The PFAS Health Study: Systematic Literature Review

Abstract

This review examined all published research into the human health effects of exposure to perfluoroalkyl and polyfluoroalkyl substances, commonly known collectively as PFAS. PFAS chemicals are very resistant to heat and to degradation in the environment, and they persist for quite long periods in the human body. They were extensively used in fire-fighting foams, which were commonly used in fire drills at airports, and in household products, such as protective coatings on furniture and non-stick surfaces on cookware. PFOS (perfluorooctane sulfonic acid) and PFOA (perfluorooctanoic acid) were the two most commonly used PFAS chemicals. We reviewed research published up until February 7th 2017. We found 221 separate scientific publications that reported new results of relevant research in humans. These publications covered effects on reproduction, on pregnant women and their newborn babies, on body metabolism, on major body systems, including brain and nerves, heart and blood vessels, airways and lungs and the immune system, on specific conditions such as overweight, diabetes and cancer, and on thyroid gland function. The people they studied included people who worked in plants manufacturing these chemicals, firefighters, people with higher than usual exposure because of contamination of water supplies and people in the general community, whose exposure was ascertained by measuring PFAS chemicals in their blood. We found sufficient evidence that higher levels of PFOS or PFOA in a person’s blood can lead to higher blood cholesterol levels. High blood cholesterol is associated with heart disease. PFOS and PFOA, however, appeared only to increase cholesterol levels by a small amount. We found limited evidence that higher levels of PFAS in the blood resulted in slightly higher levels of uric acid in the blood. Uric acid is a normal body product and is removed by the kidneys. In a small number of studies, however, we also found limited evidence that high PFAS levels in the blood reduced kidney function or were associated with chronic kidney disease. Since PFAS chemicals are excreted by the kidneys it is possible PFAS does not cause poor kidney function, rather that poor kidney function caused by something else causes increase in PFAS levels in blood. This possibility of “reverse causation” might also explain the association of higher uric acid levels with higher PFAS levels in blood. We found limited evidence in a small number of relevant studies that PFAS exposure caused kidney and testicular cancers and that higher levels of PFAS in the blood resulted in lower levels of antibodies than usual following vaccination against some vaccine preventable infections. We found inadequate evidence that PFAS caused other health effects.