What to Know About Perfluoroalkyl Substances in Biosolids

When I bought a lipstick-red Prius a few years back, I thought mine was unique, but, of course, I started seeing identical ones everywhere. It is the same with a class of compounds called here perfluoroalkyl substances, abbreviated as PFAS, but also known as perfluorinated compounds. I hardly noticed them at all until Ned Beecher’s recent conference call to discuss a serious, evolving regulatory issue in New England. Now PFAS seem to be everywhere, literally and figuratively.

In a short two weeks, both MABA and NEBRA websites have posted PFAS information. Of particular importance, and as a “first stop” for a detailed overview of the PFAS biosolids issue, is Beecher’s “Fact Sheet & Talking Points – Perfluorinated Substances in Biosolids.” If you intend to track this issue, watch for the “PFAS & Biosolids Webinar,” tentatively scheduled for Monday, May 8th at 1 pm (look for an announcement at the NEBRA Events page). As a MABA member, you have likely seen Dr. Sally Brown’s latest “blurb” entitled "Tight Bonds."

If you are like me, you are way behind on your background reading on PFAS.  When I started, I was taken aback at how this class of compounds had been implicated in some bad, though still unproved health effects. The EPA put out a 2014 document, Health Effects Document for Perfluorooctanoic Acid (PFOA), which was the basis of the 70 ppt “lifetime health advisory” for drinking water.  The Centers for Disease Control issued a serious overview of PFAS exposure for use by clinicians with patients living in contaminated areas, available also on the web.  In the report Perfluoroalkyl and polyfluoroalkyl substances and human fetal growth: A systematic review, the authors report “[H]igher PFOS and PFOA concentrations were associated with decreased average birth weight in most studies, but only some results were statistically significant. The impact on public health is unclear, but the global exposure to PFASs warrants further investigation.”  The report Association between perfluoroalkyl substance exposure and asthma and allergic disease in children as modified by MMR vaccination concluded that “Perfluoroalkyl substances (PFASs) are highly persistent chemicals that might be associated with asthma and allergy, but the associations remain unclear.”

When scientists looked at human body burdens of PFAS, clearly everyone everywhere is exposed. Even the Arctic is not spared (Perfluorinated Acids in Arctic Snow:  New Evidence for Atmospheric Formation).The massive, 1,774 page CDC report and update, Fourth National Report on Human Exposure to Environmental Chemicals, showed that, while white males had somewhat higher concentrations in their blood, no one, regardless of age or race, is without a body burden of perfluorinated compounds. One hopeful note is that over the past 15 years serum concentrations have declined significantly, approximately 70%, following the removal of the compounds from many consumer products. Also, a positive feature is that the half-life of these compounds in the human body is a little over two years: (Occurrence and Potential Significance of Perfluorooctanoic Acid (PFOA) Detected in New Jersey Public Drinking Water Systems”)

So where are PFAS coming from? EPA’s report discovered environmental hotspots, such as manufacturing locations, fire training facilities, and airports.  But, according to Impacts of daily intakes on the isomeric profiles of perfluoroalkyl substances (PFASs) in human serum “[d]ietary intake contributed > 99% of the estimated daily intake (EDI) for the general population...” The report Per- and Polyfluoroalkyl Substances (PFASs) in Food and Human Dietary Intake: A Review of the Recent Scientific Literature, claimed that “fish and other seafood seem to be the food group in which more PFASs are detected and where the concentrations of these compounds are higher.”  This was the case, too, for wild-caught bass in Comparison of perfluoroalkyl substances contamination in farmed and wild-caught European sea bass (Dicentrarchus labrax).  PFAS are in food packaging:  Fluorinated Compounds in U.S. Fast Food Packaging explains that “The prevalence of fluorinated chemicals in fast food packaging demonstrates their potentially significant contribution to dietary PFAS.” PFAS have entered our food from Teflon cookware and microwave popcorn: Quantitation of Gas-Phase Perfluoroalkyl Surfactants and Fluorotelomer Alcohols Released from Nonstick Cookware and Microwave Popcorn Bags.  But, thankfully, these sources are being withdrawn from the marketplace and from human use.

PFAS are in indoor and outdoor dust. The paper from Korea, Human exposure to per- and polyfluoroalkyl substances (PFASs) via house dust in Korea: Implication to exposure pathway, determined that “house-dust ingestion was a minor contributor in this study, but should not be ignored for toddlers….” And a nation-wide study found “substantial levels” throughout China, Nationwide Distribution of Per- and Polyfluoroalkyl Substances in Outdoor Dust in Mainland China From Eastern to Western Areas.

Among these several sources, tap water is the big issue for people and biosolids.  The first issues arose with tap water contaminated by local manufacturing activities.  In the report Detection of Poly- and Perfluoroalkyl Substances (PFASs) in U.S. Drinking Water Linked to Industrial Sites, Military Fire Training Areas, and Wastewater Treatment Plants “We find drinking water supplies for 6 million U.S. residents exceed US EPA’s lifetime health advisory (70 ng/L) for PFOS and PFOA.” New England has a few such sources, hence Ned’s urgency, but in the mid-Atlantic, Parkersburg, WV, is the home of a former DuPont Teflon plant, with a sad legacy of PFAS, reported by WV Public Broadcasting in October 2016.

The research conversation quickly turned to wastewater and biosolids.  Mass Loading and Fate of Perfluoroalkyl Surfactants in Wastewater Treatment Plants reported that “PFOS and PFOA are known to be non-biodegradable by an activated sludge process…. Therefore, a reduction in mass flow following activated sludge treatment was neither expected nor observed.”  Further, “This study provides further evidence that PFAS are not removed from wastewater by conventional treatment. An effective strategy for reducing their contamination of the environment should include the removal of PFAS and their precursors from domestic, commercial, and industrial sources.”

One famous horror story is given in Application of WWTP biosolids and resulting perfluorinated compound contamination of surface and well water in Decatur, Alabama, USA, which “describes a situation in Decatur, Alabama, where PFC contaminated biosolids from a local municipal wastewater treatment facility that had received waste from local fluorochemical facilities were used as a soil amendment in local agricultural fields for as many as twelve years.” Biosolids-borne PFAS were implicated in groundwater contamination. 

How much PFAS can you expect in biosolids. Rolf Halden at the University of Arizona weighed in with his National inventory of perfluoroalkyl substances in archived U.S. biosolids from the 2001 EPA National Sewage Sludge Survey,  which reported a national average for the dominant compound in biosolids, perfluorooctane sulfonate (PFOS), at approximately 400 ng/g dry weight.  

Analysis of more current samples show much lower concentrations today. Perfluoroalkyl substances (PFASs) in wastewater treatment plants and drinking water treatment plants: Removal efficiency and exposure risk reported the “average total PFASs concentrations in the three selected WWTPs were 19.6–232 ng/L in influents, 15.5–234 ng/L in effluents, and 31.5–49.1 ng/g dry weight in sludge.” Temporal trends of perfluoroalkyl substances in limed biosolids from a large municipal water resource recovery facility  is an important time series of measurements from Washington, DC, in which “the highest mean concentrations observed over the study period were 25.1 ng/g dw, 23.5 ng/g dw, and 22.5 ng/g dw for perfluorononanoic acid (PFNA), perfluorooctanoic acid (PFOA), and perfluorooctanesulfonic acid (PFOS), respectively…”  These recent studies confirm that today’s values are about an order of magnitude lower than those values reported for National Repository biosolids.

The million-dollar question is what happens when biosolids are land applied? We have only a few clear field studies, and some questionable pot studies. To start with, biosolids carry the larger-chain PFAS. While these resist movement in soil, microbial action mobilizes them as shorter chain compounds. Occurrence and fate of perfluorochemicals in soil following the land application of municipal biosolids showed that “trace levels of PFCs were also detected in soil cores from biosolids-amended soils to depths of 120 cm, suggesting potential movement of these compounds within the soil profile over time and confirming the higher transport potential for short-chain PFCs in soils amended with municipal biosolids.” Ed Topp in Canada looked at the pathway of PFAS from biosolids to tile drains (Brominated flame retardants and perfluoroalkyl acids in groundwater, tile drainage, soil, and crop grain following a high application of municipal biosolids to a field.) Under conditions in which the pathway is short between plowed-in biosolids and tiles, “Exponential dissipation of …  [PFCs] in [biosolids] aggregates were not significant…. {though] No [PFCs] were detected in wheat grain.” The finding on plant uptake was reassuring.

Beecher is dealing with several closely related issues in New Hampshire. What had been an advisory level put out by EPA was grabbed by state regulators as a criterion. Evidence of PFAS transport in groundwater from an industrially contaminated site is seen by state regulators as prima facie rationale for regulating land applied biosolids bearing PFAS. Regulators are tempted by “low hanging fruit” to impose a ban on land application.

Biosolids professionals are putting a stake in the ground for “sound science.” At each step in the environmental exposure chain – wastewater treatment, biosolids stabilization, land spreading/incorporation, groundwater withdrawal, and crop update -- the connection needs to be scientifically understood before regulations are imposed.  Decades of good biosolids recycling practices urge us to Stick with Biosolids.