SOURCE: Houston Chronicle

DATE: October 31, 2017

SNIP: Urban air pollution in the U.S. has been decreasing near continuously since the 1970s.

Federal regulations, notably the Clean Air Act passed by President Nixon, to reduce toxic air pollutants such as benzene, a hydrocarbon, and ozone, a strong oxidant, effectively lowered their abundance in ambient air with steady progress.

But about 10 years ago, the picture on air pollutants in the U.S. started to change. The “fracking boom” in several different parts of the nation led to a new source of hydrocarbons to the atmosphere, affecting abundances of both toxic benzene and ozone, including in areas that were not previously affected much by such air pollution.

As a result, in recent years there has been a spike of research to determine what the extent of emissions are from fracked oil and gas wells – called “unconventional” sources in the industry. While much discussion has surrounded methane emissions, a greenhouse gas, less attention has been paid to air toxics.

[W]herever hydrocarbons are produced, refined or stored, there will be some emissions of pollutants. In the age of fracking, the large operations at conventional well sites have been replaced by hundreds of well pads dotting the landscape. Each requires the transportation of water, chemicals and equipment to and from these pads as well as the removal of wastewater, and none is regulated like any larger facility would be.

As a result, unconventional production has not only increased truck traffic and related emissions in shale areas, but also established a renewed source of hydrocarbons. They enter the atmosphere from leaks at valves, pipes, separators and compressors, or through exhaust vents on tanks. Together with nitrogen oxides emissions, largely from diesel engines in trucks, compressors and drilling rigs, these hydrocarbons can form significant amounts of harmful, ground-level ozone during daytime.

[T]he increase of hydrocarbon emissions has also led to the resurgence of an air toxic thought to be a story of the past in the U.S.: benzene. Unlike ozone, which is widely monitored, benzene is not. However, since it is a known carcinogen, it has long been on the radar of regulatory agencies.