Should You Be Worried About Arsenic in Your Water?

by Gene Franks

Humans have always had to deal with contradiction. What’s good today is bad tomorrow.  Science stakes out a rigid position and in most cases eventually decides that the opposite is true. The American Medical Association would like you to forget that it endorsed smoking and told mothers that breast milk was nutritionally inadequate just a few short decades ago.  Chlorine, coffee, fluoride, knee surgery, sugar, estrogen therapy, therapeutic bleeding–you could name dozens–have had their ups and downs.

We’re so used to contradictory information that people didn’t  get too excited when the EPA announced that the allowable safe level for arsenic in water really isn’t 50 parts per billion (ppb), as “the experts” have been telling us for years, but it is really only 10 ppb.

How did the government’s mandated “safe” level of arsenic in drinking water shrink overnight from 50 to 10 parts per billion? Does this mean that arsenic suddenly has become more lethal? Should we take the 10 ppb limit seriously, or is it just another Swine Flu-style fundraiser?

The new arsenic limit should definitely be taken seriously.  Arsenic poisoning is terrible. And lowering the level took some real political courage.  Water utilities that were overnight out of compliance were faced with very expensive treatment requirements, and they screamed loudly.

The big drop in arsenic allowable actually makes sense. The  initial  limit for arsenic was set at 50 ppb simply because test labs before 1975 weren’t able to detect arsenic at levels below 50 ppb.  As tests got better, it became obvious that 50 ppb was too high.

After much deliberation, the EPA, with intense political pressure from both sides of the issue,  proposed reducing the allowable to 5 ppb in 2000, although the final rule did not take effect until 2006.  The number by that time had been negotiated up to the current 10 ppb.  (Two states, North Carolina and New Jersey, have independently set the arsenic allowable at 5 ppb.)


Arsenic Poisoning

Arsenic poisoning is implicated in cancers of the bladder, lungs, skin, liver, prostate and kidneys as well as non-carcinogenic endocrine, pulmonary, cardiovascular, and neurological damage. At around 60 parts per million in food or water it is an immediate threat to life and can result in sudden death.  (Note that that’s 60 parts per million, which is 60,000 parts per billion–or 6,000 times the current EPA allowable.)

The truth is that we get arsenic from lots of sources, including food. Rice, for instance, is often a source of unwanted arsenic. We get plenty of arsenic from our environment and certainly don’t need more in our water.  The only truly safe level of arsenic in water is zero.

From a water treatment standpoint,  arsenic reduction can be very easy or very complicated. Although plain carbon filtration can usually make a moderate reduction, the most commonly used strategies are reverse osmosis, anion exchange, distillation, and filtration with iron-based media. The complicated part is that arsenic exists mainly in two forms–As(III) and As(V).  Since As(III) is hard to remove and As(V) is relatively easy, the usual strategy is to convert As(III) to As(V) by oxidation to facilitate removal.  Here’s more detailed information.