Francis DiGiano, Professor Emeritus
UNC Department of Environmental Science & Engineering
November 2023
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Historical Background on PFAS Concerns
DuPont began using PFOA (perfluorooctanoic acid) to manufacture Teflon at its Washington Works plant in Parkersburg, West Virginia in 1951. In 1981, female employees were removed from the Teflon production line because DuPont had noted birth defects among their babies. DuPont monitored the well water around the plant in 1984 and found elevated PFOA. A 1989 DuPont report indicated elevated deaths due to leukemia and a high number of kidney cancers among male workers plant-wide. Those who were exposed directly to PFOA were not separately assessed.
The 2019 film- Dark Waters- chronicles investigation into health issues by Rob Billott, a Cincinnati lawyer with a family connection to the area. This NYT article tracks Billott’s discovery path. Billott waited 7 years for a scientific panel investigating the toxicity of PFOA at DuPont’s Parkersburg facility to issue their report. In December 2011, the panel finally concluded a probable link between PFOA and kidney cancer, testicular cancer, thyroid disease, high cholesterol, pre-eclampsia and ulcerative colitis.
In about 2013, the EPA settled its lawsuit against DuPont assessing only a $16.5 million penalty for the company’s failure to disclose health risks found for PFOA that DuPont discovered in their laboratory toxicity tests. Health effects were not part of the lawsuit. This most likely pointed to the difficulty in proving definitively a cause and effect relationship. In addition to the penalty charge, EPA required DuPont to remediate drinking water with PFOA levels exceeding 0.4 ppb and phase out PFOA by 2015. DuPont never installed filtration systems at the city’s water treatment plant because PFOA was not found to exceed 0.4 ppb consistently. Of note, recent research has lowered the concentration of health concern by a thousand fold.
The Class Action Lawsuit settlement announced in Feb 2017 was for $670 mil. Levels of exposure in Parkersburg, both to plant workers and the community, were far greater than anywhere else in the U.S. But with advances in detection, the widespread presence of PFAS, albeit at relatively low levels, has been confirmed in many rivers and lakes. The NYT article also notes the ubiquitous presence of PFAS in the environment. In addition to water, humans are exposed via air, food and many products used in the home.
Hundreds of poly- and perfluoroalkyl substances (PFAS) are used in a very wide variety of products. As a class, PFAS are considered forever chemicals because they are not broken down in nature. An in-depth review of current knowledge and strategies to inform future research on the toxicity and human health effects was published in 2020. PFOA and PFOS are by far the most studied. Although phased out of production in the US, as forever chemicals, they are still in the environment. The suspected health effects include: altered immune and thyroid function, liver disease, lipid and insulin dysregulation, kidney disease, adverse reproductive and developmental outcomes, and cancer.
Epidemiological studies of populations examine the strength of association between exposure to PFAS and health outcomes using statistical methods. The robustness of findings depends on many factors: population size; representation by gender, age, socio-economic groups; and presence of a control cohort having little exposure. Clinical studies add data on specific vulnerabilities to exposure, e.g., to pregnant women using PFAS levels found in their blood serum as indicator of exposure. Many epidemiological and clinical studies have been reported over the last decade. However, the evidence to support a cause-effect relationship is not always strong as noted in this report from an Australian research center.
Toxicology is used to investigate adverse health outcomes systematically by exposing animals (in vivo), typically mice/rats and in cells/organ tissues (in vitro), to a range of chemical dosages. A dosage-response curve depicts the pattern of greater response rate with higher dosages. However, the dosages used in these studies are orders of magnitude higher than in the environment in order to observe definitive effects in days, weeks or months rather than over a human lifetime. The scientific challenge is how to extrapolate health risk downward to the level of environmental exposures. Studies often show a threshold dose below which the test animal tolerates exposure. This is also true for humans. Thus complete removal, though never practically possible, is not necessary.
In 2002, EPA updated its Health Advisory (HA) levels for PFOA and PFOS to 0.004 and 0.02 ppt, respectively. HAs assure no adverse health outcomes but are not enforceable. The concentrations selected by EPA are orders of magnitude lower than can be currently detected. EPA primary drinking water regulations instead establish a maximum contaminant level (MCL) that is based on an acceptable risk of one excess adverse health outcome in a population of 1 million. The proposed MCLs for PFOA and PFOS, scheduled for 2025, are both 4 ppt and only slightly above the current detection limit of about 2 ppt. These apply to the finished water leaving the water treatment plant. The 5th Unregulated Contaminant Monitoring Rule (UCMR) requires all water utilities serving more than 10,000 customers to measure 29 PFAS from 2023 to 2025 in finished water leaving their water treatment plants. The UCMR data will help EPA establish regulations for additional PFAS in the future.
PFAS from NC DEQ sampling on 7 days in 2020 at 5 Stations in Jordan Lake
Conclusion: PFAS is higher in Haw River Arm (CPF055C) than at all stations North of US 64 (CPF087D is very near the Cary/N Chatham County water intake).
PFAS in OWASA Raw Drinking Water and in Discharge from Wastewater Treatment Plant
Conclusion: PFAS is higher in Haw River Arm (CPF055C) than at all stations North of US 64 (CPF087D is very near the Cary/N Chatham County water intake).
PFAS in OWASA Raw Drinking Water and in Discharge from Wastewater Treatment Plant
Conclusion: PFAS is present in the protected watershed surrounding the two lakes of the OWASA raw water supply. The suspected source of PFAS is application of biosolids hauled from wastewater treatment plants in the region to spread on agricultural land. PFAS can sorb onto biosolids that are separated out from wastewater treatment plant flows. Equally important is the increase in PFAS after leaving the water treatment plant as observed in the effluent of the OWASA Wastewater Treatment Plant. Yet, there are no significant industrial sources of PFAS in the Chapel Hill-Carrboro service area. However, PFAS can enter water through uses within homes and commercial businesses and be subsequently discharged to the sewer. Municipal wastewater treatment plants do not include a process to remove PFAS because publicly owned treatment works are required to remove trace organic contaminants. The discharge from the OWASA Wastewater Treatment Plant [8 mil gal per day] is to Morgan Creek that enters at the northern end of Jordan Lake, 10 miles above the Cary/N Chatham County Water Intake. A similar increase in levels of PFAS is likely occurring through community/light industrial water uses that accounts for PFAS measured in the effluents of the South Durham [10 mil gal per day] and Triangle (Durham County) [5 mil gal per day] Wastewater Treatment Plants. These discharge into New Hope Creek and Northeast Creek, respectively at the north end of the lake, both located about 14 miles above the Cary/N Chatham County Water Intake.
PFAS Monitoring at Cary Water Intake
Conclusion: The wide variation in PFAS concentrations could be due to changes over time in lake volume and/or mass input of PFAS in wastewater discharged up-lake from OWASA, South Durham and Durham County Regional Treatment Plants. Lake volume increases during heavy rainfalls and decreases during drought periods. If PFAS discharges remain constant (same mass amount), their concentrations will be lower when the lake level is higher than normal because of greater dilution and conversely, higher at lower than normal lake levels. Lake level can rise 10 to 15 ft during heavy rains and 30 ft during hurricanes. That’s because the Army Corps of Engineers stores water by closing the gates at the dam to minimize flood damage downstream. As a result, lake volume can increase by 25 to 50%, thereby diluting contaminant concentrations. However, the dilution effect does not explain most of the bar chart data. Lake level was near normal in November 2019 but PFAS was at its highest. PFAS was also high in February 2020 when the lake was 12 ft above normal that shows the opposite of a dilution effect. The lake was near normal for samplings in August 2019, May 2020, November 2020, May 2021 and August 2021. The only agreement with a dilution effect was in February 2021 when lake level increased by 14 ft and PFAS decreased to its lowest value. Temporary increases in mass inputs of PFAS from various sources may offer a better explanation for the highest PFAS values. PFAS entering from the Haw River would seem to have little impact. The UNC-Charlotte Reservoir Model in the 2019 UNC Collaboratory Report of Jordan Lake predicts a low percentage of water from Haw River moves as far north as the Cary/N Chatham County water intake.
Conclusion: PFOS and PFOA, the two PFAS components considered for regulation by EPA are very low (under 10 parts per trillion, ppt) at the water intake.
PFAS Monitoring at Cary Finished Water Leaving Treatment Plant
Conclusion: Activated carbon is the adsorbent used at the Cary Water Treatment Plant to remove PFAS. In 2020, a switch was made to a more effective type of activated carbon. Plant staff believe this caused the subsequent reductions in total PFAS and PFOA+PFOS.
PFAS Most Recent (5-9-23) in Cary Finished Water Leaving Treatment Plant
Conclusion: Explanation of terms. RL = reporting limit, i.e., detection limit; ng = nanograms per liter which is the same ppt, parts per trillion. Only the four PFAS components shown in blue were above detection limit, the highest level being 7.2 ppt. PFOS and PFOA are below their detection limits.
The agreement requires the City of Burlington and it’s largest industries to take specific, concrete steps designed to alleviate the polluting discharges problem. As the Haw Riverkeeper, Emily Sutton was an important participant in the negotiations that resulted in the Settlement Agreement referenced above. 