Metal mutagens and carcinogens affect RNA synthesis rates in a distinct manner.

Five metal salts (lead, cadmium, cobalt, copper, and manganese),which are mutagenic or carcinogenic, decreasing the fidelity of DNA synthesis in vitro, stimulated chain initiation of RNA synthesis at concentrations that inhibited overall RNA synthesis. In contrast, other metal salts (zinc, magnesium, lithium, sodium,and potassium) not in this category inhibited chain initiation of RNA synthesis at concentrations that inhibited overall RNA synthesis.