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Yes. This is an issue that the U.S. Environmental Protection Agency is beginning to look at now that the drinking water standard for arsenic is 10 micrograms per liter.
Since arsenic can co-precipitate with iron, it is possible for arsenic to show up at the tap at concentrations greater than the drinking water standard of 10 micrograms per liter due to past accumulation of arsenic in iron scale type residuals within a water distribution system. The likelihood of this occurring is greater for ground water sources that contain substantial arsenic. In the past, there was no requirement for water utilities to remove arsenic from their source water unless the concentration was above 50 micrograms per liter. Most ground water contains some iron. If the iron problem was not severe enough to require removal at the treatment plant, there may have been some continuous precipitation of iron as ferric hydroxide within the distribution system. If the source water contains arsenic, it is also very likely that some ferric arsenate may have co-precipitated with ferric hydroxide to form scale or residual material throughout the distribution system. Ferric arsenate has also been found as a co-product of iron oxide residuals that may originate from internal pipe corrosion. Future modifications in water chemistry may cause these arsenic-containing scales and residuals to become more soluble, thus, becoming potential sources of arsenic exposure at the tap. |
