An alarming claim, oft repeated, can take hold… but facts are stubborn things

Arsenic facts and fiction

I was somehow prescient in my prior letter to the Union editor, communicating some facts about the City of Arcata adding arsenic to our drinking water, when I suggested “Both sides of the fluoride debate can now wave their arms and raise their respective hullabaloo.” 

And then there was the Union’s associated cartoon “Clowns to the left of me, jokers to the right.” The wild rant letter to the Union from Timothy Crienjak sidestepped the arsenic facts I presented while waving red herrings from banning bullets to anti-vaccination to threatening the Great American Experiment. 

My point is simple and verifiable. The Federal MCLG and CA PHG standards state clearly that arsenic is similar to dioxin as a substance that should not be in our drinking water at any level. Despite this clear guidance, the City knowingly adds arsenic to our drinking water, yet neither measures for it nor reports arsenic on the City’s water quality “Confidence Report” [sic]. The National Sanitation Foundation (NSF), a recognized reference for drinking water standards and tests for contaminants, and the CDC, have reported on this issue.

My prior questions stand: Would the City knowingly add dioxin to our drinking water? What guidance beyond common sense would preclude the City (“Environmental Services”) from adding dioxin to our drinking water? I suggest that same guidance must be applied regarding arsenic. 

Bruce LeBel

Note: When a letter writer says “knowingly adds arsenic to our drinking water,” and repeatedly invokes the word “dioxin,” we’re well aware that these terms could, for some, become casually associated with Arcata’s drinking water, and suggest a hazard, justifiably or not. 

It’s easy to rhetorically stir some arsenic into Arcta’s drinking water with one flip phrase, but understanding what that really means requires a lengthier explanation, one using some terms of measurement. 

Rather than alarming water customers by publishing untethered claims, we have to assume that a college town full of curious people will be interested in facts and context. 


A basic principle of toxicology is that “the dose makes the poison.” Everything (other than light) is made of chemicals, including the eyeballs you’re reading this with, and the paper or screen on which you read it.

Any chemical can be poisonous in a high enough concentration, including oxygen, water, arsenic or the ones that make up organic blueberry muffins.


Barry Sutter, Klamath District engineer for the state Division of Water Quality, said his agency requires that any fluoride added to water is certified through NSF International, which tests it for contaminants. Here comes the science.

According to, “Treatment products used for fluoridation of drinking water are specifically addressed in NSF/ANSI 60. The standard requires that treatment products added to drinking water, as well as any impurities in the products, are supported by an evaluation of potential health effects resulting from exposure to the products or associated contaminants.”


The Fact Sheet on Fluoridation Products and Fluoride states that “All the fluoridation products tested by NSF, when evaluated at their maximum use level in water, meet the health effects requirements of NSF/ANSI 60. Arsenic was periodically detected in half of all samples. However, the mean arsenic concentration is 1/50th of the U.S. EPA MCL [Maximum Contaminant Limit] and none of the samples exceeded 1/10th the U.S. EPA MCL.” 

Standards and concentration

We checked with Matthew Hurst, professor of analytical chemistry and chair of Humboldt State University’s Chemistry Dept. to help us understand the actual presence of arsenic in our drinking water. Here is what we learned:

The Maximum Contaminant Limit for arsenic, according to the state Division of Water Quality, is 0.010 mg/L. That’s 10 millionths of a gram per liter or 10 parts per billion maximum. 

The NSF testing found the average arsenic concentration in water at the maximum level of fluoride level to be one-fiftieth of that, or 0.2 micrograms (millionths of a gram) per liter. In other words, the average tested amount of arsenic in the fluoridated water is 0.2 parts per billion (ppb), one part in 5 billion. That is 0.2 parts of arsenic per 1,000.000,000 parts of drinking water. 

The bathtub scale

To visualize this arsenic concentration in a liter of water, at 0.2 ppb As (ug/L), it works out to adding a speck of arsenic the size of a grain of sand to 5,500 gallons of water – enough to fill more than 150 36-gallon bathtubs.

In pennies 

The thickness (not the diameter) of a penny is 0.0598 inches, about six-hundredths of an inch.

Five billion times that is 299 million inches. 299 million inches divided by 12 is 24,916,666.7 feet. 24,916,666.7 feet divided by 5,280 (the number of feet in a mile) is 4,719.06 miles.

Thus, the amount of arsenic in a liter of fluoridated drinking water is equivalent to the thickness of one penny in a stack of pennies 4,719 miles tall. (The allowable MCL for arsenic is, in this unit of measure, 50 cents.)

You could drive from Arcata to St. Louis, Mo. and back (4,340 miles), then take a round-trip to Medford, Ore. (370 miles), and still have enough miles left over for a relaxing bike ride out to scenic Tyee City (6.3 miles), with one penny’s thickness in that journey representing the arsenic in a liter of fluoridated Arcata water.

Unless, as the NSF testing has shown, it’s one of the half of all fluoride samples that contained not even this minute trace of arsenic. 

In lifetimes

Maybe the simplest analogy is one of time. Five billion seconds is 158 1/2 years – about two human lifetimes. The amount of arsenic in samples that had any at all is equivalent to one second of that time, or a half-second – the blink of an eye – per lifetime. This is how much arsenic the city "“knowingly adds" to the water, and what all the fearful hoopla is about.

Readers may evaluate the mentions of arsenic contamination of our water in this context, and in light of the fact that the dose makes the poison. – Ed.


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