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Environmental and Health Assessment of Substances in Household Detergents and Cosmetic Detergent Products 10. Acids and bases
10.1 Acetic acidEcotoxicology Acetic acid (CAS No. 64-19-7) is a weak acid. Acetic acid is ultimately biodegradable under aerobic and anoxic conditions. E.g., 95% of the substance was degraded during 5 days in a Zahn-Wellens test (OECD 302B) with non-adapted activated sludge. The toxicity of acetic acid is generally low, with EC50 values towards algae and crustaceans around 100 mg/l, and LC50 (96 h) values towards fish in the range 75-88 mg/l (IUCLID 2000). Human health Most acidic cleaning agents will give burns on the skin, the eyes and mucous membranes in concentrated form. In diluted solutions, these agents will be strongly irritant. The skin will generally tolerate acids better than bases. When burns occur on the skin, pain is immediately sensed, and the skin becomes red and swollen. Long-term and repeated inhalation of aerosolized acidic cleaning agents may damage the lungs and give rise to chronical bronchitis. Classification Acetic acid is included in Annex 1 of list of dangerous substances of Council Directive 67/548/EEC and classified as Corrosive (C) wih the risk phrase R35 (Causes severe burns). > 90%: Cx; R35 10.2 Citric acidEcotoxicology Citric acid (CAS No. 77-92-9) is easily oxidized by a variety of oxidizing agents such as peroxides or hypochlorites. Citric acid is readily biodegradable with 98% biodegraded in 48 hours (OECD 302B, Zahn-Wellens test). Citric acid is found in almost all living systems. It is an intermediate in the tricarboxylic acid (TCA) cycle. The toxicity of citric acid towards aquatic organisms is very low with EC/LC50 values far beyond 100 mg/l (IUCLID 2000). See also sodium citrate (Section 7.4). Human health Citric acid tested on rabbit eyes as a single drop of a 2-5% solution in water caused little or no injury. Irrigation for 30 minutes with 0.5-2% solutions caused severe injury; the 0.5% solution caused permanent cloudiness of the cornea, and the 2% solution causes severe dense opacification. In one patient a splash of a large quantity of saturated solution of citric acid in the eyes caused severe conjunctival reaction and ulceration of the cornea (Grant and Schuman 1993). In conclusion, citric acid must be considered hazardous to the eyes if accidentally hit by strong solutions (> 5%). Citric acid is only mildly irritating to the skin (RTECS 1998). Inhalation of citric acid aerosols will induce cough. Long-term and repeated inhalation of aerosolized acidic cleaning agents may damage the lungs and give rise to chronical bronchitis. Classification Citric acid is not included in Annex 1 of list of dangerous substances of Council Directive 67/548/EEC. 10.3 Sulfamic acidEcotoxicology Sulfamic acid (CAS No. 5329-14-6) is a strong acid. Sulfamic acid hydrolyses slowly to ammonium hydrogen sulfate in the aquatic environment. The toxicity of sulfamic acid to aquatic organisms is related to the effects on the pH of the aquatic medium. LC50 (96 h) towards fish (Pimephales promelas) has been determined to 70.3 mg/l (IUCLID 2000). No data was found on the toxicity of sulfamic acid towards algae and crustaceans. Human health Mild irritation was observed when human skin was exposed with a 4% solution for five days, whereas 500 mg on rabbit skin for 24 hours gave a severe irritation. Instillation of sulfamic acid in the eyes of rabbits gave moderate to severe irritation. The substance has a low acute toxicity as measured by its oral rat LD50 of 3,160 mg/kg (RTECS 1998). Classification Sulfamic acid is included in Annex 1 of list of dangerous substances of Council Directive 67/548/EEC and classified as Irritant (Xi) with the risk phrases R36/38 (Irritating to skin and eyes). 10.4 Phosphoric acidEcotoxicology Phosphoric acid (CAS No. 7664-38-2) undergoes ionic dissociation as any strong acid. Phosphates are normal body or skeleton components of practically all life forms. In the aquatic environment, the acid may affect the pH of the water body and the phosphate entity may persist indefinitely. The presence of phosphate in surface waters can produce a fertiliser action and produce algae blooms. No exact LC50 values have been determined, however, for both crustaceans and fish LC50 is reached when pH decreases 3,5 (IUCLID 2000). Human health Phosphoric acid is a moderately toxic substance as measured by the oral rat LD50: 1,530 mg/kg. The dermal LD50 on rabbit skin is 2,740 mg/kg (HSDB 1998; RTECS 1998). Most acidic cleaning agents will give burns on the skin, the eyes and mucous membranes in concentrated form. In diluted solutions, these agents will be strongly irritant. The skin will generally tolerate acids better than bases. When burns occur on the skin, pain is immediately sensed, and the skin becomes red and swollen. Long-term and repeated inhalation of aerosolized acidic cleaning agents may damage the lungs and give rise to chronical bronchitis. As phosphoric acid is a hygroscopic substance inhalation of such aerosols will lead to formation of hygroscopic growth in the airways when the aerosol is deposited in the humid airways. This means that when evaluating occupational exposure with phosphoric acid, not only the respirable fraction and aerodynamic diameter must be taken into consideration, but also hygroscopic growth. Otherwise the total deliverable dose to the lungs may be underestimated by 600-700% (HSDB 1999). The US Environmental Protection Agency has calculated a so-called reference concentration (RfC) below which it is considered safe to inhale phosphoric acid for a lifetime: 0.01 mg/m3. The Danish occupational threshold limit value is 1 mg/m3 (Arbejdstilsynet 2000). Classification Phosphoric acid is included in Annex 1 of list of dangerous substances of Council Directive 67/548/EEC and classified as Corrosive (C) with the risk phrase R34 (Causes burns). > 25%: C; R34 10.5 Sulfuric acidEcotoxicology Sulfuric acid (CAS No. 7664-93-9) is a strong acid. Sulfuric acid will ultimately react with calcium and magnesium in water to form sulfate salts. Sulfate-reducing bacteria are known to utilize sulfuric acid (IUCLID 2000). The toxicity of sulfuric acid to aquatic organisms is related to the effects on the pH of the medium. EC50 (24-48 h) values towards different species of crustaceans (Daphnia magna and Crangon crangon) have been determined in the range from 43 to 80 mg/l, whereas LC50 (24-96 h) values towards fish (Gambusia affinis, Lepomis machrochirus, Danio rerio) are in the range from 42 to 82 mg/l. No data were found on the toxicity of sulfuric acid towards algae. For crustaceans and fish the LC50 is reached when pH decreases to 3,5 (IUCLID 2000). Human health Most acidic cleaning agents will give burns on the skin, the eyes and mucous membranes in concentrated form. In diluted solutions, these agents will be strongly irritant. The skin will generally tolerate acids better than bases. When burns occur on the skin, pain is immediately sensed, and the skin becomes red and swollen. Long-term and repeated inhalation of aerosolized acidic cleaning agents may damage the lungs and give rise to chronical bronchitis. Classification Sulfuric acid is included in Annex 1 of list of dangerous substances of Council Directive 67/548/EEC and classified as Corrosive (C) with the risk phrase R35 (Causes severe burns). > 15%: C; R35 10.6 Potassium hydroxideEcotoxicology Potassium hydroxide (CAS No. 1310-58-3) is a strong base, which is harmful to aquatic organisms due to alkalinity. However, following neutralization to pH 5.5 to 8.5 the substance is not harmful. The aquatic toxicity of potassium hydroxide has been investigated in tests with fish (Gambusia affinis), and a 96 h-LC50 of 80 mg/l has been determined (IUCLID 2000). Human health Burns caused by bases may be deep and destructive and give slowly healing wounds. Contact with corrosive cleaning agents do not always give immediate pain, but just a greasy feeling on the skin. When pain and redness finally occurs, damage has already occurred . Bases have a degreasing effect on the skin, facilitating penetration of the skin with irritant and allergenic substances. Inhalation of basic aerosols may give burns in the airways, giving rise to cough and respiratory distress. Long-term exposure to basic aerosols may give irreversible lung damage. Classification Pottasium hydroxide is included in Annex 1 of list of dangerous substances of Council Directive 67/548/EEC and classified as Harmful (Xn) with the risk phrase R 22 (Harmful if swallowed) and Corrosive (C) with the risk phrase R35 (Causes severe burns). < 25%: Xn; R 22 C; R35 10.7 Sodium carbonateEcotoxicology Aqueous solutions of sodium carbonate (CAS No. 497-19-8) are strongly alkaline. Sodium carbonate will hydrolyse as a function of pH. The carbon system in water is important because of the ubiquity of carbon dioxide and carbonate bearing minerals in the environment. Initial species of carbonates in the aqueous environment are H2CO3 and (CO3)2- which are in equilibrium with other forms depending on environmental conditions: closed or open system, pH, temperature, etc. The toxicity of sodium carbonate towards algae (Nitzschia sp.) is characterized by EC50 values in the range 137-242 mg/l. EC50 (48 h) values towards Daphnia magna have been determined in the range from 265 to 565 mg/l, whereas LC50 (96 h) values towards fish (Gambusia affinis and Lepomis machrochirus) have been found in the range of 300 to 740 mg/l (IUCLID 2000). Human health Sodium carbonate has low acute toxicity as measured by its oral rat LD50 of 4,090 mg/kg (RTECS 1998). Teratology tests on mice, rats and rabbits have all been negative (HSDB 1998). Classification Sodium carbonate is included in Annex 1 of list of dangerous substances of Council Directive 67/548/EEC and classified as Irritant (Xi) with the risk phrase R36 (Irritating to eyes). 10.8 Sodium hydrogen carbonateEcotoxicology In freshwater, only a minor part of the carbonate and bicarbonate form complexes with metals. It has been calculated that 99% of the total carbonate carbon exists as free ions (IUCLID 2000). In seawater, much larger proportions of CO3- and HCO3- exist as complexes. NaHCO3 (CAS No. 144-55-8) and more specifically HCO3- is a naturally occurring intermediate molecule or ion. Due to its weak base properties it is easily transformed to CO2, metal carbonate, or remaining in aqueous solutions at different concentrations depending on the environmental compartment, its alkalinity, composition, temperature, etc. The toxicity of sodium hydrogen carbonate towards aquatic organisms (algae, crustaceans and fish) is very low with EC/LC50 values far beyond 100 mg/l. Human health The acute toxicity of sodium hydrogen carbonate is low as measured by the oral rat LD50 of 4220 mg/kg (RTECS 1998). Teratology tests on mice, rats and rabbits have all been negative (HSDB 1998). Classification Sodium hydrogen carbonate is not included in Annex 1 of list of dangerous substances of Council Directive 67/548/EEC. 10.9 Sodium hydroxideEcotoxicology Sodium hydroxide (CAS No. 1310-73-2) is a strong base. It is highly soluble in water and dissociates to sodium and hydroxide ions, with the effect of increasing pH and alkalinity. Na+ and OH- persist indefinitely in the environment with equilibrium between various forms of complexes and precipitates. The aquatic toxicity of sodium hydroxide has been investigated towards crustaceans and fish. EC50 values in the range 30-180 mg/l have been determined for crustaceans, while LC50 (96 h) values for fish have been found in the range 45-125 mg/l, with rainbow trout (Oncorhynchus mykiss) being the most sensitive species (IUCLID 2000). Human health Burns caused by bases may be deep and destructive and give slowly healing wounds. Contact with corrosive cleaning agents do not always give immediate pain, but just a greasy feeling on the skin. When pain and redness finally occurs, damage has already occurred. Bases have a degreasing effect on the skin, facilitating penetration of the skin with irritant and allergenic substances. Inhalation of basic aerosols may give burns in the airways, giving rise to cough and respiratory distress. Long-term exposure to basic aerosols may give irreversible lung damage. Classification Sodium hydroxide is included in Annex 1 of list of dangerous substances of Council Directive 67/548/EEC and classified as Corrosive (C) with the risk phrase R35 (Causes severe burns). >5%: C; R35
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