potassium ferrite

Endpoint summary

Additional information

Potassium ferrite is an inorganic substance which is poorly soluble in water (< 1 mg iron/L at 20 °C) and organic solvents. However, experimental data on the hydrolysis of Potassium ferrite revealed that hydrolysis proceeds to a minor degree and results in small amounts of potassium hydroxide (KOH). As this is also expected to happen if the substance is swallowed or inhaled, potassium hydroxide as well as the remaining iron oxides have to be investigated separately for their toxicokinetic behavior.

Potassium hydroxide:

Potassium hydroxide is fully dissociated in the body fluids; therefore its systemic toxicity must be discussed for its constituting potassium and hydroxyl ions separately.

Potassium is an essential constituent of the body fluids important for neuronal and muscular cell functions regulated by K+/Na+ pumps. Severe toxic doses exceeding 310 mg/l lead to neuromuscular paralysis and, at 390 -470 mg/l death from cardiac arrest. Regulation of K+ concentration in blood is assured principally by renal excretion and reabsorption regulated by aldosterone liberation. 90% is excreted into the urine and 10% through the faeces. The systemic toxicity of hydroxyl ions correlates with an elevated blood pH. Alkalosis causes hyperactivity of the central nervous system with, above pH 7.8, tetanus, extreme excitability, convulsions and respiratory stop. Neither the concentration of potassium in the blood nor the pH of the blood will be increased above normal limits (at non-irritating doses). Therefore absorbed KOH is not expected to cause systemically toxic levels in the blood. The renal excretion of K+ can be elevated and the OH- ion is neutralized by the bicarbonate buffer system in the blood and by respiratory compensation (OECD SIDS KOH 2004).

Iron oxides:

Iron oxides are hardly soluble in water. However, due to the acidic conditions in the stomach, any oral exposure to iron oxides is expected to lead to formation of the ionic forms of iron in the gastro-intestinal tract, mainly in the ferric (Fe³⁺) and a small fraction in the ferrous (Fe²⁺) state. Absorption, distribution and elimination of the substance are expected to follow a pattern similar to that of other iron containing compounds. Intestinal absorption of iron, especially the ferrous ion, is an active (enzymatically mediated) and complex process. The fraction of the iron absorbed is usually low (approximately 1 %; equivalent to the excretion rate): the rate of uptake depends on the state of the body's iron stores. Once absorbed, iron is either stored intracellularly (bound to ferritin) or delivered to the blood stream, where it gets bound to and transported by transferrin. Systemic toxicity of iron is only observed if iron is present in the general circulation in an unbound (not bound to transferrin) state. Iron is distributed throughout the body with the largest fraction transported to the bone marrow, where it is needed for erythropoiesis. The remaining iron is found in myoglobin and other iron-requiring enzymes. In liver and spleen, it is bound to ferritin and haemosiderin. Usually iron is eliminated via the faeces due to the general poor absorption characteristics. The iron pool in the body is normally maintained and 'recycled' and the biological half-life of systemic iron is several years. Very little iron from the iron pool in the body is excreted. However in case of an overload, elimination occurs via kidney and bile.

Due to the alkaline properties of Potassium hydroxide, the absorption of unsoluble iron oxides may be facilitated.