Report: Worsening ozone pollution in a warming world could bring increase in respiratory illnesses, health costs to Massachusetts

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Union of Concerned Scientists

Boston, MA – Unchecked global warming could threaten public health and increase health costs in Massachusetts by exacerbating ground-level ozone—the primary component of “smog”—according to a peer-reviewed report written by the Union of Concerned Scientists (UCS), and released today by UCS and Environment Massachusetts. 

The report, “Climate Change and Your Health: Rising Temperatures, Worsening Ozone Pollution,” found climate change-induced ozone increases in Massachusetts could result in about 72,000 additional cases of serious respiratory illnesses and more than $141 million (in 2008 dollars) in additional health costs in 2020.  

“Even a small increase in ozone due to a warmer climate would have a significant impact on public health,” said UCS public health analyst Liz Perera, a report co-author. “It would mean more asthma attacks, respiratory illnesses, emergency room trips, and premature deaths.”

“This report confirms what scientists have been saying for years: global warming will harm the public health of Massachusetts citizens in very real and very dangerous ways,” said Ben Wright, advocate with Environment Massachusetts.  “Our elected officials need to respond by taking action now to cut the pollution that is fueling global warming.”

Ground-level ozone is generated by chemical reactions between nitrogen oxides and volatile organic compounds (VOC) triggered by heat and sunlight. Warmer average temperatures from a changing climate likely will elevate ozone concentrations in many parts of the country, especially in and around urban areas. Warmer temperatures also are associated with stagnant air conditions that can cause ozone pollution to settle over an area and remain for extended periods of time.

The most vulnerable states have a large number of residents living in urban areas, a large number of children and seniors, and high levels of nitrogen oxides and VOC emissions from industry, vehicles and power plants. 

Overall, the report calculated increased climate change-induced ozone levels in 40 states and the District of Columbia. Studies on climate change and ozone in the Southeast and Northwest are either inconclusive or show no effect, so UCS excluded states in those regions from the analysis. Hawaii and Alaska also were excluded due to model limitations.

The analysis found ozone increases from climate change likely could result in 2.8 million additional serious respiratory illnesses, 5,100 additional infants and seniors hospitalized with serious breathing problems, and 944,000 additional missed school days in the United States in 2020. These and other health-related impacts could cost Americans approximately $5.4 billion in 2020.

Clean Air Act standards have reduced ozone-forming pollutants nationally, but many counties and states still are unable to meet the federal ozone standard. In the coming months, the EPA is expected to strengthen this standard, which will be even more important to safeguard public health and improve air quality in a warming world.
Average U.S. temperatures have increased more than 2º Fahrenheit (F) during the past century. If global warming emissions continue increasing, average U.S. temperatures could rise 3º to 5.5º F by 2050. These temperature increases could result in approximately 11.8 million additional serious respiratory illnesses, 29,600 more infant and senior hospitalizations, and 4.1 million additional lost school days in 2050, according to UCS’s analysis. Conversely, if global warming emissions decline and average U.S. temperatures increase only 2º to 4º F by 2050, the health impacts associated with climate change-induced ozone could be reduced by approximately 70 percent compared with the higher emissions scenario. Of course, nitrogen oxides and VOC emissions will continue to play a dominant role in ozone formation and must be reduced significantly to mitigate ozone pollution’s threat to public health. 

“The good news is we can address both ozone pollution and climate change by cutting fossil fuel emissions,” said Todd Sanford, a UCS climate scientist and report co-author. “Doing that would protect public health, the environment, and the economy.”


The Union of Concerned Scientists is the leading U.S. science-based nonprofit organization working for a healthy environment and a safer world. Founded in 1969, UCS is headquartered in Cambridge, Massachusetts, and also has offices in Berkeley, Chicago and Washington, D.C. For more information, go to