Quintozene. Computer model of a molecule of the fungicide quintozene (pentachloronitrobenzene, formula: C6Cl5NO2). The atoms are colour-coded: carbon (blue), chlorine (green), nitrogen (light blue) and oxygen (red). It is used as a fungicide for seeds and crops, and is highly toxic. In humans, it is a carcinogen, and prolonged exposure can lead to liver and kidney damage. It can also cause methemoglobinaemia, a condition in which the blood loses its ability to carry oxygen around body, resulting in a bluish discolouration of the skin.