Chapter 6: Water Hazards General information Safe drinking-water, sanitation, and hygiene are crucial to human health and well-being.” Drinking unsafe water harms health through illness such as diarrhea. Untreated diarrhea can contaminate groundwater and surface waters used for drinking water, which can make drinking water even more unsafe (WHO, b). Some 829,000 people are estimated to die each year from diarrhea as a result of unsafe drinking-water, sanitation, and hand hygiene. Yet diarrhea is largely preventable, and the deaths of 297,000 children aged under five years could be avoided each year if these risk factors were addressed. Where water is not readily available people may decide handwashing is not a priority, thereby adding to the likelihood of diarrhea and other diseases.” Safe and readily available water is important for public health, whether it is used for drinking, domestic use, food production, or recreational purposes (WHO, 2022b). A variety of pathogenic and toxic substances can be found in drinking-water, wastewater, recreational water, and during flooding. This unit discusses many of these substances; however, several are not exclusive to one type of water but can be found in various types. For example, Cryptosporidium is discussed under recreational waters, yet it is also found in contaminated drinking-water, wastewater, and flood water. Additionally, some pathogens are present in both water and food. How many people die each year from diarrhea due to unsafe drinking water, sanitation, hand hygiene? Drinking water Globally, at least two billion people use a drinking water source contaminated with human waste. Microbial contamination of drinking-water as a result of contamination with feces causes the greatest risk to drinking-water safety(WHO, 2022b). In addition to fecal contamination, chemical contamination of water continues to cause a health burden, whether natural in origin such as arsenic and fluoride, or anthropogenic such as nitrate (WHO, b). Although not only found in drinking water, the following contaminants are of major concern: cholera, typhoid, arsenic, and nitrates. Cholera Basic Information Cholera is an acute diarrheal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae and remains a global threat to public health. Cholera transmission is closely linked to inadequate access to clean water and sanitation facilities. Researchers have estimated that each year there are 1.3–4.0 million cases of cholera, and 21,000 to 143,000 deaths worldwide due to cholera. The cholera bacterium is usually found in water or in foods that have been contaminated by human waste from a person infected with cholera bacteria. Cholera is most likely to occur and spread in places with inadequate water treatment, poor sanitation, and inadequate hygiene (CDC, 2022b). In cholera endemic countries, an outbreak can be seasonal or irregular and represents a greater than expected number of cases.