An
association between household mold levels and respiratory symptoms in infants
during their first year of life.
As mold exposure awareness increases, investigators are scurrying around to
determine the “best” method of mold sampling, the “best” endpoints to
measure, the “best” confounding factors to include in their analysis and
the “best” qualitative verses quantative aspect of specific mold genera to
measure as the independent variable. Since
the mid-nineties, there has been an explosion of articles in the peer reviewed
published scientific literature with respect to molds.
One such study, recently published by Gent et al., investigated the risk of an
increased incidence of symptoms and signs following exposure to particular
fungal genera. They assessed the
risk of an increased incidence of respiratory symptoms after exposure to
particular fungal genera in a defined susceptible population.
This population consisted of infants (within 4 months of birth)
at high risk for developing asthma because the followed infants
had at least one older sibling with physician diagnosed asthma.
The dependent variable was assessed as number of days of wheeze or
persistent cough. Information on
maternal allergy and asthma, socio-economic variables and housing
characteristics were collected over the course of the infants first year of
life. Mold assessment was
conducted by airborne sampling at one time in the infant’s life.
Fungi were identified to the genus level and recorded as 0
(undetectable), 1-499 cfu/m3 (low; colony forming units per cubic
meter), 500-999 cfu/m3 (medium), and >1000 cfu/m3
(high). The two most frequently
found genera were Cladosporium and Penicillium in 62% & 41%
of the homes, respectively. The
former genera were usually associated with water leaks.
Of the initial 1002 infants enrolled, 880 were included in the final analysis.
As noted, mold exposure samples were taken once during the infants
first year of life. The mothers
of the infants enrolled in the study completed a questionnaire regarding
demographic information, housing characteristics and medical histories.
Mothers were contacted every 3 months and reported the number of days
per month for wheeze and persistent cough.
The results showed that over half of the infants did not experience any
wheeze or persistent cough. The
authors also observed that there was significantly more wheeze and persistent
cough among boys and infants whose mothers have asthma.
In addition, they reported that infants in homes heated with an
electric baseboard system tended to have higher rates of wheeze than the homes
with forced air, steam or any other system.
They also reported no association between season of sampling and levels
of Penicillium, but an association did exist between season of sampling
and levels of Cladosporium; summer being the highest, a time when Cladosporium
reaches its peak levels outdoors.
The authors noted that the
highest level of Penicillium was associated with higher rates of wheeze
(RR 2.15; 95% CI 1.34-3.46) and persistent cough (RR = 2.06 95% CI 1.31-3.24)
when controlled for confounders and other variables.
These authors also concluded that air sampling, as compared to dust
sample analysis remains the best way to identify genera and species of molds
found in and around a house. One
limitation is that molds that are rare or not easily airborne may be missed.
In summary, these authors report that an infant’s number of days of
respiratory symptoms during the first year of life would increase by 20% for
each increase in the level of Penicillium.
When controlling for the potential confounding of seasons of mold
samples, the association holds true between respiratory symptoms and mold
exposure to Penicillium, but not for Cladosporium or other
molds.
By: Arlene L. Weiss, MS DABT
Contributing Editor for Toxicology and
Epidemiology
Source: Janneane F. Gent, Ping Ren, Kathleen Belanger, Elizabeth Triche,
Michael B. Bracken, Theodore R. Holford, and Brian P. Leaderer. 2002.
Levels of Household Mold Associated with Respiratory Symptoms in the
First Year of Life in a Cohort at risk for Asthma. Environ Health Perspect
110(2):A781-78
21 May 03
