The results of the first blood-testing study of residents of Bucks and Montgomery Counties whose water was tainted by chemicals from nearby military bases showed higher-than-average levels of chemicals in their systems, state officials said at a meeting Wednesday night, but they added that they could not give people definitive information about potential adverse effects of the chemicals on their health.

Releasing a report on the results, state health officials said that the elevated levels of chemicals belonging to a class known as PFAS were comparable to other contaminated communities in the country, and that the residents who had lived in Horsham, Warminster, and Warrington Townships the longest had the highest levels of PFAS in their blood.

The chemical amounts in participants' blood were likely even higher in past years, according to the report, because PFAS levels have been found to decline over time.

But the answers — the first ever provided about human contamination in this region — left many residents with even more questions. Chief among them: What do the test results mean for anyone’s health?

“All the charts and statistics are very nice and very interesting, but they don’t solve the question that I think most of us would like to know,” said Richard Gittis, 88, of Warminster, who had his blood tested.

It’s a question they still can’t answer, officials told an audience of about 80 at Upper Dublin High School, saying significant scientific developments are needed to understand health effects.

The results of the 235-person study are generally representative of the entire region’s exposure, the state Health Department has said, indicating that the area’s more than 70,000 residents have been affected by the PFAS that contaminated their drinking water. PFAS, a compound used in firefighting foam, leached from local military bases into the drinking water of towns neighboring two naval bases in Bucks and Montgomery County.

Pennsylvania and New York are the only states to have conducted federally funded blood testing for residents, and the state’s results -- both the blood samples and the efficacy of the overall program -- will be used by federal officials who are working to develop a wider testing program and evaluate chemical exposure in other communities across the country.

“As we learn more about the health effects of PFAS exposure, these communities will be able to use the information from this study to make better decisions to protect public health,” Christopher Reh, associate director of the the Agency for Toxic Substances and Diseases Registry, which funded the study, told the audience.

The upcoming federal studies will "expand the science about the relationships between PFAS exposure and certain health outcomes, and it will help people better understand their risk of health effects,” he said.

According to the new report, the most frequently reported health conditions among participants were high cholesterol, endocrine disruptions, and cancer. Although researchers have linked high cholesterol and some types of cancer to PFAS, the link has not been definitive.

“We cannot tell you cause and effect. We can’t tell you what level of this, of PFOA [a type of PFAS] in your blood, for example, makes you more at risk or less at risk for various outcomes,” state epidemiologist Sharon Watkins said. “They’re hoping that some of these kinds of questions can start … to be answered during that national health study.”

Four of the 11 PFAS compounds for which the blood tests were analyzed were consistently detected in the participants; the other seven were detected in fewer than 15 people. The majority of participants had levels exceeding the national average for the four types of PFAS: 75 percent exceeded the average for PFOA, 91 percent for PFOS, 94 percent for PFHxS, and 59 percent for PFNA.

The average PFHxS level was the third-highest compared with studies of other contaminated areas worldwide. It is a minor component of the firefighting foam and showed up in lower amounts than PFOA and PFOS in local drinking water systems, an ATSDR representative said, and it takes the longest to be eliminated from the body.

People with private wells had higher PFAS levels than people who had drunk public water; and people who had lived in the area longer had higher levels than those who were newer. Anybody who had worked on the military bases, about 24 percent of participants, also had higher levels.

There are no federal regulations for PFAS in drinking water. An Environmental Protection Agency guideline offers a “health advisory level” for safe drinking water, but scientists and some states have challenged the level, saying the chemicals may be hazardous in much lower amounts. Hundreds of sites have been identified for testing by the military, including bases in Pennsylvania and New Jersey, and the chemicals have also been used by private companies.

Health officials said they plan to further analyze the data from the local study.