from today's Wall Street Journal:
There's growing scientific evidence that global climate change is linked to the dramatic rise in allergies and asthma in the Western world.
Studies have found that a higher level of carbon dioxide turbocharges the growth of plants whose pollen triggers allergies. In 2001 Lewis Ziska planted ragweed -- the main cause of hay fever in the fall -- at urban, suburban and rural sites near Baltimore. The plots had the same seeds and soil and were watered in the same way. Yet the downtown plants soon exploded in size, flowering earlier and producing five times the pollen of rural plants. The city pollen was a lot more toxic, too. The likely cause? The city plants experienced warmer temperatures and 20% more carbon dioxide, the effect of more cars and pollution.
"We can see the changes now, and they already have implications for public health," says Dr. Ziska, a plant physiologist at the U.S. Department of Agriculture. Allergies and asthma are closely linked; more than 70% of asthma sufferers also have allergies.
The Intergovernmental Panel on Climate Change, a group of the world's leading climate researchers, will address the issue in its August report. According to Bettina Menne, a doctor at the World Health Organization and a lead author of the chapter on climate change and health, the report will say that higher temperatures and carbon-dioxide levels have increased the abundance of pollen, known to trigger allergies and worsen asthma. It will also conclude that spring, when allergy-causing tree pollen is at peak levels, has been arriving 10 to 15 days earlier over the past three decades, a trend expected to continue in coming years.