Ragweed and ozone are double-teaming our lungs, and both on the rise due to manmade climate change, says the National Resources Defense Council. (gingyb via Weather Underground )

A new report from the Natural Resources Defense Council finds that 109 million people in the U.S. are being double-teamed by high levels of pollen and ozone, which have been found to lead to respiratory illness in both children and adults.

The report lists the top 50 cities exposed to the combination, with Richmond taking the grand, wheezy prize. The list was compiled by the NRDC to draw attention to the connection between ozone and pollen, and global warming — both in the form of an increase in temperature and higher levels of CO2 in the atmosphere.

Juan Declet-Barreto, lead author on the report, says this connection is really bad news for people who suffer from allergies and asthma. “Ragweed pollen and high levels of ozone smog can make it more difficult to breathe, trigger asthma attacks, and worsen existing respiratory allergy symptoms in adults and children,” Declet-Barreto writes in a blog post on the study.

The NRDC’s top 10 “sneeziest and wheeziest” cities:

1. Richmond
2. Memphis
3. Oklahoma City
4. Philadelphia
5. Chattanooga, Tenn.
6. Chicago
7. Detroit
8. New Haven, Conn.
9. Allentown, Pa.
10. Atlanta

The full list ranking the NRDC’s top 50 cities can be found in the report.

The report focuses two sneeze-y and wheezy elements found in the air we breathe: ragweed and ozone, which are both known to increase in the air as temperature and CO2 climb.

Higher average temperatures and higher concentrations of CO2 — which plants consume in the process of photosynthesis — are increasing pollen levels and the allergy attacks that follow. “Along with ragweed, many other pollen-producing plants, including trees such as birch, oak, and pine, tend to produce pollen earlier, for a longer time, and in greater quantities under higher CO2 and temperature conditions,” the report says, “the kinds of conditions associated with climate change.”

The presence of ozone — the main component in smog — increases respiratory disease and asthma. Ozone, which is formed from a chemical reaction between sunlight, nitrogen oxide and VOCs, tends to be higher on warmer days.

But the two elements are not independent actors in the quality of your respiratory health. The report points out that studies show the presence of ozone can also worsen allergic reactions to pollen in people with asthma.

A map of the top 50 “asthma capitals” from the NRDC report. Green counties show where ragweed has been documented by the USDA. Red counties, on average, have at least one ozone exceedance day per year. Brown counties are the intersection of the ragweed and ozone. (Figure 1 from the NRDC report)

The NRDC also goes on to note, importantly, that the cities in the list have the highest combination of ragweed and ozone. But that doesn’t necessarily mean they are the most vulnerable locations. “While these urban areas rank as the worst for both ragweed and high ozone levels, the most vulnerable regions nationally are the Los Angeles Basin, the region around St. Louis, the Great Lakes area, the MidAtlantic States, and New England,” says the report.

Interestingly, while Washington, D.C., does have a few ozone exceedance days per year, it did not make the list since ragweed pollen data in D.C. and Maryland is not specifically tracked by the USDA. Given the nearly-continuous coverage of ragweed in the Mid-Atlantic, one could hazard that D.C. might be relatively high on the list if it were tracked. One of the recommendations of the NRDC report is pollen better tracking and reporting, and even a network of daily pollen collection sites.