Short answers, pulled from the story.
John Snow identified the source of the 1854 cholera outbreak in London's Soho district in 1854. The outbreak originated from contaminated water from the Broad Street pump. This event marked the founding of the science of epidemiology.
Natural arsenic contamination of groundwater affects 140 million people in 70 countries. This global threat causes long-term health issues that can take decades to manifest. The largest-scale mass poisoning began in Bangladesh in the 1970s and 1980s.
A 2014 study found that approximately 25% of improved water sources contained fecal contamination. This contamination leads to infectious diseases such as gastroenteritis, cholera, and typhoid. The quality of these sources varies over time and often worsens during the wet season.
The Ministry of Health in Japan revised its water quality standards in April 2004 to improve water quality and reduce the risk of water contamination. The United Kingdom defines spending of more than 3% of one's income on water as a hardship. The Drinking Water Inspectorate provides independent assurance that the privatized water industry delivers safe drinking water to consumers.
The Flint water crisis began in 2014 and involved lead and Legionella contamination of the water supply. This event demonstrated that even regulated systems can fail. The crisis highlights the need for adequate funding and political will to ensure water safety.
In 2015, 780 million people were without improved sources of drinking water. This number represents a disparity from 1990 when only 76 percent of the global population had access to drinking water. The World Health Organization considers access to safe drinking water a basic human right.