Chemical name: Arsenenous acid, sodium salt Final regulatory action has been taken for the category: Pesticide Final regulatory action: The chemical is Banned Use or uses prohibited by the final regulatory action: All applications are prohibited. Pesticide use or uses that remain allowed: None. The final regulatory action was based on a risk or hazard evaluation: Yes Summary of the final regulatory action: It is prohibited to sell, stock, store or use all applications of sodium arsenite as a pesticide. The reasons for the final regulatory action were relevant to: Human health and environment Summary of known hazards and risks to human health: The Pesticide Authorisation Board (CTB) decided to withdraw all applications of sodium arsenite mainly on the basis of the leaching potential to groundwater. In the Netherlands groundwater can be used for drinking water and therefore groundwater must remain free from pesticides (precaution principle). In the Netherlands, the limit value for the leaching to groundwater is 0.1 ug/l, which was at that time based on the detection limit. In practice this leaching limit is used as a human health standard. In the (top) soil arsenite is usually converted into arsenate, which strongly absorbs to Fe, Al and Ca and clay particles in soil. Only at low pH values ( in a reducing environment) arsenite is not converted into arsenate. Arsenate is very immobile in soil, is not further degradable and is therefore considered as persistent. The velocity of the increasing accumulation in soil is dependant on th input via spraying and the output via plants, volatilisation and leaching. The removal of the substance via plants and volatilisation appeared to be negligible. Leaching appeared to be the main removal. When sodium-arsenite is applied frequently then an equilibrium is reached between the input via spraying and the output via leaching. The equilibrium concentations in soil can reach dozens to some hundred mg/kg on a dryweight basis. At equilibrium concentrations in soil the leaching to groundwater can be equal to the spraying dose. Because of this relatively large leaching potential it was advised to prohibit all uses of sodium arsenite as a pesticide. Expected effect of the final regulatory action in relation to human health: Prevention of contamination of drinking water derived from groundwater. The final regulatory action led to a complete risk reduction. Summary of known hazards and risks to the environment: The Pesticide Authorisation Board (CTB) decided to withdraw all applications of sodium arsenite mainly on the basis of ecotoxicological properties. In the (top) soil arsenite is usually converted into arsenate, which strongly absorbs to Fe, Al and Ca and clay particles in soil, Only at low pH values ( in a reducing environment) arsenite is not converted into arsenate. Arsenate is very immobile in soil, is not further degradable and is therefore considered as persistent. The velocity of the increasing accumulation in soil is dependent on the input via spraying and the output via plants, volatilisation and leaching. The removal of the substance via plants and volatilisation appeared to be negligible. Leaching appeared to be the main removal. When sodium-arsenite is applied frequently then an equilibrium is reached between the input via spraying and the output via leaching. The equilibrium concentration in soil can reach dozens to some hundred mg/kg on a dryweight basis. At these concentration phytotoxic effects can not be excluded. There are no quantitative data available about the possible phytotoxic effects. Expected effect of the final regulatory action in relation to the environment: Prevention of phytotoxic effects. The final regulatory action led to a complete risk reduction. Date of entry into force of the final regulatory action: 11/11/1985 |