Arsenic in Water
What is arsenic?
Arsenic is a gray metal (atomic number 33, atomic weight 74.92), rarely found in the pure form, but not uncommon in combination with other elements. There are two forms of arsenic compounds, and the difference matters to our discussion.
First, there=s organic arsenic; this means arsenic combined with carbon or hydrogen, and occurs naturally in a number of life forms, particularly some shellfish (one form is colloquially called Afish arsenic@.) It is rarely very toxic, being the form most readily flushed from the body.
The second, more poisonous variety is inorganic arsenic. This means arsenic combined mainly with elements other than carbon and/or hydrogen, especially oxygen, chlorine, and sulfur. The human body has a harder time eliminating this kind of arsenic, and it does more damage.
What does arsenic do in the body?
Some scientists have hypothesized that all creatures need a faint trace of arsenic. Under laboratory conditions, animals given a diet with no arsenic in it whatsoever develop problems gaining weight or growing. However, these conditions have never arisen in the wild, nor has there ever been any evidence of arsenic deficiency occurring in human beings. Plenty of human beings have become poisoned by arsenic, however. In very carefully administered dosages, it has been used to treat certain infectious diseases, especially those caused by protozoa. They also come into use against some skin diseases and blood dyscrasias.
Arsenic poisoning can be acute or chronic. It can accumulate permanently in the body, stored especially in hair, nails, and bone. It can be quite insidious, having no smell or taste, and its symptoms can mimic other disorders. Early warning signs of arsenic poisoning may include stomache-ache, nausea, vomiting, diarrhea, and/or a pins and needles sensation in the extremities. But gradual poisoning can bypass some or all of these symptoms, at least at first.
Arsenic poisoning symptoms, in addition to or instead of the above, can include skin damage, involving dark or light spots, or keratinous lesions (Acorns@) on the palms, soles or torso. It can decrease both red and white blood cells, cause blood vessel damage, and/or abnormal heart function. It can also damage the liver and/or kidneys. It can impair nerve function in the extremities, causing tingling and numbness. While no one knows for certain what effects arsenic has on human fetuses, tests have shown that it definitely causes fetal damage in animals. Gradual arsenic poisoning can increase the risk of cancer of the skin, bladder, lungs, or kidneys, without other symptoms, and with lower doses than previously suspected when water purity standards were first set.
How do doctors test for arsenic poisoning?
There are two basic kinds of tests, that serve different purposes. Urine tests can reveal exposure to arsenic that has happened within the last one to two days, but it won=t weed out Afish arsenic@ (from eating seafood) and other relatively harmless forms from the more dangerous varieties. On the other hand, tests of the patient=s hair or fingernails can detect chronic exposure, but not short-term or low-level exposure.
How is arsenic poisoning treated?
The drug of choice is Dimercaprol. It combines with arsenic to create a chemical that the body can readily flush out of its system. It also causes nausea, vomiting, tachycardia, severe headaches, hypertension, and a sense of constriction of the chest, and smells like skunk (I=m not making this up; my medical encyclopedia says it has a Adisagreeable, skunklike odor@.) Doctors usually administer barbituates to control the side effects, which last for about an hour. This is not a treatment anybody would undergo if they could avoid it.
How does arsenic get into water supplies?
Sometimes water picks up arsenic from naturally occurring mineral deposits (inorganic form.) Both organic and inorganic forms also seep into the water system from poorly managed toxic waste. Both organic and inorganic forms of arsenic compounds can leach from pressure-treated wood (that is, wood suffused with insecticides and antifungal compounds under pressure--commonly used in foundations, fences, sheds, and anywhere that wood is going to contact the ground) and into the watershed. The most common route is pesticides; most arsenic compounds in weed-killers are organic, while inorganic compounds crop up mostly in insect and rodent pesticides, and some wood treatments. Some arsenic can also get into the air and rain back down into the watershed, especially in the vicinity of smelting, but also in some measure from burning fossil fuels.
What about regulation of arsenic levels in drinking water?
In 1975 the EPA established a maximum standard of 50 micrograms per liter, or fifty parts per billion, in the Safe Drinking Water Act. They based this on a study completed in 1943--prior to the discovery of a link between cancer and much lower arsenic levels.
In 1996, the government amended the Safe Drinking Water Act, in response to new research linking arsenic to cancer in doses lower than previously suspected. The amendment called for research to revise the standard to safer levels, and required, furthermore, that the standard be updated every six years as new research arose.
In 1999, the National Academy of Science declared that the 1943 standard Adoes not achieve the EPA=s goal for public health protection.@ Drinking water containing arsenic at the level of 50 micrograms per liter Acould easily@ lead to one person out of a hundred developing cancer--a risk one hundred times higher than allowed for any other tap-water contaminant, and ten thousand times higher than EPA-allowed levels of contamination in food.
The most conservative recommendation, and the one President Clinton signed into law, set the maximum standard at 10 micrograms per liter. Some studies, however, recommended setting the standard at 5 or even 2 micrograms per liter. 10 mcg/L is already the standard for both the European Union and the World Health Organization. This standard does not compensate for the additional risk that pregnant women, nursing mothers, and children could experience.
Who is at risk for drinking contaminated water?
According to the Sierra club, over twelve million Americans receive tap-water containing concentrations of arsenic above 10 mcg/L. But if you ask the government about this, they will tell you that since states are currently only required to report amounts above 50 mcg/L, nobody knows for sure, at least on a large-scale basis; they are currently gathering data. It does turn up more in groundwater (wells, etc.) than in water that comes from surface sources.
How does one find out about local levels of arsenic contamination?
If you are on a municipal system, you can call the phone number on your water bill and ask about local testing results. Or you can check regional information by computer on http://www.epa.gov/safewater/dwinfo.htm. If you get your water from a private well, the State Laboratory Certification Officer lists certified water testing labs in your state; to contact him or her, call the Safe Drinking Water Hotline at 1-800-426-4791 to get the phone number for the officer of your state.
AArsenic Solutions, Inc.@ offers a $15 water test. Their filter systems, however, seem aimed at heavy industrial or municipal applications.
How does one remove arsenic from tap water?
There are two main methods. Most home systems use reverse osmosis. This is effective only if arsenite has oxidized (especially with chlorine) into arsenate. This method usually works, since most tap water has been chlorinated. If you use well water that purifies by some system other than chlorination, you need to first use a sediment remover, water softener, and iron removal system, then distill the water.
You can find out about NSF
Certified product listings for drinking water treatment units on http://www.nsf.org/Certified/DWTU. This offers the option of checking units by
manufacturer, product function type, model name, or complete listings. The option you=re looking for is Aproduct function type@ where you check off Aarsenic@ in a list of contaminants
you are interested in seeing removed.