The short answer is not very much. A part per trillion, as it applies to drinking water constituents, is a measure of concentration - how much contaminant there is in a given volume of water. One ppt means that there is one gallon of contaminant per trillion gallons of water or more specifically 8.34 pounds (weight of 1 gallon of water) of contaminant per trillion gallons of water. It is an exceptionally small amount and is probably easier to visualize by the following examples.
Topsfield Public Works
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PFAS
PFAS, per- and polyfluoroalkyl substances
PFAS are a broad group of manmade chemicals used for a wide variety of purposes. Used since the 1950s, these compounds are in fire-fighting foams, clothing, flame retardants, food packaging, water proofing materials, and carpeting to name a few. These compounds, of which there are reportedly thousands, are structurally and chemically different from each other but share certain properties such as very strong carbon-fluoride bonds that make them very durable in that they do not readily breakdown in the environment, are not affected by natural biological processes, and can persist for years.
Some of these compounds were first detected in our water during the fall of 2019. Further tests conducted in 2020 have confirmed the presence of these chemicals in varying amounts. We now test for 18 of these compounds on a monthly basis. For detailed testing results please visit our water quality site at https://www.topsfieldpublicworks.org/apps/watertesting/.
MassDEP promulgated new regulations concerning PFAS which took effect in October 2020.
Water Department
279 Boston Street
Topsfield, MA 01983
978.887.1517
911 - After Hours Emergency
Office Hours: Monday-Friday 7 AM to 2:00 PM
Highway Department
279 Boston Street
Topsfield, MA 01983
978.887.1542
Hours: Monday-Friday 7 AM to 3 PM