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Contaminant Candidate List: Unregulated Tap Water Risks

Contaminant Candidate List: Unregulated Tap Water Risks


Our laws protect us from harmful chemicals getting to market and in our homes, right? That’s what we’d like to assume, but unfortunately that is not the case. Not at all.

Despite the Environmental Protection Agency’s (EPA) tireless effort to identify chemicals that may pose health risks, keeping up with the industry production of these chemicals and their release into the environment is a never-ending game of catch-up. While the EPA does work with local water authorities and set Maximum Contaminant Level Goal guidelines (MCLGs) for identified contaminant threats, hazardous chemicals still manage to make it to market (and your tap) unregulated.

Scientists and policy-makers categorize these chemicals as emerging contaminants. Some emerging contaminants are included on the Contaminant Candidate List (CCL)–but many remain unstudied and unregulated. The CCL is an ever-growing list of drinking water contaminants that are known or anticipated to occur in public water systems which are not (yet) currently subject to EPA regulations.

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Contaminant Candidate List

The current version of the CCL–CCL 4–includes 97 chemicals (and chemical groups), as well as 12 microbial contaminants. The list consists of chemicals that are used in commerce, pesticides, biological toxins, disinfection byproducts, pharmaceuticals, and waterborne pathogens–all of which can be found in drinking water and are considered potentially threatening to human health.

Despite the substantial increase of scientific literature on emerging contaminants including those on the CCL 4, this knowledge has not translated into action. Significant changes in contaminant regulation are rare and bitterly fought by industry lobbyists. One of the biggest hurdles that regulators face is due to the 1976 Toxic Substances Control Act (TSCA), a law that strives to protect humans and the environment from toxic industrial chemicals (pesticides, drugs, and cosmetics are handled under different laws) has created so many hoops for regulators to jump through that they are often rendered powerless.

The case of perchlorate–a salt used in explosives and propellants–serves as an example of how arduous the process can be to regulate an emerging contaminant. It took the EPA 10 years (2001-2011) just to conduct tests on perchlorate risk and make the decision to attempt regulation. Even so, a proposed rule to regulate this potentially harmful chemical still is not expected to go into effect until 2017. Sixteen years to achieve regulation–and that’s only one emerging contaminant.

What Are The Issues With the TSCA?

The biggest issue is that the TSCA allowed all 62,000 chemicals that were on the market prior to its implementation to stay on the market unless the EPA later found that they posed an “unreasonable risk”–a toxicology standard that is challenging to meet as it is currently defined. Assessing the risk that a chemical poses is a lengthy process and thus far, the EPA has only examined a few hundred of the chemicals on the market. While this is an alarmingly low number, subsequent regulation is also incredibly rare. So rare in fact, that the EPA has only banned five chemicals.

What Requirements Does the CCL Impose on Water Systems?

Unfortunately, the CCL has no direct impact, as far as regulation goes, on communal water systems. The EPA must decide to regulate individual contaminants on the list and if this is the case, the Agency must start a separate rulemaking process. While the list is intended to prioritize contaminants for drinking water programs, current legislation and a back-list of chemicals from the TSCA makes regulation an ever-present challenge. Regulators are certainly working hard, but they're backlogged beyond capacity.

If you are concerned about potential contaminants in your drinking water, take a look at or Tap Score home water testing kit. We now offer perchlorate testing, as well. It tests for up to 400 contaminants in your drinking water, including some priority emerging contaminants like pharmaceuticals. For more information you can contact us at

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