PFAS exposure through drinking water is well established, but the contribution of cooking with contaminated water to total dietary PFAS intake is an important and often overlooked consideration. Understanding how PFAS behaves during cooking helps households make informed decisions about which water sources to use for food preparation.
PFAS Concentration During Cooking
Cooking processes that reduce water volume — boiling pasta, making soups and stews, cooking grains — concentrate PFAS as water evaporates. A pot of contaminated water reduced by 50% through evaporation leaves behind doubled PFAS concentrations in the remaining liquid and in food that absorbs it. Steaming vegetables over contaminated water can also transfer PFAS into food through condensation on food surfaces.
Foods With High Water Absorption
Rice, pasta, oatmeal, and similar grains absorb large amounts of cooking water and therefore incorporate substantial quantities of any dissolved contaminants including PFAS. Studies have quantified PFAS transfer into cooked rice as a meaningful dietary exposure route when contaminated water is used. For families with infants consuming rice cereal prepared with tap water, this exposure pathway is particularly relevant.
Protective Practices
Using filtered water for all cooking — not just drinking — is the most straightforward protective practice. Point-of-use filters at the kitchen sink that provide both cold and hot filtered water (or pre-filtering cold water used for cooking) address this exposure pathway. For households with a single-tap RO system, filling cooking pots from the filtered water dispenser rather than the unfiltered hot tap provides meaningful exposure reduction.