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 "Prescribed burns have been done for thousands of years to maintain
the health of the forest, but there is public opposition to them due
to the smoke exposure," said lead study author Dr. Mary Prunicki of
the Stanford University School of Medicine.
"That concern has hindered the Forest Service in doing as many
prescribed burns as would be ideal to minimize the wildfires,"
Prunicki said in a phone interview.
Previous research has linked wildfire smoke exposure with an
increase in asthma attacks and hospitalizations. Children are
particularly affected due to their developing immune systems, the
authors note in the journal Allergy.
For the new analysis, Prunicki and colleagues compared Fresno area
children exposed to wildfire smoke to kids exposed to smoke from
controlled burns covering similar amounts of acreage, during a
two-year period when wildfires occurred in nearby Yosemite National
Park.
The researchers analyzed changes in markers of immune system
responses in blood samples taken three months after a prescribed
burn or wildfire, which is the time it takes for those changes to
show up, they note.
They studied three groups of children, all around 7 to 8 years old.
One group of 36 kids was exposed to smoke from controlled burns in
2015. Another group of 32 kids was exposed to wildfire smoke. And 18
children from the San Francisco Bay area had no exposure to smoke
from fires.
Children in the wildfire-smoke exposure group showed the largest
immune system changes. For example, they had fewer Th1 cells, which
defend against viruses and bacteria, than kids exposed to smoke from
prescribed fires and kids with no smoke exposure. Children exposed
to wildfire smoke also tended to report more wheezing, even without
a history of asthma, and those with asthma tended to have
exacerbated episodes.
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The researchers also measured pollutants near both cities. Compared
to areas near controlled burns, areas near wildfires had higher
levels of carbon monoxide, nitrogen dioxide, polycyclic aromatic
hydrocarbons, elemental carbon and particulate matter.
"We also need to study fires that move into urban areas that burn
not just vegetation but human structures as well, which give off
different pollutants," said Colleen Reid of the University of
Colorado at Boulder, who wasn't involved in the study.
Experts recommend that families use air purifiers if living in a
polluted area or near wildfires. Ventilation systems that have HEPA
filters and good air exchange are the best measures for protection,
Reid said. In addition, those who can wear masks should stock them,
although many masks and respirators aren't manufactured to fit
children.
"Unfortunately, we still don't know how to mitigate the health
effects of inhaled pollutant exposures in pediatric populations,"
said Lisa Miller of the University of California at Davis School of
Veterinary Medicine, who also wasn't involved in the study. "We know
even less about what fire smoke can do to health outcomes as exposed
individuals mature into adults," she said by email. "Children are
highly vulnerable to any form of inhaled pollutant because of
respiratory and immune system immaturity."
SOURCE: https://bit.ly/2Wixzi2 Allergy, online April 19, 2019.
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