Worried about tap water chemical exposure? New national data shows 45% of U.S. tap samples contain PFAS and more than 320 contaminants appear across nearly 50,000 water systems (USGS, 2023). This guide explains which chemicals in tap water matter most, health risks, how to check your water, and proven ways to reduce exposure.
Fast Facts — tap water chemical risks in 2025
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About 45% of U.S. tap water samples contained PFAS in a 2023 national survey; detections were most common in urban areas and near industry, airports, and wastewater plants.
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Across the country, utilities report hundreds of chemicals, including arsenic, lead, nitrates, disinfection byproducts, pesticides, solvents, and hexavalent chromium (EPA, 2024).
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Regulatory compliance does not always equal health safety. Many legal limits are higher than health-based guidelines; some chemicals lack enforceable federal limits.
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Public sentiment is wary. National surveys show most people worry about tap water quality and many now use a filter at home. Top concerns include chlorine/chloramine, lead, PFAS, pesticides, and germs.
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Health stakes include increased lifetime cancer risk, links to thyroid disease, hormone disruption, high cholesterol, neurodevelopmental harm, and special risks for infants and pregnancy.
If you have ever asked, What chemicals are in tap water? or Is it safe to drink tap water in the US?, you are in the right place. Let’s unpack what’s really in the glass and what you can do about it.
What chemicals are commonly found in tap water?
Public water systems work hard to control microbes that cause disease. They filter and disinfect to keep water safe from bacteria and viruses. But the same treatment process, plus older pipes and local land use, can bring along other substances. Some are added on purpose (like chlorine for disinfection or fluoride for dental health). Others enter from the environment, farming, industry, or plumbing materials. Here are the major groups to know.
PFAS (PFOA, PFOS, and related “forever chemicals”)
PFAS are used to resist stains, water, and heat in products and industrial processes. They persist in water and the human body for years. A 2023 U.S. Geological Survey study detected PFAS in about 45% of sampled taps. Health research links some PFAS to cancer risk, thyroid disease, high cholesterol, immune effects, and possible harm during pregnancy. In April 2024, EPA set the first enforceable national limits for several PFAS in drinking water, but many systems need time to monitor and install treatment.
How do PFAS reach your tap?
They can move from factories, military bases and airports that used firefighting foam, and wastewater discharges into rivers or groundwater. PFAS are tough to remove at a utility scale, and they require special filters at home.
Chlorine, chloramine, and disinfection byproducts
Every utility must control microbes. Most use chlorine or chloramine to kill germs. When these disinfectants react with natural organic matter in source water, they can form disinfection byproducts, especially trihalomethanes (THMs) and haloacetic acids (HAAs). Utilities balance two needs: strong disinfection to prevent outbreaks and careful control of reaction byproducts. High levels of some byproducts are tied to increased cancer risk and possible reproductive effects over long exposure.
Ever notice a “pool” taste or smell? That is often chlorine or chloramine. Taste does not equal harm by itself, but it is a hint your water has active disinfectant and some byproducts may be present, especially in systems with longer pipe networks and warm weather.
Lead and copper
Lead and copper come from plumbing. If you live in an older home or an area with older service lines, water can leach metals from pipes, fixtures, or solder. Lead has no safe level for children. It is linked to lower IQ, attention problems, and behavior issues. Adults can see blood pressure and kidney effects. Utilities control corrosion to limit leaching, but building plumbing still matters. Simple habits and point-of-use filters help at the tap.
Arsenic
Arsenic occurs naturally in some rocks and soils and can also come from past industrial sites. Some regions, especially parts of the West and Southwest, have higher natural arsenic in groundwater. Even low levels over time raise the risk of certain cancers and can affect the skin, nerves, and cardiovascular system. Many small systems and private wells face arsenic challenges because treatment can be costly and geology drives the problem.
Nitrates and nitrites
Nitrates come from fertilizers, septic systems, and animal manure. They move easily into groundwater, so private wells and rural systems are common hot spots. High nitrate is dangerous for infants because it can reduce blood oxygen (“blue baby syndrome”). Long-term exposure is also linked to certain cancers and thyroid issues. Levels often spike after rain or irrigation, so timing matters.
Pesticides and herbicides (for example, atrazine)
Farm chemicals can run off into streams and seep into groundwater, especially after application and storms. Atrazine is one of the most widely used herbicides and appears in many rural systems. Studies suggest endocrine (hormone) effects and developmental risks. Many pesticides have seasonal patterns, which means your yearly water report may hide short-term peaks.
Volatile and semi-volatile organics (TCE, benzene, and others)
Solvents and fuel-related chemicals can persist in groundwater from old industrial sites, dry cleaners, or leaks. Some, like trichloroethylene (TCE) and benzene, are known carcinogens. Utilities monitor and treat many of these, but private wells near old facilities should test with a certified lab panel.
Hexavalent chromium (Cr-6)
Cr-6 is a form of chromium that can come from industrial processes and, in some places, occurs naturally. Research has tied Cr-6 in drinking water to cancer risks. There is a federal drinking water limit for total chromium, but not a specific federal MCL for Cr-6. Some states have set their own Cr-6 standards or advisories.
Fluoride
Many U.S. systems add fluoride to reduce dental caries. At recommended levels, it can help prevent cavities. At higher exposures, especially during pregnancy and infancy, some studies suggest possible neurodevelopmental concerns. This is an area of active research and local policy debate. If you want to limit fluoride, look for filters verified to reduce it.
Emerging contaminants: pharmaceuticals, personal care products, and microplastics
Trace amounts of drugs, sunscreens, and household chemicals can show up in water. Microplastics are tiny plastic particles from textiles, tires, and packaging. Monitoring is expanding, and health science is still developing. Some home filters reduce many of these, but not all.
In short: chemicals in tap water come from both human activity and natural geology. Knowing your local sources helps you pick the right response.
Health harms at a glance
The health story is not one-size-fits-all. Risk depends on the specific chemical, how much you drink, and your life stage. Here’s a plain-language overview.
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Cancer risk: Long-term exposure to some PFAS, THMs/HAAs, chromium-6, TCE, and arsenic is linked to higher cancer risk estimates. Utilities aim to keep levels below legal limits, but health-based goals are often lower.
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Hormones and metabolism: PFAS and some pesticides, including atrazine, act on hormone systems. Effects may include thyroid changes, cholesterol increases, and reproductive impacts.
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Neurodevelopment: Lead has no safe level for the developing brain. Some studies suggest fluoride at higher exposures may affect early brain development, though the science is mixed and ongoing. Solvent exposure can also affect the nervous system.
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Pregnancy and infants: Nitrates can cause blue baby syndrome. Lead and arsenic pose special risks to the fetus and infant. Some disinfection byproducts and solvents are also tied to adverse outcomes when exposure is high over time.
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Cardiovascular and kidney: Heavy metals such as lead and arsenic can affect blood pressure, heart health, and kidneys.
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Microbiological vs chemical trade-offs: Disinfection is essential to prevent diseases like cholera and giardia. The task is to keep disinfection strong while minimizing byproducts. Filters at home can help reduce byproducts without removing all disinfectant residual in the plumbing.
Legal limits vs health-based guidelines
It is easy to get lost in acronyms on your water report. Here are the basics you need.
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Maximum contaminant levels (MCLs) are enforceable federal limits set by EPA. They often balance health risk with treatment feasibility and cost.
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Health-based goals include MCLGs (non-enforceable goals with a margin of safety) and other advisory levels from federal and state agencies. These are often lower than MCLs. For some chemicals, like chromium-6, there is no specific federal MCL, only a limit for total chromium; some states issue their own Cr-6 limits.
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Key update: In April 2024, EPA finalized national drinking water standards for several PFAS. Utilities will need to monitor, report, and meet these limits on a set timeline, often with major treatment upgrades.
The key point is that “compliant” water can still exceed more protective health guidelines. That is why many households choose targeted filtration at the tap, especially for vulnerable family members.
How to check your local water quality
Do you want to know exactly what’s in your tap water? Start local. Your steps differ slightly depending on whether you are on a public system or a private well.
For public water systems:
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Read your Consumer Confidence Report (CCR). Your utility must mail or post it online every year. It lists source water, detected contaminants, averages and ranges, legal limits, and any violations.
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Check federal and state portals. EPA and your state water agency host searchable tools with monitoring data and violations. Some states, like California, also post system-level dashboards and treatment updates.
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Look at USGS maps and tools for your area to see common groundwater issues (like arsenic or nitrates) and to understand PFAS findings near airports, industry, or military bases.
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Watch for UCMR5 updates. EPA’s Fifth Unregulated Contaminant Monitoring Rule expands monitoring for PFAS and other chemicals. Your utility may post results before they are in your annual CCR.
For private wells:
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Test yearly for bacteria and nitrates. Test every 3–5 years for arsenic and metals. If you live near farms, industry, airports, or firefighting training sites, consider a PFAS panel.
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Ask your county health department or a state-certified lab which tests are recommended in your area. They know local geology and common problems.
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Keep a file of your well records, wellhead location, and test results. This makes it easy to compare results over time.
Testing your water — home kits vs certified labs
You have two main ways to test: simple home tools or formal lab testing. Each has a role.
Home test strips and handheld meters:
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Pros: Fast, low cost, easy to use. Good for checking chlorine, pH, hardness, and total dissolved solids trends.
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Cons: Not sensitive enough for PFAS, many solvents, low-level lead, or most disinfection byproducts. Results can vary based on user technique.
Certified laboratory testing:
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When to choose: If you suspect PFAS, lead, arsenic, solvents, pesticides, or nitrates. Also if you have infants, are pregnant, or use a private well.
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What to request: A core panel often includes lead and copper, arsenic, nitrate/nitrite, and a metals screen. Add VOCs/SVOCs (solvents), a PFAS panel, uranium/radium in some western regions, and DBPs (THMs/HAAs) if you are concerned about disinfection byproducts.
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Sampling matters: Follow the lab’s instructions exactly. Use the right bottles, keep the chain-of-custody form intact, and ship on time. First-draw samples (water that sat in pipes overnight) are used for lead, while flushed samples may be used for other chemicals.
Interpreting results:
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Compare your numbers to EPA MCLs, to state advisory levels, and to any health-based guidelines provided by your state or federal agencies. If something is unclear, call your utility or health department. They can help you understand ranges, seasonal patterns, and next steps.
Best ways to reduce chemicals in tap water
Start with simple behaviors, then add the right filtration at the tap. Whole-house systems can help with taste and non-drinking uses but usually do not replace a drinking-water filter for PFAS or metals.
Quick habits
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Flush stagnant water. Let cold water run 1–2 minutes before the first use of the day in older homes to reduce lead that leached overnight.
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Use cold water for drinking and cooking. Hot water can pull metals from plumbing faster.
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Clean faucet aerators. Grit and corrosion particles can collect there.
Point-of-use filtration (sink, fridge, under-sink, or pitcher)
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Activated carbon: Good for many organic chemicals, chlorine taste and odor, some disinfection byproducts, and many PFAS. Look for third-party certifications that match your concerns, such as NSF/ANSI 42 (aesthetic), 53 (health effects), and 401 (emerging compounds), plus explicit PFAS reduction claims where applicable.
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Reverse osmosis (RO): A membrane system that reduces a wide range of contaminants, including PFAS, arsenic, many metals, nitrates, and VOCs. Look for NSF/ANSI 58 certification. RO water may taste “flat” to some people; you can add a remineralization cartridge if you prefer.
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Ion exchange/resins: Useful for specific targets like nitrates, hardness (water softening), and some metals. Often paired with carbon for broader coverage.
Whole-house options
Catalytic carbon: Helps reduce chloramine and some disinfection byproducts over the whole home. Combine with a good sediment pre-filter to protect the media.
Specialized media for iron, manganese, and arsenic: These systems need careful selection and maintenance based on your lab results and water chemistry. They do not replace a drinking-water RO system for PFAS or certain metals.
Maintenance matters
Replace filters on time. Overused filters can clog, lose performance, or release what they have captured.
Verify certifications. Match third-party certifications and explicit contaminant claims to your risk. A general “fits most” label is not enough when PFAS, lead, or nitrates are on your list.
Keep records. Track installation dates, filter changes, and any lab tests. If you change filter brands, consider a before-and-after test for peace of mind.
When bottled water helps
During a known contamination event or while you wait for repairs or new filters, bottled water can be a short-term option. If you buy bottled water, choose brands that publish test reports. Keep in mind the cost, plastic waste, and the fact that bottled water may also contain microplastics. A home filter gives you more control day to day.
Essential treatment guide
Use this table to match a contaminant of concern to the most effective point-of-use treatment and the certification to look for.
| Contaminant (example) | Most effective treatment at the tap | Certification to look for | Notes |
| PFAS (PFOA, PFOS) | Reverse osmosis; advanced activated carbon | NSF/ANSI 58 (RO); NSF/ANSI 53 or 401 with PFAS claims | Consider a lab test to confirm performance if PFAS are detected locally |
| Lead | Certified carbon blocks or RO; replace lead pipes if present | NSF/ANSI 53 (lead) or 58 (RO) | Use cold water and flush; check faucet fixtures |
| Arsenic | Reverse osmosis; adsorptive media (specific to arsenic) | NSF/ANSI 58 (RO) | Some systems address As(V) better; pretreatment can help |
| Nitrates/nitrites | Reverse osmosis; anion exchange | NSF/ANSI 58 (RO) | Key for infant formula; test well water regularly |
| Disinfection byproducts (THMs/HAAs) | Activated carbon/catalytic carbon | NSF/ANSI 53 | Whole-house carbon can reduce DBPs for bathing |
| Solvents (VOCs like TCE) | Activated carbon; reverse osmosis | NSF/ANSI 53 (VOCs) or 58 | Check for specific VOC claims |
| Hexavalent chromium | Reverse osmosis | NSF/ANSI 58 | Check local advisories; whole-house is not a substitute |
| Fluoride | Reverse osmosis; specialized media | NSF/ANSI 58 (RO) | If you want to reduce added fluoride, RO is a strong option |
Regional hotspots and who’s at higher risk
Location and housing age matter. Here is how risk varies around the country.
Urban and industrial corridors: Higher likelihood of PFAS and solvents, and more disinfection byproducts due to complex treatment and long pipe networks.
Agricultural regions: Nitrates, atrazine, and other pesticides are common. Private wells face the highest risk, especially after fertilizer application and heavy rain.
Arid and western states: Arsenic and uranium can be elevated due to geology. Some small systems have a harder time meeting limits or installing new treatment.
Homes with older plumbing or service lines: Lead and copper leaching are key concerns. If your home was built before 1986, fixtures or solder may contain lead.
Sensitive groups: Infants (especially formula-fed), pregnant people, those with thyroid disease, kidney issues, or compromised immune systems should be more cautious. Using a certified point-of-use filter is a simple step that lowers risk.
Case study — PFAS in U.S. drinking water
PFAS is a clear example of why many homeowners are asking, What makes tap water unhealthy in some places? The U.S. Geological Survey tested for 32 PFAS types at taps across the country in 2023. About 45% of samples had detectable PFAS. Hotspots included areas near airports, military bases, and industry, and detections were more common in urban settings than rural areas on average.
What did people do with this information? Many households near known PFAS sources moved to point-of-use systems that handle PFAS well, such as RO water systems or high-capacity certified carbon filters. Some utilities also started pilot treatment with granular activated carbon or ion exchange, and they began posting more PFAS data online. If you live in a PFAS hotspot, a certified tap filter and a PFAS lab test are a strong one-two strategy.
Quick guide to reading your water report
Your CCR is your best snapshot. Here is how to make sense of it.
Sources: Is your water from rivers, reservoirs, or groundwater wells? Note any “source water assessment” info on local risks.
Detected contaminants: Look for a table with “detected” values. Pay attention to both the average and the range. Seasonal peaks can hide behind a low average.
MCL vs MCLG: The MCL is the legal limit. The MCLG is a health-based goal that may be lower. For lead, the report may show an “action level” and percentiles rather than a strict MCL.
Violations: These include treatment or monitoring issues. Your utility must explain what happened and how they fixed it.
Upcoming changes: Many reports mention planned upgrades, PFAS monitoring, or new well sources. These can change your risk picture within a year.
What to ask your utility:
How are you controlling disinfection byproducts while keeping disinfection strong?
Do you have an inventory of lead service lines, and how are you replacing them?
Have you monitored for PFAS under UCMR5? What were the results?
Are treatment upgrades planned in the next two years?
FAQs
1. What chemicals are in tap water?
Tap water chemical content varies, but common chemicals in drinking water include PFAS chemicals, chlorine, arsenic, nitrates, and lead. Many tap water supplies are contaminated with chemicals from industry, plumbing, and farming. These harmful substances in water can cause serious health problems like cancer or thyroid disease when concentration levels are high. Water treatment plants remove microbes, but not all chemicals from water are filtered out. The Environmental Protection Agency monitors US water quality, yet tap water may still contain toxic residues, especially in areas near industrial zones or old tanks.
2. What’s in tap water besides H₂O?
Tap water contains more than pure H₂O — it often carries disinfectants like chlorine or chloramine, minerals, and tap water chemicals that enter during the water treatment process. Common chemicals in drinking water include PFAS chemicals, lead, arsenic, and nitrates. Some systems become contaminated with chemicals from industry, plumbing, or agriculture. While utilities aim to meet Environmental Protection Agency standards, the supply may still hold harmful substances in water that can cause serious health problems if concentration levels rise.
3. Is it safe to drink tap water in the US?
Most US water systems meet EPA standards, but “safe” depends on what tap water chemical levels are present. Even legally compliant water may contain trace PFAS chemicals, lead, or disinfection byproducts that long-term exposure could make toxic. Tap water is contaminated more often near industrial or agricultural areas. Using certified filters helps remove harmful substances in water that the water treatment process may not fully eliminate. For sensitive groups, filtered or mineral water can lower risk.
4. What are the top 5 harmful chemicals found in human drinking water?
The most concerning tap water chemicals are PFAS, lead, arsenic, nitrates, and disinfection byproducts (THMs/HAAs). These chemicals in drinking water can cause serious health problems like cancer, hormone disruption, or developmental harm. Some types of PFAS chemicals—used in stain-resistant products—linger in the body for years. Tap water may also be contaminated with chemicals from corroded pipes or agricultural runoff. Even low concentrations can accumulate, which is why the Environmental Protection Agency continues to tighten water safety rules.
5. Does boiling remove chemicals in tap water?
Boiling helps kill germs but does not remove most tap water chemicals. PFAS chemicals, nitrates, and metals like lead remain after boiling and may even become more concentrated. When tap water is contaminated with chemicals, boiling alone cannot make it safe. Only certified filters or reverse osmosis systems effectively reduce harmful substances in water. The Environmental Protection Agency recommends testing if you suspect contamination, as heat does not remove toxic chemicals from water.
6. What is added to tap water in the USA?
Water treatment plants add disinfectants such as chlorine or chloramine to kill microbes and, in many regions, fluoride to protect teeth. Corrosion inhibitors prevent metals from leaching into the supply. However, these processes can create new tap water chemicals known as disinfection byproducts. Although utilities follow Environmental Protection Agency guidelines, the tap water may still become contaminated with chemicals during transport through old pipes or tanks. Monitoring ensures safety, but filters provide extra protection from harmful substances in water.
7. What makes tap water unhealthy?
Tap water is contaminated when harmful substances in water exceed safe limits. Tap water chemical exposure often comes from PFAS chemicals—stain-resistant compounds that persist for years. Some types of PFAS, lead, and disinfection byproducts can cause illness or chronic effects. Although the water treatment process removes germs, it can also form new tap water chemical byproducts. Unlike mineral water, treated water may still hold contaminants. The Environmental Protection Agency enforces rules, but even regulated US water can remain chemically unsafe without proper filtration.