Researchers found "significantly higher" rates of birth defects in babies born near mountaintop removal mining sites than those in non-mining areas, according to a new study released last week.

Mountaintop removal mining is a particularly environmentally destructive type of resource extraction that involves using explosives to blow the tops off of mountains to expose coal underneath the soil and rock. The unusable dirt and gravel are then disposed of in adjacent valleys and streams. MTR is used prominently in the Appalachian region of the eastern United States.

The mining study, published in the journal Environmental Research, examined over 1.8 million live birth records from 1996 to 2003 using National Center for Health Statistics data from the central Appalachian states of West Virginia, Virginia, Kentucky and Tennessee.

It found that rates for six out of seven types of birth defects -- circulatory/respiratory, central nervous system, musculoskeletal, gastrointestinal, urogenital and "other" -- were increased near MTR sites. The research suggests that contaminants are released into nearby environments from MTR, and that many of the contaminants are known to impair fetal development.

"Rates for any anomaly were approximately 235 per 100,000 live births in the mountaintop mining area versus 144 per 100,000 live births in the non-mining area," the study says. Although not as high as near MTR sites, it also found increased incidences of birth defects in communities near underground mines.

"This is monumental," said Bob Kincaid, the president of Coal River Mountain Watch (CRMW). He told The Huffington Post that this latest research is just one more among a dozen or so earlier studies "that shows that the coal industry, especially mountaintop removal, is engaged in the wholesale poisoning of Appalachia."

"For those who actually pay attention to science, it's irrefutable,” Kincaid said. "Would it be more obvious if the coal industry were using machine guns or gas chambers?"

Another study published in May by researchers from West Virginia University found that residents of communities near MTR mining sites suffered poorer health and a lower quality of life.

While the recent Environmental Research study reveals a spike in birth defects near MTR operations, the data can't be used to conclusively pin any specific environmental factor as the cause, the study's co-author said. "What we think is happening is that there isn't just one type of exposure. There is air quality problems in some areas, water quality problems in other areas," Dr. Michael Hendryx told The Huffington Post.

Furthermore, the study noted various socioeconomic factors could account for a variance in birth defects, but said that they "remain elevated after controlling for those risks." Critics of the research argue that these factors weren't fully accounted for.

A spokesperson for the World Coal Association told The Huffington Post that it hasn't yet "processed the results of this study." Still, WCA claimed, "It is clear that focusing on only one aspect of an issue will inevitably lead to skewed results."

The response from the National Mining Association was similar.

"While the authors say they controlled for [socioeconomic factors], it does not appear, based on their summary, they have done so," said Carol Raulston, the senior vice president of communications for the NMA, in an emailed statement. While she conceded that her organization hasn't had the opportunity to thoroughly review the study, Raulston said that other papers by the same researchers "have had methodological deficiencies" and that this particular study "merits further investigation."

"Our studies have limitations, they do not have 'deficiencies' and the choice of this word illustrates the bias of the mining industry," said Hendryx. He asserts that any study published in any journal has "limitations," but insists they used available data to control for risks -- from education to smoking during pregnancy, among others.

This study is unprecedented, Hendryx added, in the amount of individual records that were looked at: It extends previous research beyond mere county aggregates. He also said it's the first academic paper to truly look at the potential effects MTR could be having on children.

Moving forward, Hendryx hopes to begin doing direct field assessments, such as collecting air and water samples in the communities experiencing high birth defects near MTR sites. Preliminary results could come within a year, but a definitive study would likely take at least several more.

But for some activists, these initial findings are all the evidence they need to escalate their fight against MTR operations.

"If a foreign power was doing this to us, we'd be at war with them," Bob Kincaid said of the mining companies behind the controversial process. The new health findings will be the "the centerpiece" of CRMW's fight against what he calls "the single greatest human rights crisis facing the Unites States today."

Nothing about the research is surprising to Kincaid. In fact, he just considers it validation for what anti-MTR mining activists have been alleging for years.

"We are going forward with a very plain message: They are killing us," he said. "It is scientifically proven now."

But not all activists agree the study is a silver bullet needed to end MTR mining.

"I don't know that having one more piece of scientific evidence that coal is hurting our health is going to tip the balance," said Mary Anne Hitt, director of Sierra Club's Beyond Coal campaign. "It's kind of like tobacco: We had piles and piles of evidence that it was bad for our health, but took years and years of work to turn around."

Regardless, Hitt said Sierra Club, which recently launched an interactive website about coal pollution's effect on health, plans to draw attention to the latest research.

The practice of MTR mining has recently become a subject of the national dialogue, with opponents' efforts being backed by a variety of notable figures and celebrities. A new film featuring Robert Kennedy Jr., "The Last Mountain," has drawn a lot of attention to the issues surrounding the mining controversy in Appalachia, and more than a thousand people recently descended on Blair Mountain in West Virginia to protest planned MTR operations at the historic site. Earlier in the year, the Environmental Protection Agency revoked a permit for West Virginia's largest MTR mine due to environmental and health concerns.

Despite a renewed sense of purpose among activists, some in the industry remain undaunted.

"It's an injustice to everyone involved and to the science itself to present this data as though its worthy of some conclusion," Vice President of the West Virginia Coal Association Jason Bostic told The Huffington Post. He contends that there is "no connection" between coal mining and birth defects, and brushes off the study as "a fairy tale."

"If anything, the involvement of the coal industry helps offset what would otherwise be worse health defects from poverty, isolation and lack of access to preventative medicine," Bostic said. "We're the ones providing health benefits and wellness plans to our employees and their dependents. Take us away and see how well it goes."

Paige Lavender contributed to this report.