The annual siege of ragweed pollen has peaked for hay fever sufferers, but weather conditions this summer may prolong the season -- and the sniffling, sneezing, red-eyed agony -- for another month.
According to daily samplings of Baltimore air the past two months, ragweed pollen hit its seasonal peak on Sept. 7 at a count of 1,756, one of the highest levels since heavy rains during tropical storm Agnes in 1972 stunted the area ragweed crop.
"That's high," said Frank Ward, the retired Johns Hopkins University allergy technician who has determined the Baltimore pollen count for three decades.
"It could definitely cause problems. Even counts of 200 or 300 can set some people off," Mr. Ward said.
The numbers represent grains of pollen per square centimeter, painstakingly counted one-by-one on a sticky microscope slide exposed to the air for 24 hours outside the Johns Hopkins Asthma & Allergy Center at the Francis Scott Key Medical Center.
Although Mr. Ward performed the early-morning ritual for years on the grounds of Good Samaritan Hospital in North Baltimore, he now shares the pollen-count duties with Dr. Robert Hamilton and his staff at the Key Medical Center site on Eastern Avenue.
The ragweed season generally has followed its normal course this year, with the first measurable pollen arriving on Aug. 13 and thepeak, as expected, near Labor Day weekend. Other high counts were recorded on Aug. 28, 1,381, and Sept. 3, 1,204.
Pollination of ragweed is triggered by hours of sunlight. Levels of pollen in the air are heavily influenced by the weather, with dry, warm days and nights ideal for high counts.
Nearly a week of heavy rain in late August suppressed pollen counts briefly before they rebounded toward the Sept. 7 peak, an interruption that may result in an extended season of a gradually decreasing ragweed assault on sufferers.
The rain also contributed to unusually high counts of mold spores, which add to the plague of runny noses, sneezing, aching sinuses and red, watery eyes.
"Although [the season] can last up to the first frost, it normally peters out at the end of September," said Dr. Martin Valentine, clinical director of the Asthma & Allergy Center. "This may go well into October. I predict it's going to drag on."
That's bad news for area residents like Dr. Bruce Marsh, chairman of the Earth and Planetary Sciences department at Johns Hopkins University, who said Baltimore ragweed "hit me like a sledgehammer" as he returned recently from a summer stay in Maine.
"My nose and sinuses let me know when the pollen peaks, believe me," he said. "It's just a misery until it ends."