Second Opinion: Safety of Water Supply

Oct. 25, 2001 -- How difficult would it be for a terrorist group to contaminate drinking water with microbes or hazardous chemicals that cause illness or even death? If you are looking for a simple answer, there isn't one.

Because of fears that the water supply could be attacked, the Association of Metropolitan Water Agencies lobbied congress earlier this month for $5 billion to improve water safety and security.

For one thing, water systems — about 170,000 separate ones in the U.S. — need more guards. One ongoing concern cited by the association has been the possibility that terrorists could disrupt the flow of water to large communities by destroying dams or reservoirs. Since Sept. 11, water utilities have been reassessing their security procedures.

As for the contamination of drinking water, it is often emphasized by government officials, infectious disease specialists, and water-utility experts that an enormous quantity of a biological or chemical agent would be required to poison a large water source such as a reservoir.

But should that occur, the water treatment plant would likely detect the invasion and trap the harmful substance in its filters. For extra good measure, the chlorine that is typically used in treating water would, in most cases, greatly diminish the agent's chances for survival.

That's more or less what U.S. Environmental Protection Agency Administrator Christine Whitman highlighted last week about anthrax and other possible contaminants. After touring a Maryland water-testing lab, she said it would likely take truckloads of, say, anthrax, to be introduced to a major water system before it had any chance of doing harm.

A Local Threat?

Whitman is probably correct in concluding that the risk in these circumstances is likely to be low. But the key phrase in the paragraph above is "major water system." What about a much smaller arm of a water system — some part of the network of distribution pipes that delivers water to homes, apartments and office buildings?

What are the chances that someone or some group with a basic knowledge of hydraulics and some good maps could gain access to pipes that transport water after it is treated for contaminants to a particular neighborhood? How much of a biological or chemical agent would you then need in order to launch a successful terrorist attack?

Some water utilities have not ignored this potential threat and have been installing alarms in tunnels and locking up access doors to their pipes. Scientists at both the EPA and CDC have also expressed concern about this scenario.

And how about access to a fire hydrant? Could the harmful agent be successfully pumped into the distribution system? This is far from clear, although there is one documented North Carolina case in 1997 of foam used by firefighters that backed into a neighborhood water supply via a hydrant when the fire truck pump was turned on before a safety valve was closed.

A Need for Data

More research is also needed on how agents such as anthrax, smallpox, plague and botulism toxin perform in water. For example, how stable and virulent are they? And under what conditions?

We also need to know more about the effectiveness of the chlorine used at water treatment facilities. For example, it is often claimed that anthrax can be neutralized by chlorine treatments. Yes, but how much chlorine are we talking about? A 10 percent chlorine solution is said to kill most anthrax spores, but how many would survive, say, an initial 4 percent solution treatment and then a second 2-percent treatment at a water treatment plant? Some good data might help ease concerns.

In fact, we need a lot more good data about how well or poorly our water supply is actually being protected day in and day out. Forget the threat of terrorism for the moment and consider an estimate from the CDC that close to one million Americans annually become ill and about 1,000 die because of a variety of microbes carried in the nation's water supply.

Bugs and Drugs

One ongoing threat is cryptosporidium, a protozoa excreted in human and animal feces that sickened 400,000 people in the Milwaukee area in 1993. Since then, utilities have generally improved their treatment systems, but cryptosporidium that resists standard chemical disinfection still infects many thousands annually via drinking water.

Then there's a growing concern about pharmaceuticals finding their way from medicine cabinets, sewage and production industries into the nation's water supply . Research in the U.S., Canada and Europe is showing that low concentrations of a wide range of prescription drugs — everything from antibiotics to birth-control pill hormones to blood pressure medications — are turning up in ground, surface, and drinking water. No one is clear on what the cumulative effect of this onslaught will turn out to be.

I think that what we know and don't know should be detailed, as best we can, particularly in these troubling times, and that it might be wise to avoid making facile generalizations about safety and preparedness.