Over the past couple of decades, the ability to measure traces of chemicals in various matrices in minute quantities has expanded significantly. We’re finding anthropogenic and natural substances in many places we look. Many chemicals that have been in use for decades are of “emerging concern,” because we can now “see” them in soils, groundwater, surface water, and drinking water — even though they have been there, and we’ve been exposed to them. But this new awareness causes unease.
Those involved in recycling organics are well aware of contaminants of emerging concern (CECs) and have wrestled with them many times. These include:
• PCBs, priority pollutants, and “heavy metals” were some of the prominent persistent toxins that spurred industrial pretreatment requirements that protected wastewater treatment biology, effluent quality, and biosolids produced at water resource recovery facilities (WRRF).
• Clopyralid and related persistent herbicides crippled several composting operations.
• The antimicrobials triclosan and triclocarban were found to be persistent in soils and raised red flags about antibiotic resistance; water quality and biosolids professionals joined others in urging their phase out — which has happened.
• Discussions and actions are ongoing regarding persistent brominated flame retardants (e.g. PBDEs).
Managers of organic waste streams also recognize that not all potentially toxic contaminants in wastewater, biosolids, and the organic fraction of municipal solid waste (MSW) can be easily replaced or phased out, and the details of fate and transport and exposure are important. Pharmaceuticals are an obvious example. We won’t phase out the ones that pass through humans (or their degradation products). This is why WRRFs and water quality professionals have been strong partners in drug take-back programs and messaging about not disposing of unused drugs down the toilet. Green chemistry can help too, with drugs and other chemicals designed to break down without creating adverse effects or secondary chemicals of concern.
A key concept to keep front and center is that biosolids, anaerobic digestion, and composting are solutions for managing the myriad traces of chemicals in our daily lives. Healthy soils are an excellent medium for sequestering and/or degrading them — the billions of bacteria per gram do this. Most of the trace chemicals of concern that have been studied related to biosolids, digestates, and composts break down — it’s an efficient and sustainable system that allows the organic matter and nutrients in organic residuals to be utilized for building soils and growing crops. Thus, upstream pretreatment and source reduction perhaps need to focus on persistent and/or highly bioaccumulative contaminants like PCBs, dioxins, and PBDEs.

And Now PFAS

As discussed in Part I (“PFAS And Organic Residuals Management,” July 2018), poly- and perfluorinated alkyls substances (PFAS) — including PFOA and PFOS — are the current compounds of greatest emerging concern for the public, media, and regulatory agencies. These compounds have been in ubiquitous use for decades and are, therefore, widely found in trace levels in biosolids, composts, and other residuals. Recent investigations at land application sites in the Northeast and limited published literature indicate some leaching of PFAS to groundwater — although, to date, no drinking water exceedance has been linked to biosolids or residuals application in the Northeast. However, a few WRRFs around the U.S. that have had large, ongoing discharges from industries using PFAS as a major part of their operations (metal plating, manufacturing of PFAS, coating paper), have caused exceedances of the 70 ppt EPA public health advisory for drinking water because of leaching to groundwater.
To date, there have been no formal, general restrictions on recycling of biosolids and other organic residuals as a result of PFAS concerns, although it is far from certain that there will not be any in the future. Regulatory and legislative scrutiny around PFAS has been increasing in several Northeast states, despite the significant data gaps and considerable uncertainty about the potential fate, transport, and impacts from land applied biosolids and other residuals. Legislative sessions in 2017 and 2018 saw more than two dozen PFAS-related bills around the Northeast. Some would lower the drinking water screening level or impose other enforcement standards.
Over the past year, Northeast biosolids stakeholders have teamed with drinking water, groundwater, and other environmental professionals to comment on proposed regulations and legislation, concerned that the unintended consequences of stricter water quality criteria will make recycling of biosolids and residuals even more challenging (for example, see here: https://www.nebiosolids.org/nebra-publications). But the scrutiny on PFAS and biosolids has already begun to create unease among some farmers and other end users who have relied on biosolids for many years. A few are considering withdrawing from biosolids recycling programs.

What Can Biosolids And Residuals Managers Do?

In a nutshell, pay attention and be engaged, starting with these suggestions:
• Support targeted, practical research on this potentially disrupting topic.
• Consider testing biosolids and residuals products for PFOA and PFOS and other PFAS to gain a sense of where you stand in comparison to other biosolids and residuals. Before testing, design a careful sampling program and determine, in advance, how the resulting data will be managed and reported, to be sure they are not misunderstood and are presented with appropriate context. Utilize the North East Biosolids and Residuals Association’s (NEBRA) Guidance: “Sampling & Analysis of PFAS in Biosolids and Associated Media” (contact: info@nebiosolids.org). Perhaps send split samples and field blanks to different labs for quality assurance. (See discussion of current analytical challenges in the Sampling & Analysis guidance.) Consider sharing results with NEBRA, which is compiling data, without attribution, so no source of any particular data will be publicized. These compiled data will help advance understanding of current residuals and inform ongoing policy and research.
• Consider testing soils and groundwater around biosolids utilization sites. However, do so only in accordance with the cautions and guidance just noted.
• Evaluate potential sources of PFAS in wastewater influent and/or feedstocks; sample and test. For example, metal plating facilities are a potential source, as is landfill leachate. A straightforward way to reduce potential risk in the short term is to cut off any source(s) that contribute elevated levels of PFAS coming into your operation. Perhaps also test for precursor PFAS compounds that may break down to PFOA and/or PFOS during the treatment process.
• Calculate cumulative application rates to determine potential soil levels of PFOA or PFOS. The very limited literature on leaching potential has suggested that, based on the most conservative assumptions, minimal risk is likely if the concentration of PFOA or PFOS in soil is no greater than 3 ppb (Vermont DEC has recently suggested 2.1 ppb). However, other modeling suggests a reasonable maximum acceptable level may be as high as 140 ppb in soil. More research is needed, but this range of soil concentration values can serve as initial guidance for now.
• Apply all biosolids and residuals (including Class A/EQ and composts) in accordance with the agronomic rate and other best management practices, including setbacks from surface and groundwater. This limits the total mass of any trace contaminant applied on any one site. Lower application rates and lower concentrations of PFAS in biosolids and residuals products present lower potential risk.

• Support societal efforts to reduce the use of PFAS, at least any persistent, bioaccumulative (longer-chain) versions. Societal use of any highly persistent chemical of known toxicity, perhaps PFOA and PFOS included (whose toxicities are the subject of ongoing debate), is a threat to wastewater effluent, biosolids, and compost quality and should be discouraged.
• Communicate with regulatory agencies. Every state in the U.S. allows the use of biosolids products, recognizing their beneficial value. Watch closely for state actions regarding regulatory standards for PFAS in drinking water and other media. The U.S. EPA guidance value for drinking water (70 ppt) is a health advisory — it was never intended to be an enforcement standard (although a few states are using it as such). With the current state of knowledge regarding PFAS, a drinking water advisory level — as U.S. EPA has established — is appropriate. An advisory allows for regulatory flexibility, letting each jurisdiction determine how best to respond to its local situations.
• Encourage states to use the U.S. EPA health advisory during this period of rapidly developing science and understanding. There is no consensus on the level of potential risk to public health from low and moderate levels of PFAS exposure. However, at least two states have already created challenging regulatory situations by adopting enforceable standards instead of following the health advisory. Because of how ubiquitous PFOA and PFOS are, Vermont’s 20 ppt drinking water and groundwater standard is likely exceeded in numerous groundwaters around the state, making enforcement almost impossible.
States will be receiving even more pressure to establish low drinking water PFAS levels because of how some citizens, groups, and media are interpreting the new Centers for Disease Control (CDC) ATSDR Toxicological Profile for PFAS released in June (ATSDR, 2018). Some are claiming it means drinking water should not exceed 7 to 12 ppt PFOA/PFOS. Meanwhile, an expert medical panel convened by the Australian government to advise policy released a similar extensive review of the PFAS health literature in March that found “limited, or in some cases no evidence, that human exposure to PFAS is linked with human disease” (Expert Health Panel, 2018).
Conflicting advice and uncertainty plagues the PFAS issue, resulting in wide ranges of regulatory response. For example, Minnesota has been dealing with this issue for more than two decades because of contamination from industrial facilities that manufactured and used PFAS. It had groundwater standards of 300 ppt each for PFOA and PFOS until May 2017, when the state adopted standards of 35 ppt and 27 ppt, respectively. These standards total close to the EPA’s 70 ppt health advisory for PFOA and PFOS combined. In April 2017, Australia issued final drinking water advisory values of 70 and 560 ppt, respectively. And, in November 2017, Canada issued screening values of 200 ppt and 600 ppt, respectively. This wide range of screening values indicates the levels of uncertainty still associated with these compounds.
• And, again, it is only drinking water and groundwater quality concerns (caused by PFAS leaching and, possibly, run-off) that are driving concerns about application to soils of biosolids and other residuals. There is no other exposure pathway of any significant concern (e.g. dermal, ingestion, inhalation).

In Summary…

The only significant issue for biosolids and organic residual management related to PFAS is potential leaching that impacts drinking water (and possibly surface water). The mere presence of PFAS in organic residuals is not evidence of risk or even significant exposure in excess of current PFAS exposure in our daily lives. Home exposure to these compounds remains a major, significant pathway for the vast majority of individuals. Some initial leaching modeling of PFAS from biosolids amended soils raised red flags, but such modeling lacks scientific rigor at this time, due to a paucity of appropriate data. (U. S. EPA confirmed this in new 2013 and 2015 biennial reviews of contaminants in biosolids, released earlier this year.)
The 70 ppt drinking water advisory level issued by EPA is based on best current understanding. Because PFAS were used in so many products for so long it is very difficult to isolate the impact of chronic exposure to these compounds from other environmental stressors. Regulatory agencies that adopt low (<70 ppt) PFAS standards for drinking water or groundwater are finding it hard to enforce and mitigate all locations, because there are many. EPA stresses that the 70 ppt public health advisory level covers lifetime drinking water and sensitive populations, and some scientists call it overly conservative (while some push for lower limits). With PFOA and PFOS levels already declining dramatically in humans, states need to assess what public health benefit is gained for considerable cost in chasing groundwater and surface water protection at lower levels and possibly disrupting wastewater treatment operations and the recycling of organic residuals.
The environmental, social, and economic benefits of recycling biosolids and residuals are large and significant. However, state regulatory overreaction to PFAS concerns could result in reductions in beneficial uses — just when more is being done to divert organics from landfills to reduce greenhouse gas emissions and utilize the resources in these materials.
Careful thinking is needed. The most concerning and regulated PFAS — PFOA and PFOS — are already mostly phased out of use, concentrations in biosolids and other residuals are declining as a result, and most of today’s biosolids and organic residuals are not major conveyors. Measured steps can be taken to reduce potential risks. But PFAS in biosolids, composts, and residuals is not a large, urgent, immediate threat to public health and the environment.
And remember, with regards to potential impacts of biosolids-borne PFAS on environmental organisms: these compounds have been in use for long enough that long-term studies – including bioassays — of biosolids applications have, although not deliberately, tested the potential hazards of PFOS and PFOA in a variety of land application scenarios. Not only have these long-term sites found minimal to no negative impacts, overall significant benefits have been shown. Soils have higher organic matter, higher micronutrient concentrations, better water-holding capacity, and better tilth. As a result, plant growth and resilience have been improved. And environmental receptors, from soil organisms to animals, have not been found to be detrimentally impacted; indeed, many have responded positively. The residuals used in those experiments almost certainly contained higher levels of PFOA and PFOS than materials being generated today. Therefore, those studies suggest minimal risk to site ecology and environmental organisms from these two widely used, longer-chain, more concerning PFAS in land applied biosolids and other residuals.
One likely future regarding the presence of PFAS in organic residuals is this: As is currently the case with PCBs, society will come to recognize that some PFAS will be in the environment in trace amounts for a long time. That’s reality. As long as they are not in concentrations that have been clearly found to be detrimental to public health or the environment, it may not be worth expending extraordinary effort and funds to reduce them further.
Currently, evaluations and treatments are needed, appropriate, and ongoing at industrially-impacted sites that are highly contaminated with PFOS and PFOA, where drinking water concentrations are above current health advisories — sometimes by orders of magnitude. These include sites that had petroleum-based fires (e.g., oil, gas) and PFAS industry waste sites. Efforts will and should continue to identify other sites where drinking water has been affected. Those may include evaluations of some sites where industrially-impacted biosolids and paper mill residuals were applied in the past.
Looking forward, now that PFOA and PFOS are phased out of use, appropriate steps should focus on developing robust data for modeling and corroborating acceptable levels in biosolids and other organic residuals and soils such that leaching will not affect drinking waters above public health advisory levels. These two chemicals may end up being added to the list of chemicals that are monitored in organics recycling programs. A further stage will be evaluation of the many other PFAS, including precursors that can break down to PFOA and PFOS, and whether or not they need to have screening levels and be monitored going forward or whether some of them, too, need to be phased out.
Those managing organic residuals should engage in the PFAS debate, to help guide thoughtful, science-based responses and understanding — in order to avert the potential that biosolids and other organics recycling programs will be disrupted by regulatory overreaction and public misconceptions related to the PFAS issue.
Ned Beecher is Executive Director of NEBRA, the Northeast Biosolids and Residuals Association (ned.beecher@nebiosolids.org). Sally Brown is a Research Associate Professor at the University of Washington in Seattle and a member of BioCycle’s Editorial Board.