We’re from New Orleans,
currently exiled in Austin, Texas, and wanting information about
pollutants and mold. I know that New Orleans on a good day has high
mold spore levels and now they are very high. What would be typical
mold spore levels and how do they compare to today’s levels (as
shown on National Resource Defense Council website).-Catherine,
New Orleans
Unfortunately there is no
historical information on outdoor levels of mold for the city of New
Orleans. The National Bureau of Allergy does maintain a sampling and
counting site in Baton Rouge. Outdoor levels reported in the city
of Baton Rouge for October 4, 2005 were 13,173 S/m3 and
for November 4, 2005 19,082 S/m3. On the scale used by
The National
Allergy Bureau, these levels are considered to be high. The
high NAB category is defined by the range 13-50,000 S/m3.
The very high category is >750,000 S/m3.
In October, 2005 scientists from
The Natural Resources Defense Council
(NRDC) and the University of California-Berkeley conducted tests
in flooded and non-flooded areas in 12 locations in New Orleans. In
addition a few samples were collected in the suburban community of
Metairie. Mold testing was conducted using a Burkard spore trap
over a period of 6 hours.
In the flooded areas
of New Orleans outdoor air concentrations averaged ~60,000 S/m3,
in non-flooded areas ~45,000 S/m3 and in Metairie which
was distant from the flooding ~25,000 S/m3. Outdoor
levels varied from a low of 26,000 S/m3 in the French
Quarter to a high of 102,000 at Mid-City.
Based on the NAB classification,
NRDC concluded that airborne outdoor mold levels in New Orleans
East, the Lower Ninth Ward ,Chalmette, uptown and Mid-City were
“very high” with levels in Lakeview and Gentilly “High.” In two
indoor locations, mold levels were reported to be extremely high
(>600,000 S/m3). Most samples were reported to by
dominated (both indoors and outdoors) by Cladosporium and
Aspergillus/Penicillium-type spores.
When outdoor mold levels in New
Orleans are compared to those of Metairie and Baton Rouge, it is
apparent that observed levels in flooded areas of New Orleans were
much higher.
Outdoor mold levels are affected by
a number of factors. Most importantly they are affected by the
season or time of year, and the location where sampling is
conducted. Many NAB sites are located on top of buildings in urban
areas and of course are affected by mold sources nearby as well in a
broader area around such sites.
My personal experience in the
Indianapolis area is that reported mold spore concentrations at the
NAB city site are usually much lower then those in suburban
residential neighborhoods. The differences are likely due to where
the sampler is located relative to the ground as well as local
sources of mold. In the suburban areas mulch and surrounding
croplands appear to have a very profound effect on outdoor
concentrations.
Here in the Midwest in late summer
through late fall, mold spore concentrations in the range of
40-80,000 S/m3 are quite common in suburban
neighborhoods. These counts are usually dominated by certain
species of Cladosporium and yeast (often counted as
Aspergillus/Penicillium). Many observed values would be
classified very high under the NAB classification system.
High outdoor mold concentrations
can be expected as vegetation begins to mature and die. It is of
course the role of fungal species to decompose such organic matter.
Based on mold sampling conducted by
NRDC at sites in New Orleans in October, 2005, outdoor airborne mold
concentrations were likely to be higher than they normally would
have been for October. This would be consistent with the fact that
as a result of the flood, much organic debris was in the process of
being “cleaned up” by a variety of fungal species.
Were such levels unusually high
compared to the Midwest in suburban areas? The answer based on my
personal experience is of course no.
December 2, 2005
