compounds/

/SRP:/ Basic treatment: Establish a patent airway (oropharyngeal or nasopharyngeal airway, if needed). Suction if necessary. Watch for signs of respiratory insufficiency and assist ventilations if necessary. Administer oxygen by nonrebreather mask at 10 to 15 L/min. Monitor for pulmonary edema and treat if necessary ... . Monitor for shock and treat if necessary ... . Anticipate seizures and treat if necessary ... . For eye contamination, flush eyes immediately with water. Irrigate each eye continuously with 0.9% saline (NS) during transport ... . /Phosphine and Related Compounds/

/SRP:/ Advanced treatment: Consider orotracheal or nasotracheal intubation for airway control in the patient who is unconscious, has severe pulmonary edema, or is in severe respiratory distress. Positive-pressure ventilation techniques with a bag valve mask device may be beneficial. Consider drug therapy for pulmonary edema ... . Monitor cardiac rhythm and treat arrhythmias if necessary ... . Start IV administration of D5W /SRP: "To keep open", minimal flow rate/. Use 0.9% saline (NS) or lactated Ringer's (LR) if signs of hypovolemia are present. For hypotension with signs of hypovolemia, administer fluid cautiously. Consider vasopressors if patient is hypotensive with a normal fluid volume. Watch for signs of fluid overload ... . Treat seizures with diazepam or lorazepam ... . Use proparacaine hydrochloride to assist eye irrigation ... . /Phosphine and Related Compounds/

/SRP:/ Immediate first aid: Ensure that adequate decontamination has been carried out. If patient is not breathing, start artificial respiration, preferably with a demand-valve resuscitator, bag-valve-mask device, or pocket mask, as trained. Perform CPR as necessary. Immediately flush contaminated eyes with gently flowing water. Do not induce vomiting. If vomiting occurs, lean patient forward or place on left side (head-down position, if possible) to maintain an open airway and prevent aspiration. Keep patient quiet and maintain normal body temperature. Obtain medical attention. /Inorganic acids and related compounds/

For more Antidote and Emergency Treatment (Complete) data for Hypophosphorous acid (6 total), please visit the HSDB record page.

/ALTERNATIVE and IN VITRO TESTS/ The Corrositex assay is a standardized and quantitative in vitro corrosivity test. The potential corrosivity of the test item was assessed by measuring the time that is required for the test item to pass through a biobarrier membrane and produce a change in a Chemical Detection System (CDS). 4 vials of 50% Hypophosphorous acid solution used in the test. According to the results (average breakthrough point: 12 min 05 sec) the substance is considered to be corrosive. ...

Hypophosphorus acid's production and use in electroplating baths, in the preparation of hypophosphites and as a bleaching agent, reducing agent and catalyst may result in its release to the environment through various waste streams. If released to air, a vapor pressure of 0.00323 mm Hg at 25 °C indicates hypophosphorus acid will exist solely as a vapor in the atmosphere. Vapor-phase hypophosphorus acid will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air can not be estimated appropriately with current estimation methods. Hypophosphorus acid is miscible in water, and therefore, may dissolve in precipitation, cloud or fog water and be removed from air via wet deposition. If released to soil, hypophosphorus acid is expected to have very high mobility based upon a measured Koc range of 3.7 to 15 for the analogous sodium hypochorite. The pKa of hypophosphorous acid is 2.27, indicating that this compound will exist almost entirely in ionized form in the environment. Since ionized forms do not volatilize, volatilization from moist soil is not expected to be an important fate process. Hypophosphorus acid is not expected to volatilize from dry soil surfaces based upon its vapor pressure. If released into water, hypophosphorus acid is not expected to adsorb to suspended solids and sediment based upon the Koc. Biodegradation data in water or soil were not available. Volatilization from water surfaces is not expected to be an important fate process since the compound ionizes in water. An estimated BCF of 3 suggests the potential for bioconcentration in aquatic organisms is low. Based on hydrolysis results for sodium hypophosphite, hypophosphorus acid is stable to hydrolysis in water. Occupational exposure to hypophosphorous acid may occur through inhalation and dermal contact with this compound at workplaces where hypophosphorous acid is produced or used. Exposure to the general population may be possible in the vicinity of its use as a reagent during illicit drug manufacture. Hypophosphorous acid is on the US DEA (Drug Enforcement Administration) list of special surveillance chemicals used in clandestine drug manufacture. (SRC)

Hypophosphorus acid's production and use in electroplating baths, in the preparation of hypophosphites(1) and as a bleaching agent, reducing agent and catalyst(2) may result in its release to the environment through various waste streams(SRC). Hypophosphorus acid is on the US DEA (Drug Enforcement Administration) list of special surveillance chemicals used in clandestine drug manufacture(3).

TERRESTRIAL FATE: Based on a classification scheme(1), a measured Koc range of 3.7 to 15 for the analogous sodium hypophosphite (which dissociates into the hypophosphorus acid ion in water)(2) indicates that hypophosphorus acid is expected to have very high mobility in soil(SRC). The pKa of hypophosphorous acid is 2.27(3), indicating that this compound will exist almost entirely in ionized form in the environment(SRC). Since ionized forms do not volatilize, volatilization from moist soil is not expected to be an important fate process(SRC). Hypophosphorous acid is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 0.00323 mm Hg at 25 °C(3). Biodegradation data in soil were not available(SRC, 2017).

AQUATIC FATE: Based on a classification scheme(1), a measured Koc range of 3.7 to 15 for the analogous sodium hypophosphite (which dissociates into the hypophosphorus acid ion in water)(2) indicates that hypophosphorus acid is not expected to adsorb to suspended solids and sediment(SRC). The pKa of hypophosphorous acid is 2.27(3), indicating that this compound will exist almost entirely in ionized form in the environment(SRC). Since ionized forms do not volatilize, volatilization from water surfaces is not expected to be an important fate process(SRC). According to a classification scheme(4), an estimated BCF of 3(SRC), from an estimated log Kow of -1.72(5) and a regression-derived equation(5), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Biodegradation data in water were not available(SRC, 2017). Based on hydrolysis results for sodium hypophosphite(2), hypophosphorus acid is stable to hydrolysis in water(3).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), hypophosphorus acid, which has a vapor pressure of 0.00323 mm Hg at 25 °C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase hypophosphorus acid may be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); however, the half-life for this reaction in air can not be estimated appropriately with current estimation methods since hypophosphorus acid in an inorganic compound(3). Hypophosphorus acid is miscible in water(4), therefore, atmospheric hypophosphorus acid may dissolve in precipitation, cloud or fog water and be removed from air via wet deposition(SRC).

Sodium hypophosphite dissociates into hypophosphorus acid ions in water(1). Using OECD Guideline 111 (Hydrolysis as a Function of pH), sodium hypophosphite showed very minor hydrolytic degradation at pH values of 4.0, 7.0 and 9.0 and 50 °C(1). The estimated hydrolysis half-life is greater than one year under representative environmental conditions at 25 °C; therefore, sodium hypophosphite is considered to be hydrolytically stable(1). This should also apply to hypophosphorus acid(SRC).

An estimated BCF of 3 was calculated in fish for hypophosphous acid(SRC), using an estimated log Kow of -1.72(1) and a regression-derived equation(1). According to a classification scheme(2), this BCF suggests the potential for bioconcentration in aquatic organisms is low(SRC).

Using OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method) and five different soil types, sodium hypophosphite had Koc values ranging from 3.7 to 15(1). Since sodium hypophosphite dissociates into hypophosphorus acid ions in water(1), the Koc results will also apply to hypophosphorus acid(2). According to a classification scheme(3), these Koc values suggests that hypophosphorous acid is expected to have very high mobility in soil.

The pKa of hypophosphorous acid is 2.27(1), indicating that this compound will exist almost entirely in ionized form in the environment(SRC). Since ionized forms do not volatilize, volatilization from water surfaces or moist soil is not expected to be an important fate process(SRC). Hypophosphorous acid is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 0.00323 mm Hg at 25 °C(1).

According to the 2012 TSCA Inventory Update Reporting data, 2 reporting facilities estimate the number of persons reasonably likely to be exposed during the manufacturing, processing, or use of hypophosphorous acid in the United States may be as low as <10 workers and as high as 25-49 workers per plant; the data may be greatly underestimated due to confidential business information (CBI) or unknown values(1).

NIOSH (NOES Survey 1981-1983) has statistically estimated that 14,405 workers (2,961 of these are female) were potentially exposed to hypophosphorous acid in the US(1). Occupational exposure to hypophosphorous acid may occur through inhalation and dermal contact with this compound at workplaces where hypophosphorous acid is produced or used(SRC). Exposure to the general population may be possible in the vicinity of its use as a reagent during illicit drug manufacture. Hypophosphorous acid is on the US DEA (Drug Enforcement Administration) list of special surveillance chemicals used in clandestine drug manufacture(2).

Hypophosphorus acid's production and use in electroplating baths, in the preparation of hypophosphites and as a bleaching agent, reducing agent and catalyst may result in its release to the environment through various waste streams. If released to air, a vapor pressure of 0.00323 mm Hg at 25 °C indicates hypophosphorus acid will exist solely as a vapor in the atmosphere. Vapor-phase hypophosphorus acid will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air can not be estimated appropriately with current estimation methods. Hypophosphorus acid is miscible in water, and therefore, may dissolve in precipitation, cloud or fog water and be removed from air via wet deposition. If released to soil, hypophosphorus acid is expected to have very high mobility based upon a measured Koc range of 3.7 to 15 for the analogous sodium hypochorite. The pKa of hypophosphorous acid is 2.27, indicating that this compound will exist almost entirely in ionized form in the environment. Since ionized forms do not volatilize, volatilization from moist soil is not expected to be an important fate process. Hypophosphorus acid is not expected to volatilize from dry soil surfaces based upon its vapor pressure. If released into water, hypophosphorus acid is not expected to adsorb to suspended solids and sediment based upon the Koc. Biodegradation data in water or soil were not available. Volatilization from water surfaces is not expected to be an important fate process since the compound ionizes in water. An estimated BCF of 3 suggests the potential for bioconcentration in aquatic organisms is low. Based on hydrolysis results for sodium hypophosphite, hypophosphorus acid is stable to hydrolysis in water. Occupational exposure to hypophosphorous acid may occur through inhalation and dermal contact with this compound at workplaces where hypophosphorous acid is produced or used. Exposure to the general population may be possible in the vicinity of its use as a reagent during illicit drug manufacture. Hypophosphorous acid is on the US DEA (Drug Enforcement Administration) list of special surveillance chemicals used in clandestine drug manufacture. (SRC)

Hypophosphorus acid's production and use in electroplating baths, in the preparation of hypophosphites(1) and as a bleaching agent, reducing agent and catalyst(2) may result in its release to the environment through various waste streams(SRC). Hypophosphorus acid is on the US DEA (Drug Enforcement Administration) list of special surveillance chemicals used in clandestine drug manufacture(3).

TERRESTRIAL FATE: Based on a classification scheme(1), a measured Koc range of 3.7 to 15 for the analogous sodium hypophosphite (which dissociates into the hypophosphorus acid ion in water)(2) indicates that hypophosphorus acid is expected to have very high mobility in soil(SRC). The pKa of hypophosphorous acid is 2.27(3), indicating that this compound will exist almost entirely in ionized form in the environment(SRC). Since ionized forms do not volatilize, volatilization from moist soil is not expected to be an important fate process(SRC). Hypophosphorous acid is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 0.00323 mm Hg at 25 °C(3). Biodegradation data in soil were not available(SRC, 2017).

AQUATIC FATE: Based on a classification scheme(1), a measured Koc range of 3.7 to 15 for the analogous sodium hypophosphite (which dissociates into the hypophosphorus acid ion in water)(2) indicates that hypophosphorus acid is not expected to adsorb to suspended solids and sediment(SRC). The pKa of hypophosphorous acid is 2.27(3), indicating that this compound will exist almost entirely in ionized form in the environment(SRC). Since ionized forms do not volatilize, volatilization from water surfaces is not expected to be an important fate process(SRC). According to a classification scheme(4), an estimated BCF of 3(SRC), from an estimated log Kow of -1.72(5) and a regression-derived equation(5), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Biodegradation data in water were not available(SRC, 2017). Based on hydrolysis results for sodium hypophosphite(2), hypophosphorus acid is stable to hydrolysis in water(3).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), hypophosphorus acid, which has a vapor pressure of 0.00323 mm Hg at 25 °C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase hypophosphorus acid may be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); however, the half-life for this reaction in air can not be estimated appropriately with current estimation methods since hypophosphorus acid in an inorganic compound(3). Hypophosphorus acid is miscible in water(4), therefore, atmospheric hypophosphorus acid may dissolve in precipitation, cloud or fog water and be removed from air via wet deposition(SRC).

Sodium hypophosphite dissociates into hypophosphorus acid ions in water(1). Using OECD Guideline 111 (Hydrolysis as a Function of pH), sodium hypophosphite showed very minor hydrolytic degradation at pH values of 4.0, 7.0 and 9.0 and 50 °C(1). The estimated hydrolysis half-life is greater than one year under representative environmental conditions at 25 °C; therefore, sodium hypophosphite is considered to be hydrolytically stable(1). This should also apply to hypophosphorus acid(SRC).

An estimated BCF of 3 was calculated in fish for hypophosphous acid(SRC), using an estimated log Kow of -1.72(1) and a regression-derived equation(1). According to a classification scheme(2), this BCF suggests the potential for bioconcentration in aquatic organisms is low(SRC).

Using OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method) and five different soil types, sodium hypophosphite had Koc values ranging from 3.7 to 15(1). Since sodium hypophosphite dissociates into hypophosphorus acid ions in water(1), the Koc results will also apply to hypophosphorus acid(2). According to a classification scheme(3), these Koc values suggests that hypophosphorous acid is expected to have very high mobility in soil.

The pKa of hypophosphorous acid is 2.27(1), indicating that this compound will exist almost entirely in ionized form in the environment(SRC). Since ionized forms do not volatilize, volatilization from water surfaces or moist soil is not expected to be an important fate process(SRC). Hypophosphorous acid is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 0.00323 mm Hg at 25 °C(1).

According to the 2012 TSCA Inventory Update Reporting data, 2 reporting facilities estimate the number of persons reasonably likely to be exposed during the manufacturing, processing, or use of hypophosphorous acid in the United States may be as low as <10 workers and as high as 25-49 workers per plant; the data may be greatly underestimated due to confidential business information (CBI) or unknown values(1).

NIOSH (NOES Survey 1981-1983) has statistically estimated that 14,405 workers (2,961 of these are female) were potentially exposed to hypophosphorous acid in the US(1). Occupational exposure to hypophosphorous acid may occur through inhalation and dermal contact with this compound at workplaces where hypophosphorous acid is produced or used(SRC). Exposure to the general population may be possible in the vicinity of its use as a reagent during illicit drug manufacture. Hypophosphorous acid is on the US DEA (Drug Enforcement Administration) list of special surveillance chemicals used in clandestine drug manufacture(2).

SRP: Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in air, soil or water; effects on animal, aquatic and plant life; and conformance with environmental and public health regulations. If it is possible or reasonable use an alternative chemical product with less inherent propensity for occupational harm/injury/toxicity or environmental contamination.

Product: Offer surplus and non-recyclable solutions to a licensed disposal company. Contact a licensed professional waste disposal service to dispose of this material. Dissolve or mix the material with a combustible solvent and burn in a chemical incinerator equipped with an afterburner and scrubber; Contaminated packaging: Dispose of as unused product. /Hypophosphorous acid solution/

Corrosive