What does the U.S. health care system have in common with cattle farms and power plants? It is responsible for a fair chunk of the nation's greenhouse gas emissions. The system, especially via hospitals and the pharmaceutical industry, contributes 8 percent of those climate-warming gases, according to a study published in the November 10 issue of the Journal of the American Medical Association.

Related to this, the idea of shrinking the nation's carbon footprint by greening its health care has been brewing for a number of years, and several hospitals around the country have received the U.S. Green Building Council's Leadership in Energy and Environmental Design (LEED) certification. But no study as of yet has endeavored to estimate the health care industry's contribution to emissions of greenhouse gases (GHG)—carbon dioxide, methane, nitrous oxide and chlorofluorocarbons (CFCs).

"Quantifying the environmental impact of health care is important to determine the potential value of mitigation efforts," wrote the authors of the study led by Jeanette Chung, a professor in the Department of Medicine at the University of Chicago. Dr. David Meltzer was the co-author on the study.

The researchers started by looking at the amount of money spent in different areas of health care, including hospitals, home heath services, prescription drugs and scientific research, based on 2007 records. Then they subjected these numbers to a model developed at the Carnegie Mellon University Green Design Institute called the Economic Input-Output Life Cycle Assessment (EIO-LCA). Because the most up-to-date EIO-LCA model is based on 1997 industry reports, the authors adjusted 2007 spending to 1997 U.S. dollars to account for inflation.

The EIO-LCA estimates environmental impacts, such as GHG emissions, pollutants and energy usage, associated with the money spent in a number of sectors in different industries. For GHG emissions, the model provides the approximate amount of metric tons of each gas released for every dollar spent in a given sector. To make estimates of emissions associated with a hospital, for example, the model considers all hospital-associated goods and services, such as electricity, waste removal and food services. The entire lifecycle of these goods and services, from their manufacturing and transportation to retail, is taken into account. In other sectors, the EIO-LCA can be used, for example, to gauge the methane emissions of a cattle farm, or the carbon emissions associated with investing a million dollars in the automobile industry.

The authors summed the estimated emissions of the four greenhouse gases for each health care sector to arrive at the finding that the industry is responsible for 8 percent of the nation's emissions. Of those four gases, carbon dioxide accounted for the most emissions. The health care industry represented 7 percent of the nation's total carbon released in 2007. The researchers note that a similar EIO-LCA analysis found that health care in the United Kingdom accounted for 3 percent of that nation's carbon footprint in 2004. And for another comparison, the generation of electricity—and primarily fossil fuel combustion—creates about 40 percent of carbon emissions today in the United States, according to the U.S. Environmental Protection Agency. Health care made up less than 1 percent of the country's methane and CFC emissions in 2007.

Far and away the most important GHG emitters within the health care sector were hospitals, which came in at 39 percent, followed by the prescription drug sector at 14 percent. The other runners-up were physician and dental services, nursing home care and health equipment, which contributed 13, 9 and 10 percent, respectively.

As the first study to estimate the GHG emissions from different sectors of U.S. health care, the authors wrote that their "results suggest that key points along the health care supply chain should be identified where environmental mitigation efforts may achieve greatest net health and environmental benefits."

Image of a hospital courtesy of iStockphoto/PeterSpiro