How Our Tap Water Is Regulated: The Truth About Legal Limits & Health Guidelines

Our 148,000+ public water systems here in the U.S. provide drinking water to 90% of the population. All of these community water systems, regardless of location, must abide by federal regulations for water quality that are enforced by federal law. Each state also has the option to set its own standards for specific drinking water contaminants as long as they are at least as stringent as existing national standards. 

Despite these layers of protection, hundreds of dangerous drinking water contaminants affect millions of Americans like us each year. Dozens of common contaminants are completely unregulated while others are legally allowed in community water systems at worrisome levels. If you’re wondering how our public drinking water supplies are regulated, then this is for you. 

National Standards Were Established In 1974.

In 1974, the Safe Drinking Water Act (SDWA) was enacted to establish national quality standards for all public water supplies in the United States. These national standards are set and monitored by the U.S. Environmental Protection Agency (EPA), and are enforced by federal law. Therefore, all public drinking water systems in our nation must abide by them. 

National standards include:

    • Water-testing schedules. All public water supplies are tested regularly. 
    • Water-testing methods. Consistent protocols apply to all testing. 
    • Drinking water quality control. Legal limits set by the EPA determine the maximum amount of specific contaminants allowed in public water supplies. These standards impact disinfection and treatment techniques to help protect drinking water quality.


What Are Legal Limits?

The EPA has set legal limits for more than 90 contaminants. These legal limits are measured as maximum contaminant levels (MCLs) assigned to each specific contaminant. Therefore, contaminants can legally be in public drinking water, so long as they are not detected at levels above their established MCL.  


How Are MCLs Established?

According to the EPA, MCLs are set at a level that “protects human health and that public water systems can achieve using the best available technology.” As you can see here, the EPA also takes cost into consideration. In other words, your safety is not the only factor for establishing legal limits; it’s just one of three key considerations:

Key considerations include:

  • Human health.
  • Testing technology.
  • Cost.

Are MCLs Ever Updated?

Every 6 years, the EPA reviews existing regulations and revises them if appropriate.

The truth is MCLs haven’t been updated for the majority of contaminants in almost 50 years.

In the context of public health, the latest data, studies, and research reveal many MCLs are often too high to protect us from the health hazards associated with specific contaminants. For example, lead has an MCL of 15 parts per billion (ppb), but no amount of lead in drinking water is safe


What About New & Unregulated Contaminants?

No, the EPA does not have standards for all contaminants detected in tap water. More than 160 unregulated contaminants have been found in our public water supplies. Plus, new contaminants emerge regularly from the surface water that fills our water supplies, byproducts created during treatment, aging and damaged infrastructure, and more. 

Said differently, there are hundreds of dangerous contaminants that can legally be floating in your water right now, at any level, without repercussion. For example, perchlorate (a known thyroid-disruptor), BPA (an endocrine-disruptor that affects fetuses and children), and PFAS (cancer-linked “forever chemicals”) do not have established legal limits and therefore remain unregulated today. 


How The EPA Handles Emerging Contaminants:

The Safe Drinking Water Act requires the EPA to publish a Contaminant Candidate List (CCL) every five years. The EPA then decides whether or not to monitor these contaminants and eventually regulate them based on three key factors:

  • Adverse health effects.
  • Likelihood of contamination at levels of concern.
  • If regulation offers a “meaningful opportunity” for health risk reductions.  

A review of EPA historical records reveals no new contaminants that first appeared on a CCL have been assigned national regulations to date. However, the agency is prioritizing the assessment and regulatory evaluation of PFAS. At time of publication, no regulatory determinations have been made.

States, Territories, & Authorized Tribes Can Establish Their Own Standards Under Certain Conditions:

The Safe Drinking Water Act (SDWA) gives individual states, territories, and authorized tribes the opportunity to set and enforce their own standards for public water supplies as long as they are at a “minimum as stringent as EPA national standards.” To be clear, a state cannot set a drinking water standard that is less protective than its national standard. 

For example, New Jersey and New Hampshire lowered their statewide arsenic limits to 5 ppb. That’s just half of the EPA MCL of 10 ppb. In other words, these states have set a standard twice as protective as the nationwide standard due to health concerns. 

States can also develop standards for unregulated contaminants. For example, there is no legal limit for perchlorate. However, California has set a statewide MCL of 0.006 mg/L for the chemical. 

How these standards work:

  • All national standards apply to all public water supplies, even if states, territories, or authorized tribes have created their own standards.
  • States, territories, and authorized tribes can set and enforce their own standards under one condition: State standards must be at least as protective as national standards.
  • If national standards do not exist for specific contaminants, states, territories, and authorized tribes can develop their own standards. 

What Are Health Guidelines?

The Environmental Working Group (EWG), an American non-profit organization that specializes in the research and advocacy of various public health threats including drinking water pollutants, has its own set of “health guidelines” for water quality. These guidelines are designed to protect public health. Unlike EPA legal limits, they are just recommendations that are not enforceable by law.  

Health Guidelines vs Legal Limits (MCLs):

As mentioned earlier, the EPA openly admits cost and technology are both factors in determining national standards / legal limits. That’s why the EWG reviews the latest science, data, and research to create their own standards, also known as “health guidelines.” 

EWG health guidelines are not based on political or economic compromise”; a clear shot at EPA legal limits. The group adds: “Too often, legal limits are based on what can be achieved cheaply, with little or no regard for public health. And water treatment facilities in many communities … are outdated, overloaded or underfunded.” 

Remember, the majority of regulated contaminants haven’t received updated MCLs in decades—even though studies have shown many contaminants can be dangerous below legal limits.

The EWG points out that EPA legal limits are often hundreds of times higher than the health standards recommended by scientists and public health agencies.

Plus, nationwide standards are non-existent for hundreds of contaminants proven to pose health risks. We shared a few examples of these unregulated contaminants earlier, including perchlorate, BPA, and PFAS.  

What About Well Water?

Private well water is not regulated by the EPA, Centers for Disease Control and Prevention (CDC), Food and Drug Administration (FDA), or any other government agency. Instead, the property owner is responsible for maintaining water quality. According to the CDC, more than 15 million U.S. households rely on a private well for drinking water. Given wells collect groundwater that can be littered with fertilizer, fuel, pesticides and other dangerous contaminants, it’s crucial owners get their well water tested regularly. The EPA offers several resources to point people who own property with private wells in the right direction here. Next up, let’s talk about bottled water.

What About Bottled Water?

Bottled water is regulated by the FDA because it’s classified as food. Many of the FDA’s bottled water regulations match the EPA’s National Primary Drinking Water Regulations. Therefore, bottled water can contain the same contaminants as tap water, as well as unregulated and emerging contaminants too. 

Plus, bottled water is riddled with its own dangers. Harmful shreds of plastic, known as microplastics, can tear up your stomach, plastic bottles can leach chemicals into water, and overused plastic bottles are breeding grounds for bacteria. In short, bottled water is typically no cleaner or safer than drinking water provided by public water utilities. In most cases, bottled water is virtually the same water that pours out of your tap.

The Bottom Line: 

Federal, state, and local government agencies are responsible for the safety of our public water supplies. However, contaminants detected below legal limits—and therefore deemed safe by national standards—can still be dangerous. Remember, legal limits have not been updated in decades for the majority of regulated contaminants, and therefore they likely do not account for new science and data. Plus, hundreds of dangerous contaminants already detected in our public water supplies remain unregulated today. 

The best thing you can do to protect yourself and your family is to invest in a water filter certified to remove contaminants known to plague our public drinking water sources. Click here to find the right filter for you. 

Wondering What’s In Your Water?

Our free database linked here compiles all of the test results from our public water supplies so you can see exactly what’s in your water, how it can affect you, and how to best protect yourself and your family. As you’ll see, we’ve included the legal limit for each regulated contaminant as well as EWG health guidelines for every contaminant to give you a complete and transparent assessment of your water.

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