Fracking isn't just a serious threat to drinkable groundwater supplies in the U.S. It turns out this controversial method of extracting underground natural gas might make the air we breathe unbreathable.

New York state's decision last December to ban fracking (technically called "hydraulic fracturing") within its borders was the most potent step yet taken to highlight the air pollution dangers caused by fracking.

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New York based its prohibition on a public health review that pointed out fracking's many health risks. These include "air impacts that could affect respiratory health due to increased levels of particulate matter, diesel exhaust, or volatile organic chemicals".

In September, an air monitoring study in New York, Arkansas, Colorado, Ohio, Pennsylvania and Wyoming found high levels of toxic pollutants such as the banned carcinogens benzene and formaldehyde in communities near drilling sites.

About 40 percent of the samples were above pollution concentrations considered unsafe by the federal government.

As a result, the air quality near fracking sites might not be safe to breathe, said the new study "Air Concentrations of Volatile Compounds Near Oil and Gas Production: A Community-Based Exploratory Study" published in the journal, Environmental Health. The report was produced by the Natural Resources Defense Council (NRDC).

The study also pointed out the analysis of air samples gathered in fracking sites in these states found those health risks could be considerable. It discovered many toxic chemicals in the air can cause at least five serious types of health problems: respiratory problems, cancer, birth defects, blood disorders and nervous system problems.

A study of birth defects in areas in Colorado with high concentrations of oil and gas activity discovered that mothers living near many oil and gas wells were 30 percent more likely to have babies with heart defects.

The study noted benzene and formaldehyde were in amounts hundreds of times higher than what is considered safe in some cases. Disturbingly, it found levels of eight volatile chemicals (including benzene, formaldehyde and hydrogen sulfate) exceeded federal guidelines for health-based risk.

"The citizens in these communities were experiencing health problems that they believe are linked to the oil and gas production near their homes," said study lead author David Carpenter and director of the Institute of Health and the Environment at New York State University at Albany.

"Chemical exposure is insidious and cumulative, and so it may take years to really understand the magnitude of impacts on people's health from oil and gas development."

About one in four Americans live within a mile of an oil or gas well.

"The health risks from fracking are not limited to what's in our drinking water--oil and gas operations are also poisoning the air we breathe," said NRDC senior scientist Miriam Rotkin-Ellman.

The report said Americans living near oil and gas drilling wells are vulnerable to fracking-related air pollutants such as formaldehyde and benzene.

A 2014 study in the peer-reviewed journal Environmental Health Perspectives found people residing near natural-gas wells were more than twice as likely to report upper-respiratory and skin problems compared to those living farther away.

The oil and gas industry, however, disputes these claims and said "Natural gas delivers local air and health benefits".

Energy in Depth, a group of the Independent Petroleum Association of America, claims the Pennsylvania Department of Environmental Protection reported that "cumulative air contaminant emissions across the state have continued to decline," despite a rise in fracking operations from 2008-12.