May 03, 2002
The above photo should help explain ragweed's ability to make you feel lousy. Examples of four different pollens are shown here which were imaged from a scanning electron microscope (SEM); ragweed (upper left), coleus (upper right), a composite called cosmos (lower left), and mint (lower right). The magnification bar on each image is in micrometers. Since it's about mid spring now, the pollen/allergy season is in full bloom. Dry, windy weather has made this one of the worst pollen seasons in recent years in the Mid Atlantic region. In the Washington DC area, pollen counts in mid April were as high as 2,500 grains per cubic meter! This is 5 to 10 times the level normally expected at this time of year and more than 20 times the value needed to make people sensitive to certain pollens feel miserable. A green tinge was noticeable on most anything left outside - especially cars and trucks. In late March through much of April, tree pollen was dominant, but currently, pollen from grasses and weeds are causing many people to wheeze and sneeze.