• 54 of the compounds are organic; of these 27 are considered readily biodegradable.

• 21 chemicals have high theoretical oxygen demands and are used in concentrations that present potential treatment challenges.

• Most of the HF chemicals evaluated were non-toxic or of low toxicity.

• 4 were classified as Category 2 oral toxins and 1 as a Category 1 inhalation toxin according standards in the Globally Harmonized System of Classification and Labeling of Chemicals; however, toxicity information was not located for thirty-four of the HF chemicals evaluated.

Volatilization is not expected to be a significant exposure pathway for most HF chemicals, they noted. However, the gaps in toxicity and other chemical properties suggests deficiencies in the current state of knowledge, they concluded, highlighting the need for further assessment to understand potential issues associated with HF chemicals in the environment.

Dr. William Stringfellow said he conducted the review of fracking contents to help resolve the public debate over the controversial drilling practice. Fracking involves injecting water with a mix of chemical additives into rock formations deep underground to promote the release of oil and gas. It has led to a natural gas boom in the US, but it has also stimulated major opposition.

The industrial side was saying, “We’re just using food additives, basically making ice cream here.” On the other side, there’s talk about the injection of thousands of toxic chemicals. As scientists, we looked at the debate and asked, “What’s the real story?”

—William Stringfellow

The analysis revealed some validity to the claims of both sides, but with big caveats. Fracking fluids do contain many nontoxic and food-grade materials, as the industry asserts. But if something is edible or biodegradable, it doesn’t automatically mean it can be easily disposed of, Stringfellow noted.

Even ice cream manufacturers have to treat dairy wastes, which are natural and biodegradable. They must break them down rather than releasing them directly into the environment.

—William Stringfellow

The team found that most fracking compounds will require treatment before being released. And, although not in the thousands as some critics suggest, the scientists identified eight substances, including biocides, that raised red flags. These eight compounds were identified as being particularly toxic to mammals.

There are a number of chemicals, like corrosion inhibitors and biocides in particular, that are being used in reasonably high concentrations that potentially could have adverse effects. Biocides, for example, are designed to kill bacteria—it’s not a benign material.

—William Stringfellow

They’re also looking at the environmental impact of the fracking fluids, and they are finding that some have toxic effects on aquatic life.

Support for the study came from the University of the Pacific, the Bureau of Land Management and the state of California.