The Ultimate Drinking Water Contaminants Reference Guide: Sources, EPA Standards & Testing

People often assume that the water delivered to their homes meets applicable drinking water standards. In many situations, it does. Water, however, can be contaminated with a multitude of chemicals from natural geology, old pipes, farms, industries, and household products. 

Some pollutants occur naturally in the soil and rock. Others are introduced by human activity, including manufacturing, mining, farming, or water treatment. Contaminants and levels may differ widely from one community to another, from one source to another, from one vintage to another, and within the processes used to treat water in communities before it is delivered to your tap.

Federal and state agencies actively regulate pollutants, providing reassurance that public water is monitored and protected, which is essential for your peace of mind.

Consumers can make informed decisions about water quality, testing, and monitoring by understanding common contaminants and their sources, which helps build confidence in protecting their household.

How to Use This Guide

The purpose of this guide is to provide a practical reference to the most commonly discussed drinking water contaminants in the United States.

For each contaminant, you'll learn:

✔️ What it is

✔️ Where it comes from

✔️ The route by which it gets into drinking water.

✔️ The current EPA guidance and regulations.

✔️ Who could be most concerned?

✔️Available testing methods

The content here is educational and based on publicly available guidance from regulatory agencies, water utilities, and environmental health organizations.

This guide is intended for educational purposes only. Water quality conditions vary by location, and consumers should consult local water utilities, certified laboratories, or relevant regulatory agencies for information specific to their area.

Table of Contents

• Quick Reference Summary Table
• Understanding EPA Drinking Water Standards
• Public Water Systems vs. Private Wells
• Lead
• Arsenic
• PFAS
• Chlorine
• Chloramines
• Nitrates
• Chromium-6
• Copper
• Volatile Organic Compounds (VOCs)
• Microplastics
• Radium
• Pharmaceuticals
• Heavy Metals
• Hard Water Minerals
• How to Interpret Water Quality Reports
• Frequently Asked Questions
• Conclusion

Quick Reference Summary Table

Contaminant	Typical Source	EPA Regulated?
Lead	Older plumbing and service lines	Yes
Arsenic	Natural deposits, mining activities	Yes
PFAS	Industrial chemicals and consumer products	Yes (certain PFAS)
Chlorine	Water treatment processes	Yes
Chloramines	Water disinfection treatment	Yes
Nitrates	Agricultural runoff and fertilizers	Yes
Chromium-6	Industrial activities and natural deposits	Yes (under total chromium standards)
Copper	Household plumbing corrosion	Yes
VOCs	Industrial solvents and chemicals	Yes
Microplastics	Plastic degradation and consumer waste	No federal standard currently
Radium	Natural radioactive deposits	Yes
Pharmaceuticals	Human and veterinary medication residues	No federal standard currently
Heavy Metals	Industrial activity and natural geology	Some are regulated
Hard Water Minerals	Natural mineral deposits	Not regulated for health reasons

Understanding EPA Drinking Water Standards

What Is the EPA's Role?

Under the Safe Drinking Water Act, the U.S. Environmental Protection Agency (EPA) sets national drinking water standards. These standards are designed to safeguard public health by establishing maximum contaminant levels for public water systems.

EPA collaborates with state agencies and local water utilities to determine the need for monitoring, treatment standards, reporting requirements, and enforcement.

Maximum Contaminant Levels (MCLs)

Maximum Contaminant Levels are the highest permissible amount of contaminants in public drinking water systems.

MCLs are based on scientific studies, health information, treatment feasibility, and cost. Public water systems are required to regularly test contaminant concentrations in their water supply and take action if concentrations exceed the limits.

Treatment Technique Requirements

Measuring the concentration of some contaminants is not enough. Under these circumstances, the EPA could mandate that utilities use certain treatment processes, known as Treatment Techniques (TTs). This may include filters and disinfection processes that reduce the risk of contamination.

Monitoring and Reporting Requirements

Public water systems must test and report regularly to the regulatory bodies. Most utilities also provide annual Consumer Confidence Reports (CCRs) that present local water quality data.

Public Water Systems vs. Private Wells

The most critical difference that consumers should know is between public water systems and private wells.

Public Water Systems

Federal and State drinking water regulations govern public water systems. Utilities must regularly test and maintain treatment systems and inform consumers of major water quality concerns.

Private Wells

EPA does not typically regulate private wells. The well owner is responsible for testing, maintenance, and treatment.

Groundwater conditions may vary over time, and private well owners may be encouraged to have their wells tested periodically, particularly if land use changes in the area or if flood events have occurred.

Lead

What Is It?

Lead was historically used in pipes, solder, and plumbing fixtures, and remains a concern in older homes and water systems. Lead is one of the most closely monitored contaminants in drinking water, although its use in drinking water infrastructure has been significantly reduced.

Lead is of particular concern because it can be introduced into water after treatment as it is distributed through service lines and household plumbing.

Where Does It Come From?

Common sources include:

• Lead service lines

• Lead pipes

• Older plumbing fixtures

• Brass parts that contain lead

• Solder was applied before the regulatory changes.

Older houses are at higher risk of containing lead in their materials, as they were not built to modern plumbing codes.

How Can It Enter Drinking Water?

Lead generally enters drinking water through corrosion.

Lead may leach into the water supply from pipes, solder, or plumbing when it comes into contact with water. Corrosion is affected by:

• Water acidity

• Mineral content

• Temperature

• Pipe age

• Treatment chemistry

Water leaving the treatment plant that is free of lead can become contaminated as it travels through old pipes, pipes with lead solder, and lead service lines.

EPA Guidance

The Lead and Copper Rule regulates lead.

The EPA does not establish a traditional Maximum Contaminant Level, but instead a framework of Action Levels that encourages utilities to implement remedial measures when lead levels exceed thresholds in sampled residences.

Public water systems must perform routine monitoring at specified sampling points on a set schedule, implement corrosion control programs as needed, and report results to consumers. There are also utility requirements regarding inventories of lead service lines and lead service line replacement work.

Who May Be Most Concerned?

Some of the groups which are usually thought of as priorities for monitoring are:

• Families with young children, since lead exposure can cause delayed development in children, and there may also be other sources, such as old paint chips or dust

• Pregnant women

• Residents of older homes, where contamination often originates from plumbing materials within the distribution system or the home.

• Older buildings, schools, and childcare facilities

How Can You Test for It?

There are several options for lead testing:

• Certified laboratory testing

• Water quality reports are produced for all the utilities.

• First-draw sampling programs

• Home testing programs accepted by the State of California

Testing at the tap provides the most location-specific information, as levels can vary within properties.

For more details on this topic, read our related guide: Does Berkey Water Filter Remove Lead From Drinking Water?

Fluoride

What Is It?

Fluoride is a naturally occurring mineral found in rocks, soil, groundwater, and surface water. It is also added to many public water supplies in the United States to help prevent tooth decay and support dental health.

At recommended levels, fluoride can help strengthen tooth enamel and reduce the risk of cavities. It has been studied extensively for decades and remains a topic of interest among public health professionals, researchers, and consumers.

Where Does It Come From?

Fluoride in drinking water can come from both natural and human-made sources, including:  

• Natural mineral deposits
• Groundwater that has contacted fluoride-containing rocks and minerals
• The natural weathering of rocks and soil
• Community water fluoridation programs

The amount of fluoride in drinking water varies depending on local geology and whether a water utility adjusts fluoride levels during treatment.

How Can It Enter Drinking Water?

Fluoride can enter drinking water naturally as water moves through rocks and soil that contain fluoride-bearing minerals.

In many communities, water suppliers also add fluoride at levels recommended for dental health. As a result, fluoride may be present in both municipal water systems and private wells.

Naturally occurring fluoride concentrations can vary significantly from one region to another, which is why testing may be especially useful for private well owners.

EPA Guidance

The U.S. Environmental Protection Agency (EPA) regulates fluoride in public drinking water systems and has established a Maximum Contaminant Level (MCL) of 4.0 milligrams per liter (mg/L) to help protect public health.

Public water systems must monitor fluoride levels and comply with federal drinking water standards established by the EPA.

Who May Be Most Concerned?

Monitoring fluoride levels may be particularly important for:

• Parents of infants and young children
• Private well owners
• Individuals who use fluoride supplements
• Residents of areas with naturally high fluoride concentrations

If you have concerns about fluoride in your drinking water, reviewing your local water quality report or arranging independent testing can help you better understand your water's fluoride levels.

How Can You Test for It?

Fluoride can be tested using several methods, including:

• Certified laboratory testing
• State-certified water testing programs
• Private well testing services
• Home test kits designed for fluoride screening

Home test kits can provide a preliminary screening, though laboratory testing typically offers more accurate results.

Consumers served by public water systems can also review their annual Consumer Confidence Report (CCR), which often includes information about fluoride monitoring and water quality results.

Disinfection Byproducts (DBPs)

What Are They?

Disinfection Byproducts (DBPs) are chemical compounds that can form when disinfectants such as chlorine or chloramines react with naturally occurring organic matter in water.

Water disinfection is a standard part of drinking water treatment and helps utilities maintain water quality throughout distribution systems. While this process plays an important role in water treatment, it can also produce byproducts that water utilities routinely monitor.

Two of the most common categories of regulated DBPs are Total Trihalomethanes (TTHMs) and Haloacetic Acids (HAA5).

Where Do They Come From?

DBPs develop through the interaction of disinfectants and naturally occurring materials found in source water, including:

• Chlorine disinfection
• Chloramine disinfection
• Naturally occurring organic matter
• Organic material present in the source water
  

The amount of DBPs that form can be influenced by several factors, such as water chemistry, disinfectant type and dosage, temperature, and the concentration of organic material present.

How Can They Enter Drinking Water?

Unlike many contaminants that originate from industrial activities, agriculture, or natural deposits, DBPs are formed during the water treatment process itself.

After treatment, some DBPs remain in the water as it moves through the distribution system. In certain cases, additional byproducts may continue to form before the water reaches consumers' taps.

DBP levels can vary based on:

• Source water quality
• Treatment practices
• Seasonal changes
• Water temperature
• Distribution system conditions

Because disinfection is a standard part of drinking water treatment, DBPs can be found in many public water systems, even when those systems are operating in compliance with regulatory requirements.

EPA Guidance

The U.S. Environmental Protection Agency (EPA) regulates several disinfection byproducts under federal drinking water standards.

Public water systems are required to monitor DBP levels and comply with Maximum Contaminant Levels (MCLs) established by the EPA. Current limits include:

• Total Trihalomethanes (TTHMs): 80 micrograms per liter (µg/L)
• Haloacetic Acids (HAA5): 60 micrograms per liter (µg/L)

Water utilities may adjust treatment methods, disinfectant strategies, and distribution system operations to help minimize DBP formation while maintaining compliance with drinking water regulations.

Who May Be Most Concerned?

Although DBPs are routinely monitored and regulated, some individuals and organizations may be particularly interested in reviewing local monitoring results, including:

• Consumers who want to better understand their drinking water quality
• Communities that rely heavily on surface water sources
• Individuals tracking long-term water quality trends
• Public health professionals and environmental organizations

Many public water systems publish DBP monitoring results in their annual water quality reports.

How Can You Test for Them?

DBPs can be evaluated through:

• Certified laboratory testing
• Utility monitoring data
• Specialized drinking water testing services

For most consumers, the easiest way to learn about local DBP levels is by reviewing their annual Consumer Confidence Report (CCR). These reports typically summarize monitoring results, regulatory compliance information, and other important drinking water data.

Arsenic

What Is It?

Arsenic is a naturally occurring element in rocks, soil, and groundwater in many areas of the United States.

Arsenic is naturally present in the earth and in industrial pollution.

Where Does It Come From?

Common sources include:

• Natural mineral deposits

• Weathering of rock formations

• Mining operations

• Industrial activities

• Historical agricultural uses

Arsenic is more likely to be present in groundwater than in surface water.

How Can It Enter Drinking Water?

As water travels through rock formations containing arsenic-bearing minerals, it can dissolve arsenic. Local geology may lead to higher concentrations in private wells that draw from affected aquifers.

EPA Guidance

EPA prescribes arsenic standards for public drinking water and sets a Maximum Contaminant Level to protect public health. Long-term arsenic exposure can increase cancer risk. It may also cause skin lesions, which is one reason the standard is enforced.

Arsenic testing is required, and public water systems must take action when arsenic levels exceed regulatory limits.

Who May Be Most Concerned?

The following may be more important to consider:

• Private well owners

• In areas where the soil naturally contains higher levels of arsenic

• Groundwater-dependent communities

How Can You Test for It?

Testing options include:

• Certified laboratory analysis

• State-certified water testing programs

• Private well testing services

Arsenic is not detectable by taste, smell, or appearance, and requires lab testing.

For a deeper explanation, see our related article: What Is Arsenic Poisoning? What Are the Effects of Arsenic?

PFAS

What Is It?

PFAS are a class of synthetic chemicals, known as per- and polyfluoroalkyl substances, that are produced in industry and used in products.

These compounds are also known as “forever chemicals” because they can persist in the environment for a long time.

Where Does It Come From?

PFAS sources can be:

• Industrial manufacturing facilities

• Foam Training Areas or Fire Sites.

• Chemical production plants

• Consumer product manufacturing

• Some coatings and special materials

Contamination can occur from decades of usage, as PFAS have been around for many years.

How Can It Enter Drinking Water?

PFAS may travel through soil and groundwater to drinking water sources.

Potential pathways include:

• Industrial discharge

• Landfill leachate

• Firefighting foam releases

• Contaminated groundwater migration

All types of water systems may be affected, including public water systems and private wells.

EPA Guidance

EPA has set drinking water standards for certain PFAS compounds and is building on monitoring and regulatory activities.

Affected water systems may be mandated to test, report, and treat water.

Who May Be Most Concerned?

Communities located near:

• Industrial manufacturing sites

• Military facilities

• Airports

• Firefighting training areas

may have a greater interest in PFAS testing programs.

How Can You Test for It?

PFAS testing typically uses specialized laboratory techniques to measure very low levels of individual compounds.

To conduct PFAS tests, consumers can contact accredited environmental laboratories or consult monitoring results from local water utility providers (if available).

For additional information about PFAS and filtration options, read our guide: The Best Water Filters That Remove PFC and PFOA From Drinking Water

Chlorine

What Is It?

In municipal water treatment systems, chlorine is a common disinfectant.

It is intentionally used as a treatment chemical and is among the most widely used disinfectants in public water systems.

Where Does It Come From?

Unlike other pollutants, chlorine is intentionally added during water treatment.

Chlorine is added to the water before it enters the water distribution system.

How Can It Enter Drinking Water?

Chlorine is introduced into water during normal treatment processes and acts as a residual disinfectant as the water travels through pipes.

A residual is used to manage water quality through the distribution system as water travels to customers.

EPA Guidance

EPA sets limits for residual disinfectants in drinking water and regulates chlorine levels in public water systems.

Water utilities regularly test chlorine concentration in water systems to meet regulatory requirements.

Who May Be Most Concerned?

People who might detect chlorine are:

• People who are sensitive to the smell and flavor.

• Aquarium owners

• People using specialized medical equipment involving water

How Can You Test for It?

Home test strips, liquid test kits, or laboratory analysis can be used to measure chlorine.

The consumer can also review the local utilities' water quality reports to learn how chlorine is managed in their water system.

Chloramines

What Is It?

When chlorine combines with ammonia, it creates chloramines.

Chloramines are commonly used as a substitute for free chlorine because they do not react as readily in the distribution system.

Where Does It Come From?

Chloramines are intentionally created during municipal water treatment.

Utilities determine chloramines based on operational objectives and distribution system parameters.

How Can It Enter Drinking Water?

Chloramines are introduced during treatment and remain in the water as it flows through pipes.

They enable a wide distribution of water with disinfectant protection.

EPA Guidance

EPA regulates chloramines as drinking water disinfectants and sets standards for their use in public systems.

Levels must be monitored, and utilities must meet disinfection byproduct requirements.

Who May Be Most Concerned?

Groups that may pay closer attention to chloramine levels include:

• Dialysis patients

• Aquarium owners

• Consumers who are sensitive to changes in taste or odor.

How Can You Test for It?

Testing methods include:

• Home water test kits

• Utility reporting data

• Certified laboratory analysis

Nitrates

What Is It?

Nitrogen and oxygen react and form nitrates. Nitrogen is necessary for all plant growth, and nitrate is a common ingredient in fertilizers in agriculture, landscaping, and gardening.

Nitrates occur naturally in the environment but are also associated with human activities when present at high levels in drinking water.

Where Does It Come From?

Common sources include:

• Agricultural fertilizers

• Animal manure

• Septic systems

• Wastewater discharges

• Natural decomposition of organic matter

Nitrogen can be transported to groundwater through rainfall and irrigation in agricultural areas, leading to elevated nitrate levels.

How Can It Enter Drinking Water?

Nitrates are highly soluble in water and therefore highly mobile in the environment.

Common pathways include:

• Agricultural runoff to streams and reservoirs

• Groundwater recharge from fertilizers.

• Leaking septic systems

• Stormwater flows over and through agricultural land

Private wells connected to shallow groundwater may be particularly at risk.

EPA Guidance

EPA regulates nitrate levels in public drinking water systems and has set a Maximum Contaminant Level (MCL).

Regular monitoring and corrective measures are required if concentrations exceed the prescribed levels.

Who May Be Most Concerned?

Nitrate monitoring can be an important practice for:

• Private well owners

• Rural households

• Agricultural communities

• Homes with septic systems nearby

How Can You Test for It?

Nitrate testing may be performed at a certified laboratory, state-approved water testing program, or private well testing service.

Local health departments and agricultural extension offices also offer information on nitrate testing recommendations, especially for private well owners in agricultural areas.

Chromium-6

What Is It?

The element chromium exists in many forms, including hexavalent chromium (chromium-6). It has been put in the spotlight because of concerns about environmental pollution and ongoing research.

There are several forms of chromium; some of the more widely discussed are chromium-3 and chromium-6.

Where Does It Come From?

Sources may include:

• Industrial manufacturing

• Metal plating operations

• Stainless steel production

• Chemical manufacturing

• Natural geological deposits

There are natural and human-made ways chromium can enter the environment.

How Can It Enter Drinking Water?

Sources of chromium-6 contamination to water include:

• Industrial discharge

• Contaminated groundwater

• Natural rock formations

• Historical manufacturing activities

When chromium is detected in groundwater, the groundwater system is often the focus of concern.

EPA Guidance

EPA currently sets a standard for total chromium in drinking water and mandates monitoring concentrations in public water systems as part of its compliance monitoring programs.

While there is a lot of focus on chromium-6, the current federal standards are for total chromium and do not include a separate standard for chromium-6 in drinking water. The regulatory process and scientific research in this field are constantly changing.

Who May Be Most Concerned?

Communities with higher levels of interest in chromium testing may be:

• Residents who live in proximity to industries

• Groundwater-dependent communities

• The owners of the private wells in these areas

How Can You Test for It?

Testing generally requires:

• Certified laboratory analysis

• Specialized chromium test techniques

• State-certified environmental laboratories

Consumers seeking chromium-6 should ask the laboratory whether it can be done.

Copper

What Is It?

Copper is a naturally occurring metal used in plumbing for its durability and corrosion resistance.

Copper found in drinking water most commonly originates from plumbing materials rather than the source water itself.

Where Does It Come From?

Common sources include:

• Copper pipes

• Plumbing fittings

• Household fixtures

• Service connections

Plumbing materials are the source of most copper in drinking water, not source water.

How Can It Enter Drinking Water?

Corrosion is the main way copper gets into water.

The following factors may affect copper release:

• Water acidity

• Water temperature

• Water chemistry

• Pipe age

• Time of water storage in the plumbing system

Older pipe water may contain higher levels than newer water flushed from pipes.

EPA Guidance

The Lead and Copper Rule regulates copper.

When necessary, utilities should monitor copper levels and implement corrosion control measures.

Who May Be Most Concerned?

Residents of houses with a lot of copper pipe might want to be tested if they:

• Plumbing is aging

• The chemistry of the water has changed

• Problems with appearance or flavor occur

How Can You Test for It?

Testing methods include:

• Certified laboratory testing

• Utility monitoring programs

• First-draw household sampling

Volatile Organic Compounds (VOCs)

What Are They?

Volatile Organic Compounds (VOCs) are a general term for a wide range of carbon-based chemicals that easily turn into the air.

Numerous VOCs are utilized in production, cleaners, fuels, and industrial activities.

Where Do They Come From?

Common sources include:

• Industrial solvents

• Petroleum products

• Manufacturing facilities

• Chemical storage areas

• Dry cleaning operations

• Fuel spills and leaks

How Can They Enter Drinking Water?

VOCs can enter water supplies via:

• Groundwater contamination

• Industrial discharge

• The leaking of underground storage tanks.

• Improper chemical disposal

• Soil contamination migration

Many VOCs migrate easily through soil and can travel long distances underground.

EPA Guidance

Many VOCs regulated by the EPA for drinking water standards are also regulated for public water systems.

Who May Be Most Concerned?

Some possible problem areas are:

• The surrounding communities of industrial sites.

• The areas where contamination is known to exist in the groundwater.

• Community areas that border former manufacturing sites

How Can You Test for Them?

Testing generally requires:

• Certified laboratory analysis

• VOC-specific testing panels

• Environmental sampling services

For more background on this category, visit our related guide: Volatile Organic Compounds (VOCs) in Drinking Water

Common VOCs Table

VOC	Common Source	EPA Regulated?
Benzene	Petroleum products	Yes
Trichloroethylene (TCE)	Industrial solvents	Yes
Tetrachloroethylene (PCE)	Dry cleaning operations	Yes
Vinyl Chloride	Plastic manufacturing	Yes

Microplastics

What Are They?

Microplastics are small pieces of plastic, usually less than 5mm in size.

They may be produced by the fragmentation of larger plastic objects or created intentionally for particular purposes.

The increasing presence of microplastics in water, soil, food, and air has made it an important topic of environmental research.

Where Do They Come From?

Potential sources include:

• Degrading plastic waste

• Synthetic textile fibers

• Tire wear particles

• Packaging materials

• Consumer products

Over time, plastic materials break down into smaller pieces due to sunlight, weather, and physical damage.

How Can They Enter Drinking Water?

Possible pathways include:

• Surface water contamination

• Wastewater discharge

• Stormwater runoff

• Atmospheric deposition

• Distribution system contamination

Experts are working to understand the transport of microplastics in drinking water systems.

EPA Guidance

Currently, there is no federal drinking water standard for microplastics.

Government bodies and research institutes are still working on possible impacts, surveillance, and future regulation.

Who May Be Most Concerned?

Due to their widespread presence in the environment, microplastics are of broad consumer interest.

How Can You Test for Them?

Testing is still limited and is typically performed by:

• Research institutions

• Specialized laboratories

• Academic programs

Current consumer testing tools are still quite limited.

Radium

What Is It?

Radium is a radioactive element that occurs naturally in some geologic formations.

Small amounts of local rock and soil types may be present in groundwater where they occur.

Where Do They Come From?

Sources include:

• Deposits of naturally radioactive minerals

• Underground rock formations

• Regional aquifers

Typical sources of radium contamination are natural geology, not industry.

How Can They Enter Drinking Water?

Water can dissolve radium and other radioactive materials as they pass through rock beds that contain radium.

The highest concentrations are likely to be found in private wells and groundwater-dependent communities.

EPA Guidance

EPA regulates drinking water systems for radium and requires monitoring if suitable.

If the level of utility exceeds regulatory standards, corrective measures are required.

Who May Be Most Concerned?

The following groups are usually interested in radium testing:

• Private well owners

• Groundwater users

• People in radioactive geological areas

How Can You Test for Them?

Specialized radiological analysis is needed for radium testing in certified laboratories.

In areas with known natural radioactive mineral sources, private well owners may want to check with their state environmental agencies for recommended testing schedules and resources.

Pharmaceuticals

What Are They?

Pharmaceuticals in drinking water include trace levels of prescription and over-the-counter (OTC) medications, as well as veterinary drugs.

Usually, these substances occur at low concentrations.

Where Do They Come From?

Potential sources include:

• Human medication use

• Veterinary medicines

• Wastewater discharges

• Improper medication disposal

• Agricultural operations

How Can They Enter Drinking Water?

Pharmaceutical compounds can be found in water systems via:

• The treated water from a wastewater treatment plant.

• Septic system releases

• Surface water contamination

• Agricultural runoff

The use of advanced analytical techniques has increased sensitivity in detecting these substances at extremely low levels.

EPA Guidance

Until now, there have been no federal drinking water standards for most pharmaceutical products.

But pharmaceuticals remain a subject of ongoing scientific research and environmental monitoring.

Who May Be Most Concerned?

Consumers who are interested in emerging contaminants tend to pay attention to pharmaceutical monitoring and research.

How Can You Test for Them?

Testing typically requires:

• Specialized laboratory services

• Advanced analytical methods

• Research-grade contaminant screening

Regular household testing is seldom available.

Heavy Metals

What Are They?

Heavy metals, a class of naturally occurring metallic elements, are present in rocks, soils, groundwater, and industrial products.

Certain heavy metals are regulated in drinking water since high levels can impact water quality and public health.

Where Do They Come From?

Sources may include:

• Natural geology

• Mining activities

• Manufacturing operations

• Industrial emissions

• Corroding infrastructure

How Can They Enter Drinking Water?

Heavy metals can be released into water by means of:

• The water that flows through the rocks.

• Industrial contamination

• Mining runoff

• Corrosion, corrosion of plumbing materials

EPA Guidance

There are federal drinking water regulations for several heavy metals.

The monitoring requirements are different for each metal.

Who May Be Most Concerned?

Examples of concerns that may arise are:

• Communities near industrial, mining, or manufacturing activities.

• Industrial areas

• Private well owners

• Older plumbing in homes.

How Can You Test for Them?

Water quality testing panels are available from certified laboratories and can detect multiple metals in a single test.

Testing can be particularly helpful for older plumbing systems, private wells, and land near historic industrial or mining operations.

Common Heavy Metals in Drinking Water

Metal	Typical Sources	EPA Regulated?
Mercury	Industrial emissions	Yes
Cadmium	Manufacturing activities	Yes
Nickel	Industrial processes	Some monitoring
Antimony	Mining and manufacturing	Yes

Hard Water Minerals

What Is It?

Hard water is not generally considered a contaminant issue. Rather, it refers to water with high levels of naturally occurring dissolved minerals, particularly calcium and magnesium.

In many homes, there is hard water but no water safety issues. 

Where Does It Come From?

Hardness occurs naturally as the water passes through mineralized rock formations.

Common sources include:

• Limestone

• Chalk

• Dolomite

• Other calcium-rich geological deposits         

How Can It Enter Drinking Water?

In natural processes, minerals dissolve in groundwater and surface water.

As water moves through mineral-rich rock formations, it can dissolve calcium and magnesium minerals.

EPA Guidance

EPA does not consider water hardness a health issue.

Water hardness is a characteristic of water, not a contaminant. Federal drinking water standards do not usually regulate hardness, but it is a naturally occurring mineral.

Who May Be Most Concerned?

The consumer can notice hard water in the following ways:

• Scaling on fixtures.

• Reduced soap lathering

• Mineral stains on plates

• Rising maintenance requirements for water-using appliances and fixtures.

How Can You Test for It?

Home test strips, water testing kits, or lab analysis can be used to measure hardness.

In addition, many local water utilities include hardness data in either their water quality reports or customer water quality summaries.

For a detailed explanation of hardness and filtration, read: What Causes Hard Water & Why Most Water Filters Don’t Remove It

Hard Water Classification Table

Hardness Level	mg/L as CaCO₃
Soft	0–60
Moderately Hard	61–120
Hard	121–180
Very Hard	180+

How to Interpret Water Quality Reports

Understanding Consumer Confidence Reports (CCRs)

Public water systems usually report water quality data from around the area in annual Consumer Confidence Reports.

What CCRs Contain

Typical information includes:

• • Water source descriptions

  • Detected contaminants

  • Regulatory limits

  • Monitoring results

  • Educational information

Where to Find Them

CCRs can be found on the Internet in a variety of ways, including:

• • Utility websites

  • Annual mailings

  • Local government offices

  • Customer service departments

Key Terms and Measurements

A few simple terms will help to interpret reports.

Common Water Testing Terms

Parts Per Billion (ppb)

Equals one part of a substance for every one billion parts of water.

Parts Per Million (ppm)

Measures the concentration of a substance in units per million of water.

Maximum Contaminant Level (MCL)

The maximum contaminant concentration allowed by law in a drinking water system.

Action Level (AL)

A concentration that triggers remedial response actions or further monitoring.

Detection Limit

The lowest level detectable by the test.

Frequently Asked Questions

► Does the EPA regulate all drinking water contaminants?

No. While many contaminants are regulated, federal drinking water standards for most pharmaceuticals and some microplastic contaminants do not currently exist.

► What's the difference between a contaminant and a water quality characteristic?

A contaminant is a substance that can impact water quality or safety. A water quality characteristic is a property of the water that could be of interest but is not a health concern.

► Should private well owners test their water?

Generally, private wells do not have the same monitoring requirements as public water systems, and regular testing is recommended.

► How often should drinking water be tested?

The frequency of testing will be based on the water source, local conditions, and whether any problems have been identified previously. Owners of wells frequently adopt the testing recommendations of the State or Local Authority.

► Can contaminant levels vary throughout the year?

Yes. Contaminant levels may be affected by seasonal weather conditions, rainfall, agricultural activities, water requirements, and treatment methods.

► Where can consumers find official water quality information?

Reliable sources include:

• Local water utilities

• State environmental agencies

• State health departments

• The EPA drinking water resources

• Certified water testing labs

Conclusion

Water contaminants may enter drinking water from a variety of sources, including geologic materials, aging water systems, farming, manufacturing, and water treatment.

Federal and state regulations regulate many contaminants, but standards are continually evolving as scientific information grows and new contaminants are discovered.

Access to reliable information helps consumers make informed decisions about their drinking water. Knowing the sources of contaminants, how they enter drinking water, and which testing options are available can help you better understand water quality reports and assess local conditions.

When it comes to water, whether from a public utility or a private well, water quality information is available, and testing can be done as needed to gain insight into the water used daily for drinking, cooking, and household use.

Consumers can rely on credible information to make informed, confidence-based decisions about the quality of their drinking water and the need for continued monitoring.