Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS) are two of the most widely used and studied chemicals in the PFAS group. PFOA and PFOS have been replaced in the United States in recent years. In chemical and product manufacturing, GenX chemicals are considered a replacement for PFOA, and perfluorobutane sulfonate (PFBS) is considered a replacement for PFOS. The health advisory levels for drinking water include all four chemical compounds: PFOA, PFOS, GenX, and PFBS.
Unfortunately, PFAS contamination has turned out to be ubiquitous. PFAS contamination has appeared in soil, water and crops and is an emerging national issue, and the unfolding information about PFAS in farming is alarming. High levels of PFAS have appeared in rural water wells used not only as drinking water (and not subject to limits and testing requirements under the Safe Drinking Water Act), but also used for irritation at farms. Maine has found itself the unfortunate leader in learning about PFAS, their impacts on agriculture and human health, and in learning about how to address PFAS contamination in agriculture land.
In 2016, milk at a dairy in Arundel, Maine was found to contain high levels of PFOS. The Maine CDC created an Action Threshold for PFOS in milk: 210 parts per trillion (ppt). (The new EPA Health Advisory for PFOS = 0.02 ppt and for PFOA = 0.004 ppt.) Since then, Maine regulators have conducted statewide retail milk samples three times. The regulators worked with processors to successfully identify a contaminated farm in Fairfield, Maine that was producing milk with high levels of PFOS. How did this contamination happen?
Agriculture and PFAS chemicals can enter farm products through air, water, and soil. One way that PFAS may enter soil is through the application of wastewater treatment plant residuals called biosolids. The application of biosolids on agricultural land is a common in agriculture as they contain nutrients and other organic matter that can enhance soils and agricultural production and are generally free. While the amount of biosolids produced annually in the United States is not tracked, the EPA believes that about seven million dry metric tons of biosolids are produced in the U.S. annually.
Waste water treatment plants uses screens to remove crude solids of human waste and skim off grease, oil and fat. Wastewater sits in settling tanks where most of the heavy solids fall to the bottom and become a thick slurry known as primary sludge. The sludge is separated from the wastewater during the primary treatment is further screened and allowed to gravity thicken in a tank. Then the sludge is mixed with the solids collected from the secondary and denitrification units. The combined solids are pumped to tanks where they are heated to destroy pathogens and further reduce the volume of solids. With treatment sludge is transformed (at least in name) to Biosolids. The problem, however, is how to dispose of the never ending supply of Biosolids.
To ensure that Biosolids applied to the land as fertilizer do not threaten public health, the EPA created the 40 CFR Part 503 Rule in 1989 that is still in effect today. It categorizes Biosolids as Class A or B, depending on the level of fecal coliform and salmonella bacteria in the material and restricts the use based on classification. Biosolids that meet standards for very low pathogen content are Class A. Class A biosolids that are considered "Exceptional Quality" meet the most stringent requirements. The metals content is low, pathogens are low or non-existent, and the organic matter is stabilized so there is little odor or possibility of attracting pests that spread disease. Exceptional Quality biosolids can be used on a farm without a site permit, or they can even be sold to consumers for garden use. There is no way to track them. Class B biosolids have higher pathogen content than Class A, and must have a site permit obtained by the wastewater treatment facility for agricultural use.
Biosolids were not tested nor regulated for PFAS and the presence of other emerging contaminants in the Biosolids is not known. The land application of Class B Biosolids has been a growing area of concern. Research at the University of Virginia (about 20 years ago) found that organic chemicals persist in the Class B Biosolids and can be introduced into the food chain and be carried into the groundwater.
If the Biosolids that is applied to farmland, contains PFAS substances they can enter soil and water, and be taken up by the crops grown on the field, and into the animals (and humans) eating those crops or deinking the water. The level at which PFAS contaminants are taken up is highly variable, depending on the amount spread, the PFAS concentrations in the soil and water, the type of plant(s) grown, the type of soil, and other factors. PFAS generally break down very slowly, meaning that concentrations can accumulate in people, animals, and the environment over time. It was reported that the dairy in Maine had applied biosolids back in the 1990's. The current owners knew nothing about that history.
This is an emerging crisis for the farmers and the public at large. Wastewater in some locations has been found to contains various amounts of PFAS from traces to much higher levels coming from commercial and industrial operations. Waste water treatment plants have historically accepted waste water from industry- blow back from fracking, rinse water from manufacturing and other places despite not being designed to remove more than biological waste. This is believed to be what happened in Maine.
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