|Substance Group: Perboric acid, sodium salt, mono and tetrahydrate |
Sodium perborate tetra and monohydrates are mainly used as bleaching agents in laundry detergents and machine dishwashing products. The amount of sodium perborate that was used in household cleaning products was estimated to be about 280,000 tons in 2000 (calculated as sodium perborate tetrahydrate).
Sodium perborate hydrates readily dissolve in water. In aqueous solution equilibrium between boric acid, hydrogen peroxide and sodium perborate exists. For sodium perborate acute aquatic toxicity data are available for all 3 trophic levels and the LC50 values range from 51-125 mg/l for fish, 11 to 30 mg/l for Daphnia magna and 3.3 to 20 mg/l for algae for the mono- and tetrahydrate respectively. The available data show that the acute toxicity of sodium perborate can be explained by the formation of hydrogen peroxide.
In the fabric washing or dishwashing process the hydrogen peroxide is consumed and the equilibrium is shifted to the reaction products. After washing, the active oxygen is rapidly degraded in the sewer so that boric acid is the only relevant species that enters the environment. As boric acid is an inorganic substance it will not be degraded in the sewage treatment plant. Adsorption to sediment is also considered negligible. Consequently the risk assessment is concentrating on boric acid (calculated as boron) in the water compartment.
A large amount of chronic toxicity data for boric acid is available for all trophic levels and a probabilistic PNEC that covers 95% of the species was derived. This PNEC was 3.45, or in a more conservative approach 1.34-mg boron/l. PEC calculations were based on a large amount of monitoring data and the PEC/PNEC ratio is well below 1. Thus it can be concluded with confidence that there is no risk to the environment from the use of sodium perborate containing household cleaning products.
Sodium perborate mono and terahydrates have a long history of safe use in bleach-containing cleaning products, in particular in laundry detergents and machine dishwashing agents. The substances are of low to moderate acute toxicity via the oral and inhalation route and of low toxicity via the dermal route. In aqueous media their toxicological properties are mainly determined by hydrogen peroxide and boric acid.
The local toxicity of sodium perborate hydrates is mediated by hydrogen peroxide. Hydrogen peroxide is known for its local irritant and cytotoxic properties that are also used in the physiological defence systems of the human body. Effective detoxification mechanisms are in place in the body to effectively destroy and detoxify hydrogen peroxide. The detoxification systems are practically unsaturable.
With regard to genotoxicity and carcinogenicity the properties of sodium perborate also resemble those of hydrogen peroxide and it can be concluded that there is no concern for humans with regard to a possible genotoxicity or carcinogenicity of the products.
Boric acid, which is the species that is potentially systemically available from sodium perborate, is also of low acute toxicity and does not have any genotoxic or carcinogenic potential. The systemic availability of boric acid from sodium perborate hydrates is, however, limited by the formation of hydrogen peroxide at the same time.
The toxicologic endpoints of concern for boric acid from studies in rodents were effects on fertility as well as developmental toxicity at high dose levels. The most sensitive endpoint indicative of possible effects on fertility of boric acid are effects on the histology of male sex organs in repeated dose studies. In a repeated dose study in rats with sodium perborate tetrahydrate it was shown that at the maximum tolerated dose levels no test compound related effects on the sex organs were observed. Effects on developmental toxicity were only observed at maternally toxic dose levels.
Human exposure to products containing sodium perborate hydrates under normal handling conditions is so low, that it will neither lead to significant local irritation nor to any systemic effects.
Accidental exposure to eyes may result in transient irritation that is normally readily reversible. Accidental swallowing may lead to irritation of mucous membranes in the gastro-intestinal tract and in some cases vomiting. These effects are normally also readily reversible and no fatal or severe poisoning cases have been reported.
Thus, it can be concluded that no risk for the consumer is anticipated from the use of sodium perborate hydrates in household detergent and cleaning products.