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June 2002
Vol. 5, No. 6, p 9.
news in brief

More CO2 = more allergens

opening artThrough blooming flowers, trees, and grasses, nature unleashes pollen, one of the most common and irritating allergens. Unfortunately, an increase in CO2 levels over the next 50 years could significantly increase pollen production, according to a study conducted by Harvard University researchers (Ann. Allergy Asthma Immunol. 2002, 88, 279–282).

“By basic photosynthesis, CO2 increases the growth of plants. This work demonstrates that the plant allocates more growth to pollen than to just boosting its own size,” explains Paul Epstein, the study’s coauthor and associate director of the Center for Health and the Global Environment at Harvard Medical School. “We are experiencing very high pollen counts in [recent] springtimes. There may be several factors contributing to this, and one may be that CO2 levels are up.”

The Intergovernmental Panel on Climate Change (IPCC) predicts that atmospheric CO2 could double between 2050 and 2100. Epstein explains that the IPCC looks at atmospheric models to project the future quantity of CO2 and other greenhouses gases, such as methane and ground-level ozone, and what impact they will have on climate, temperature, and patterns of precipitation.

Epstein and his colleagues analyzed ragweed from seeds cultivated in two different greenhouse atmospheres. The first environment was sustained at the current level of CO2, which is around 350 parts per million (ppm) of CO2 in air, while the second atmosphere was maintained at 700 ppm of CO2. The plants were then harvested, and the pollen was evaluated. Researchers found that the ragweed grown in the second atmosphere produced 61% more pollen than that grown in the first atmosphere.

“The burning of coal, oil, and natural gas is the chief contributor to the increase of CO2 and other greenhouses gases,” says Epstein. “Since carbon is taken up by plants in photosynthesis, deforestation also contributes to the buildup of CO2.”

Much focus has been placed on indoor air pollutants in connection with asthma mortality and illness, but Epstein suggests that researchers need to look outside and include a broad picture of the impact of changes in atmospheric gases and global climate change. “We need to look at changes in global concentrations of greenhouse gases and some of nature’s response, such as warmer winters and earlier arrival of spring,” he said. “These global changes may be major contributors to asthma and hay fever and allergies in the future.”


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