WHAT ARE PFOS/PFOA?                                                                                                                                                      

Perfluorooctane sulfonate (PFOS) and Perfluorooctanoic acid (PFOA) are part of a man-made class of chemicals called Perfluorinated compounds (PFCs). These chemicals are long lasting in the environment and have been used since the 1950s in many products  because of their stain and water repellant properties and have been present in regular household items such as fabric for upholstered furniture, carpets, nonstick cookware, floor wax.  These chemicals are also found in Aqueous Film Forming Foam, or AFFF, used to control petroleum-based fires. PFOS/PFOA have been globally distributed in the environment and have been detected in the blood of humans, wildlife, and fish. 

The Environmental Protection Agency is continuing to develop a maximum contaminant level for PFAS chemicals allowed in drinking water.  More information concerning EPA’s rule development can be found at

AFFF USE IN THE AIR FORCE                                                                                                                                              

Aqueous Film Forming Foam, or AFFF, is a firefighting agent used commercially and by the Department of Defense, including the Air Force since 1970. Most commonly used to combat petroleum fires in aircraft accidents, hangars and during live-fire training exercises, this formulation of AFFF contains perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) - two perfluorinated compounds that persist in the environment and are not known to degrade by any natural process. 

In March 2011, the Air Force Civil Engineer Center initiated an informal plan for Air Force fire chiefs to dispose of “excess” PFOS-based AFFF Air Force-wide over a 10-year period. In November 2015, more environmentally responsible formulas were added to the DOD’s qualified products list for firefighting agents. The Air Force began replacing both PFOS-based and other legacy AFFF products with a new formula in August 2016. The Air Force completed new foam delivery in August 2017. The Air Force is eliminating legacy AFFF through incineration at authorized disposal facilities. 

AFFF USE AT THE 166TH AIRLIFT WING                                                                                                                       

The 166th Airlift Wing's fire department used AFFF beginning in 1970. Two helicopter crashes occurred one in 1991 involving the MV-22 Osprey, and a second in 1994 involving an AH-64 Apache Longbow. Both crashes occurred in the grass on the north side of runway #9 between taxiway K5 and K4. In 1992 a corporate plane crashed into an area with trees at the end of runway #19.  The most recent crash occurred in 2007. The aircraft crashed on taxiway F between taxiway F3 and H. In addition to using AFFF to extinguish fires at aircraft crash sites, the 166 AW Fire Department routinely conducted Federal Aviation Administration required monthly testing of spray nozzles used to apply AFFF.  The equipment testing and training using small amounts of AFFF continued at the 166 AW in accordance with Air Force guidelines over the years until a cease and desist order was given in July 2015.  The final containers of legacy AFFF were removed from the 166th AW in June 2017. 

166TH AW and New Castle Area PFAS EVENT TIMELINE                                                                                            

In 2014 EPA tested the public drinking water in the New Castle area.  Two public drinking water systems owned by Artesian Water and the City of New Castle were found to contain PFAS levels exceeding EPA’s preliminary health advisory level for combined concentrations of PFOS and PFOA. After receiving these results both systems upgraded their systems to reduce PFAS exposures by installing granular activated carbon filtration systems.  This reduced the concentrations of PFAS below the EPA health advisory levels at that time 

The National Guard Bureau conducted a preliminary assessment in August 2015 at the 166th AW to identify potential sites of historic environmental releases of perfluorinated compounds, specifically from AFFF usage and storage. Nine locations on the 166th AW installation were identified where PFAS releases may have occurred including a wash rack, a fire training station, a stormwater outfall, and the location of a former fire station. Eight of these nine locations were recommended for further testing. 

In 2016, EPA established the lifetime health advisory level of 70 parts per trillion for PFAS chemicals in drinking water. In June 2022 EPA lowered the lifetime health advisory level to .004 parts per trillion for PFOA, and .02 parts per trillion for PFOS.  More information concerning the most recent EPA lifetime health advisory levels can be found at:   

The State of Delaware Department of Natural Resources and Environmental Control (DNREC) also had conducted preliminary assessments and site inspections on surrounding properties in the New Castle area. DNREC has evaluated sixteen other properties for their potential to contribute to PFAS contamination in groundwater in the local area. 

The National Guard Bureau conducted a site inspection in 2017 to determine the presence of PFAS in soil and groundwater at eight possible release sites located on the 166 AW installation.   PFAS was detected in groundwater at all eight possible release sites, and in one surface water sample at a stormwater outfall. All of the possible release sites were further recommended for additional investigation to determine the nature and extent of the contamination.  

The Centers for Disease Control and Prevention and the Agency for Toxic Substances and Disease Registry announced in February 2019 that the New Castle area was one of eight sites selected for a PFAS exposure assessment.  During the exposure assessment, the CDC/ATSDR tested the blood and urine of over 200 people for seven PFAS compounds and compared the results to national averages. Thirteen households also had their drinking water tested.  Summary results from the PFAS exposure study can be found at the following link: 

In March 2023, the EPA finalized their listing of PFAS Contaminaiton in Groundwater on the Comprehensive Environmental Response and Liabilities Act (CERCLA) National Priorities List.  The listing means that EPA will now be the lead agency for overseeing the environmental cleanup activities that occur at the Delaware Air National Guard.   The National Guard Bureau will continue as the lead agency responsible for performing the cleanup activities and will now submit all the plans and reports associated with the cleanup to EPA for review and approval. Prior to the listing decision, the State of Delaware was the lead oversight agency.  More information related to EPA’s NPL site listing decision can be found at:  

Additional Information can be found at the following links: 

ANGRC Draft Final New Castle RRSE Fact Sheet and Scoring Summaries 

State of Delaware PFAS Investigation Sites 

Air Force Civil Engineer Center Administrative Record 

For Further Information please call or email Mr. Alex Rittberg 
DE Air National Guard Environmental Manager 
Phone 302-323-3331; Email