Minnesota Pollution Control Agency Suppressed Report by its Environmental Science Contractor

As supporting information for a presentation at SETAC 2015 on White Hat Bias, this post includes a link to the report prepared by Earth Tech, an environmental consulting company, for the Minnesota Pollution Control Agency (MPCA) in 2008. The report was an attachment to an email that was included in MPCA’s response to a FOIA request filed by PCTC in 2011. The report, titled Identification of Sources of PAHs in Urban Stormwater, included this summary of the USGS identification of refined coal tar-based pavement sealants (RTS) as a significant source of PAHs in urban sediments:

Mahler, 2005 studied PAH concentrations in coal tar sealants used for asphalt. During this study, a signature or ratio of PAH components specific to pavement sealers was not identified…Thus, fingerprint or signature analyses can not yet be used to separate sealant source PAHs from various other urban sources yielding heavy PAHs… Scoggins et al. (2007), tried to identify the sources of PAHs in Austin, Texas, area stream using ratio methods, but were unsuccessful, having found no significant clustering of field data with known source data. [Earth Tech (2008). Identification of Sources of PAHs in Urban Stormwater. Prepared for MPCA. p. 34.]

The report was reviewed by MPCA research scientist Bruce Wilson. Stormwater Management Unit scientist Keith Cherryholmes forwarded Wilson’s review to Dr. Judy Crane noting that Wilson did not believe the Earth Tech report supported RTS as the source of PAHs:

Would you have a little time to look at the re-write of the first PAH report you reviewed for us. Bruce Wilson does not think it really makes a case for coal tar-based sealants as being the source of PAHs in stormwater sediments.

The email is available here.

The outcome was that MPCA did not release the Earth Tech report. Instead, Dr. Crane and several colleagues wrote their own report that did not let what had been known for years about the inadequacies of using PAH ratios as  source identification method stand in the way of identifying RTS as the source of PAHs in storm water detention ponds. As a source identification method, Dr. Crane relied on the PAH ratio comparisons that appeared in Mahler et al. (2005).

Years later, in another paper published in 2014, Dr. Crane admitted what was already well known at the time she wrote her report, what Earth Tech had explained in its 2008 report, about the limitations of using PAH ratios as a method of source identification:

Although many of the ponds corresponded to a source profile for CT-sealants, scatter in the double-ratio plots was indicative of multiple sources of PAHs. …. Some ponds that were within the range of CT-sealants in one or two plots were outside the range in another double ratio plot. … These types of environmental forensic analyses are semi-quantitative, do not account for varying rates of weathering of PAH compounds, and work best at sites dominated by a single source (Battelle Memorial Institute et al. 2003). Application of PAH ratios for air samples has also shown that these ratios can produce contradictory source results (Katsoyiannis et al. 2011). [Crane 2014].

It is unknown whether Dr. Crane returned the awards she received from legislative groups for “identifying the source of PAH contamination.” What is known is that the report Dr. Crane and her employer, MPCA, should withdraw, was used as a rationale for banning RTS in Minnesota. What is also known is that MPCA had this information in 2008, explained in the suppressed Earth Tech report.

UPDATE: Because of time constraints, the final presentation on White Hat Bias at SETAC 2015 did not include discussion of MPCA’s lapse in scientific integrity.


Leave a Response