Another study has further cemented how fracking can be a human health hazard. People who live close to fracking wells have a higher risk of asthma attacks among asthma patients, according to a Johns Hopkins Bloomberg School of Public Health study.

The location of spudded wells (drilling begun) as of December 2012 and residential locations of Geisinger patients with asthma

The paper, published yesterday in JAMA Internal Medicine, focused on Pennsylvania's Marcellus Shale, one of the country's most active and notorious fracking regions. In the years between 2005 and 2013, the area has seen 6,253 unconventional natural gas wells spudded (the start of drilling) on 2,710 pads. Another 4,728 wells were stimulated and 3,706 were in production.

For the study, lead author and PhD candidate Sara G. Rasmussen, MHS and her colleagues analyzed health records from 2005 through 2012 from the Geisinger Health System, a health care provider that covers 40 counties in north and central Pennsylvania. The researchers identified more than 35,000 asthma patients between the ages of five and 90 years, identifying 20,749 mild attacks, 1,870 moderate ones and 4,782 severe attacks. They then mapped where these patients lived relative to nearby well activity.

The data revealed that people who live nearby a large number or bigger active natural gas wells were 1.5 to 4 times more likely to suffer from asthma attacks compared to those who live farther away. The risk also showed up in all four phases of well development: pad preparation, drilling, stimulation—the actual fracturing—and production.

While the exact cause of the trend was not identified, the authors of the paper suggested that exposure to air pollution and psychosocial stress—increased truck traffic, loud noises and bright lights disrupting sleep—from drilling operation can exacerbate asthma.

“Ours is the first to look at asthma but we now have several studies suggesting adverse health outcomes related to the drilling of unconventional natural gas wells," Rasmussen said. “Going forward, we need to focus on the exact reasons why these things are happening, because if we know why, we can help make the industry safer."

Fracking can induce asthma attacks in three ways, as Barbara Gottlieb, the Environment and Health program director at Physicians for Social Responsibility who was not involved in the study explained to USA TODAY. As USA TODAY writes, "the release of volatile organic compounds can interact with other chemicals in the fracking sites to form ground-level ozone, an asthma-inducing pollutant. Increased industrial activity near fracking sites, such as transportation, also aggravates asthma symptoms. And natural gas, or methane, leaks that occur at fracking sites add to asthma exacerbation as well by accelerating climate change and increasing temperatures which increases ground-level ozone."

This paper adds to the mounting research linking the fracking industry to various health impacts. Fracking, or hydraulic fracturing, involves injecting water and silica sand, and a slurry of toxic chemicals at high pressures into the ground to release gas deposits.

"We are concerned with the growing number of studies that have observed health effects associated with this industry," said Brian S. Schwartz, MD, MS, an author of the study and professor in the Department of Environmental Health Sciences at the Bloomberg School. "We believe it is time to take a more cautious approach to well development with an eye on environmental and public health impacts."

"Asthma is a common disease with large individual and societal burdens, so the possibility that UNGD [Unconventional natural gas development] may increase risk for asthma exacerbations requires public health attention," the authors concluded. "As ours is the first study to our knowledge of UNGD and objective respiratory outcomes, and several other health outcomes have not been investigated to date, there is an urgent need for more health studies. These should include more detailed exposure assessment to better characterize pathways and to identify the phases of development that present the most risk."

Earlier this year, researchers found that at least five chemicals associated with unconventional oil and gas operations are linked to respiratory health issues on infants and children, including asthma, reduced lung and pulmonary function, increased susceptibility to infection, chest discomfort, difficulty breathing, lung inflammation and other adverse outcomes.

For environmental advocates, this study is further evidence why fracking is unsafe.

"This study's findings confirm what we have known for years—that fracking is an inherently hazardous process that threatens human health and safety every day," Wenonah Hauter, founder and executive director of Food & Water Watch said. "More than 17 million Americans live within a mile of a fracking site, and they are all at risk. Despite countless dollars spent by the oil and gas industry in numerous attempts to sway public opinion, the truth is winning out. As recent polling proves, the more Americans hear about fracking, the more they oppose it."

Karen Feridun of Berks Gas Truth and Pennsylvanians Against Fracking said, "This Johns Hopkins study should be a wake-up call to Governor Wolf and Physician General Levine that fracking is causing serious harm to Pennsylvania children and families. How can Governor Wolf sit idly by as study after study comes out out revealing severe health impacts to his constituents as a result of his pro-fracking policies?"

In related news, environmentalists are currently preparing for the March for a Clean Energy Revolution at the Democratic National Convention in Philadelphia on Sunday, July 24 to demand that the country end its reliance on fossil fuels and dirty energy and shift towards renewable energy.