Our Air

It’s getting harder to breathe.


Pollen allergies have gotten worse because warming temperatures are causing the pollen season to lengthen and higher CO2 is causing plants to produce more pollen.

How is the environment changing?

  • In the central US, ragweed pollen season length has increased by 13-27 days in response to higher temps.

Source: Ziska, L., K. Knowlton, et al. Recent warming by latitude associated with increased length of ragweed pollen season in central North America. P Natl. Acad. Sci. USA 108:4248–4251.

  • Plants grown in today’s CO2 produced about twice as much pollen as in CO2 of last century.

Source: Ziska, World Resource Rev 2000.

  • Average U.S. pollen count increased by 42-46 % in 2000’s, relative to 1990’s.

Source: Zhang et al, Global Change Biology, 2015.

Source: Projected Carbon Dioxide to Increase Grass Pollen and Allergen Exposure Despite Higher Ozone Levels, Jennifer M. Albertine , William J. Manning, Michelle DaCosta, Kristina A. Stinson, Michael L. Muilenberg, Christine A. Rogers Published: November 5, 2014 https://doi.org/10.1371/journal.pone.0111712, accessed 5/29/2017.

 How is our health affected?

  • The prevalence of hay fever has increased from 10% of the population in 1970 to 30% in 2000.

Source: Fann, N., T. Brennan, P. Dolwick, J.L. Gamble, V. Ilacqua, L. Kolb, C.G. Nolte, T.L. Spero, and L. Ziska, 2016: Ch. 3: Air Quality Impacts. The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment. U.S. Global Change Research Program, Washington, DC, 69–98.

  • Oak pollen was associated with 21,200 asthma emergency department visits in the Northeast, Southeast, and Midwest U.S. in 2010, with damages valued at $10.4 million. Nearly 70% of these occurred among children age under 18 years. Severe climate change could increase oak pollen season length and associated asthma emergency department visits by 5% and 10% on average in 2050 and 2090.

Source: Anenberg, S. C., K. R. Weinberger, H. Roman, J. E. Neumann, A. Crimmins, N. Fann, J. Martinich, and P. L. Kinney (2017), Impacts of oak pollen on allergic asthma in the United States and potential influence of future climate change, GeoHealth, 1, doi:10.1002/2017GH000055.


As temperatures rise, smog increases and air quality is degraded.

How is the environment changing?

  • A study looking at the impact of long-term weather changes on air quality and health in the US 1994-2012 found that average temperatures have increased and average wind speed has decreased in most of the U.S. (trends we expect to see with climate change), causing increases in smog-causing ozone and fine particulate matter.  

Source: Jhun et al., Environmental Research Letters 12 August 2015, The impact of weather changes on air quality and health in the US in 1994-2012

 How is our health affected?

  • Health outcomes from particulate matter and peak ground-level ozone concentrations include heart attacks, cardiovascular hospital admissions, respiratory hospital admissions, and premature death.

Source: Nature Climate Change, US power plant carbon standards and clean air and health co-benefits, Driscoll et al, 4 May 2015.

  • Air quality changes have significant mortality impacts. From 1994-2012, there were approximately 1100 excess deaths per year attributable to the weather penalty on air quality -- or a total of 20,300 excess deaths.  The weather effects on air quality had greatest mortality impacts in the Eastern US.

Source: Environmental Research Letters 12 August 2015, The impact of weather changes on air quality and health in the US in 1994-2012; Jhun et al.


More frequent wildfires and longer wildfire seasons, caused by rising US temperatures, lead to emergency rooms increasingly packed with Americans in respiratory distress.

How is the environment changing?

  • Wildfires emit fine particles and ozone precursors that in turn increase the risk of premature death and adverse chronic and acute cardiovascular and respiratory health outcomes. Climate change is projected to increase the number of naturally occurring wildfires in parts of the United States, increasing emissions of particulate matter and ozone precursors and resulting in additional adverse health outcomes.

Source:https://health2016.globalchange.gov/air-quality-impacts Accessed 6/2/2017.

  • Studies are limited in number but they suggest that warming of 1ºC (relative to 1950-2003) is expected to produce increases in median area burned by about 200-400%.

Source: National Research Council. 2011. Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millennia. Washington, DC: The National Academies Press. doi:https://doi.org/10.17226/12877.

  • A recent study found that, between 2003 and 2012, the average area burned each year in Western national forests was1,271% greater than it was in the 1970s and early 1980s.

Source: Westerling ALR. 2016 Increasing western US forest wildfire activity: sensitivity to changes in the timing of spring. Phil. Trans. R. Soc. B 371: 20150178. http://dx.doi.org/10.1098/rstb.2015.0178.

  • A recent study of California projects the following: the area burned by wildfire will likely double in Southwestern California by midcentury; increase by 35% in the Sierra Nevada and 10% in central western California.

Source: Yue, Xu, Mickley, Loretta J., Logan, Jennifer A. Projection of wildfire activity in southern California in the mid-21st century Climate Dynamics. Oct 2014, Vol. 43 Issue 7-8, p. 1973-1991.

 How is our health affected?

  • The main health effects of wildfire smoke are cardiorespiratory. Associations between exposure to wildfire emissions and increasing of hospital admissions and emergency room visits for respiratory and cardiovascular diseases has been observed in the most studies.

Source:Hassani Youssouf,Catherine Liousse,Laurent Roblou,Eric-Michel Assamoi,Raimo O. Salonen,Cara Maesano,Soutrik Banerjee,andIsabella Annesi-Maesano. Non-Accidental Health Impacts of Wildfire Smoke. Int J Environ Res Public Health. 2014 Nov; 11(11): 11772–11804.

  • In one study in California, forest fires increased ER visits for asthma by 40% and for chronic obstructive pulmonary disease by 30%.  A study in Florida showed forest fire increased ER visits for asthma by 91%, and for bronchitis by 132%.

Source: Naeher et al, Woodsmoke Health Effects:  A Review, Inhalation Toxicology, 19:67-106 2007, Informa Healthcare.


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