Hidden pollutants in shale gas development raise environmental concerns, new review finds

Shale gas has become a cornerstone of the global energy transition, supplying large amounts of natural gas through horizontal drilling and hydraulic fracturing. But a new scientific review warns that the extraction process also generates vast quantities of waste that carry a complex mixture of emerging contaminants, many of which pose potential risks to ecosystems and human health.

In a comprehensive review published in New Contaminants, researchers systematically examined the sources, characteristics, and environmental risks of emerging contaminants released throughout the shale gas lifecycle. The study highlights that solid wastes and wastewater produced during drilling, hydraulic fracturing, and gas production act as major carriers of persistent and biologically active pollutants.

“Shale gas is often promoted as a cleaner fossil fuel, but its waste streams are far from benign,” said corresponding author Lilan Zhang. “Our review shows that these wastes consistently contain emerging contaminants that are difficult to remove and may persist in the environment for long periods.”

The researchers identified a wide range of contaminants, including persistent organic pollutants such as polycyclic aromatic hydrocarbons and per and polyfluoroalkyl substances, endocrine disrupting chemicals like nonylphenol ethoxylates and phthalates, antimicrobial biocides, microplastics, and antibiotic resistance genes. Many of these substances are known for their persistence, toxicity, and potential to accumulate in living organisms.

According to the review, drilling operations generate large volumes of solid waste known as drilling cuttings, which can contain high levels of organic pollutants originating from chemical additives in drilling fluids. Improper storage or disposal of these materials may allow contaminants to leach into soil and water over time.

Hydraulic fracturing produces even greater environmental challenges. Large volumes of water mixed with chemical additives are injected underground, and a portion of this fluid returns to the surface as flowback and produced water. This wastewater has been shown to contain a complex mixture of chemical and biological contaminants, including antibiotic resistance genes that could contribute to the global spread of antimicrobial resistance.

“Even when these contaminants occur at low concentrations, the sheer volume of wastewater generated worldwide means that the total environmental release can be substantial,” said co first author Yuejia Zhang. “This creates long term risks that are often overlooked in conventional environmental assessments.”

The review also raises concerns about current waste treatment technologies. Existing methods are primarily designed to remove oils, salts, and suspended solids, not trace level emerging contaminants. In some cases, treatment processes may transform pollutants into new compounds that are equally or more toxic.

“Treating shale gas waste is not just a matter of meeting discharge standards,” Zhang explained. “Without targeted strategies for emerging contaminants, treatment systems may simply shift pollutants from one form to another.”

The authors emphasize the need for integrated management strategies that combine improved chemical disclosure, advanced treatment technologies, and long term environmental monitoring. They also note that shale gas producing regions such as the United States and China face different contamination profiles and regulatory challenges, underscoring the importance of region specific solutions.

By bringing together evidence from studies around the world, the review provides a clearer picture of how shale gas development can act as a pathway for emerging environmental contaminants. The authors hope their findings will inform policymakers, industry leaders, and researchers working to balance energy production with environmental protection.

“Our goal is not to halt shale gas development,” Zhang said. “It is to ensure that energy security does not come at the cost of long term environmental and public health risks.”

=== 

Journal reference: Zhang Y, Chen K, Zhang Y, Zhang L. 2026. Emerging contaminants in shale gas extraction: sources, characteristics, and potential risks. New Contaminants 2: e001  

https://www.maxapress.com/article/doi/10.48130/newcontam-0025-0021  

=== 

About the Journal:

New Contaminants (e-ISSN 3069-7603) is an open-access journal focusing on research related to emerging pollutants and their remediation.

Follow us on Facebook, X, and Bluesky.