Untreated water can host plenty of harmful bacteria and viruses. That’s why starting in the early 1900s, U.S. cities began disinfecting their drinking water with chlorine. Afterward, rates of waterborne disease, such as cholera (KAH-lur-uh) and typhoid (TY-foid), dropped sharply. Typhoid, caused by a type of Salmonella bacteria, used to sicken one in every 1,000 people in 1900. By 2006, the rate was down to one in every million.
2) By-products of disinfection
Chlorine and bromine can kill many dangerous waterborne germs. But these disinfectants also can react with other chemicals in the water. The results may be new and dangerous by-products. One that can show up: chloroform. This chemical is toxic to the kidneys, liver and brain.
3) Industrial chemicals
Many companies use perfluorinated (Per-FLOR-ih-nay-ted) compounds, or PFCs, to make everything from nonstick coatings (like Teflon) to firefighting foams. They are so widely used that these chemicals have been showing up in water. They also are hard to remove from drinking water and hard to track.
With super-strong chemical bonds between their carbon and fluorine atoms, these pollutants won’t break down naturally in the environment. And water treatment plants were never designed to remove them.
Some research has linked PFCs to a higher risk of certain cancers, to learning problems, to growth deficits and to fertility problems. Close to 5,000 different PFCs exist today, very few of which are regulated, says Jamie DeWitt. She’s a toxicologist at East Carolina University in Greenville, N.C. Chemical companies are not required to report what they use if that chemical isn’t already regulated, she notes. In June 2018, a report by the U.S. Centers for Disease Control and Prevention suggested lowering exposure limits for some PFCs below current federal guidelines. Some states, including New Jersey and Vermont, have set such stricter limits.
Arsenic is a concern for the two in every 15 U.S. residents who draw their drinking water from private wells instead of city water systems. Arsenic occurs naturally. It also can get into groundwater from its use in agriculture or mining. Exposure to high levels of this element has been linked to skin, bladder and lung cancers. It also can lower IQ and trigger birth defects. An estimated 2 million people or more in the United States may be exposed to levels of arsenic above the federal limit of 10 parts per billion. That’s according to a 2017 report in Environmental Science and Technology.
Nitrates are commonly used as a plant fertilizer. So these pollutants can enter water when rains run off of farms and fertilized lawns. In excess, these chemicals can prevent red blood cells from carrying enough oxygen around the body. The Clean Water Act of 1972 limits factories from polluting waterways. Farms pollution, however, is largely unregulated.
Farming states like Iowa have been hardest hit by nitrate pollution, says Christopher Jones. He’s an engineer at the University of Iowa in Iowa City. Curbing this pollution has proven difficult. For instance, the Mississippi River is a source of drinking water for several U.S. states. Yet despite a decade of work to reduce nitrates entering this river, nitrate levels in waters getting Iowa runoff are consistently higher today than they were 20 years ago. Jones reported the finding in April 2018 in PLOS ONE.
Lead pipes still carry water within 11,000 U.S. communities. These provide tap water to some 15 million to 22 million people. That’s according to a 2016 survey by the American Water Works Association. Very acidic or corrosive water can leach lead from plumbing pipes. That’s why the EPA mandates that cities adjust water chemistry to minimize such leaching. But those control measures are not foolproof. For instance, the Flint, Mich., lead crisis occurred when the city switched to a more corrosive source of drinking water, but didn’t adjust the chemicals used to compensate. Some communities have committed to replacing every lead water line — a very costly measure.
acidic An adjective for materials that contain acid. These materials often are capable of eating away at some minerals such as carbonate, or preventing their formation in the first place.
agriculture The growth of plants, animals or fungi for human needs, including food, fuel, chemicals and medicine.
arsenic A highly poisonous metallic element. It occurs in three chemically different forms, which also vary by color (yellow, black and gray). The brittle, crystalline (gray) form is the most common. Some manufacturers tap its toxicity by adding it to insecticides.
bacteria (singular: bacterium) Single-celled organisms. These dwell nearly everywhere on Earth, from the bottom of the sea to inside other living organisms (such as plants and animals).
bladder A flexible bag-like structure for holding liquids. (in biology) The organ that collects urine until it will be excreted.
bond (in chemistry) A semi-permanent attachment between atoms — or groups of atoms — in a molecule. It’s formed by an attractive force between the participating atoms. Once bonded, the atoms will work as a unit. To separate the component atoms, energy must be supplied to the molecule as heat or some other type of radiation.
cancer Any of more than 100 different diseases, each characterized by the rapid, uncontrolled growth of abnormal cells. The development and growth of cancers, also known as malignancies, can lead to tumors, pain and death.
carbon The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.
cell The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells.
Centers for Disease Control and Prevention, or CDC An agency of the U.S. Department of Health and Human Services, CDC is charged with protecting public health and safety by working to control and prevent disease, injury and disabilities. It does this by investigating disease outbreaks, tracking exposures by Americans to infections and toxic chemicals, and regularly surveying diet and other habits among a representative cross-section of all Americans.
chemical A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.
chemistry The field of science that deals with the composition, structure and properties of substances and how they interact. Scientists use this knowledge to study unfamiliar substances, to reproduce large quantities of useful substances or to design and create new and useful substances. (about compounds) Chemistry also is used as a term to refer to the recipe of a compound, the way it’s produced or some of its properties. People who work in this field are known as chemists.
chlorine A chemical element with the scientific symbol Cl. It is sometimes used to kill germs in water. Compounds that contain chlorine are called chlorides.
chloroform A colorless, sweet-smelling chemical solvent. Long ago, doctors would have patients inhale vapors of this chemical to render them unconscious — and painfree — during surgery.
cholera A bacterial disease that infects the small intestine, causing severe diarrhea, vomiting and dehydration. It is spread by germs from feces that contaminate water or food.
corrode (adj. corrosive) A chemical process that weakens or destroys normally robust materials, such as metals or rock.
current A fluid — such as of water or air — that moves in a recognizable direction. (in electricity) The flow of electricity or the amount of charge moving through some material over a particular period of time.
element A building block of some larger structure. (in chemistry) Each of more than one hundred substances for which the smallest unit of each is a single atom. Examples include hydrogen, oxygen, carbon, lithium and uranium.
engineer A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.
environment The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of things in the vicinity of an item of interest).
environmental science The study of ecosystems to help identify environmental problems and possible solutions. Environmental science can bring together many fields including physics, chemistry, biology and oceanography to understand how ecosystems function and how humans can coexist with them in harmony. People who work in this field are known as environmental scientists.
Environmental Protection Agency, or EPA A national government agency charged with helping create a cleaner, safer and healthier environment in the United States. Created on Dec. 2, 1970, it reviews data on the possible toxicity of new chemicals (other than foods or drugs, which are regulated by other agencies) before they are approved for sale and use. Where such chemicals may be toxic, it sets limits or guidelines on how much of them may be released into (or allowed to build up in) the air, water or soil.
federal Of or related to a country’s national government (not to any state or local government within that nation). For instance, the National Science Foundation and National Institutes of Health are both agencies of the U.S. federal government.
fertility Ability to reproduce.
fertilizer Nitrogen, phosphorus and other plant nutrients added to soil, water or foliage to boost crop growth or to replenish nutrients that were lost earlier as they were used by plant roots or leaves.
fluorine An element first discovered in 1886 by Henri Moissan. It takes its name from the Latin word meaning “to flow.” Very reactive, chemically, this element had little commercial use until World War II, when it was used to help make a nuclear-reactor fuel. Later, it was used as ingredients (fluorocarbons) in refrigerants and aerosol propellants. Most recently, it has found widespread use to make nonstick coatings for frying pans, plumbers’ tape, and waterproof clothing.
germ Any one-celled microorganism, such as a bacterium or fungal species, or a virus particle. Some germs cause disease. Others can promote the health of more complex organisms, including birds and mammals. The health effects of most germs, however, remain unknown.
groundwater Water that is held underground in the soil or in pores and crevices in rock.
host (in biology and medicine) The organism (or environment) in which some other thing resides. Humans may be a temporary host for food-poisoning germs or other infective agents.
IQ Short for intelligence quotient. It’s a number representing a person’s reasoning ability. It’s determined by dividing a person’s score on a special test by his or her age, then multiplying by 100.
kidney Each in a pair of organs in mammals that filters blood and produces urine.
leach (in geology and chemistry) The process by which water (often in the form of rain) removes soluble minerals or other chemicals from a solid, such as rock, or from sand, soil, bones, trash or ash.
lead A toxic heavy metal (abbreviated as Pb) that in the body moves to where calcium wants to go (such as bones and teeth). The metal is particularly toxic to the brain. In a child’s developing brain, it can permanently impair IQ, even at relatively low levels.
liver An organ of the body of animals with backbones that performs a number of important functions. It can store fat and sugar as energy, break down harmful substances for excretion by the body, and secrete bile, a greenish fluid released into the gut, where it helps digest fats and neutralize acids.
nitrate An ion formed by the combination of a nitrogen atom bound to three oxygen atoms. The term is also used as a general name for any of various related compounds formed by the combination of such atoms.
oxygen A gas that makes up about 21 percent of Earth's atmosphere. All animals and many microorganisms need oxygen to fuel their growth (and metabolism).
pollutant A substance that taints something — such as the air, water, our bodies or products. Some pollutants are chemicals, such as pesticides. Others may be radiation, including excess heat or light. Even weeds and other invasive species can be considered a type of biological pollution.
red blood cell Colored red by hemoglobin, these cells move oxygen from the lungs to all tissues of the body. Red blood cells are too small to be seen by the unaided eye.
resident Some member of a community of organisms that lives in a particular place. (Antonym: visitor)
risk The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)
runoff The rainwater that runs off of land into rivers, lakes and the seas. As that water travels through soils, it picks up bits of dirt and chemicals that it will later deposit as pollutants in streams, lakes and seas.
Salmonella A genus of bacteria that can cause disease in people and animals.
survey (v.) To ask questions that glean data on the opinions, practices (such as dining or sleeping habits), knowledge or skills of a broad range of people. Researchers select the number and types of people questioned in hopes that the answers these individuals give will be representative of others who are their age, belong to the same ethnic group or live in the same region. (n.) The list of questions that will be offered to glean those data.
technology The application of scientific knowledge for practical purposes, especially in industry — or the devices, processes and systems that result from those efforts.
toxic Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by such a poison is its toxicity.
toxicologist A scientist who investigates the potential harm posed by physical agents in the environment. These may include materials to which we may be intentionally exposed, such as chemicals, cigarette smoke and foods, or materials to which we are exposed without choice, such as air and water pollutants. Toxicologists may study the risks such exposures cause, how they produce harm or how they move throughout the environment.