Thursday, 29 January 2015

Shale gas health studies from the USA: Are they relevant to the UK?

Public Health England has looked into the potential health impacts of shale gas extraction in the UK, and concluded that "the potential risks to public health from exposure to the emissions associated with shale gas extraction will be low if the operations are properly run and regulated".

Nevertheless, it is clear that concerns remain among the public at large, promoted in no small part by the claims of anti-fracking groups. Claims about the public health impacts of shale gas extraction seem to run amok, but there are precious few peer-reviewed publications that actually document actual public health impacts from the process.

Indeed, the only peer reviewed studies to document any such effect is that published by the Colorado School of Public Health, McKenzie et al. (2012) and McKenzie et al. (2014). These papers feature prominently in  anti-fracking literature. Indeed, they are a particular favourite of electrical engineer Mike Hill, who features prominently in the Lancashire anti-fracking movement (and recently gave evidence to the Lancashire County Council on Cuadrilla's current planning applications). In his much-vaunted letter to the Lancet, the McKenzie papers are the only cited papers that document any potential health impacts.

As an aside, note that the claims made by Mr Hill in his public presentations on the topic, as documented on the Drillordrop website, are not actually backed up in his Lancet letter. Mr Hill claims to cite peer-reviewed papers by MIT and Princeton, however no such papers are present in his Lancet letter. He claims that he "conclude[s] that there was a 30% increase in birth defects if you live within 10 miles of a fracking well [and] there was a 38% increase in cancers and congenital heart defects". However, a brief perusal of the Lancet letter itself will reveal that Mr Hill made no such conclusions.

The failings of the McKenzie papers have been discussed at length. In the 2012 paper, McKenzie et al. fail to account for the fact that her "drilling" samples were taken 1 mile downwind of a major interstate (motorway), while her baseline samples were taken 4 miles upwind of the motorway. It is hardly surprising therefore that they found an increase in air pollution in the "drilling" samples.  

Meanwhile, the 2014 paper was publicly disavowed by Dr. Larry Wolk, Chief Medical Officer and Executive Director of the Colorado Department of Public Health and Environment. In his rebuttal, he noted that
"the authors did not consider the effect that other risk factors may have played (examples: smoking, drinking, mother’s folic acid intake during pregnancy, access to prenatal care, etc)" 
"the study showed decreased risk of pre-term birth with greater exposure. [...] Example: The study data showed that the nearer the mother lived to a well, the less likely the mother was to give birth prematurely or to have a low-birth-weight baby." 
"the statistical differences in birth defects were minuscule"
concluding that:
"we disagree with many of the specific associations with the occurrence of birth defects noted within the study. Therefore, a reader of the study could easily be misled to become overly concerned."
However, lets leave these criticisms and rebuttals to one side for a minute, and pretend that the McKenzie et al. findings are robust and genuine. Would they in that case be relevant to the current UK discussion?

No, they would not. The data collected by McKenzie et al. cover practices that are not allowed in the UK. Therefore the McKenzie data is meaningless for the UK context, and self-professed "experts" such as Mr Hill should desist from claiming otherwise.

From McKenzie et al. (2012) we learn about the activities being conducted at the well pads examined in their studies:
"The GCPH worked closely with the NGD operators to ensure these air samples were collected during the period while at least one well was on uncontrolled (emissions not controlled) flowback into collection tanks vented directly to the air." 
"Samples were collected over 24 to 27-hour intervals, and samples included emissions from both uncontrolled flowback and diesel engines." 
"Of the 12 wells on this pad, 8 were producing salable natural gas; 1 had been drilled but not completed; 2 were being hydraulically fractured during daytime hours, with ensuing uncontrolled flowback during nighttime hours; and 1 was on uncontrolled flowback during nighttime hours."
Uncontrolled flowback, where gases are vented directly to the atmosphere, is not allowed in the UK. Operators will be required by the Environment Agency to use green completions, where these emissions are captured. From the government response to the MacKay and Stone report:
"The Environment Agency considers that ‘green completions’ are BAT (Best Available Technology) for production facilities. Making green completions part of BAT will mean that producers will be required to use new technologies that will help limit or stop emissions"
To conclude, the McKenzie et al. papers are the only peer-reviewed documentation of shale gas public health impacts. The flaws in these papers are well established. Even so, the data they present are not relevant to a UK setting, because they are measuring processes that are not allowed in the UK. When commentators refer to important differences between USA and UK regulations, this is the kind of thing they are talking about. Self-appointed "experts" who reference these papers in a UK context without highlighting this important distinction are misleading the public.

1 comment:

  1. It doesn't add up...6 February 2015 at 02:42

    Prof Paul Younger (writing in The Times) has an interesting observation to make about wilful ignorance of studies in the UK: