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
c_ Q.
i Q_
E I=
o i.m.
q_ °,w..
,4= qw
0
q) q_O
I=
°l.b
c_ 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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22
