NASEM Recommended Summation

PFAS are manufactured chemicals that don't break down easily. The seven chemicals in this total leave the body slowly, so a blood test can reflect exposure from years ago as well as exposure still happening now.

NASEM is the National Academies of Sciences, Engineering, and Medicine. In 2022, it recommended adding seven PFAS measured in serum or plasma into one total for people with a meaningful exposure history. The point is to decide how much follow-up makes sense, not to diagnose a PFAS disease.

What This Number Measures

PFAS stands for per- and polyfluoroalkyl substances. They are a large family of thousands of chemicals used since about the 1950s to make things resist water, grease, and heat. You can find them in nonstick coatings, stain-resistant fabric, some food packaging, firefighting foam, and some drinking water, especially near contaminated sites.

The NASEM total sums seven specific PFAS measured in serum or plasma from a standard blood draw. Serum and plasma are the liquid parts of blood after the cells are separated. The seven are PFOA, PFOS, PFHxS, PFNA, PFDA, PFUnDA, and MeFOSAA. For PFOA and PFOS, the lab should include both straight-chain and branched forms. That is why some labs describe measuring nine analytes for a seven-chemical total: they count the branched and straight-chain forms of PFOA and PFOS separately.

Adding them makes sense because exposure usually comes as a mixture. A single PFAS can miss the pattern. A sum is blunt, but it is closer to the question you care about: how much long-lived PFAS is in your blood.

How NASEM Uses the Total

NASEM groups the sum into exposure bands. Lower values generally point toward usual care. Raised values point toward exposure reduction and more deliberate screening: lipids first, then thyroid and symptom-focused checks when exposure is higher.

The bands are not disease labels. They are a way to match follow-up to stored exposure.

Higher Cholesterol

The most consistent human finding is higher PFAS levels tracking with higher cholesterol. NASEM judged the evidence sufficient for children and adults, which is why a raised result points first to checking lipids. If your cholesterol has crept up without an obvious reason, PFAS is one exposure worth looking for, especially if your water or work history fits.

A Weaker Antibody Response

NASEM judged the human evidence sufficient that higher PFAS levels are linked to a lower antibody response after some vaccines. Antibodies are one part of vaccine protection. NASEM did not find enough evidence that PFAS makes infections more common or vaccines fail.

Kidney Cancer

For harder outcomes, kidney cancer in adults is the one NASEM judged to have sufficient human evidence. That is why a higher total should not be shrugged off. It is still a population association, not a personal forecast. Most people with raised PFAS levels never develop kidney cancer.

Pregnancy and Infant Size

Higher PFAS exposure is linked in human studies to slightly lower birth weight. The shift is small for any one pregnancy, but it is consistent enough that NASEM counted the evidence as sufficient. Knowing your number before or early in pregnancy can help you find and cut any ongoing source.

Why One Reading Tells You More Than You'd Think

Most blood markers are a snapshot. PFAS blood levels are less jumpy because these chemicals clear slowly. One reading is not a full biography: a low level today does not rule out higher exposure in the past, and a high level today does not tell you where it came from. But it is a useful baseline.

When the Number Can Mislead

• Which chemicals the lab measures: the NASEM total only works if the lab includes all seven PFAS in the sum. A panel that measures a different set cannot be compared with NASEM's bands.
• Serum or plasma versus other samples: the NASEM total is defined for serum or plasma. Finger-prick capillary blood and urine can give different readings.
• Pregnancy timing: PFAS measured later in pregnancy can be affected by blood volume expansion, kidney filtering, and transfer to the fetus.
• Kidney function: reduced kidney filtering can raise serum PFAS, and pregnancy-related kidney changes can complicate interpretation.
• Recent blood or plasma donation: repeated donation can lower PFAS over time by removing PFAS-containing blood components. That matters when you compare one result with another.
• PFAS-lowering treatment: cholestyramine and related binders can lower some serum PFAS in highly exposed people, so treatment history belongs with the result.