Adding fuel to the fire

respiratory diseases such as hay fever and asthma may increase in the near future due to global warming, indicates a recent study conducted by scientists from us-based Harvard University and Harvard Medical School. The researchers assert that global warming would result in greater production of airborne allergens such as pollen through quicker and more abundant growth of plants ( www.newswise.com , March 28, 2002).

The researchers studied ragweed plant that produces one of the most common allergens. They grew these plants in two different enclosed environments -- one was maintained at 350 parts of carbon dioxide (co₂) to a million parts of air -- roughly the current level. The other, an indoor module, was maintained at 700 parts of co₂ to a million parts of air. Such a doubling of atmospheric co₂ is expected to occur between 2050 and 2100.

The researchers found that the indoor ragweed pollen were 61 per cent more than the ones grown in normal co₂ conditions. These findings echo the results of a recent study conducted in North Carolina, usa. In that study, excess co₂ pumped into an in virto pine forest, tripled the number of pine cones and seeds.

"Such studies are very important because they show how co₂ affects different plant parts," he said. Taken together, the studies suggest that under co₂-enriched conditions, plants may boost production of their propagative elements to enhance their reproductive success. In addition to producing more allergens, and possibly more allergy sufferers, such a trend could alter competitive relationships among different plants, encouraging the growth of weedy species. According to the researchers, the study highlights the need to reduce co₂ levels. "The study can help us understand the true costs of burning fossil fuels," said Paul Epstein, one of the researchers and an associate director of the Centre for Health and the Global Environment at Harvard Medical School.

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