Water Quality Reports

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Read the 2018 City of Wilmington Water Quality Report

The Environmental Protection Agency (EPA) requires the City of Wilmington, and all other water suppliers in the US, to report yearly on specific details about testing for a number of contaminants in our water. Chemical and biological monitoring provides the data that helps suppliers such as the City of Wilmington make key water quality management decisions to ensure the freshness and purity of our drinking water.

Drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants. The presence of contaminants does not necessarily indicate that water poses a health risk. To ensure that tap water is safe to drink, the EPA prescribes regulations which limit the amount of certain contaminants in water provided by public water systems. The Food and Drug Administration (FDA) regulates bottled water, which must provide the same protection for public health.

Water Quality Reports

Informe de la calidad del agua

About PFAS

The City of Wilmington is committed to providing our customers with high quality drinking water. You may have heard about PFAS in the news recently. Due to increasing national concerns regarding these contaminants, the City of Wilmington proactively decided to conduct sampling of our drinking water. For results and more information please refer to our frequently asked questions.

Infographic: How PFAS Cycle Through the Environment

What is PFAS?

Per- and polyfluoroalkyl substances (PFAS) are a group of man-made chemicals that includes PFOA, PFOS and GenX chemicals. Since the 1940s, PFAS have been manufactured and used in a variety of industries around the globe, including in the United States. PFOA and PFOS have been the most extensively produced and studied of these chemicals. Both are very persistent in the environment and in the human body. Exposure to certain PFAS can lead to adverse human health effects.

Who is responsible for regulating PFAS in drinking water?

In Delaware, the Department of Health and Social Services Office of Drinking Water (ODW) and the Environmental Protection Agency (EPA) set and regulate drinking water standards.

The EPA identifies the contaminants to regulate in drinking water, and they set regulatory limits for amounts of certain contaminants. The EPA currently regulates 90 chemicals in drinking water with “limits” called maximum contaminant levels (MCLs). The City of Wilmington compiles with the EPA’s maximum contaminant levels to ensure water quality.

There are some contaminants for which the EPA develops health advisories that do not have set regulatory limits. The health advisories provide technical information on health effects. PFAS are included in those contaminants that have no regulatory limit but are associated with a health advisory.

What are the health advisory levels for PFAS?

The EPA’s current health advisory level is 70 parts per trillion (ppt) PFOA and PFOS combined, as set in May 2016.

The health advisory level was calculated to offer a margin of protection against adverse health effects to the most sensitive populations: fetuses during pregnancy and breastfed infants. The health advisory levels are calculated based on the drinking water intake of lactating women, who drink more water than other people and can pass these chemicals along to nursing infants through breastmilk.

What are the levels of PFAS in City of Wilmington drinking water?

In the spring of 2019 the City’s Water Quality Laboratory conducted voluntary sampling using the most current version of EPA Drinking Water Method 537 which tests for a total of 18 types of PFAS including long-chain PFAS such as perfluorooctanoic sulfonate (PFOS) and perfluorooctanoic acid (PFOA) and the shorter chain PFAS such as GenX and Adona. As shown below, out of the 18 types of PFAS tested 6 were detected. However all finished water results were below EPA’s current Health Advisory Level of 70 ppt.

  Brandywine Filter Plant Porter Filter Plant
PFAS Result (ppt) Result (ppt)
Perfluorobutanesulfonic acid (PFBS) 2.4 2.2
Perfluoroheptanoic acid (PFHpA) 3.8 6
Perfluorohexanoic acid (PFHxA) 5.5 8.2
Perfluorononanoic acid (PFNA) 2.2  3.5
Perfluorooctanesulfonic acid (PFOS) 3.3 3.4
Perfluorooctanoic acid (PFOA) 7.1 9.2
Total PFOA & PFOS Combined 10.4 12.6

What is the City of Wilmington doing to protect our drinking water from PFAS?

The City of Wilmington has a history of protecting it source water through its award winning Source Water Protection Plan which was established in 2010. Under the umbrella of this program the Water Quality Laboratory has begun to monitor the City’s source water (Brandywine Creek and Hoopes Reservoir) for PFAS. The monitoring results will be used to identify treatment needs to comply with future regulations.

What are the health effects of PFAS exposure?

There is evidence that exposure to PFAS can lead to adverse health outcomes in humans. If humans, or animals, ingest PFAS (by eating or drinking food or water than contain PFAS), the PFAS are absorbed, and can accumulate in the body. PFAS stay in the human body for long periods of time. As a result, as people get exposed to PFAS from different sources over time, the level of PFAS in their bodies may increase to the point where they suffer from adverse health effects.

Studies indicate that PFOA and PFOS can cause reproductive and developmental, liver and kidney, and immunological effects in laboratory animals. Both chemicals have caused tumors in animal studies. The most consistent findings from human epidemiology studies are increased cholesterol levels among exposed populations, with more limited findings related to:

  • infant birth weights,
  • effects on the immune system,
  • cancer (for PFOA), and
  • thyroid hormone disruption (for PFOS).

Can I use any home devices to remove PFAS?

Global public health organization NSF International has developed a test method and protocol — P473: Drinking Water Treatment Units - PFOA and PFOS — to verify a water treatment device’s ability to reduce perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) to below the health advisory levels set by EPA. Consumers can find NSF International-approved devices by visiting:


(Click on “reduction devices” at the bottom of the page for PFOS and PFOA).

I have a question that wasn’t answered. What should I do?

If you have additional questions or concerns, please feel free to contact the City’s Water Quality Laboratory at (302) 571-4158. 

SPOTLIGHT: From River to Tap

Learn how the Department of Public Works Water Division processes the water you use in your home.

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