scent of the holiday season into homes, according to a new study.
The study, which was presented at The American College of Allergy, Asthma
& Immunology Annual Scientific Meeting in Dallas, examined the relationship
between mold growth on live Christmas trees and poor indoor air quality.
This study grew out of a consistent and dramatic increase in asthma and
sinus complaints among patients every winter, which is especially pronounced
during the holiday season, notes study researcher John Santilli, MD.
"As mold growth is common in the area surrounding outdoor foliage, we
hypothesized that the presence of a live Christmas tree may be contributing to
indoor mold," he says.
Indoor Mold Levels Rise
Twelve times during a two week period, researchers measured mold counts in a
room containing a live Christmas tree, beginning when the tree was
brought inside and decorated. The tree was located 10 feet from a heat vent,
and the indoor temperature was maintained at between 65 and 68 degrees.
For the first three days, counts remained at 800 spores per cubic meter of
air, then began escalating, rising to a maximum of 5,000 spores per cubic meter
by day 14, when the tree was taken down.
Mold allergy affects up to 15% of the population, according to Santilli, and
people with sensitivity to certain molds commonly experience nasal, eye, and
throat irritation; nasal stuffiness; and headache. Additionally, there is a
well-documented link between asthma attacks and molds, and the added risk of
invasive fungal disease among people with compromised immune systems.
Santilli says normal indoor air has a mold level of 500-700 spores per cubic
meter; anything higher indicates a source of mold growth inside the
"Ventilation systems and water-damaged areas have long been recognized
as sources of mold, but we need to continue to search for new and unique
sources of contamination," Santilli says.
Avoiding Indoor Mold
"Our study demonstrates that a live Christmas tree can be a significant
source of mold spores. Therefore, we recommend families with allergies in
general and mold allergies in particular not keep a live Christmas tree in
their homes for more than a few days at most, and remove it sooner if there are
signs of increased allergy symptoms," Santilli says.
Rebecca Gruchalla, MD, PhD, chief of allergy at the University of Texas
Southwestern Medical School in Dallas, says the relationship between live
Christmas trees and a rise in indoor mold spores comes as no surprise,
particularly since most Christmas trees are cut well in advance of the holidays
and stored in a moist environment before being placed on a lot for sale. Then
they're then taken home and placed in water too, she says.
Gruchalla notes that artificial trees and ornaments collect dust in storage
and, therefore, are another source of allergy irritation.
She suggests taking both live and artificial trees outside and shaking them
out before bringing them inside to decorate.
By Patricia Kirk
Reviewed by Louise Chang
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