Natural Gas Storage: Actions Needed to Assess Inspection Workload and Progress Toward Safety Outcomes, Report to Congressional Requesters [open pdf - 3MB]
From the Highlights: "About 400 natural gas storage sites are important to the U.S. natural gas system, providing about 30 percent of the nation's energy. [...] GAO [Government Accountability Office] was asked to review the health and environmental effects of activities at natural gas storage sites. This report, among other objectives, (1) assesses the extent to which PHMSA [U.S. Department of Transportation's Pipeline and Hazardous Materials Safety Administration] has developed its natural gas storage inspection program and (2) describes what is known about the potential health effects from chemicals in stored natural gas."
Government Accountability Office: https://www.gao.gov/