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What Are EPA's MCLs?







Maximum Contaminant Levels


In Drinking water





Those of you who have studied your water quality reports as I've suggested have been astounded by a number of things...


First, there's a lot more in your water than just water.


That's why I have you look at them. Once you know the contaminants that are present you can actually buy the right treatment system by making sure you buy a system with the treatments that will remove or reduce the contaminants in your water.


Then there's the language of the report, a study in its own right. And there are lists of chemicals that you've never begun to hear of.


In this space those I wish to discuss one column you'll always find. That's the MCL or Maximum Contaminant Level. I want to describe what this column is and how it's arrive at.


The MCL is the level established by the federal government (EPA) that cannot be exceeded by a public water supply system. Unless your water supplier is in violation or has a temporary exemption they must keep the regulated contaminants below the level set by EPA.


Many people think that because EPA set these levels that water with contaminants lower than this is safe. That's where I take exception to the MCL as a standard to strive for.


Here's the process, in brief:


It all starts with a well intentioned team of scientists and staff within EPA that analyzes the health affects of a particular contaminant. They study the health effects of a particular contaminant and make a recommendation for a limit.


That recommendation works its way up to the level of the Administrator of EPA. This person is appointed by the President.


The Administrator may, or may not, find the recommendation of the EPA staff to be 'politically palatable'. If not, they have to raise it.


Eventually, the Administrator takes his or her recommendation to the President. The President then makes a recommendation to Congress. Congress then wrestles with the number. Are their constituents feeling environmentally friendly or is money tight due to high gas prices… Get the picture?


What it boils down to is an evaluation of health risks or health impacts versus cost. When EPA sets a standard that means that every public water supplier must spend whatever it takes to meet that standard. This is weighed against the number of deaths or illnesses at each level of attainment.


Take arsenic for example. The EPA staff wanted a standard of 3 ppm. The new standard set this past January is 10 ppm. Before that it was 50 ppm.


Or take nitrates. The EPA standard is 10 ppm. But if you do a google search of nitrates you'll find serious health affect on women (bladder cancer) and young children at 3 ppm.


So when a customer calls me to talk about achieving healthy water, I consider the EPA standard but I also consider what I know about the health impacts of that particular contaminant.


Take mercury for example - you don't want any of it in your water. None. That's likely not even possible anymore, but its impacts are highly pervasive.


Your water provider will most often tell you that your water meets all EPA standards and is therefore safe and you do not need any treatment system. And I think most of them truly believe this. But I don't. I think someday we'll discover that allowing these relatively high levels of contaminants in water are at the root of much of the cancer in the United States.


I hope this discussion helps you to distinguish between a recommended level of contaminants and striving to achieve healthy water for your family. The process of determining maximum contaminant levels for drinking water is a political one. It's roots may be in health, but in the end politics prevail.




In a future issue, I'll talk more about unregulated contaminants, which are not listed or tested for in your water.


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James P McMahon Ecologist

"What's in YOUR Water?"

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JPM Biography


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