On Monday, we published a letter from NC State University Researcher Detlef Knappe, answering our question: Bottom line: is it safe to drink our water? Dr. Knappe is one of the scientists who teamed with the state to study the water in the Cape Fear River, and discovered a number of contaminants including GenX and 1,4-dioxane in our water supply.
His letter to us contained the helpful perspective of an expert in assessing the risk of drinking the tap water. After our story aired, a viewer contacted us wanting to know if Dr. Knappe would drink the water if he lived here. We asked him that question and several others. Here are his answers, along with a copy of his original letter that you may find helpful in deciding if the water is safe for your family to drink:
Q: Would you drink the water?
Dr. Knappe: “If I lived in the Wilmington area, I would get an under-the-sink reverse osmosis system for the water I use for drinking and cooking. I would use the tap water for bathing, dishwashing, and laundry (and toilet flushing of course). I would get a rain barrel for my garden. Reverse osmosis units can be purchased in the form of under-the-counter treatment systems that are available for ~$200.”
Q: If we boil the tap water instead, is that enough to get the toxins out?
Dr. Knappe: “Boiling would not help for 1,4-dioxane, GenX, or the other PFECAs. The chemicals would stay in the water because they love being in the water. Also, they are thermally stable chemicals at the temperature of boiling water.”
Q: Since there are multiple emerging contaminants in the Cape Fear River, is the risk cumulative? For example, since the latest data shows that the level of 1,4-dioxane in the CFPUA treated water supply is 3 times the EPA safe level, and the precise level of GenX risk is unknown but an educated guess puts it around 9 times a potential safe level, is it safe to assume our risk when drinking the water is 12 times the safe level (3+9)?
Dr. Knappe: "The risk assessment for mixtures of chemicals is an area of ongoing research. In some cases, risk can be additive (like what you are assuming). In that case, risks of 3 in a million and 6 in a million would add up to a total risk of 9 in a million. But in some cases, there are synergistic effects between chemicals, meaning the total risk is greater than the sum of the risks. In other cases, there are antagonistic effects, meaning that the total risk is lower than the sum of the risks."
Q. CFPUA is considering purchasing new filtering technology that would remove GenX from our water supply. But you have expressed concern that some filtering methods that remove GenX do not remove other contaminants, like certain PFECAs that have been found in our water that are also harmful. Is there filtering technology available that would remove all the contaminants from our water that we are currently aware are present?
Dr. Knappe: "The two water treatment technologies that have the greatest chance of removing PFECAs are reverse osmosis and anion exchange. There are no data currently available for the effectiveness of reverse osmosis systems for the removal of GenX and the other PFECAs, but data for a similar compound, perfluorobutanoic acid, suggest that GenX and the other PFECAs should be well removed by reverse osmosis. 1,4-dioxane is also well removed by reverse osmosis, but not quite as well as GenX and the PFECAs. We are beginning to evaluate the effectiveness of a reverse osmosis system for GenX and PFECA removal in our lab, and we are also beginning to collect field samples."
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