Fracking can pollute the air with carcinogenic formaldehyde at levels twice as high as medical students experience when dissecting dead bodies, a new report has found.
Tests around shale gas wells in the US also found that levels of benzene were up to 770,000 higher than usual background quantities.
The quantities were up to 33 times the concentration that drivers can smell when filling up with fuel at a petrol station.
Levels of hydrogen sulfide, were also up to 60,000 times an acceptable odour threshold.
The exposure a person would get in five minutes at one Wyoming site is equivalent to that living in Los Angeles for two years or Beijing for eight and half months.
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Tests have shown that one hour of exposure to chemicals at that level would cause fatigue, loss of appetite, headache, irritability, poor memory and dizziness. Both benzene and formaldehyde cause cancer.
“Community-based monitoring near unconventional oil and gas operations has found dangerous elevations in concentration of hazardous air pollutants under a range of circumstances,” said Lead researcher, David Carpenter from the University at Albany in New York.
“Our findings can be used to inform and calibrate state monitoring and research programs.”
The UK Government has argued that gas can play an important role in tackling climate change cost-effectively by replacing much dirtier coal-fired power plants.
Studies have predicted that the new energy source could provide more than a third of the nation’s gas supplies within 20 years.
But communities have reacted with anger to plans for fracking, claiming that chemicals used to fracture rock to extract the gas could leech out into the environment.
However experts claim that Britain would monitor sites more thoroughly than in the US and that companies which allowed ‘fugitive emmissions’ would face prosecution under the Clean Air Act.
Prof Paul Monks, Professor of Atmospheric Chemistry and Earth Observation Science at the University of Leicester, said:
“The work suggests significant emissions of a wide range of volatile compounds from shale gas extraction. Many of these compounds are of concerns to air quality and therefore health, but the situation in the US is not directly transferable to the UK owing to the different legislative regulation regime and the different nature of UK shales.
“Recent UK work looking at Lancashire shales has shown significantly lower concentrations of these air toxins such as benzene.”
Dr Rob Westaway, Senior Research Fellow at the University of Glasgow, added: “One of the key difficulties faced by the incipient UK shale gas industry is that it will be required to operate to far higher environmental standards than currently prevail for shale gas projects in North America, as regards a whole host of environmental issues.
“For example, DECC has determined that (except as a safety precaution in emergencies) all UK shale gas wells will have to capture and process or treat all gases released rather than venting or flaring them as is customary in the USA and Canada.
“Furthermore, at all UK sites the water required for fracking will have to be stored, between fracking operations, in enclosed tanks rather than in open ‘lagoons’.
Prof Andrew Aplin, Professor of Unconventional Petroleum at Durham University, said: “Whilst pollutants such as benzene and toluene occur in the atmosphere of every urban environment, this study shows that very high concentrations of hydrocarbons and hydrogen sulphide were found in the very local vicinity of some specific oil and gas operations in the US.
“Poor industrial practice and insufficient regulation can of course result in locally elevated concentrations of atmospheric pollutants in many urban and industrial situations – this is why the UK passed the Clean Air Act in 1956.
“Industrial emissions are tightly regulated in the UK and these regulations currently apply to those who have been producing conventional oil and gas in the UK for many years. The same rules will apply to any future producers of shale gas and it is incumbent upon us to make sure that the same rules are followed and enforced.”
The fracking industry also said it was unlikely that dangerous chemicals would be vented into the atmosphere.
Ken Cronin, chief executive of UK Onshore Oil & Gas (UKOOG), the industry trade body: “In the UK, at all sites where drilling for shale gas will take place, air quality will be monitored before, during and after any activity, with strict controls on emissions overseen by the Environment Agency.
“Leading experts, including Professor David Mackay and Doctor Timothy Stone, have praised the industry’s standards which set out good practice for minimising fugitive emissions.”
The research was published in the journal Environmental Health.