fracking protest
© AP Photo/Matt Rourke
Fracking opponents protest before the Tom Corbett inauguration to become the 46th governor of Pennsylvania at the state capitol in Harrisburg, Pa., Tuesday, Jan. 18, 2011.

More than 1,000 doctors and other health care professionals are calling on President Obama to take steps to protect Americans from the risks posed by fracking.

On Thursday, Environment America delivered a letter with more than 1,000 signatures from health care professionals that asked Obama to declare certain areas in the U.S. off-limits to fracking and to ensure that fracking is no longer exempt from environmental laws like the Clean Water Act and Clean Air Act. The letter outlined the dangers fracking poses to health and the environment, including drinking water contamination, carcinogenic air pollution, acute and chronic health effects, and greenhouse gas emissions.

"Given this toll of damage, the prudent and precautionary response would be to stop fracking," the letter reads. "Instead, the oil and gas industry is seeking to expand fracking at a frenzied pace, even into areas that provide drinking water for millions of Americans."

The letter highlights the possible health effects of fracking, many of which have been well-documented: it notes, for example, research that found that people living within a half-mile of fracking wells "had a higher excess lifetime risk of developing cancer than people living farther away." It also noted the "growing number of documented cases of individuals suffering acute and chronic health effects while living near fracking operations - including nausea, rashes, dizziness, headaches and nose bleeds." A report from Pennsylvania last year documented the range of health problems affecting residents living near natural gas operations - however, in Pennsylvania, a gag order prevents doctors from telling their patients what chemicals from fracking solutions might be the cause of their illnesses.

The letter also noted the dangers of fracking wastewater, which has spilled and leached into groundwater in the past. An October report found that fracking wells in the U.S. generated 280 billion gallons of toxic wastewater in 2012, some of it radioactive. This wastewater is often stored in deep wells, but over time these wells can fail and can end up contaminating water resources - in New Mexico alone, chemicals from oil and gas pits have contaminated water sources at least 421 times, according to the October report.

Right now, fracking regulations are largely left up to the states. Earlier this year, the EPA did issue guidance on injecting diesel fuel into the ground during the fracking process, a practice which companies must get EPA approval for. But for the most part, fracking laws vary widely from state to state. California last year enacted one of the country's stricter fracking laws, which among other things will require oil and gas companies to list the chemicals they use in the fracking process online.