In Response to the U.S. EPA Health Advisories
"Perfluorinated Compounds Monitoring in Response to the U.S. EPA Health Advisories"
Presented by: Andy Eaton, Vice President and Technical Director
In May of this year, U.S. EPA issued new Health Advisories (HAs) of 70 ng/L for PFOS and PFOA, two ubiquitous chemicals that are used in many products and part of a family of a large number of short and long chain perfluorinated compounds (PFCs). A number of states have already established guidance levels for these two compounds, some as low as 20 ng/L. From 2013-2015, the UCMR3 program included monitoring of these two compounds plus 4 other PFCs, using EPA method 537, an LC/MS/MS method with solid phase extraction to concentrate the PFCs.
Reporting limits in the UCMR3 program ranged from 10 to 90 ng/L, depending on the compound, with PFOS and PFOA at 40 and 20 ng/L respectively. At these reporting levels nearly 200 systems had detections of PFCs, and over 150 had detections of PFOS and/or PFOA. Although this is a very small fraction of the total number of systems tested in UCMR3 (~3%), detections were found in 20 states, and the high reporting limits in UCMR3 relative to the HAs makes it likely that the actual occurrence of PFCs in water supplies may be significantly higher. A review of Eurofins Eaton Analytical’s UCMR 3 data set, representing ~40% of the national UCMR3 database, shows more than 10% of samples with detectable PFCs, versus only about 1-2% of samples if the data are screened at the UCMR3 MRL. Studies conducted by Glassmeyer et al (2013) have also shown that PFC frequency of PFC detection in finished drinking waters goes up markedly at lower reporting limits. The potential for much greater frequency of detection demonstrates the need for both proactive monitoring and well thought out communications.
Although the UCMR3 reporting limits were high, method 537 has internal minimum reporting levels in the low ng/L range and many labs have demonstrated the ability to measure accurately and precisely below the UCMR3 MRL level. It is likely that most new monitoring will be conducted using the lower MRLs of 2 to 5 ng/L, which will inevitably result in more detections as noted from our own experience. As utilities and states respond to the HA with recommendations for monitoring it is important to understand some of the implications and to try to provide guidance to help with monitoring.
EPA Method 537 includes a requirement for a Field Blank (FB) with each set of samples from the same site. The FB is used to reduce the possibility that detections of PFCs are due to contamination during sampling as opposed to in the sample itself. In the UCMR3 program there were very few PFC detections that required resampling of field samples. However this was at least in part due to the fact that field blanks were screened at levels that were higher than the method reporting limits (screening instead was at 1/3 of the UCMR3 MRLs). While our own experience is that even at 2-5 ng/L reporting limits FB do not seem to be a problem, it is important that both labs and utilities take this into consideration to avoid reporting false positives.
While the UCMR3 program monitored 6 PFCs, there are a large number of PFCs and precursors that are present in the environment and EPA 537 includes 12 PFCs (and the ability to potentially measure others). Based on UCMR3 experience it is clear that monitoring will likely detect additional PFCs beyond PFOS and PFOA. These PFCs are anthropogenic compounds with unknown health effects and it will be important to try to put detections in context. Detection will likely engender concern from utilities and the public alike. ASDWA is in a unique position to help utilities respond to these detections.
We will discuss existing data sets, taking into consideration the different reporting levels, and provide some suggestions on key elements that should be considered going forward.