Soaring pollen levels to boost hay fever

Hay fever could soar around the world over the next century, according to US scientists who predict higher levels of carbon dioxide (CO2) in the atmosphere will boost the amount of airborne grass pollen.

Despite increases in ozone, which suppresses plant growth, pollen production is expected to more than treble in the next 100 years.

The scientists exposed grass plants grown in special reactor chambers to different atmospheric gas concentrations, with different ratios of carbon dioxide and ozone tested to show their effects on grass and pollen