if you don't know what chemicals are, you can't conduct pre-drilling tests and establish a baseline to prove that chemicals found postdrilling are from hydraulic fracturing. The researchers recommended requiring disclosure of all hydraulic fracturing fluids, that nondisclosure agreements not be allowed when public health is at risk, testing animals raised near hydraulic fracturing sites and animal products (milk, cheese, etc.) from animal raised near hydraulic fracturing sites prior to selling them to market, monitoring of water, soil and air more closely, and testing the air, water, soil and animals prior to drilling and at regular intervals thereafter. CNN has reported flammable tap water in homes located near hydraulic fracturing sites in Portage County, Ohio. On October 18, 2013, the Ohio Department of Natural Resource-Division of Oil & Gas Resources Management found that the Kline's pre-drilling water sample showed methane was present in August 2012 before gas wells were drilled near their home. The report further states the gas was microbial in origin and not thermogenic like gas produced from gas wells. Research done by the ODNR found that naturally occurring methane gas was present in the aquifers of Nelson and Windham Townships of Portage County, Ohio. A 2014 study of households using groundwater near active natural gas drilling in Washington County, Pennsylvania found that upper respiratory illnesses and skin diseases were much more prevalent closer to hydraulic fracturing activity. Respiratory problems were found in 18% of the population 1.2 miles or more from drilling, compared to 39% of those within 0.6 miles of new natural gas wells. People with clinically significant skin problems increased from 3% to 13% over the same distances. Methane leakage is one hazard associated with hydraulic fracturing natural gas. Methane is a prominent greenhouse gas. Over a twenty-year period, it is 72 times more potent than carbon dioxide. In 2012 it accounted for 9% of all US greenhouse gas emissions. Natural Gas and Petroleum Systems are the largest contributor, providing 29% of the emissions. Natural gas drilling companies are beginning to incorporate technologies called green completion to minimize methane leakage. The indirect effects of the increase in the supply of natural gas from fracking have only recently started to be measured. A 2016 study of air pollution from coal generation in the US found that there may have been indirect benefits from fracking through the displacement of coal by natural gas as an energy source.