Exposure (toxicology)
Ingestion of toxins is very common in developing countries, where many people do not have safe drinking water.  There are many different toxins that can be carried in water.  They can be chemicals, like lead.  They can also be biological toxins, like the bacteria that causes cholera, and the viruses that cause Hepatitis A and polio.  People ingest these toxins by drinking the contaminated water, or eating food made with the water.  The World Health Organization says that about 502,000 people die every year because of toxins in water and the diseases they cause.