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

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