HC Deb 05 March 2004 vol 418 c1163W
Mr. Paterson

To ask the Secretary of State for Environment, Food and Rural Affairs what the mode of action of(a) aluminium phosphide and (b) hydrogen cyanide is in terms of its effects on small mammals when used as a pesticide. [157930]

Alun Michael

The following modes of action apply to all mammals, not just small ones.

(a) Phosphine:

The primary mode of toxic action of phosphine is considered to be inhibition of cytochrome oxidase in the respiratory metabolism pathway, with additional direct cytotoxicity. Exposure to high concentrations of phosphine leads in vertebrates to a profound fall in blood pressure, followed by death. Lower concentrations cause pulmonary oedema and respiratory failure which may be fatal.

(b) Hydrogen Cyanide:

Cyanide combines with the ferric iron atom in haem proteins (eg cytochromes) in vertebrate tissues, impairing their capacity to undergo oxidation and reduction in the normal electron transport process. It can cause death extremely rapidly, primarily by inactivating cytochrome oxidase in tissues.

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