How healthy is Barnett Shale?

The hydraulic fracturing process carried out in horizontal shale gas wells has had a lot of criticism for its environmental record. The process is very water-intensive and there are many claims that it can contaminate nearby drinking water. The Texas Commission on Environmental Quality, meanwhile, has carried out a study into air pollution from 94 oil and gas sites in the Barnett Shale area of Northern Texas – all within half a mile of residential areas – and found elevated concentrations of benzene, a known carcinogen, in several places.

The TCEQ’s very diplomatic media statement says two locations had “relatively high” concentrations – they were many, many times the organisation’s own short-term health-based comparison value of 180 parts per billion (ppb).  The long-term value of 1.4ppb was exceeded in another 19 sites.

At Targa’s North Texas LP Bryan Compressor Station, the maximum 1-hour average concentration was more than double the recommended level, at 370ppb, and as high as 1,100ppb at one sample. Another sample from a Devon Energy natural gas wellhead in Wise Country was 15,000ppb, although the study notes that this was only 5 feet from the source – most other samples ranged from 50 feet to half a mile. In both cases the companies were notified and undertook maintenance, which resulted in far lower concentration registering at subsequent tests. The hit rate for high levels was fairly low, as this graph shows:

TECQ

Source: TECQ

But one of the complicating factors is that long-term exposure is very different to short-term exposure. As the TCEQ notes, short-term exposure to such levels aren’t known to harm people in themselves, but “elevated short-term levels are of potential concern due to their contribution to long-term (ie lifetime) cumulative exposure levels because benzene is a known human carcinogen”.

There was no mention we could find of the other 19 sites that exceeded long-term comparison levels, or of other sites that had elevated levels of other compounds such as ethane and carbon disulfide – but the TCEQ pledges to take various actions to guard against such high levels, including installing two auto-monitors, carrying out more investigations, and responding to citizen complaints within 12 hours. Whether it’s enough for nearby residents remains to be seen.

Critics of the shale gas industry such as Matt Simmons have pointed to the potential health risks of extracting the gas as a reason for scepticism about a shale gas boom. Meanwhile those in the industry either maintain that there are no health risks, or suggest, as one analyst we spoke to put it, ‘technology will take care of it’.

H/T to the Houston Chronicle, which has the full-text of the report.

Related links:
No concern from natural gas in Fort Worth, says state
(Houston Chronicle)
Fracking defended, just in case anyone planned to regulate it (FT Energy Source)
EPA: Chemicals found in Wyoming drinking water might be from fracking (ProPublica)

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