Some cancer-initiating epigenetic changes are probably the result of random chance – drift (see here) – or an error during mitosis. Some environmental exposures can also initiate cancers via epigenetic changes. For example, DNA methylation patterns change after exposure to well-known cancer-causing agents such as tobacco smoke, and to new threats like Bisphenol A (BPA), a component of some plastics that has been found to leach out of drinking bottles and into the body.
