11.6: Clean Water
Humans cannot survive without water. Nearly all cities and towns have been built around sources of freshwater for drinking and agricultural uses. While our “blue planet” may be covered in water, the majority of it is too salty to be used for these purposes. In fact, only about 1% of the water on earth is both freshwater and accessible to humans via the water cycle (aka hydrological cycle). Water from melting snowpack and rain flows through rivers and streams to lakes and oceans and sinks into underground aquifers. From lakes and oceans it is evaporated into the atmosphere as water vapor. Eventually once this water vapor condenses into clouds and gets heavy enough, it is returned to the ground via precipitation (rain, snow, etc.) Freshwater is accessible to humans from two sources. Surface water includes any water source open to the air: lakes, rivers, streams, ponds, etc. The other source is groundwater which comes from underground aquifers, wells, and springs. Groundwater has long been considered more ideal for human use since it has been filtered through soil and rock, and will thus require less treatment. Surface water is often full of dirt, microbes, and pollutants which requires an extensive filtration and disinfection process in order to be drinkable (Frumkin, 2016).
Drinking water can get contaminated by pollutants, chemicals, or biological contaminants from a variety of sources. Point source contamination occurs when there is a single source or multiple identifiable sources - such as a specific pipe dumping industrial chemicals into a stream, or several septic tanks leaching fecal matter into groundwater. Nonpoint source contamination occurs from an array of different sources - such as pesticides from agricultural runoff, or when rainwater picks up gasoline and oil on roadways. There are many different types of contaminants; they may be organic or inorganic chemicals, biological contaminants (such as bacteria, viruses, or protozoa), and even pharmaceuticals - which can lead to antibiotic resistance (see chapter on infectious diseases). Drinking water must therefore be properly filtered, disinfected, transported (via well-maintained pipes), and regularly tested in order to prevent toxic exposures or waterborne illnesses in humans and animals (Frumkin, 2016).
Particularly in developing countries around the world, many infectious diseases and toxic exposures can be prevented with improved access to water, sanitation, and hygiene practices. Combined, these are called WASH. The WHO estimates that despite major progress in the last 30 years, diseases caused by unsafe WASH still account for over 1.4 million deaths (in 2019), the majority of those related to diarrheal diseases - which affect hundreds of thousands of young children each year (WHO, 2023a). Sanitation and the proper treatment and disposal of wastewater also significantly impact exposure to pathogens. While wastewater can be an important source of water recycling (such as greywater from sinks and showers), many countries may lack sewage facilities, and open defecation is still practiced in many low-income countries, particularly in rural areas. Overall, inadequate sanitation accounted for the highest percentage of diarrheal disease deaths (38%). Yet sanitation is closely related to safe drinking water, which accounted for 35% of diarrheal disease deaths (WHO, 2023a). Open defecation or inadequate disposal of fecal matter can easily contaminate surface water, which may be collected downstream for drinking and agricultural uses. Proper handwashing behaviors (i.e. using soap, washing after potential fecal contact or before preparing food), are also extremely effective at reducing pathogen transmission. Both the resources - soap and water - and the education (knowing why it is important) are necessary to change behaviors. Yet even in high income countries these behaviors are not universally practiced (WHO, 2023a).
Although improving WASH is of particular importance in low and middle income countries, there are many potential sources of contamination in high income countries as well. In the U.S. there are two laws that primarily govern safe water sources: the Clean Water Act (CWA, 1972), and the Safe Drinking Water Act (SDWA, 1974, amended in 1986 and 1996). The CWA empowers the EPA to regulate surface water for fishing and recreation, as well as wastewater management - requiring industries and municipalities to pre-treat any wastewater before it enters into waterways. This law also prevents oil spills that could affect inland water and tasks the EPA with responding to those that do happen. The SDWA governs the treatment and delivery of drinking water to municipalities; protecting surface and groundwater sources of drinking water, as well as enforcing health standards for all public drinking water systems (Frumkin, 2016, and EPA, 2013). Even with these protections in place, water contamination still occurs, and tends to most often impact historically marginalized communities.