Miscellaneous Dangerous Substances : This was introduced in the United Kingdom to identify other hazardous substances and consists of a black exclamation mark on a white background.

 Charts showing UN Hazard class symbols on transportation of hazardous goods.

Besides the above recognised classes for hazardous chemicals, there is another very important class of compounds which you should be aware of. 'These are called carcinogens. These are the substances which cause cancer. There are a number of substances which are known to induce cancer many months or years after the initial exposure. Some substances which are known or suspected carcinogens are aniline, chloroform, benzyl chloride, chromates of lead and zinc, hydrazine etc. Ninhydrin - the reagent used in biological and biochemical tests for the presence of amino acids and proteins, is also thought to be a possible carcinogen, but this has yet to be confirmed. Similarly some stains like fusion used in biology lab also belong to this category and extreme care should be exercised in their use. The examples given here are very few, however more and more substances are being shown to be carcinogenic and the fact that even quite common substances may have some carcinogenic activity emphasizes the necessity of consulting reference literature before starting work with materials when you are ignorant of their potential hazards.

Before proceeding further you can try to answer the following question based on the nature of hazardous substances.