NASA study

*,ed_
F
N/LRA
INTERIOR LANDSCAPE
PLANTS FOR
INDOOR AIR POLLUTION ABATEMENT
FINAL
REPORT--SEPTEMBER
B.C.
Wolverton,
Principal
Anne
15, 1989
Ph.D.
Investigator
Johnson,
M.S.
and
Keith
Bounds,
Sverdrup
This
work
was
jointly
Programs--Technology
Contractors
of America
National
Aeronautics
John
Science
Stennis
Technology,
supported
Utilization
(ALCA).
by
and
Inc.
the
Division,
NASA
Space
Technology
Center,
Office
Administration
Center
Laboratory
MS
of
and the Associated
and Space
C. Stennis
Space
M.S.
39529-6000
Commercial
Landscape
CONTENTS.
Abbreviations
and
Introduction
Acronyms
Chemicals
Economical
Used
Benzene
Solution
In The
Plant
Formaldehyde
and
and
.....................
2
Tests .................................
3
............................
Selective
Analysis
Discussion
3
5
5
Detector
6
Analysis
for Trace
Metabolites
......
....................................................
Air Filter
8
8
System ................................
8
......................................................
9
.................................................................
Acknowledgments
References
Pollution
.....................................................
Carbon-Houseplant
Summary
Screening
Air
.........................................................
Methods
Microbiological
Results
to Indoor
......................................................
Chromatograph-Mass
Activated
1
..................................
Trichloroethylene
Gas
v
...............................................................
A Promising,
Materials
................................................
18
..........................................................
18
................................................................
19
FIGURES
1.
Indoor
2.
Man's
air purification
interaction
microorganisms,
3.
Removal
inside
4.
filter
Removal
inside
carbon
and
filter
houseplants
and
activated
carbon...
experimental
of benzene
chambers
and
using golden
4
trichloroethylene
pothos
from
in an 8-in.
the air
activated
system ....................................................
experimental
of benzene
chambers
using
3
soil,
water .............................................
of high concentrations
sealed
combining
with his environment--plants,
of low concentrations
sealed
carbon
system
and
golden
16
trichloroethylene
pothos
from
in an 8-in.
the air
activated
system ....................................................
17
.°°
III
PREC, EDING
P:IGE
E-,;'LA_',!K
't.,..
_,"_':" FILMED
TABLES
°
Trichloroethylene
Houseplants
.
Benzene
Chemicals
During
.
Benzene
Removed
a 24-h Exposure
Benzene
Removing
Benzene
after
from
in Potting
Removal
Being
Period
Exposed
and
from
a Sealed
by
11
......................
Experimental
Chamber
12
Chamber
by Houseplants
12
..........................................
a Sealed
Exposure
Experimental
Period
Experimental
Soil and
the Same
During
for Several
10
Chamber
Period
Experimental
Soil Bacterial
Chamber
by
..........................................
a Sealed
Foliage
Chamber
Experimental
from
by
..............................
a 24-h Exposure
a Sealed
a 24-h
All Plant
Experimental
a Sealed
Period
Removal
During
Removal
Houseplants
.
from
Period
Chamber
..............................
Experimental
by Houseplants
Removed
Houseplants
°
from
Experimental
Period
Exposure
Soil During
Trichloroethylene
a Sealed
a Sealed
a 24-h
a 24-h Exposure
During
.
from
Removed
and
from
a 24-h Exposure
During
Formaldehyde
Houseplants
o
During
Removed
Houseplants
,
Removed
24-h
Chamber
Potting
Soil after
Periods
24-h Periods
by
13
by
Exposure
Counts
of a Chinese
to Benzene
.................................................
iv
Chamber
..............................
14
.................
Evergreen
Plant
in a Sealed
14
ABBREVIATIONS
AND
Term
ACRONYMS
Definition
ALCA
Associated
EPA
Environmental
GC
gas chromatograph
HP
Hewlett-Packard
NASA
National
PCA
plate
TCE
trichlorethylene
UF
urea formaldehyde
UFFI
urea-formaldehyde
cfu/g
colony
cm
centimeter
cm 2
square
g
gram
h
hour
in.
inch
m
meter
mE
milliliter
min
minute
m3
cubic
meter
p/m
parts
per million
S
second
yr
year
/zL
microliter
°C
degrees
Landscape
Contractors
Protection
Aeronautics
count
and
Agency
Space
agar
foam
forming
units
centimeter
Celsius
V
of America
insulation
per gram
Administration
INTERIOR
LANDSCAPE
INDOOR
AIR
.PLANTS
POLLUTION
FOR
ABATEMENT
INTRODUCTION
During
the late
in heating
to help
1970s, when the energy
and cooling
alleviate
efficiency
costs,
spiraling
included
buildings
energy
other
allergy-related
contributed
designed
reduced
fresh
are also
manufacture
energy
changes
improved
that
air exchange.
It was determined
to the
workers'
health
a contributing
factor
that
However,
the airtight
problems.
various
equipment
because
of the
energy
upon
the
health problems
headaches,
and
sealing
Similarly,
and
efficiency
of buildings
synthetic
building
organic compounds,
have been
and furnishings
placed in these
types
of materials
used
in their
and design.
Man himself
should
living in a closed,
of people
to maximize
the workers began to complain
of various
drowsiness,
respiratory
and sinus congestion,
materials,
which are known to emit or "off-gas"
linked to numerous
health complaints.
The office
buildings
felt at both the gas pump
Two of the design
and
symptoms.
significantly
was being
costs.
superinsulation
occupation
of these buildings,
such as itchy eyes, skin rashes,
crunch
were being
be considered
poorly
are present
ventilated
health
or remodeled
buildings
recently
have varying
have been reported in the United
nations of the western world.
of indoor
to a phenomenon
estimated
degrees
air pollution,
very apparent
place such as an airplane
contribute
organization
source
area. This becomes
in a confined
All of these factors collectively
One world
another
of indoor
period
called "sick building
Problems
of time.
syndrome."
30 percent
air pollution.
when
when a large number
for an extended
that approximately
States and Canada
especially
of all new
of this type
as well as in most other highly developed
Two major problems with indoor air pollution are the identification
of the trace chemicals
and their correlation
with diseaselike
symptoms.
Energy-efficient
buildings that are filled
with modern
possibly
furnishings
interact
of these chemicals
The problems
over
the
symptoms
and reactive
of indoor
past
Manchester,
and high-tech
with each other.
ten
byproducts
air pollution
years.(1-27)
England,
off-gas
hundreds
of volatile
below present
may adversely
Dr.
Tony
Pickering
sick building
in naturally
ventilated
of the
syndrome
buildings
which
indicate
can be attributed
Now
pollution
that most
that it is unlikely
that symptoms
associated
some
of these buildings.
Hospital
near
and has learned
contained
the highest
of microorganisms.
On the other hand, the highest levels of symptoms
mechanically
ventilated
buildings containing
low levels of microorganisms.
his analyses
which
limits,
by many investigators
Wythenshawe
extensively
organics
detection
affect inhabitants
have been studied and documented
has studied
are minimal
equipment
Even at concentrations
that
levels
are found
The results
with sick building
in
of
syndrome
to microorganisms.
environmental
is a realistic
threat
scientists
to human
and government
health,
agencies
how can the problem
agree
that
be solved?
indoor
air
A PROMISING,
ECONOMICAL
TO INDOOR
AIR POLLUTION
SOLUTION
The first and most obvious step in reducing
from building materials and furnishings before
indoor air pollution is to reduce off-gassing
they are allowed to be installed. The National
Aeronautics
Space Administration
(NASA)
identified
indoor
with sealed
space
16 years
ago.(1)
Although
contamination
habitats
problems
for off-gassing
over
in these sealed environments
all new materials
that
air pollution
problems
a final
solution
has not been found,
are to be used in future
space
associated
to the
NASA
trace
does screen
structures.
Another promising approach
to further reducing trace levels of air pollutants inside future
space habitats
is the use of higher plants and their associated
soil microorganisms.(28-29)
Since man's
existence
relationship
on Earth
with plants
he attempts
problems
to isolate
will arise.
himself
answer
to these
on Earth
or in space,
achieved,
however.
this ecological
in tightly
Even without
off-gassing
into tightly
air pollution
problems.
The
depends
sealed
buildings
the existence
problems
take
along
C. Stennis
for over 15 years.
system
an intricate
be obvious
from
this ecological
of synthetic
own waste products
If man
is to move
nature's
life support
Space Center,
NASA
Professor
involving
it should
away
of hundreds
man's
is obvious.
he must
a life support
microorganisms,
sealed environments,
At John
puzzle
upon
and their associated
organic
would
into closed
system.
that when
system,
chemicals
cause indoor
environments,
This is not easily
has been attempting
Josef Gitelson
of the USSR
to solve
and his team
of scientists and engineers have also been working with closed ecological
systems for many
years in Krasnoyarsk,
Siberia.(30)
Only recently, however, have critical parts of this complex
puzzle begun to come together. Although
maintaining
the balance of the complete
cycle involves treating and recycling sewage, toxic chemicals, and other industrial
air pollutants,
only indoor
In this study
evaluated
of using
the leaves,
as a possible
plant
air is addressed
systems
roots,
means
here.
soil, and associated
of reducing
for removing
indoor
microorganisms
air pollutants.
high concentrations
cigarette
smoke, organic solvents,
and possibly radon
This air filter design combines
plants with an activated
The rationale
for this design,
volumes
moving
large
organic
chemicals,
by the
carbon
which
of contaminated
pathogenic
filter.
evolved
Plant
air through
and
their
being conducted
National
As NASA
base, along
to test this hypothesis
Laboratories
looks
in Oak
toward
Ridge,
associated
the possibility
with large numbers
studies,
carbon
and possibly
such as
microorganisms
is based on
bed where
radon
then
smoke,
are absorbed
destroy
the
eventually
converting
all of these
that the decayed radon products
in the plant tissue. Experiments
for NASA
been
a novel approach
air pollutants
treatment
an activated
(if present),
up by the plant roots and retained
have
has been designed from this work.
carbon filter as shown in Figure 1.
pathogenic
viruses, bacteria,
and the organic chemicals,
air pollutants
into new plant tissue.(31"37)
It is believed
would be taken
of plants
Additionally,
of indoor
from wastewater
microorganisms
roots
ecological
water and
at the Department
are currently
of Energy
Oak Ridge
Tennessee.
of sealing
people
inside
a Space Station,
of plants the ecology of such a closed environment
2
or moon
(interactions
GOLDEN
POTHOS .........
..
ACTIVATED
CARBON ........
POTTING
\
SQUIRREL CAGE FAN
(15-30 CFM)
SOIL
ELECTRIC
MOTOR
/
TIMER
EXCESS
Figure 1. Indoor air purification
between
man,
plants,
system combining
microorganisms,
soil, etc.) must
As plant studies continue
at Stennis Space
identifying
trace chemical
contamination,
metabolites
that
This joint
(ALCA)
may be off-gassed
effort
covers
between
two years
of data
be further
and activated
evaluated.
carbon.
See Figure
2.
Center, emphasis
is being placed not only on
but also on identifying
any volatile organic
by plants
NASA
houseplants
themselves.
and the Associated
on the potential
Landscape
Contractors
use of houseplants
of America
as a tool in solving
indoor air pollution
problems
on Earth, and has gone a long way toward reminding
man
of his dependence
on plants for his continued
existence and well-being
on our planet.
CHEMICALS
USED
IN THE
PLANT
SCREENING
TESTS
Benzene
Benzene
gasoline,
is a very commonly
inks,
of detergents,
Benzene
to
be
oils, paints
explosives,
plastics,
mutagenic
to
and is also present
and rubber.
pharmaceuticals,
has long been known
carcinogenicity
used solvent
bacterial
to irritate
cell
in some tests. Evidence
In addition,
and
in many
it is used in the manufacture
dyes.
the skin and eyes. Furthermore
cultures
basic items including
and
has
shown
also exists that benzene
it has been shown
embryotoxic
activity
may be a contributing
and
factor
4q_o
E
0
o
0
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Q.
i
Q_
E
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o
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q)
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I=
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c_
14,.
4
to chromosomal
causes
aberrations
drying,
benzene
and leukemia
inflammation,
has been reported
blistering,
in humans.
Repeated
and dermatitis.
to cause dizziness,
Acute
weakness,
skin contact
inhalation
euphoria,
with benzene
of high levels of
headache,
nausea,
blurred
vision, respiratory
diseases, tremors, irregular heartbeat,
liver and kidney damage, paralysis,
and unconsciousness.
In animal tests, inhalation
of benzene led to cataract
formation
and
diseases
causes
of the blood
headaches,
diseases
and lymphatic
loss of appetite,
of the blood
system,
systems.
Chronic
drowsiness,
including
exposure
nervousness,
anemia
to even relatively
psychological
and bone
marrow
low levels
disturbances,
and
disease.
Trichloroethylene
Trichloroethylene
Over
(TCE)
90 percent
industries,
of the
is a commercial
TCE
produced
but it is also used in printing
1975, the National
carcinomas
Cancer
was observed
this chemical
a potent
Institute
with a wide variety
in the
inks, paints,
reported
in micegiven
product
is used
metal
lacquers,
that an unusually
TCE by gastric
of industrial
degreasing
and
varnishes,
and adhesives.
high incidence
intubation.
uses.
dry-cleaning
In
of hepatocellular
The Institute
considers
liver carcinogen.
Formaldehyde
Formaldehyde
is a ubiquitous
chemical
found
in virtually
all indoor
environments.
The
major sources, which have been reported and publicized,
include urea-formaldehyde
foam
insulation
(UFFI) and particle board or pressed-wood
products.
Consumer
paper products,
including
grocery
bags, waxed papers,
facial tissues,
and paper
towels,
are treated
with urea-
formaldehyde
(UF) resins. Many common household
cleaning agents contain formaldehyde.
UF resins are used as stiffeners, wrinkle resisters, water repellants, fire retardants,
and adhesive
binders
in floor
formaldehyde
kerosene.
covering,
include
Formaldehyde
reactive chemical
disease
cigarette
backing,
smoke
and permanent-press
and heating
and cooking
clothes.
Other
sources
fuels such as natural
of
gas and
irritates the mucous membranes
of the eyes, nose, and throat. It is a highly
that combines with protein and can cause allergic contact dermatitis.
The
most widely reported
of the upper
carpet
symptoms
respiratory
attributed
Protection
Agency
is strongly
homes.
suspected
tract
from exposure
to formaldehyde
(EPA)
has recently
of causing
to high levels of this chemical
and eyes and headaches.(2,3)
exposure
conducted
was
asthma.
research
a rare type of throat
Until
cancer
recently,
However,
which indicates
in long-term
include irritation
the most
serious
the Environmental
that formaldehyde
occupants
of mobile
MATERIALS
The
AND
following
METHODS
ALCA
plants
Common
Bamboo
Chinese
English
Ficus
original
a healthy
cane
Chemical
constructed
from
nurseries
in our local area.
soil, just as they were received
between
tests. Stern's
Craig"
Miracle-Gro
They were kept in their
from the nursery,
fertilizer
and were maintained
was used to keep the plants
in
for the project.
contamination
to the following
Two chambers
Two larger
"'Janet
Spathiphyllum
"'Mauna Loa'"
Chrysanthemum
morifolium
Dracaena deremensis
"'Warneckei'"
were obtained
condition
Ficus benjamina
Gerbera jamesonii
Dracaena deremensis
Dracaena marginata
Dracaena massangeana
Sansevieria
laurentii
tongue
pots and potting
in a greenhouse
Name
Chamaedorea
seifritzii
Aglaonema
modestum
Hedera helix
palm
evergreen
ivy
Mother-in-law's
Peace lily
Pot mum
Warneckei
tested
Scientific
Name
Gerbera
daisy
Janet Craig
Marginata
Mass cane/Corn
All plants
were screened:
tests were
measuring
chambers
conducted
in four
Plexiglas
chambers,
which
were
dimensions:
measuring
Width*
Depth*
Height*
0.76
0.76
0.76
(30)
(30)
(30)
0.76
0.76
1.53
(30)
(30)
(60.5)
The tops of the small chambers
and side sections of the large chambers
were removed to
allow entry. Bolts and wing-nuts
ensured complete
sealing of the lids and created airtight
chambers
for testing. Constant
illumination
was provided
during the testing from a bank
of Damar Gro-lights
that encircled the outside of each chamber.
Mounted
on the inside of
each chamber has a coil of copper tubing through which water at a temperature
of 7 °C
was circulated.
This cooling coil prevented the Gro-lights from causing excessive heat buildup
inside the chambers
and minimized any fogging from plant respiration
in the chambers.
The
chambers also contained two small removable ports, each 0.6 cm (1/4 in.) in diameter, through
which contaminants
could be introduced
and air samples could be obtained.
A small fan
was used to circulate air within each chamber.
*Each dimension
is given in meters
(m); the equivalent
in inches
(in.) is given in parentheses.
All testswereconductedfor a periodof 24h. Experimental
testingincludedsealinga selected
plant in the Plexiglaschamber,injectingoneof the threechemicalsinto the chamberin the
methoddescribed
below,andcollectingairsamplesimmediatelyfollowingchemicalintroduction, at 6 h and, finally, 24 h later. Leak testcontrols,whereinthe samechemicalswere
injectedinto an empty,sealedchamber,wereconductedperiodicallythroughoutthe study.
In addition, soil controlswithout plantsweretestedto determineif the potting soil and
associatedmicroorganisms
wereeffectivein removingthe different chemicals.Thesecontrol testswereconductedby usingpotsof the samesizecontainingthe samepottingsoil as
the pottedplantsusedin actualtesting.Experimental
procedurethenfollowedthesameorder
asdescribedabove.
Benzenetestingat high concentrations
wasperformedby introducing35#L of benzene
into thechamberusinga 50#L microsyringe.The benzenewasinjectedonto a ,_:mall
metal
trayattachedto the chamberwalljust belowtheintroductionport andallowedto evaporate
with the helpof the fan insidethe chamber.A periodof 30min wasallowedfor complete
evaporationof the benzeneprior to withdrawingthe initial sample.
Samplingwasdonewith a Sensidyne-Gastec
air samplingpumpandgasdetectortubes
specificfor benzeneconcentrations
rangingbetween1 and100p/m. In sampling,a 200-mL
volumeof air fromthechamberwasdrawnthrougha Gastectube.Detectionof a colorchange
in the benzene-specific
indicatorreagentpresentin the tubemeasuredthe concentrationof
benzene.
Introductionandsamplingof TCE wasperformedin a similar manner,exceptthat the
indicatingreagentin the Gastectubeswasspecificfor TCE. The levelsof TCE that could
be detectedrangedfrom 1 to 25 p/m.
Because
formaldehydeis a water-soluble
chemicalandis routinelysuppliedasa 37.9percentsolutionin water,it wasnecessary
to utilizea differentmethodto introducethischemical
into thetestchambers.
The formaldehyde
solution was placed into a gas scrubber apparatus,
which
was attached
Tygon
tubing,
to both
an air pump
Air was bubbled
through
chamber as a gas. The time necessary
in the two chambers
was determined
120 s for the large chamber.
benzene
Sampling
and to the chamber
the formaldehyde
range
was performed
Because
air pump
of the formaldehyde-specific
the Sensidyne-Gastec
1 p/m concentrations,
solution
inlet using
pieces
and introduced
of
into the
to achieve the desired concentrations
of formaldehyde
experimentally
to be 50 s for the small chamber
and
and TCE using a Sensidyne-Gastec
detection
sample
equipment
tubes
in the same
as that used for
tubes.
The
was 2 to 20 p/m.
was not sensitive
a gas chromatographic
manner
and formaldehyde-specific
method
enough
was developed
for testing
less than
for low-concentration
analysis of benzene and TCE simultaneously
in single sample. For the low-concentration
benzene-TCE
studies, two chambers of similar size were used, having volumes of 0.868 and
0.694
m 3. Benzene
equal
volume
and allowed
formed
and TCE were introduced
mixture
of benzene
to evaporate
by using
and TCE.
for a 30-min period
the air pump
to withdraw
into the chambers
The sample
before
using a I-#L
was injected
the initial
of an
tissue
sampling.
200 mL of air through
7
volume
onto a Kimwipe
Sampling
a glass tube
was percontaining
Tenaxadsorbent.The sampleswereanalyzed
promptly
interfaced
5890 gas chromatograph
to a Hewlett-Packard
an HP Ultra
2 capillary
(HP)
column
and
flame
GAS CHROMATOGRAPH-MASS
FOR TRACE
After
chemical
injection,
(1/4-in.)
outside
air samples
diameter
air pump.
beginning
using a Tekmar
Model
cooled
ended
separation
the sample
ANALYSIS
was conducted
both
reached
entered
onto 18-cm
with Tenax
adsorbent,
contaminants
were desorbed
from
desorber
Rtx--volatiles
dioxide,
from the chambers
the
into a HP 5890 GC equipped
capillary
column.
and then followed
The GC oven
a temperature
at 0 °C, and a rise in temperature
when the temperature
MICROBIOLOGICAL
Using
unit
with
steel tubes packed
chemical
Restek
to 0 °C using carbon
on the GC, the sample
were collected
5000 automatic
at 0 °C, with a 30-s hold
program
air desorption
(GC) equipped
detector.
DETECTOR
stainless
Trace
with a 30-m, 0.32 mm inside diameter,
was initially
ionization
SELECTIVE
500-mL
using the Sensidyne-Gastec
tubes
using a Supelco
METABOLITES
(7-in.) by 0.6-cm
Tenax
Model
program
of 8 °C/min.
The
200 °C, for a total run time of 25.5 min. After
an HP 5970 mass
using a scanning
range
selective
detector.
of 35 to 400 atomic
mass
Analysis
of
units.
ANALYSIS
potted
plants
and potting
soil controls,
surface and subsurface
regions (approximately
analyzed by means of the pour plate technique
1-g samples
of soil were taken
from
10 cm in depth). Samples were subsequently
to determine the number of "colony forming
units"
per gram of sample (cfu/g).
Plate count agar (PCA) was utilized
microbiological
medium.
Plate count data reflect bacteriological
counts.
as the primary
Triplicate
samples were taken both before and after exposure
of the plants and soil to
benzene and TCE. Following incubation
at 25 °C for 24 h, samples were examined
for the
presence
of bacteria.
Due to the inherently
these microorganisms
After
plate count
cultures
on PCA
were then subjected
identification.
of asexual
Fungal
and
ACTIVATED
as shown
removal
Complete
described.
and fungal
Sabouraud's
dextrose
of biochemical
were examined
samples
agar,
have elapsed.
were isolated.
respectively.
Stock
Bacterial
tests in order to aid in preliminary
by light microscopy
of benzene
Analysis
Samples
of 2 h, or until all trace
AIR FILTER
in Figure
tissue taped
volatilization
tube and air pump.
and actinomycetes,
to search
for the presence
spores.
onto a Kimwipe
previously
and
rate of fungi
until three to five days of incubation
CARBON-HOUSEPLANT
for simultaneous
growth
both bacterial
to a series
isolates
sexual
Air filters designed
injected
be detected
data were recorded,
were maintained
isolates
5-min.
cannot
slower
l were tested in one of the large Plexiglas
and TCE.
inside
occurred
followed
Benzene
the chamber
and TCE in 500/_L
and were allowed
and 100-mL
air samples
on the Supelco
desorber
were drawn
chemicals
SYSTEM
initially
were removed.
8
chambers
volumes
to evaporate
were drawn,
for
using a Tenax
and HP GC that have
and at 15-min intervals
were
been
for a minimum
RESULTS
AND
DISCUSSION
The ability of houseplants
sealed experimental
shown
in Tables
shown
in Tables
chambers
1 through
Plants
in Tables
range.
1 through
suited
investigations
through
exposures
to the removal
found
in indoor
benzene,
in Tables
during
during
4 were exposed
these
were conducted
and more sophisticated
is demonstrated
8 were collected
Although
the levels commonly
soil to remove
3 was accomplished
4 through
to 20 p/m
be particularly
or potting
1 through
of chemicals,
of which
indication
of one or more of these chemicals,
During
methods.
Results
the final
of benzene
in the
plants
1. Trichloroethylene
(TCE)
Chamber
by Houseplants
they are far above
year of this project,
are shown
Removed
from a Sealed
During
a 24-h Exposure
Plant
Leaf
Area
(cm 2)
Gerbera
daisy
(Gerbera
jamesonii)
English
ivy
(Hedera
heix)
Marginata
(Dracaena
in Tables
(Spathiphyllum
"Mauna
Mother-in-law's
tongue
(Sansevieria
deremensis
Removed
Plant
4,581
38,938
981
7,161
7,581
27,292
7,960
27,064
3,474
9,727
7,242
13,760
10,325
16,520
7,215
10,101
15,275
18,330
"Warneckei")
seifritzii)
cane
massangeana)
Craig
(Dracaena
Micrograms
laurentii)
Bamboo
palm
(Chamaedorea
(Dracaena
Total
Loa")
Warneckei
(Dracaena
Experimental
Period
marginata)
lily
deremensis
"Janet
Craig")
15
might
and TCE (less than 1 p/m)
from these studies
Surface
Janet
data
and final year of this project.
to high concentrations
atmospheres.
of plants
while
gave a good
Total
Mass
8. The screening
from
8.
Table
Peace
and formaldehyde
the first year of studies,
the second
using low concentrations
analytical
TCE,
per
5
Table
2. Benzene
Removed
Houseplants
from
During
a Sealed
a 24-h
Total
Experimental
Exposure
Plant
Surface
Leaf
Area
(cm 2)
Gerbera
daisy
(Gerbera
jamesonii)
Pot mum
(Chrysanthemum
English
(Hedera
Mother-in-law's
tongue
(Dracaena
Peace
deremensis
(Spathiphyllum
(Aglaonema
Bamboo
"Silver
107,653
4,227
76,931
1,336
13,894
2,871
28,710
7,242
39,107
7,960
41,392
3,085
14,500
7,581
30,324
10,325
34,073
15,275
25,968
Loa")
Queen")
palm
seifritzii)
Craig
(Dracaena
4,581
marginata)
(Chamaedorea
Janet
"Mauna
evergreen
Marginata
(Dracaena
Micrograms
Removed
Plant
"Warneckei")
lily
Chinese
Total
laurentii)
Warneckei
deremensis
"Janet
Craig")
]0
by
Period
morifolium)
ivy
helix)
(Sansevieria
Chamber
per
Table
3. Formaldehyde
Removed
from
and Soil
During
by Houseplants
a Sealed
Experimental
a 24-h
Total
Exposure
Plant
Surface
Leaf
Area
(cm 2)
Banana
(Musa
Period
Total Micrograms
Removed
per
Plant
1,000
11,700
2,871
31,294
985
9,653
14,205
76,707
1,696
8,480
2,323
9,989
2,471
10,378
2,723
8,986
15,275
48,880
7,581
20,469
8,509
16,167
2,373
8,656
1,894
4,382
713
1,555
oriana)
Mother-in-law's
(Sansevieria
tongue
laurentii)
English
ivy
(Hedera
helix)
Bamboo
palm
(Chamaedorea
Heart
leaf
seifrizii)
philodendron
(Philodendron
Elephant
oxycardium)
ear philodendron
(Philodendron
Green
domesticum)
spider
plant
(Chlorophytum
Golden
Janet
elatum)
pothos
(Scindapsus
aureus)
Craig
(Dracaena
deremensis
"Janet
Craig")
Marginata
(Dracaena
Peace
marginata)
lily
(Spathiphyllum
Lacy tree
Chinese
(Aglonema
"Mauna
Loa")
philodendron
(Philodendron
Aloe
Chamber
selloum)
evergreen
modestum)
vera
]!
Table
4. Chemicals
Experimental
Removed
Chamber
by Household
During a 24-h
Formaldehyde
Plants from a Sealed
Exposure
Period
Trichloroethylene
Benzene
Initial
Final
Percent
(p/m)
(p/m)
Removed
Mass cane
20
6
70
14
11
21.4
16
14
12.5
Pot mum
18
7
61
58
27
53
17
10
41.2
Gerber daisy
16
8
50
65
21
67.7
20
13
35
8
4
50
27
13
52
20
18
10
Ficus
19
10
47.4
20
14
30
19
17
10.5
Leak control
18
17.5
2.8
20
19
5
20
18
10
Warneckei
Note:
Plants were maintained
Initial
Final
Percent
(p/m)(p/m)Removed
in a commercial-type
greenhouse
Initial
Final
Percent
(p/m)
(p/m)Removed
until ready for test-
ing. Each test, 24-h in duration, was conducted
in a sealed chamber with
temperature and light intensity of 30 °C +1 and 125 footcandles
_+5, respectively.
Table
5. Benzene
Removal
from
Houseplants
During
Golden
Final
Percent
(p/m)
(p/m)
Removed
ivy
0.235
0.024
89.8
Craig
0.432
0.097
77.6
0.127
0.034
73.2
0.166
0.034
79.5
0.204
0.107
47.6
0.176
0.037
79.0
0.156
0.074
52.6
0.182
0.055
70.0
0.171
0.162
5.3
0.119
0.095
20.1
pothos
Peace
lily
Chinese
evergreen
M argi n ata
Mother-in-law's
Warn ec kei
Leak
Soil
by
Initial
English
Janet
a Sealed
Experimental
Chamber
a 24-h Exposure
Period
test
control
control
tongue
12
Table
6. Trichloroethylene
Chamber
(TCE)
Removal
by Houseplants
During
from
a Sealed
a 24-h
Exposure
Experimental
Period
Initial
Final
Percent
(p/m)
(p/m)
Removed
ivy
0.174
0.155
10.9
Craig
0.321
0.265
17.5
0.207
0.188
9.2
0.126
0.097
23.0
Warneckei
0.114
0.091
20.2
Marginata
0.136
0.118
13.2
0.269
0.233
13.4
0.121
0.120
0.141
0.128
English
Janet
Golden
pothos
Peace
lily
Mother-inolaw's
Leak test
Soil
tongue
control
control
During
the first-year
studies,
for loss of chemicals
from
It was then assumed
that
sealed
chambers
and metabolic
high chemical
In an effort
could
rates
chamber
after
leakage
correcting
be attributed
expected
removal
the only controls
to determine
free of plants
and pots with fresh potting
to the plant
the exact
9.2
used were chambers
for controls,
from these plants
rates attributed
<1.0
leaves.
the removal
Because
to test
soil without
of chemicals
plants.
from
of the low photosynthetic
at light levels of 125 to 150 footcandles,
to these low-light-requiring
mechanism(s)
involved
the
houseplants
in chemical
the
were puzzling.
removal
from
the
plant-soil system, plants were tested with foliage and then the same pots and soil were tested
again after removing all foliage. Controls using full plant foliage with pea gravel covering
the soil were also tested (Table 7). A microbiologist
themicrobial
profile
found
Early tests demonstrated
in the potting
that potting
effective in removing
benzene
studies and careful observation
amounts
of foliage
covered
the air inside the chamber.
was brought
into these studies to determine
soils.
soil, after
all foliage
had been removed,
than pots containing
full foliage
determined
that this phenomenon
the potting
Thus,
soil surface,
reducing
contact
between
some of the lower leaves were removed,
contact between the soil-root zone and the chamber air containing
of these new studies are shown in Tables 7 and 8.
13
was more
and soil. However,
further
occurred only when large
toxic
the soil and
allowing
chemicals.
maximum
Results
Table
7. Benzene
After
Removal
Houseplants
Removing
from
a Sealed
in Potting
Soil
all Plant Foliage
Experimental
Chamber
and the Same Potting
During
24-h Exposure
by
Soil
Periods
Initial
Final
Percent
(p/m)
(p/m)
Removed
0.343
0.144
58.0
0.348
0.175
49.7
control
0.206
0.164
20.4
chamber
0.215
0.199
7.4
0.176
0.037
79.0
0.205
0.069
66.3
0.369
0.077
79.1
0.321
0.176
45.2
0.122
0.040
67.2
removed
0.175
0.062
64.6
Fresh potting
soil control
Leak test, empty chamber
0.099
0.091
8.1
0.262
0.254
3.1
Marginata
Full
foliage
Foliage
removed
Fresh
potting
Leak test,
soil
empty
control
Marginata
Full
Full
with
Janet
Full
foliage
foliage
covered
pea gravel
Craig
foliage
Foliage
Golden
Full
and soil
removed
pothos
foliage
Foliage
Table
Chinese
8. Benzene
control
Removal
and Soil
Bacterial
Evergreen
Plant After Being Exposed
to Benzene
in a Sealed Experimental
for
Counts
Several
Chamber
of a
24-h
Periods
Soil
Initial
exposure
After
six weeks
of intermittent
exposure
]4
Bacterial
Percent
Counts
Removed
(cfu/g)
47.6
3.1 x 104
85.8
5.1 x 104
Although
the bacterial
studies as shown
biological
counts
in Table
factors
8, this finding
with increased
Data
soil are constantly
their capacity
to continuously
since it is a well-established
genetically
thereby
increasing
exposed
when continuously
exposed to such chemicals.
toxic chemicals
from wastewater. (31-37)
Bacterial
isolates
a long period
Myxococcus,
found
to air containing
fact that
indicate
microorganisms
This phenomenon
Bacillus, Curtobacterium,
Arthrobacter,
Bacillus,
of the
in Table
have
8. This
the ability
to
as a food source
is currently
tongue
that when
such toxic chemicals
as shown
to utilize toxic chemicals
in the soil in which mother-in-law's
were Alcaligenes,
and Pseudomonas.
in some
other yet unidentified
study
the air improves
their ability
removal
Therefore,
from this two-year
clean
is not surprising,
adapt,
chemical
was not consistent.
may also be important.
the same plants and potting
as benzene,
correlated
used to remove
had been growing
Flavobacterium,
and Leuconostoc
for
Micrococcus,
were found in
marginata
root soil. Bacteria such as Bacillus, Flavobacterium,
Leuconostoc,
and Micrococcus
were also found in the Chinese evergreen potting soil. The peace lily potting soil contained
A ureobacterium,
These
Bacillus,
are common
toxic
chemicals
Results
when
activated
of the activated
this research
component
Curtobacterium,
soil microorganisms
effort
Micrococcus,
by plant
part
in the development
studies
of an indoor
such as cigarette
system
plant
roots
and
the potted
plant
study
from
large volumes
of air through
To assure
that no disease-causing
carbon-plant
filter,
no pathogenic
certain
exhaust
knowledge
conditions,
carbon
the filters
have
been
Tenax
that
off-gassing
or any other metabolite.
adsorption
tubes
to analyze
the levels of plant
metabolites
As temperature
rates will increase
and carbon
rates
dioxide
of trace
should
organic
as a food
into the room
for microorganisms.
Gas chromatograph-mass
air;
move
and
source;
from
the
To date,
air.
organic
were conducted
the air inside the sealed
indoor
air pollutants
them
in the filter exhaust
plants were normally
not expect significant
chemicals
by screening
maintained
off-gassing
selective
detector
experimental
under
several
of
at relatively
of ethylene,
studies
chamber
using
indicated
were negligible.
along with some plant metabolite
volatile
can utilize
were released
studies
and light levels are increased,
removal
to purify
that plants give off trace levels of volatile
so metabolic
This biological
a fan is used to rapidly
was analyzed
found
solvents.
This filter adsorbs
microorganisms
the ALCA plants. These low-light-requiring
low metabolic
rates; therefore,
one would
terpenes,
filter.
it is an essential
system with plants to remove
microorganisms
here in that
microorganisms
air from
microorganisms
It is common
reported
an activated
control
3 and 4. Although
study,
smoke and organic
their associated
holds them until the plant roots and
therefore,
bioregenerating
the carbon.
of biodegrading
in Figures
two-year
air pollution
of pollutants
also utilizes
are shown
of the NASA-ALCA
high concentrations
it differs
and Streptomyces.
to be capable
root growth.
carbon-houseplant
was not
Pseudomonas,
and most are known
also increase
chemicals.
15
it is expected
off-gassing.
that indoor
Increased
pollution
removal
oxygen production
the rate of leaf participation
in the removal
0.250
0.225
0.200
0.175
E
Z
I-Z
ILl
0.150
0.125
Z
0.100
0.025
0.000
,
,
,
,
0.5
,
'
1.0
TIME (h)
Figure
'
1.5
2.0
[WO
3, Removal of low concentrations
of benzene and trichloroethylene
from the air inside sealed experimental
chambers
using
golden
pothos
in an 8.in. activated
]6
carbon
filter
system.
LV8"9-0031
4O
3G
32
28
E
Q.
Z
C_
el=
I.,.Z
LLI
(_
Z
24
20
f...1
16
12
8
Figure
4. Removal of high concentrations
of benzene and trichloroethylene
from the air inside sealed experimental
chambers
using
golden
pothos
in an 8.in. activated
]7
carbon
filter
system,
Studies
closed
effects
of the beneficial
system
have been limited.
can be expected
microorganisms.
Arizona,
or detrimental
NASA
and USSR studies
can expect to experience
of life support.
However,
with complete
studies
effects
available
ecological
at Stennis
in Siberia
on man
of volatile
data
Center,
are beginning
when sealed inside facilities
metabolites
do not demonstrate
closure
Space
plant
involving
private
to present
with plants
man,
studies
a clearer
in a
that harmful
plants,
and
by Biosphere
picture
soil
2 in
of whatman
and soil as his major
means
SUMMARY
Low-light-requiring
houseplants,
along
demonstrated
the potential
for improving
pollutants
from the air in energy-efficient
with
activated
carbon
plant
filters,
have
indoor
air quality by removing
trace organic
buildings.
This plant system is one of the most
promising means of alleviating the sick building syndrome associated with many new, energyefficient buildings. The plant root-soil zone appears to be the most effective area for removing
volatile organic chemicals.
Therefore,
maximizing
air exposure to the plant root-soil
area
should be considered
when placing plants in buildings for best air filtration.
Activated
carbon
filters containing
fans have the capacity
of polluted air and should be considered
solving indoor air pollution
problems.
an integral
part
for rapidly
filtering
large volumes
of any plan using houseplants
for
ACKNOWLEDGMENTS
The authors
and the editorial
wish to recognize
contribution
the technical
of Yvonne
contribution
Travis
18
of Willard
to the preparation
L. Douglas,
of this report.
Ph.D.,
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