We all need clean water. People need it to grow crops and to operate factories, and for drinking and recreation. Fish and wildlife depend on it to survive.

Many different pollutants can harm our rivers, streams, lakes, and oceans. The three most common are soil, nutrients, and bacteria. Rain washes soil into streams and rivers. The soil can kill tiny animals and fish eggs. It can clog the gills of fish and block light, causing plants to die. Nutrients, often from fertilizers, cause problems in lakes, ponds, and reservoirs. Nitrogen and phosphorus make algae grow and can turn water green. Bacteria, often from sewage spills, can pollute fresh or salt water.

You can help protect your water supply:

• Don't pour household products such as cleansers, beauty products, medicines, auto fluids, paint, and lawn care products down the drain. Take them to a hazardous waste collection site.
• Throw away excess household grease (meat fats, lard, cooking oil, shortening, butter, margarine, etc.) diapers, condoms, and personal hygiene products in the garbage can.
• Clean up after your pets. Pet waste contains nutrients and germs.

What is in the water?

Is it safe for drinking? Can fish and other aquatic life thrive in streams and lakes that are affected by human activities? What is the water quality? To answer these questions, it is helpful to understand what "water quality" means, how it is determined, and the natural processes and human activities that affect water quality.

What do we mean by "water quality"?

Water quality can be thought of as a measure of the suitability of water for a particular use based on selected physical, chemical, and biological characteristics. To determine water quality, scientists first measure and analyze characteristics of the water such as temperature, dissolved mineral content, and number of bacteria. Selected characteristics are then compared to numeric standards and guidelines to decide if the water is suitable for a particular use.

How is water quality measured?

Some aspects of water quality can be determined right in the stream or at the well. These include temperature, acidity (pH), dissolved oxygen, and electrical conductance (an indirect indicator of dissolved minerals in the water). Analyses of individual chemicals generally are done at a laboratory.

Why do we have water-quality standards and guidelines?

Standards and guidelines are established to protect water for designated uses such as drinking, recreation, agricultural irrigation, or protection and maintenance of aquatic life. Standards for drinking-water quality ensure that public drinking-water supplies are as safe as possible. The U.S. Environmental Protection Agency (USEPA) and the States are responsible for establishing the standards for constituents in water that have been shown to pose a risk to human health. Other standards protect aquatic life, including fish, and fish-eating wildlife such as birds.

How do natural processes affect water quality?

Natural water quality varies from place to place, with the seasons, with climate, and with the types of soils and rocks through which water moves. When water from rain or snow moves over the land and through the ground, the water may dissolve minerals in rocks and soil, percolate through organic material such as roots and leaves, and react with algae, bacteria, and other microscopic organisms. Water may also carry plant debris and sand, silt, and clay to rivers and streams making the water appear “muddy” or turbid. When water evaporates from lakes and streams, dissolved minerals are more concentrated in the water that remains. Each of these natural processes changes the water quality and potentially the water use.

What is naturally in the water?

The most common dissolved substances in water are minerals or salts that, as a group, are referred to as dissolved solids. Dissolved solids include common constituents such as calcium, sodium, bicarbonate, and chloride; plant nutrients such as nitrogen and phosphorus; and trace elements such as selenium, chromium, and arsenic.

In general, the common constituents are not considered harmful to human health, although some constituents can affect the taste, smell, or clarity of water. Plant nutrients and trace elements in water can be harmful to human health and aquatic life if they exceed standards or guidelines.

Dissolved gases such as oxygen and radon are common in natural waters. Adequate oxygen levels in water are a necessity for fish and other aquatic life. Radon gas can be a threat to human health when it exceeds drinking-water standards.

How do human activities affect water quality?

Urban and industrial development, farming, mining, combustion of fossil fuels, stream-channel alteration, animal-feeding operations, and other human activities can change the quality of natural waters. As an example of the effects of human activities on water quality, consider nitrogen and phosphorus fertilizers that are applied to crops and lawns. These plant nutrients can be dissolved easily in rainwater or snowmelt runoff. Excess nutrients carried to streams and lakes encourage abundant growth of algae, which leads to low oxygen in the water and the possibility of fish kills.

Chemicals such as pharmaceutical drugs, dry-cleaning solvents, and gasoline that are used in urban and industrial activities have been found in streams and ground water. After decades of use, pesticides are now widespread in streams and ground water, though they rarely exceed the existing standards and guidelines established to protect human health.

Some pesticides have not been used for 20 to 30 years, but they are still detected in fish and streambed sediment at levels that pose a potential risk to human health, aquatic life, and fish-eating wildlife. There are so many chemicals in use today that determining the risk to human health and aquatic life is a complex task. In addition, mixtures of chemicals typically are found in water, but health-based standards and guidelines have not been established for chemical mixtures.

What about bacteria, viruses, and other pathogens in water?

The quality of water for drinking cannot be assured by chemical analyses alone. The presence of bacteria in water, which are normally found in the intestinal tracts of humans and animals, signal that disease-causing pathogens may be present. Giardia and cryptosporidium are pathogens that have been found occasionally in public-water supplies and have caused illness in a large number of people in a few locations. Pathogens can enter our water from leaking septic tanks, wastewater-treatment discharge, and animal wastes.

How can I find out more about my water quality?

Contact your local water supplier and ask for information on the water quality in your area. The USEPA requires public-water suppliers to provide water-quality data to the public on an annual basis in an understandable format. State agencies that deal with health, environmental quality, or water resources also can provide information on the quality of your water. 

Introduction

Water is essential for life. People depend on safe water for their health and livelihood. But contaminated water leads to millions of deaths and even more illnesses every year. 

Water pollution is any contamination of water with chemicals or other hazardous substances that are detrimental to human, animal, or plant health.

Possible sources of water contamination are:

• Corroded water pipes that leach harmful chemicals, such as lead
• Hazardous waste sites and industrial discharges
• Pesticides and fertilizers from agricultural operations
• Naturally occurring hazardous chemicals, such as arsenic
• Sewage and food processing waste

Drinking Water

Drinking water in the U.S. comes from a variety of sources, including public water systems, private wells, or bottled water. Worldwide, nearly 2 billion people drink contaminated water that could be harmful to their health. Though more of a concern in developing countries, safe drinking water is a U.S. public health priority.

Health Effects

Examples follow of potential drinking water contaminants and reported health effects, which can range from subtle to severe depending on the chemical and total exposure.

• Arsenic – a known human carcinogen associated with skin, lung, bladder, kidney, and liver cancer 
• Lead – behavioral and developmental effects in children; and cardiovascular and kidney problems 
• Hydraulic fracturing (fracking) chemicals – damage to the immune and reproductive systems 
• Pesticides – neurodevelopmental effects and Parkinson’s disease 

Wastewater is used water. It includes substances such as human waste, food scraps, oils, soaps and chemicals. In homes, this includes water from sinks, showers, bathtubs, toilets, washing machines and dishwashers. Businesses and industries also contribute their share of used water that must be cleaned.

What is wastewater, and why treat it?

We consider wastewater treatment as a water use because it is so interconnected with the other uses of water. Much of the water used by homes, industries, and businesses must be treated before it is released back to the environment.

If the term "wastewater treatment" is confusing to you, you might think of it as "sewage treatment." Nature has an amazing ability to cope with small amounts of water wastes and pollution, but it would be overwhelmed if we didn't treat the billions of gallons of wastewater and sewage produced every day before releasing it back to the environment. Treatment plants reduce pollutants in wastewater to a level nature can handle.

Wastewater also includes storm runoff. Although some people assume that the rain that runs down the street during a storm is fairly clean, it isn't. Harmful substances that wash off roads, parking lots, and rooftops can harm our rivers and lakes.

Why Treat Wastewater?

It's a matter of caring for our environment and for our own health. There are a lot of good reasons why keeping our water clean is an important priority:

FISHERIES: Clean water is critical to plants and animals that live in water. This is important to the fishing industry, sport fishing enthusiasts, and future generations.

WILDLIFE HABITATS: Our rivers and ocean waters teem with life that depends on shoreline, beaches and marshes. They are critical habitats for hundreds of species of fish and other aquatic life. Migratory water birds use the areas for resting and feeding.

RECREATION AND QUALITY OF LIFE: Water is a great playground  for us all. The scenic and recreational values of our waters are reasons many people choose to live where they do. Visitors are drawn to water activities such as swimming, fishing, boating and picnicking.

HEALTH CONCERNS: If it is not properly cleaned, water can carry disease. Since we live, work and play so close to water, harmful bacteria have to be removed to make water safe.

Effects of wastewater pollutants

If wastewater is not properly treated, then the environment and human health can be negatively impacted. These impacts can include harm to fish and wildlife populations, oxygen depletion, beach closures and other restrictions on recreational water use, restrictions on fish and shellfish harvesting and contamination of drinking water. Environment Canada provides some examples of pollutants that can be found in wastewater and the potentially harmful effects these substances can have on ecosystems and human health:

• Decaying organic matter and debris can use up the dissolved oxygen in a lake so fish and other aquatic biota cannot survive;
• Excessive nutrients, such as phosphorus and nitrogen (including ammonia), can cause eutrophication, or over-fertilization of receiving waters, which can be toxic to aquatic organisms, promote excessive plant growth, reduce available oxygen, harm spawning grounds, alter habitat and lead to a decline in certain species;
• Chlorine compounds and inorganic chloramines can be toxic to aquatic invertebrates, algae and fish;
• Bacteria, viruses and disease-causing pathogens can pollute beaches and contaminate shellfish populations, leading to restrictions on human recreation, drinking water consumption and shellfish consumption;
• Metals, such as mercury, lead, cadmium, chromium and arsenic can have acute and chronic toxic effects on species.
• Other substances such as some pharmaceutical and personal care products, primarily entering the environment in wastewater effluents, may also pose threats to human health, aquatic life and wildlife.

Wastewater treatment

The major aim of wastewater treatment is to remove as much of the suspended solids as possible before the remaining water, called effluent, is discharged back to the environment. As solid material decays, it uses up oxygen, which is needed by the plants and animals living in the water.

"Primary treatment" removes about 60 percent of suspended solids from wastewater. This treatment also involves aerating (stirring up) the wastewater, to put oxygen back in. Secondary treatment removes more than 90 percent of suspended solids.

Over the past few decades, the increase in population and advances made in farming technology has increased the demand for crops and livestock from the agricultural industry. This growth in agricultural production has resulted in an increase in contaminants polluting soil and waterways. The increase in contaminants has prompted efforts to reduce the amount of pollutants in waterways in order to improve overall water quality.

Sources

Agriculture in many parts of the world is highly efficient in producing and delivering high-quality products to consumers. However, when agricultural activities are not well-monitored and managed, certain practices can negatively affect water quality.

Agricultural Runoff

According to the U.S. Environmental Protection Agency (EPA), nonpoint source (NPS) pollution is pollution that comes from many diffuse sources, unlike pollution from point sources such as industrial and sewage treatment plants. “Polluted runoff is created by rainfall or snowmelt moving over and through the ground. As the runoff moves, it picks up and carries away natural and human-made pollutants, finally depositing them into watersheds via lakes, rivers, wetlands, coastal waters, and even our underground sources of drinking water”.

In 2002, in the National Water Quality Inventory report to U.S. Congress, the states reported that agricultural nonpoint source (NPS) pollution is the leading cause of river and stream impairment and the second leading cause of impairment in lakes, ponds, and reservoirs.

Agricultural activities that cause nonpoint source pollution include:

• Poorly managed animal feeding operations
• Overgrazing
• Overworking the land (for example, plowing too often)
• Poorly managed and ineffective application of pesticides, irrigation water, and fertilizer

Effects

Agricultural water can become contaminated through a variety of ways and can potentially spread bacteria, viruses, and parasites to crops and animals.

Crop Production

Fresh fruits and vegetables come in contact with water during various stages of the production process. Contaminated water that is used during crop production, harvesting, and processing can lead to health issues.

Below is a list of the potential food production points where contaminated water sources can affect crop production:

• Chemical Application
  Crops with contaminated water used for pesticide or herbicide application. Water used for mixing chemicals should be of appropriate quality.
• Irrigation
  Irrigating crops with contaminated water. Water used for irrigation should be of appropriate quality.
• Worker Hygiene
  Lack of potable water for hand hygiene. There should be an established handwashing and hygiene policy for farm workers.
• Food Processing
  Wash crops in the final wash process with quality water. Water should be of drinking water quality and should not be recycled.

People who consume fruit or vegetables that were exposed to contaminated water are at risk of developing a foodborne illness. Some of the bacteria that are spread through water within the United States include E. coli, Salmonella spp., Shigella spp., Cryptosporidium, Giardia, Toxoplasma, norovirus, and hepatitis A virus. Irrigation of foods imported from international locations can spread these and other microbes (for example, Cyclospora) not usually found in developed countries. Small amounts of any of these organisms can cause foodborne illness. In order to keep microbes out of water sources, growers should use practices that are appropriate for their operation and make sure that they are using the best quality water. Water quality is also important in ensuring post harvest quality by decreasing decay.

Animal Health

It is important that livestock are provided with adequate amounts of quality water, free of contamination. Contaminated water can contain disease-causing organisms which can rapidly spread if animals are drinking from the same trough. If there is reason to question the quality of the water that is provided to livestock, it is important to test the water to ensure its safety. There are many chemicals and microorganisms that can be potentially dangerous to livestock. Some chemicals include nitrates, sulfates, and chemicals found in pesticides like DDT, Chlordane, and Endrin. Certain microorganisms such as blue-green algae, Cryptosporidium, or Staphylococcus, can be toxic to animals and cause symptoms like diarrhea, lack of coordination, labored breathing, or death. Ill animals can then release millions of infectious microbes into the soil that can further contaminate other water sources.

A watershed – the land area that drains to one stream, lake or river – affects the water quality in the water body that it surrounds. Like water bodies (e.g., lakes, rivers, and streams), individual watersheds share similarities but also differ in many ways. Every inch of the United States is part of a watershed – in other words, all land drains into a lake, river, stream or other water body and directly affects its quality. Because we all live on the land, we all live in a watershed — thus watershed condition is important to everyone.

Watersheds exist at different geographic scales, too. The Mississippi River has a huge watershed that covers all or parts of 33 states. You might live in that watershed, but at the same time you live in a watershed of a smaller, local stream or river that flows eventually into the Mississippi. EPA’s healthy watersheds activities mainly focus on these smaller watersheds.

What is a Healthy Watershed?

A healthy watershed is one in which natural land cover supports:

• dynamic hydrologic and geomorphologic processes within their natural range of variation,
• habitat of sufficient size and connectivity to support native aquatic and riparian species, and
• physical and chemical water quality conditions able to support healthy biological communities.

Natural vegetative cover in the landscape, including the riparian zone, helps maintain the natural flow regime* and fluctuations in water levels in lakes and wetlands. This, in turn, helps maintain natural geomorphic processes, such as sediment storage and deposition, that form the basis of aquatic habitats. Connectivity of aquatic and riparian habitats in the longitudinal, lateral, vertical, and temporal dimensions helps ensure the flow of chemical and physical materials and movement of biota among habitats.

A healthy watershed has the structure and function in place to support healthy aquatic ecosystems. Key components of a healthy watershed include:

• intact and functioning headwater streams, floodplains, riparian corridors, biotic refugia, instream habitat, and biotic communities;
• natural vegetation in the landscape; and
• hydrology, sediment transport, fluvial geomorphology, and disturbance regimes expected for its location.

*A stream’s flow regime refers to its characteristic pattern of flow magnitude, timing, frequency, duration, and rate of change. The flow regime plays a central role in shaping aquatic ecosystems and the health of biological communities. Alteration of natural flow regimes (e.g., more frequent floods) can reduce the quantity and quality of aquatic habitat, degrade aquatic life, and result in the loss of ecosystem services.

Are Healthy Watersheds Very Common?

Unfortunately not. Healthy watersheds are uncommon, particularly in the eastern U.S. as well as in most other parts of the nation that are urbanized, farmed, or mined. Large tracts of protected wildlands, mostly in the western U.S., are where most healthy watersheds can be found. However, some healthy watersheds exist in many regions of the country where water pollution has been prevented or well controlled, and where communities maintain the benefits of their clean waterways.

How Might Healthy Watersheds Affect Me?

You may potentially benefit from healthy watersheds in numerous ways, generally unseen and unrecognized by the average citizen:

• Healthy watersheds are necessary for virtually any high quality outdoor recreation sites involving the use of lakes, rivers, or streams. Great fishing opportunities are usually due to healthy watersheds that surround the waters that people love to fish.
• Your drinking water, if it comes from a surface water source, might be substantially less expensive to treat, if a healthy watershed around the water source filters pollution for free.
• Your property values may be higher, if you are fortunate enough to reside near healthy rather than impaired waters.

You and your community’s quality of life may be better in these and other ways due to healthy watersheds; now, imagine how unhealthy watersheds might affect you as well.

Why Do Watersheds Need to Be Protected?

Healthy watersheds not only affect water quality in a good way, but also provide greater benefits to the communities of people and wildlife that live there.

A watershed – the land area that drains to a stream, lake or river – affects the water quality in the water body that it surrounds. Healthy watersheds not only help protect water quality, but also provide greater benefits than degraded watersheds to the people and wildlife that live there. We all live in a watershed, and watershed condition is important to everyone and everything that uses and needs water.

Healthy watersheds provide critical services, such as clean drinking water, productive fisheries, and outdoor recreation, that support our economies, environment and quality of life. The health of clean waters is heavily influenced by the condition of their surrounding watersheds, mainly because pollutants can wash off from the land to the water and cause substantial harm.

Streams, lakes, rivers and other waters are interconnected with the landscape and all its activities through their watersheds. They are influenced by naturally varying lake levels, water movement to and from groundwater, and amount of stream flow. Other factors, such as forest fires, stormwater runoff patterns, and the location and amount of pollution sources, also influence the health of our waters.

These dynamics between the land and the water largely determine the health of our waterways and the types of aquatic life found in a particular area. Effective protection of aquatic ecosystems recognizes their connectivity with each other and with their surrounding watersheds. Unfortunately, human activities have greatly altered many waters and their watersheds. For example:

• Over the last 50 years, coastal and freshwater wetlands have declined; surface water and groundwater withdrawals have increased by 46%; and non-native fish have established themselves in many watersheds (Heinz Center, 2008).
• A national water quality survey of the nation's rivers and streams showed that 55% of the nation's flowing waters are in poor biological condition and 23% are in fair biological condition (U.S. EPA, 2013). Compared to a 2006 survey (U.S. EPA, 2006), which only assessed wadeable streams, 7% fewer stream miles were in good condition.
• Nearly 40% of fish in North American freshwater streams, rivers and lakes are found to be vulnerable, threatened or endangered; nearly twice as many as were included on the imperiled list from a similar survey conducted in 1989 (Jelks et al., 2008)
• Rainbow trout habitat loss from warmer water temperatures associated with climate change already has been observed in the southern Appalachians (Flebbe et al., 2006).

How is a Healthy Watershed Identified?

There are literally hundreds of watershed characteristics (such as environmental traits, sources of degradation, and community factors) that may influence environmental health and quality of life, for better or worse. Identifying and comparing these characteristics is known as watershed assessment. This process is the main way to compare watershed condition across large areas such as states, and find the healthy watersheds among the rest.

Acid rain, or acid deposition, is a broad term that includes any form of precipitation with acidic components, such as sulfuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms.  This can include rain, snow, fog, hail or even dust that is acidic.  

What Causes Acid Rain?

Acid rain results when sulfur dioxide (SO₂) and nitrogen oxides (NO_X) are emitted into the atmosphere and transported by wind and air currents. The SO₂ and NO_X react with water, oxygen and other chemicals to form sulfuric and nitric acids.  These then mix with water and other materials before falling to the ground.

While a small portion of the SO₂ and NO_X that cause acid rain is from natural sources such as volcanoes, most of it comes from the burning of fossil fuels.  The major sources of SO₂ and NO_X in the atmosphere are:

• Burning of fossil fuels to generate electricity.  Two thirds of SO₂ and one fourth of NO_X in the atmosphere come from electric power generators.
• Vehicles and heavy equipment.
• Manufacturing, oil refineries and other industries.

Winds can blow SO₂ and NO_X over long distances and across borders making acid rain a problem for everyone and not just those who live close to these sources. 

Forms of Acid Deposition

Wet Deposition

Wet deposition is what we most commonly think of as acid rain. The sulfuric and nitric acids formed in the atmosphere fall to the ground mixed with rain, snow, fog, or hail.  

Dry Deposition

Acidic particles and gases can also deposit from the atmosphere in the absence of moisture as dry deposition. The acidic particles and gases may deposit to surfaces (water bodies, vegetation, buildings) quickly or may react during atmospheric transport to form larger particles that can be harmful to human health. When the accumulated acids are washed off a surface by the next rain, this acidic water flows over and through the ground, and can harm plants and wildlife, such as insects and fish.

The amount of acidity in the atmosphere that deposits to earth through dry deposition depends on the amount of rainfall an area receives.  For example, in desert areas the ratio of dry to wet deposition is higher than an area that receives several inches of rain each year.

Measuring Acid Rain

Acidity and alkalinity are measured using a pH scale for which 7.0 is neutral. The lower a substance's pH (less than 7), the more acidic it is; the higher a substance's pH (greater than 7), the more alkaline it is. Normal rain has a pH of about 5.6; it is slightly acidic because carbon dioxide (CO₂) dissolves into it forming weak carbonic acid.  Acid rain usually has a pH between 4.2 and 4.4.

Policymakers, research scientists, ecologists, and modelers rely on the National Atmospheric Deposition Program’s (NADP) National Trends Network (NTN) for measurements of wet deposition. The NADP/NTN collects acid rain at more than 250 monitoring sites throughout the US, Canada, Alaska, Hawaii and the US Virgin Islands. Unlike wet deposition, dry deposition is difficult and expensive to measure. Dry deposition estimates for nitrogen and sulfur pollutants are provided by the Clean Air Status and Trends Network (CASTNET). Air concentrations are measured by CASTNET at more than 90 locations.

When acid deposition is washed into lakes and streams, it can cause some to turn acidic. The Long-Term Monitoring (LTM) Network measures and monitors surface water chemistry at over 280 sites to provide valuable information on aquatic ecosystem health and how water bodies respond to changes in acid-causing emissions and acid deposition.

Swimming at beaches with pollution in the water or in the sand can make you ill. EPA supports local and state efforts to protect and clean up beaches. EPA also supports monitoring and notification efforts by local beach programs by providing grant money. In the event that beaches are closed or advisories are posted, it is most often because water samples for certain bacteria indicate that harmful bacteria, viruses, protozoa, or parasites are likely present in the waters.

Polluted runoff (water that drains after rainfall) and untreated sewage released into the water can expose swimmers to harmful microorganisms called “pathogens.” These pathogens can be present at or near the site where polluted discharges enter the water. Pollution can also come from high concentrations of farm animals like pigs and chickens that can contaminate local waterways with runoff, which is then carried to beaches and swimming areas. In addition, pollution is created by people who leave trash or animal wastes at beaches.

Beach-related Illnesses

Children, the elderly and people with weakened immune systems are the most likely populations to develop illnesses or infections after coming into contact with polluted water, usually while swimming. Fortunately, while swimming-related illnesses are unpleasant, they are usually not very serious.  They require little or no treatment or get better quickly upon treatment, and they have no long-term health effects.

The most common illness associated with swimming in water polluted by sewage is gastroenteritis. It occurs in a variety of forms that can have one or more of the following symptoms: nausea, vomiting, stomachache, diarrhea, headache or fever. Other minor illnesses associated with swimming include ear, eye, nose and throat infections. In highly polluted water, swimmers may occasionally be exposed to more serious diseases.

Another potential source of illness includes some types of cyanobacteria that form algal “blooms” (discolored water) and the toxins they produce. When people are exposed to cyanotoxins, they may have hay fever-like symptoms, skin rashes, sore throat, cough, nausea, vomiting, diarrhea, or even kidney or liver damage. Pets can be poisoned by drinking or swimming in toxin-contaminated water.

Not all illnesses from a day at the beach are from swimming. Food poisoning from improperly refrigerated picnic lunches may also have some of the same symptoms as swimming-related illnesses, including stomachache, nausea, vomiting and diarrhea.

Staying Safe at the Beach

Look for Signs

Be aware of any signs indicating the beach is closed or the water is not safe because of bacteria, riptides, or other hazards. In areas that are not monitored regularly, choose swimming sites in less developed areas with good water circulation, such as beaches at the ocean. Avoid swimming at beaches where you can see discharge pipes or at urban beaches after a heavy rainfall.

Avoid Swallowing Water

When waterborne pathogens are present, most swimmers are exposed when they swallow the water. You will be less likely to get sick if you wade or swim without putting your head under water.

Keep Open Wounds Out of Water

People can get some infections simply from getting polluted water on their skin or in their eyes. In rare cases, swimmers can develop illnesses or infections if an open wound is exposed to polluted water.

Dirt

Dirt is a big cause of pollution in our rivers and streams. Rain washes dirt into streams and rivers. Dirt can smother fish and other animals that live in the water. If plants can't get enough sunlight because the water is murky, they die.

Most of the dirt washing into lakes and streams comes from exposed earth. This exposed earth includes plowed fields, construction sites, and areas that have been logged or mined. Some of the dirt polluting streams comes from the stream banks.

The solution is to stop the dirt from getting into the stream in the first place by disturbing the land as little as possible. Farmers and construction workers are using new methods to reduce the amount of earth they disturb.

Bacteria

Bacteria are also a big water quality problem. Not all bacteria are harmful, but germs and viruses that can make you sick might be in the water. Bacteria can come from combined sewers after rainstorms and runoff of animal waste from farms, pets, and wildlife.

Sewage systems can be improved to keep untreated sewage from overflowing. Farmers are developing better ways to manage livestock manure. Dog owners are picking up after their pets.

Nutrients

Nutrients are element needed for animal or plants to grow. The two most common nutrients found in water are nitrogen and phosphorus. They cause algae to grow and can turn the water green.

The major sources of nutrients are runoff of fertilizers from farms and lawns, animal waste, sewage treatment plants, and septic systems.

Farmers, homeowners, cities, and towns are all working to reduce the amount of nutrients that get into rivers and streams.

Ponds, Lakes, and the Sea

Water in streams and rivers flows into ponds, lakes, and the sea. Keeping streams and rivers clean helps keep all the water downstream clean, too.

Our drinking water originates from groundwater, wells, rivers, lakes, streams, and reservoirs. Water treatment plants help to clean the water to make it safe to drink.

Common drinking water, or tap water, contains different combinations of naturally occurring minerals, which can affect the water’s taste.

Why is Drinking Water a concern?

All water contains some level of impurities, minerals, and contaminants. In most cases, these levels are very low, and the water is still safe to drink. The U.S. Environmental Protection Agency (EPA) sets acceptable limits for more than 90 contaminants that may be in drinking water and pose a risk to human health. At low levels they may not harm you, but if the levels of certain contaminants get too high, these waer pllutants can cause short-term and long-term health effects.

Who is at risk?

People in cities usually drink water filtered through water treatment plants. This water is tested at regular intervals. But if a contaminant passes through a water treatment system, it can potentially affect many people at once.

People living in rural areas frequently drink water pumped from a private well. Wells are tested less frequently for pollutants.

What pollutants are of greatest concern?

• Arseniccan enter the water supply through natural deposits or through industrial and agricultural pollution.
• Leadpipes and connectors were commonly used in plumbing in the past. Lead pipes may corrode if the levels of certain elements in the water fall out of balance. This can cause unsafe levels of lead to build up in drinking water. Monitoring water and adding anti-corrosive agents when necessary can prevent this from happening.

Reduce your risk

Evaluate

• Do you use well water?
• Do you live in a city that uses lead pipes and connectors?

Avoid and Address

• Routinely test well water for chemical contamination.
• If your well water has high levels of chemicals, contact your local or state health agency or the Centers for Disease Control and Prevention for information on how to reduce your exposure to these chemicals.
• Learn more about the quality of tap water in your area by reading your Consumer Confidence Report to avoid potential dangers.
• Have your drinking water tested by contacting a laboratory certified by your state or territory.