Can global warming change your life? If you are an allergy sufferer, it probably already has.

Climate change may already be making life worse for you and the roughly 30 million to 40 million allergy sufferers nationwide, according to a study released earlier this year. Rising carbon dioxide levels are driving the growth of the plants that make us sneeze, wheeze and sniffle each spring, summer and fall.

We humans consider carbon dioxide to be an inconvenient truth about our addiction to fossil fuels, but to plants, carbon dioxide is breakfast, lunch and dinner. Via photosynthesis, plants use carbon dioxide and sunlight to create the energy they need to grow.

Plants not only are growing more quickly and larger but they are also making more pollen than they used to. One study suggests that the pollen may be more allergenic. In addition to this carbon overdrive, warmer temperatures are triggering plants to release pollen earlier and survive longer, extending the overall allergy season. A study in Switzerland published in fall 2008 found that birch trees are, on average, releasing pollen 15 days earlier than they used to.

As designed by nature, trees pollinate in the spring, grasses in the summer and weeds in the fall. But now, pollen from these three sources are overlapping, increasing the suffering for people whose allergies are triggered by more than one type of pollen. The warming climate is also extending the range of plants, allowing allergy-inducing species to spread into new areas of the world.

The link between global warming and allergies is not limited to hay fever. Some researchers suspect that higher carbon dioxide levels are responsible for a rapid rise in food allergies. Higher carbon dioxide is also boosting the growth of two species with toxic oils, poison ivy and poison oak, which affect two out of every three people who come in contact with them.

Climate change is not the only way human activity is helping allergy-related plants thrive. Our land-use patterns are also a factor. New construction disturbs the soil and provides the perfect conditions for the spread of pollen-producing weeds. Landscapers bring in nonnative plants that produce pollen. Cities like Tucson, Ariz., were once havens for allergy sufferers until developers started changing the desert landscape into an oasis using irrigation. The city now routinely appears on a list of the nation's "allergy capitals."

Ragweed and ozone

Global warming isn't just making our planet hotter. Studies have shown that our changing climate could mean more ozone pollution in some areas, intensifying health problems stemming from allergenic pollen such as ragweed. Ragweed and ozone have been linked to respiratory ailments such as asthma and to allergic symptoms in adults and children. And studies show that people exposed to both ragweed and ozone are likely to become sicker than people exposed to just one of these pollutants.

Among the most vulnerable regions are the Los Angeles basin, the southern Mississippi River Valley, the Great Lakes area, the Mid-Atlantic states, the New York area and New England. Download the map and zoom in on your area to learn more, or read the full 2007 report on the NRDC Web site.

What you can do

Check daily pollen reports and air quality conditions, especially on sunny days with little or no wind, because these are the days when ozone concentrations can be especially high. When pollen or ozone levels are high, minimize your time outdoors, keep windows closed, and postpone your most strenuous outdoor activities for days with relatively low ozone levels. 

Wash bedding frequently to remove pollen that settles on pillows and sheets, and vacuum regularly, preferably with a vacuum cleaner that uses a high-efficiency particulate (HEPA) filter. Minimize your family's exposure to other known allergens because of the cumulative effect of multiple allergens in producing symptoms.

Beyond your home, you can tell your elected officials to support cap-and-trade legislation and the American Clean Energy and Security Act of 2009 (ACES).

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