Residents in Bucks and Montgomery Counties who participated in a blood-testing program because their drinking water was contaminated by chemicals on nearby military bases have a dramatically higher presence of some chemicals in their blood than the general U.S. population — in the case of one chemical, five times more than the typical American.

The Pennsylvania Department of Health mailed the averaged results to the 235 residents in Horsham, Warminster, and Warrington Townships who participated in the testing program, which was completed at the end of September.

The letter — obtained by the Inquirer and Daily News — offers a first look at the potential health effects of the water contamination on more than 70,000 residents in the affected towns.

The test results, from randomly selected participants across the area, allow for "a general idea of the amount of exposure in the community as a whole," the letter said.

Health officials said last week they were working on a full report to be released to the public in December, when they will also hold a public meeting to discuss the results. The federal government hopes to use the data to create a nationwide testing program.

Residents' blood was drawn and analyzed for measurements of several types of chemicals, known as PFAS, that were present in firefighting foams used on military bases in Willow Grove and Warminster, and seeped into drinking water supplies. Since being alerted to the contamination in 2014, residents and lawmakers had demanded blood testing, pointing to other states where health tests had been offered, and continue to raise questions and voice fears about the situation.

"This is a huge indication that something needs to be done, that the [Department of Defense] needs to start stepping up to the plate and start helping people," said Hope Grosse, who grew up near the Warminster naval base and has become an advocate for residents concerned about the issue. "I'm grateful these numbers came out, and I sure hope they don't keep suppressing and delaying remediation for people and for the groundwater."

She called the results the "tip of the iceberg" and said the government needs to provide biomonitoring, conduct a health study, and provide education and financial assistance to residents, among other things.

PFAS are present in everyday items, such as pizza boxes and nonstick cookware, and can be found in the bloodstreams of many Americans. The same water contamination occurred near military bases in New Jersey and other communities across the country. In the Bucks-Montgomery area, the chemicals have also been found in lower amounts in several surrounding municipalities.

The average for one type of PFAS, known as PFHxS, in the Pennsylvania residents sampled was 7.63 micrograms per liter — more than five times the national average. And the 95th percentile for local residents tested was almost nine times higher than the 95th percentile for all U.S. residents.

The local average for PFOS was more than double the national average, and PFOA was more than 1.5 times the national average.

Scientists have linked the PFAS group of chemicals to health problems, which include increased risk of liver damage, high cholesterol, thyroid disease, decreased fertility, and certain types of cancer. However, it's difficult to determine whether exposure could have contributed to someone's illness in any specific case, experts say.

State officials cautioned that the results cannot be directly correlated to current medical conditions or the risk of developing health problems.

"It is important to remember that scientists are not sure about the health effects of human exposure to PFAS and do not know what these levels mean, if anything, in terms of affecting your health now or later in life," the letter stated. "Currently, these results cannot tell you if an existing health problem is related to your PFAS levels: how, where, when, or how often or how long you were exposed to PFAS; nor how much of the chemical you were exposed to."

A Department of Health spokesperson declined to elaborate on the test results and said they will be formally released at the public meeting next month. A date has not been set.

In 2016, the Environmental Protection Agency updated a "health advisory level" that created a recommended threshold for the maximum amount of PFAS chemicals in drinking water. The agency has not set any guidelines for how much chemical is cause for concern in the human bloodstream, although a draft of a federal study released during the summer proposes a level of the chemicals that is safe for humans to ingest. The study suggested that the toxins are more dangerous than the EPA had previously indicated.

The EPA's drinking-water guideline has also been contested by some experts, and the Horsham, Warrington and Warminster water agencies sought undetectable levels of the chemicals when cleaning their water supplies. Last year, New Jersey set its own safe drinking-water level, much lower than the EPA's. Pennsylvania has not followed suit, although Gov. Wolf has made recent pledges to address PFAS, and a state action team is set to publicly meet in Harrisburg on Friday.

Pennsylvania was chosen by federal agencies for the pilot program to help officials examine how best to do studies in areas nationwide affected by the contaminants.

The results here showed lower amounts of the chemical in the blood of those tested than for residents of the Hoosick Falls, N.Y., area, but higher than or similar to some results for residents in the Pease Tradeport region of New Hampshire, both places where blood testing has been conducted by state agencies for the same contaminants. Compared with Newburgh, N.Y., the results were also mixed; Newburgh had higher average blood levels then the Philly-area testing for some chemicals but not for others. But in each of those locations, as is the case locally, the average presence of the chemicals in bloodstreams was higher than national averages.