Discussion
Considering
the data in Table 1, the
number of total colonies
detected varied considerably
between sites. In most cases,
the number of total microbes
at a given site was similar
for both high use and low
use areas of the field.
In general, indoor fields
tended to have lower overall
microbial populations (0-7267
CFU) than outdoor fields.
At one facility where indoor
and outdoor fields were
sampled on the same day,
the indoor fields contained
0-67 CFU/g crumb rubber,
while the outdoor field
contained 2.8-3.3×104 CFU/g
crumb rubber. While indoor
fields represent only 20%
of the fields sampled in
this study a consistent
trend is apparent.
Total microbial
populations for the two
natural turf athletic fields
were an order of magnitude
higher than populations
for the infill systems with
the highest numbers. Also,
observationally, there appeared
to be a greater diversity
in the types of organisms
isolated from soil samples
than crumb rubber samples.
However, no specific determinations
of any cultures were made
other than to positively
or negatively identify S.
aureus.
One factor
that may influence total
microbial populations of
infill surfaces is use.
Of the 11 fields with at
least one subsample having
greater than 1×104 CFU/g
crumb rubber, one of those
fields had been heavily
used within 7 days of sampling
and two fields had been
used within 24 hours of
sampling. Tracking microbial
population fluctuations
of a field over time may
be of interest.
It is perhaps
not surprising that no S.
aureus colonies were found
on any fields, given that
the temperature range for
growth of S. aureus is 7-48°C,
with the optimal temperature
for growth being 37°C (Baird-Parker,
1990). Surface temperatures
of infill surfaces outdoors
often exceed the temperature
range of S. aureus (McNitt,
2005). However, high surface
temperatures do not explain
the relatively low numbers
of total microbes on indoor
playing surfaces. These
low numbers may, in part,
be explained by the permanently
very low moisture content
of indoor infilled surfaces.
In conclusion,
there are generally lower
numbers of total microbes
present in the infill or
fibers of the synthetic
turf systems tested compared
to natural turfgrass rootzones
and Staphylococcus aureus
bacterium were not found
on any of the playing surfaces.
Staphylococcus aureus bacterium
were found on towels and
other devices used by athletes.
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Main Infill Study 
