First of two articles

When I purified three quarts of tap water by distilling it, I got a pitcher of clean water and a residue of gray gunk. Naturally, I wanted to know what I had saved my family from ingesting. Harmless mineral salts, my local water authority assured me.

If you tried the same experiment, your results would probably be similar.

Despite the occasional sensational news story about drinking water contamination -- recently, the high lead level in the District's water -- American water utilities produce safe drinking water. But, and there is a big but here, the water can become contaminated between the time it leaves a water treatment plant and when it comes out of your faucet. You may also have contamination issues if your drinking water source is a private well, increasingly a possibility as suburban development and new-home building move farther out into rural areas.

Ben H. Grumbles, chief of the Environmental Protection Agency's water program, said 15 percent or more of new houses rely on private wells for their drinking water.

Given this, prudence dictates that you get your drinking water tested at a drinking-water-certified laboratory. Your local health department should have a list of state-certified labs. If you have city water, your testing will not have to be as comprehensive because your local water authority is required to test the water it treats and to publish the results in its annual report.The EPA requires every water authority to test for nearly 100 substances; many water utilities monitor additional ones as well (mine monitors 280). These results must be posted by July 1 of the following year. That is, the 2003 test must be posted by July 1, 2004.

If you ask a lab to test for all the substances that might be in your water, or even the 100 that the EPA requires, the cost will be exorbitant, running to several thousand dollars. Rather going the whole nine yards, you should ask a lab to test for the substances that would most likely be there. Which ones are those? Richard P. Maas, a professor of environmental sciences at the University of North Carolina-Asheville and an authority on water treatment issues, said that 95 percent of the worrisome contaminants fall into five broad categories.

Of the five categories, Maas said the most serious -- more than the other four put together -- is lead because even small amounts can cause permanent neurological damage in children.

Lead is rare in source water, but it can get into your tap water in several ways. Most of them are older-house problems. Lead can leach out of the lead pipes that are common in the distribution network in older cities. Lead can also leach out of a lead service line from your house to the street; your brass water meter, which can be made with lead; lead solder joints in copper plumbing lines (commonly used until 1988); or out of your chrome-plated brass water faucets (these were made with as much as 30 percent lead until 1988 and as much as 8 percent lead until 1998). A new house on a private well would not have this problem, but lead can be an issue if you are building in an urban area or tearing down part of an old house and building on top of it, to add a second story, for example.

Maas, who has researched the lead issue for years, said that about 85 percent of the time, the lead test comes up negative. Of the 15 percent of homeowners who do have a problem, 85 percent of them (13 percent of all homeowners) can solve it by letting the water run for one minute before using it. Only 15 percent of homeowners with a lead problem (2 percent of all homeowners) need to install a filter mechanism to remove the lead. But, Maas noted, the convenience factor -- most people are too impatient to let the tap run for a full minute every time they turn it on -- leads many homeowners to get a filter.

The second-most serious contaminant to drinking water in America, in Maas's estimation, is arsenic, a naturally occurring element that can contaminate ground water. If the drinking water in your new house will come from a well -- either your own or the utility's -- you should get it tested for arsenic, he said.

Arsenic is well known as a poison when given in large doses. In the past few years, scientists have discovered that arsenic is also a powerful carcinogen when ingested in small doses over a long period of time. For this reason, the EPA has lowered the allowable amount of arsenic in drinking water from 50 parts per billion to 10 ppb, but many researchers, including Maas, think the standard should be lower. Maas said that 1 ppb is reasonable, but most labs cannot detect arsenic at levels lower than about 5 ppb.

Some areas of the country, including parts of Arizona, New Mexico and Michigan, are known to have arsenic in ground water, but Maas urges everyone who gets tap water from a ground water source to test for arsenic.

The third contaminant on Maas's list is disinfection byproducts (DBPs), which are created when a disinfecting agent such as chlorine reacts with a small amount of organic matter in the water. Since all drinking water contains some organic matter, DBPs are ubiquitous in municipal drinking water.

The most common one is chloroform. Though the risk is very small, DBPs are carcinogenic, Maas said.

The simplest and most cost-effective way to remove chloroform and any other DBPs from your drinking water is to fill a pitcher with water and let it sit for four or five hours while the DBPs evaporate, Maas said.

Fourth on Maas's list are toxic chemicals discharged into rivers and lakes by manufacturers in industrial areas. Although individual manufacturers may meet the EPA's discharge requirement, their collective discharge can be "a lot of stuff," Maas said. Industrial chemicals can also affect ground water, in some cases over a wide area. When MBTE, an additive to gasoline, leaks out of an underground storage tank, "it can flow for miles," Maas said.

The last contaminant on Maas's list is microbiological pathogens -- cysts that cause intestinal parasites cryptosporidium and giardia. These can contaminate surface water sources such as rivers and lakes, and the disinfecting agents in the local water treatment plant do not always kill them. The pathogens can cause a disease outbreak, but Maas said this would be a "pretty rare event."

Giardia can be treated with antibiotics, but there is no drug treatment for cryptosporidium. Symptoms of fever and diarrhea quickly pass in healthy people, but giardia is a concern for people with compromised immune systems, infants and the elderly.

Should you discover, after having your water tested, that one or more of these contaminants is in sufficient amount to warrant a filter, you'll have to do some additional research to find the right one -- different filters remove different substances.

In two weeks: More about filters

Katherine Salant can be contacted at www.katherinesalant.com.

{copy} 2004, Katherine Salant

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