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Reporting deadline nears for lead in drinking water.

The U.S. Environmental Protection Agency recently focused media attention on the results of the first round of monitoring for lead in drinking water conducted by large public water supply systems (those serving 50,000 or more people).

With lead monitoring by medium sized communities (those serving between 3,300 and 50,000 people) due to be reported at the end of 1992--and additional press coverage likely--it is essential for city officials to understand the lead in drinking water issue so that the sampling results can be accurately interpreted for the public, and appropriate steps taken, if needed.

During the October press conference, EPA implied that because 130 of the 660 (50 of which did not report test results) large systems did not meet the agency's "action level" for lead(defined at 15 parts per billion [ppb] in 90 percent of "worst case" samples) that 32 million people were impacted by the results. They also said that only systems that exceeded the agency's "action level" were required to reduce their lead levels.

The facts are that under EPA's regulation all large public water systems, not just those reporting exceedance of the "action level," are required to optimize their treatment processes for lead reduction regardless of the levels found at the tap. (The monitoring results for large systems serve as a benchmark for determining effective corrosion control treatment).

In addition, because "worst case" sampling is required, and not representative sampling, the implication that 32 million people are impacted by "high levels" of lead is very misleading.

EPA's press release also contained stand-alone lines that read, for example: "Potomac Plant, WSSC, lead level 39 parts per billion." Several Washington, D.C. area print and broadcast news reports understandably interpreted this to mean that treated water leaving the Potomac Plant had more than twice the action level of 15 ppb.

Tests show, however, that over several years water leaving WSSC's Potomac Filtration Plant never exceeds more than one or two ppb, according to Wayne Fallin, Director of WSSC's Operations Bureau. "The 39 parts per billion in the EPA press release refers only to test results of 18 high risk homes in a sampling of 184 homes tested for lead levels," Fallin said.

What is "Worst Case" Sampling?

Understanding "worst case" sampling is key to putting into proper perspective the first round of monitoring results and to solving the problem of lead leaching into drinking water. It is also key to providing an accurate portrayal of the results of the water system's monitoring program.

First, it should be understood that sources of lead in drinking water may come from either the source water or the service lines delivering the water, but more often than not lead contamination comes from inside the home--from lead solder and flux and/or from faucets, fixtures, fittings or lines connecting the home to the water systems' service lines.

A useful "worst case" analogy would be to compare a municipal water system and its consumers to a local television network and each of our TV sets. The television network is responsible for delivering the appropriate audio signal to each TV set just as the municipal water supplier is responsible for delivering high quality drinking water to each of its customers.

If the audio control on your TV is broken, you would not expect the television network either to be able to fix the problem at its headquarters, or to come to your home and fix your TV. The same is true for the water system. The water system cannot "fix" the problem with the plumbing in homes from the treatment plant nor can municipal water systems realistically be expected to replace in-home plumbing.

To take the analogy one step further, and to highlight "worst case" sampling, the FCC might require the television network to go to those homes where the audio control is broken and to adjust the network's audio signal based on these "worst cases."

By considering the "worst case," the network can help to ensure that their signal is not accelerating or promoting the malfunction of the control knob. This is exactly what EPA requires municipal water suppliers to do under the 1991 lead regulation. Water suppliers must go to the "worst cases"--in this case defined as where you would expect to find lead--and adjust the corrosivity and the water so that lead leaches less in "worst case" situations.

It would be inaccurate to say that because 15 homes have TVs with broken audio controls, that all homes in the city have broken audio controls. It would be accurate, however, to say that all homes have the potential to benefit from an audio adjustment based on "worst case" situations. It is equally misleading to imply that because the lead action level is exceeded in a certain number of homes that all homes have levels above 15 ppb. It would be accurate to say that all homes have the potential to benefit from adjustments made to the municipal system's corrosion control program.

Why "Worst Case" Sampling?

Lead is harmful--to children in particular. Studies show that its effects can be permanent. Although lead that leaches into drinking water is not the primary source of childhood lead poisoning, water suppliers--through corrosion control efforts--may be able to lessen exposure particularly in "worst case" situations.

Cities place the protection of public health at the top of the list of priorities. By testing in "worst case" homes, municipal water suppliers are taking on extra responsibility for public health protection by ensuring that the water delivered to homes is water treated so that it is optimal for "worst case" situations. Also by testing in homes, citizens become more aware that they need to act in concert with the city to ensure that the water consumer does not have high lead levels.

*note: Small systems that meet the 15 ppb lead level in 90 percent of the homes tested are not required to implement any further measures. Large systems must implement additional measures regardless of their test results.
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Title Annotation:includes related information on facts concerning lead in drinking water
Author:VanDe Hie, Diane
Publication:Nation's Cities Weekly
Date:Nov 9, 1992
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