Fun with Acronyms: PFAS, PFOA, NRDA, and NEBA, and their relation to Environmental Risk Assessment
NEBA
NEBA (pronounced like “knee bah”) stands for “net environmental benefit analysis.” Here is the most common way that term arises: A PRP, potentially responsible party, contaminates the environment, for example a marine oil spill. Quickly, a decision must be made about what to do with the contamination. There are several choices of clean-up options, such as “do nothing,”, and, for example, use chemical dispersants. The decision-maker does a risk assessment of each option, in this case, usually, an ecological risk assessment. Often, each option has (pardon the judgement terms) many good effects and bad effects, and by evaluating, considering the good and bad, each option will have some net effect.
So, the decision-maker starts with the “do nothing” alternative and looks at its likely good and bad effects on the environment. That net is then compared to the net of the good and bad effects of chemical dispersion. Now the decider compares chemical dispersion with doing nothing. If the chemical dispersion has a net benefit compared doing nothing, then chemical dispersion is a viable option. If not, then it would be rejected and the choice would be do nothing. Next, if chemical dispersion was viable, it would be compared with other options, such as burning in place, and the option with the greater net benefit would be the option chosen. Of course a real decision in a large oil spill or other massive contamination is complex and effects of the contamination and the cleanup options might be quite different for different areas and could vary with time – but the concept that the net benefits of the options should be compared is a solid criteria – and it makes clear that any response option, as well as doing nothing, will have both beneficial and unwanted effects.
NRDA
NRDA (pronounced like “nerd ah”) stands for “Natural Resources Damage Assessment.” The need for a NRDA arises from two laws, the Superfund (CERCLA) and OPA (Oil Pollution Act). Besides requiring the cleanup of the contamination by the PRP, both laws require that natural resources be restored to the state that they were at before injury from the environmental contaminants. If the natural resources cannot be restored, some compensation is required. Who gets the compensation - federal, state, tribal, local – all of the above? The laws allow the appointment of trustees to oversee and adjudicate the process. One of the primary responsibilities of Trustees under both CERCLA and OPA is to assess the extent of injury to a natural resource and determine appropriate ways of restoring and compensating for that injury. A natural resource damage assessment (NRDA) is the process of collecting, compiling, and analyzing information to make these determinations. Trustees have the option of using the methodologies prescribed by the Department of the Interior (DOI), 43 CFR Part 11, or the Department of Commerce's National Oceanic and Atmospheric Administration (NOAA), 15 CFR Part 990. (https://www.epa.gov/superfund/natural-resource-damages-primer#nrt ) Generally, the NOAA regulations are used for marine incidents and the DOI for land. In general, a “risk assessment” of the type we have been studying is not done. So when they (the trustees, the courts, whoever) are deciding, how much value is placed on an eagle versus a seagull? A green hill versus a brown hill? When there is a lot of money available, including money for the PRP’s lawyers, the NRDA can be an ongoing donnybrook. For smaller incidents, the PRP, agencies, and NGOs sort it out. There is no “right” answer to the value of a seagull.
PFOA and PFOS
PFOA, Perfluorooctanoic acid, PFOS Perfluorooctanesulfonic acid or more generic, PFAS, perfluoroalkyl and polyfluoroalkyl substances, a term that includes PFOA, PFOS, and similar compounds, are contaminants of note and should require environmental risk analyses. What are they? Chemically, they are 8 or so hydrocarbon units in a tail, attached to a hydrophilic head. Except that hydrocarbons have the hydrogen replaced by fluorine – they are fluorocarbons. The fluorocarbon tail has the useful property that it is repels both water and non-polar compounds, they are both hydrophobic and lipophobic, while the hydrophilic head attracts water. PFAS are anthropogenic chemicals that do not exist in nature, unless we put them there. They are very persistent. They have many very useful properties, and were used in many consumer products that required resisting staining. However, for the last 20 years they have been phased out of most of those products. While it is possible to ingest PFAS, for example it was used in carpets and children playing on the carpet could ingest the chemical directly, or ingest via dust, or in food that was contaminated – fish or meat, those exposures should lessen with time, as the chemical is phased out. Regarding risk assessment, though, the current issue is most often PFAS in groundwater. And, most often, groundwater that has been contaminated by firefighting foam from fire training areas. Those foams often contained PFAS. Since it was water soluble and did not cling to soil particles, rainwater or fire suppression water carried the PFAS to groundwater. Since PFAS are persistent and easily transported in groundwater, the fate and transport is as straight forward as any groundwater contamination. So, given a few million dollars for test and monitoring wells and a few hundred thousand for groundwater experts and modeling, one can compute the concentration in drinking water wells. However, unlike consumer products, the exposure via groundwater may increase with time, as the plume of chemicals moves down gradient and into drinking water wells.
So, the risk assessment issue is the toxicology – the dose response relationship. Here my friend, the font of all knowledge, Wikipedia, lets us down or up. “PFOA is a carcinogen, a liver toxicant, a developmental toxicant, and an immune system toxicant, and also exerts hormonal effects from reduced birth size, physical developmental delays, endocrine disruption, and neonatal mortality.” It is true that there have been myriad studies: of human epidemiology, animal toxicity testing, animal studies and so on. Many have shown some relation between PFAS exposure and disease. But other studies have not noted such effects at relevant doses. Wikipedia does a disservice by uncritically reporting these positives. The likely beneficiaries of the overstatements are lawyers, who can draw “victims” from anyone who can prove an exposure to PFAS and one of the many diseases or conditions attributed to PFAS.
The question is the response at relevant doses. For one, it turns out that most people have some PFAS in their blood – it was ubiquitous and leaves the body very slowly. But the concentrations in the body are very low. Epidemiology seems to show some relation to disease, in some studies, but not in others. Most animal studies were done at very high doses – far higher than likely human exposures. Unlike the definitive statements in Wikipedia, the ASTDR says, “Studies in humans and animals are inconsistent and inconclusive but suggest that certain PFAS may affect a variety of possible endpoints. Confirmatory research is needed.” https://www.atsdr.cdc.gov/pfc/docs/pfas_clinician_fact_sheet_508.pdf .
I poked around the scientific literature and would agree with ASTDR. So, how do you do a dose-response if the science is “inconsistent and inconclusive?” The EPA did publish some “advisories” and now requires public drinking water suppliers to monitor PFOS and PFOA in drinking water and also published a “health advisory” as follows: “To provide Americans, including the most sensitive populations, with a margin of protection from a lifetime of exposure to PFOA and PFOS from drinking water, EPA has established the health advisory levels at 70 parts per trillion.” Note how small a concentration that is, 0.07 ppb. Since the science can’t give you a reliable dose-response relation, a risk assessor would need to work to the 70 ppt standard, but have no real assurance about the effects of that dose. We would expect it is very conservative. But let me play with some numbers. The ASTDR give a half-life of PFOS of 6 years. It also announces the body burden of 95% of the population as 6.3 ppb. That would be in the body water, which is about 45 liters. I’ll spare you my pharmacokinetic calculations, but the concentration in water that would result in a steady state body burden of 6.3 ppb, is 69 ppt, almost exactly the concentration EPA recommends in the drinking water. That could be a coincidence, it could be Dr. Perkins’ faulty back-of-the-envelope calculations, or it could be that the EPA just did about what I did and assumed that 95% of the population has that level of PFOS and doing well, the amount of PFOS in the water that supports that level seemed “safe.” With that, I’ll stop this brief treatise and bid you all – have fun with acronyms.