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lSX=UTIV~ SW - ARY
Many people spend large shunts of each day Indoors -in many
cases, 80-908- in a bouse, an automobile, ~ waiting room, an office or
other workplace, or ~ confined space accessible to the general public,
sueb as ~ store or a'~estaurant. It has been abown that indoor
exposure to en~rironmenta1 pollutants can be subetantial. Although
there is little epidemiologic evidence on the health effects of indoor
pollutants, indoor concentrations of Bore pollutants that already beve
primary ambient-air quality standards exceed those standarde. Indoor
exposure teas been largely overlooked in researob on the health effects
of environmental pollutants, but it can constitute an isportant
fraction of tbe total exposure to many pollutants.
Indoor pollution in residences, public building, and offices is
created for the most part by the occupante' activities and their use
of appliances, power equipment, and chemicals, by wear and tear and
outgassing of ewe structural or decorative materials, by thermal
factors, and by the intrusion of outdoor pollutante.
In some cases, the outdoor pollutants that penetrate to the
indoors may represent the most important pollutant stress on human
health and welfare, and such effects base been addressed at length in
reports of previous National Researeb Council committees. Ibis report
is focused primarily on the indoor air contaminants tbat are liberated
indoors. When they attain high concentrations, they may cause
nuisances, irritation of sensitive tissues, illness, and death fras
acute as well as chronic ensures. She pollutant sources such as
cigarette saoking--have been recognized for a long tis - , but their
importance "e only recently been evaluated. Othere arise fro. new
products or from old products in new uses, such as building materials,
pesticides, and insulation. A number of sources are of concern only
in the indoor environment, e.g., cooking, use of con suer products,
space-heating devices, and floor and wall ooveringe. me expanded use
of wood and coal for residentis1 speck beating, of home bobby and
craft products, and of products that liberate organic subetances is a
potential contributor to the contamination of indoor en~riror~ente.
Infectious microbes and allergenic agents can grow indoor e or be
transmitted into indoor environments.
1
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2
Ventilation alone (whether natural or forced) may not be
sufficient to dilute indoor pollution to an acceptable point. Natural
ventilation may be inappropriate because it is variable and generally
not controllable in a precise way for many indoor settings. Exclusive
dependence on forced ventilation is inappropriate because it i" not
universally available; moreover, introduction of untreated outdoor air
may not always be desirable. Also, natural ventilation and forced
ventilation may have substantial energy penalties, owing to heating
and cooling losses. He adoption of energy-saving proposals to reduce
ventilation rates could aggravate problems in indoor air quality,
create new problems, and perhaps be generally detrimental to health
and property, unless appropriate pollution-control measures are also
taken.
Public-health laws are broad enough to permit evaluation and, when
required, control of indoor environments. The public expects a safe
and healthful outdoor environment, and the same expectation applier to
public indoor environments. The regulatory authority to control
contaminant sources, to set or recommend building codes, and to
support or conduct research on or monitoring of indoor contaminants
rests with diverse federal, state, and local government units, but no
specific government unit has been directly charged with the
responsibility for protecting the quality of indoor environments.
For all the reasons stated above, the present quality of the
indoor environment and how this quality may change are matter. of
immediate and great concern.
SCOPE OF TEE REPORT
This report was prepared, at the request of the Environmental
Protection Agency (EPAl, by the Committee on Indoor Pollutants, which
was appointed by the National Researct; Council in the Board on
Toxicology and Environmental Bealth Hazards, Assembly of Life
Sciences. It is intended to characterize the quality of the indoor
environment--primarily with respect to airborne pollutants, although
others are discussed--and to determine the potential adverse health
effects of indoor pollutants. The charge was to review, compile, and
appraise the available knowledge. The Committee has also identified
the research needed for abatement of indoor pollution. .Indoor.
refers to the environments in homes, schools, public buildings, and
similar spaces to which the ~ blic has accese' industrial working
environments, however, are excluded from consideration here.
It is beyond the scope of this report to list all the pollutants
found indoors that are hazardous to human health. The examples given
make it plain that humans are exposed to a variety of potentially
hazardous indoor pollutants from diverse sources. It ts hoped that
this report will encourage researchers to broaden the list of
hazardous indoor pollutants and to characterize the hazards, so that
the general public and those responsible for pollution control and
abatement can be informed.
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Throughout this report, pollutants are mentioned without
dissuasion of their health effects. Thin does not constitute an
oversight on the part of the Committee, but rather reflects a decision
that the discussion here be adequate to show that there are indoor
pollutants that cause adverse health effects in humans. The reader's
attention is directed to Chapter III, which offers gone
recommendations for further health research with respect to these
pollutants, for further exposure studies, and for public education
about effective ways of reducing exposure to many contaminants
encountered indoors. The Committee on Indoor Pollutants and its
contributors prepared concise reviews of such physical aspects as
sources and concentrations and of such biologic aspects as the
physiologic and toxicologic effects of B variety of contaminants
encountered indoor=. In addition , the of feats of those contaminants
that bear on human well-being in a Ore general way, such as soiling
and corrosion, and the available means of controlling the presence of
the contaminants are discussed in some detail. The report attempts to
focus personal, corporate, and government attention on present and
potential problems related to indoor contaminants.
The Committee notes that documentation of excessive indoor air
pollution should not in itself be considered sufficient reason to
relax standards for ambient air. m e barriers between indoor air and
outdoor air are not absolute, and ambient air contributes to indoor
air. Furthermore, outdoor and indoor air pollutants may interact
chemically and physiologically. The Committee recognizes the
complexity of human exposures that have multiple sources. The
development of effective and efficient strategies for mitigating
hazardous contamination requires improved understanding of responses
to exposure and of pollutant interactions.
The Committee has not attempted to set priorities for research on
or regulation or control of indoor pollutants. Nor has it attempted
to develop risk analyses for these pollutants. The order in which
contaminants are presented in this report does not constitute a
ranking of importance by the members of the Committee.
To set priorities for differentiating among indoor contaminants
and to establish objectives for research and control program=, there
must be a system for comparison. The dimensions of this system
include the numbers of people exposed, the severity of exposures, and
the consequences of the exposures. To be comprehensive. the system
must also deal with ecologic and material damage, loss of
productivity, degradation of artifacts, and other kinds of impact not
related to health. Priorities could be derived from a ranking of
these variable" for pollutants of interest, but proper risk analysis
would require measurement of exposures by population subgroups and
weighting of exposure-response relationships by importance of outcome.
The Committee unanimously agreed that e';tabli'3hing firm priorities
for research on indoor pollutants that ranks one contaminant as save
important than another is premature. In most instances, we do not
appreciate the extent of population exposures. Available reports on
indoor air pollutants contain almost no data on the incidence of
disease or even annoyance related to changes in pollutant
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ooncentratione. Nevertheless, the Committee has made judg~aents based
on its interpretation of reported concentrations, of prevalence of
sources, and of evidence of effects on health and welfare. The
Committee offers guidance for research, development, and educational
programs by specifying current gaps in information and scientific and
engineering deficiencies. Priorities within these program will have
to depend on the extent of federal and private funding the Committee
believes that the determination of such priorities is urgent.
OmANI ZATION OF ]= REPORT
The introduction, sugary and conclusions, and recommendations of
the Committee are in Chapters I, IT, and TII, respectively. This
material is based OR both the body of the report and Committee
deliberations. Some conclusions and recommendations were derived from
consideration of the documented information in specific sections of
the report and the substantiating discuselons therein. Opera, based
on Committee consensus, were formulated from a Fore comprehensive
perspective on the subject of indoor pollutants.
After the introduction, awry and conclusions, and
recommendations in Chaptcre I, II, and III, the treatment of indoor
pollutants is presented in three primary chapters and three secondary
chapters. The three primary chapters are Chapter IV, on the sources
and characterization of indoor pollution' Chapter VII, on the health
effectes and Chapter ~X, on the control of indoor pollutants. They
are the most voluminous chapters and respond got directly to the
Co~ittee's charge to review and appraise the available knowledge on
indoor air pollution. me other chapter-Chapter V, on factor e that
influence indoor pollutions Chapter VT, on the measurement of indoor
pollution and exposures' and Chapter VITI, on other non-health-related
effecter offer tepor ten t additional information. They elaborate on
material presented in the primary chapters, and they introduce factus1
and conceptual material that the Committee feels essential for
evaluating indoor pollution c:o~rehensively.
Chapter TV, on the sources and characterization of indoor
pollution, covers radon and its decay products, formaldehyde and other
organic subetances, asbestos and fibrous glass, combustion produce,
tobacco Ike, consumer products, odors, temperature and humidity, and
other pollutants not specifically treated. The objective of "e
chapter, as of Chapter WI {on health effects), is not a global
treatment of every possible hazard encountered Indoors, but rather a
selective treatment. me chief criterion for selection is direct or
ct~cu~tantial evidence that ~ contaminant causes or is reasonably
likely to cause human stress, iliness,.or material damage indoors.
Chapter I, on factors that influence indoor pollution, expands on
the physical characterization of indoor pollutions in Chapter nit.
Aspects of geography, building design, and hit - n activity that lead to
variations in ventilation rates and in the distribution of pollutant
sources are presented.
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s
Chapter VI, on the aessurement and monitoring of indoor pollution
and exposure. reviews the design and components of indoor and personal
monitors, mathematical models for esti~ting indoor pollutant
concentrations, and methods of estimating total personal exposure.
Chanter VII, on the health effects of indoor Pollution, relates
the current understanding of the toxicologic and physiologic effects
of specific contaminants that are found at high enough concentration
and in a broad enough range of indoor environments to constitute an
actual or reasonably likely challenge to the occupants of those
environments. In some cases, as in Chapter Tv, the diecuse$on is
structured by source, such as involuntary Poking or indoor combustion
productes the health effects may be attributable to specific
components of a mixture of gases and particles, or tt soy be
attributable to the general, mixed exposure. The chapter also
considers indoor airborne contagion and allergens.
Chapter VTII, on the effects of indoor pollution on human welfare,
covers a number of items related to comfort, productivity, and
mater ial protection in indoor environments .
Chapter TX, on the control of indoor pollution, emphasizes the
engineering aspects of air-conditioning and indoor sir-cleaning.
Ventilation codes and standards are reviewed, and mechanical systems
for conditioning and cleaning air are described. The chapter
discusses strategies for controlling contaminants to Contain
acceptable indoor air quality in general. Some pollutants, because of
their sources or their physical and chemical properties, cannot be
treated with conventional control systems, and strategies for
controlling these pollutants are described specifically.
Appendix A lists national primary ambient-air quality standards
and occupational-health standards (for ache industrial environment)
established for the United States . In addition, it lists indoor-air
pollution standards and guidelines of several foreign countries.
Ventilation standards for dwellings are also listed. This appendix ts
not exhaustive with respect to relevant pollution or ventilation
standards, but it does offer a point of reference for some of the more
commonly used standards.
Appendix B presents an example of the interactions among energy
conservation, comfort, and indoor air pollution in a residence. This
simulation exercise illustrates the tradeoffs among energy-cost
savings, retrofit costs, and thermal comfort under the constraints of
maintaining various hypothetical conditions of indoor air quality in
particular kind of single-fa~ily residence.
PRINCIPAL FINDINGS ON SPl3CIFIC POLL=~S
-
CLASSES OF POLLUTANTS
RADON
Radon and its alpha-emitting decay products contribute ~ major
portion of the biologically significant dose associated which natural
background radiation. Many natural substances contain radium, a
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precursor of radon gas. Soil, construction materials, and groundwater
are the major sources of indoor radon. Indoor radon concentrations
are often an order of magnitude greater than outdoor concentrations.
The dose-response relationships for alpha-emitting radionucliaes are
not sufficiently well accepted to allow quantitation of tbe health
risk associated with measured indoor concentrations, and surveys of
radiation In homes are very limited. Expansion of the date base on
the variation of indoor radon exposure with time and Ovation is a
necessary prerequisite for assignment of a health risk to indoor
radon. In theory, techniques for controlling radon exposure are
available; but they need development and evaluation before they can be
applied economically on a large scale. The effectiveness of several
contaminant control strategies, other than ventilation, has not been
demonstrated in practice. awes for new construction may be necessary
to prevent the occurrence of high radon concentrations in modern or
refurbisbed dwellings. In any event, prudent judgment concerning
reduced ventilation in residences must be based on a better
understanding of radiation exposures in present houses.
FoRMALDEEryDE
The major indoor sources of formaldehyde have been identified.
Aldehydes and other organic substances emanate from outgassing of
urea-formaldehyde foam insulation, particleboard, plywood, fabrics
and, to a lesser extent, cigarettes and indoor combustion sources.
The high surface-to~volume ratio of particleboard and plywood used as
building materials in mobile bones, as well as lower air~exabange
rates, causes the high measured formaldehyde concentrations.
Formaldehyde can cause skin, eye, and throat irritation in occupants.
Moreover, potential health problems associated with formaldehyde
exposure. are readily identified in acute cases when concentrations
a re high and tolerance is low. In addition to ire itation, respiratory
disorders and allergies have been associated with high formaldehyde
concentration". There i" evidence of a decreased threshold of
sensitivity with prolonged exposure. Recent studies have indicated
that exposure of rats and mice to formaldehyde produces nasal cancer.
Owing to the ubiquitous and increasing use of resins and solvents in
building materials and furnishings, indoor formaldehyde concentrations
have increased. U"tes~ent technology is available, although at times
expensive, new and less expensive techniques are being developed. Me
Committee is especially concerned with long-term and essentially
continuous indoor exposures to low concentrations of formaldehyde.
ASBESTOS AND OTHER FIBERS
The health hazard posed by indoor exposure to asbetos has been
perceived as a problem by virtue of tbe presence of asbestos fibers in
insulating and decorative materials. Abrasion, mechanical vibration,
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or deliberate disruption of asbestos-containing surfaces can result in
increased`.fiber Concentration in the indoor environment. There have
been ~ small number of studies in which fiber counts bare been
documented in association with normal building use. Extrapolation
from what we currently understand about the expo~ure-response
relationehips for asbestos fibers to the very low concentrations
reported in indoor spaces, such as saboole, suggests ~ small health
risk under conditions of normal use. However, deliberate Edification
of surfaces to remove asbestos from buildings may create a risk of
exposure of occupants and workers. Buildings in which asbestos
exposure is likely to occur can be identified. m e risk of exposure
from dislodged fibers can be reduced by containment. m e occurrence
of me~othelioma (a specific form of cancer believed to result only
from the inhalation of asbestos fibers) may provide a very sensitive
indicator of the exposure of the qaneral population. Bbme exposure to
asbestos due to aging, cracking, or physical disruption of insulated
pipes or asbestos-containing ceiling tiles and speckling compounds may
be greater than public exposures in schools, which beve received the
most attention. Bomes built before 1950 in northern climates are more
likely to beve pipes insulated with asbestos plaster. Given the very
common use of asbestos in bones, sclmole,and other buildings, there i.
a need for further aseesament to identify structures where actual
asbestos exposure constitutes substantial risk to humane.
The extent of exposure of the geners1 public to asbestos fibers
teas not been assesseds however, the occurrence of me~othelioma should
be carefully monitored in the general population. Man-made fibers
have produced skin irritation, but have not otherwise been
demonstrated convincingly as hazardous to health. Epidemiologic and
toxicologic investigation of synthetic fibers abould continue. On the
basis of present knowledge, synthetic fibers in the indoor environment
should not cause undue concern.
TOBACCO SMOKE
Virtually every member of our society is exposed to tobacco
smokes 331 of the population smokes, and the rest are exposed to the
smoke released by others. Tbe constituents of tobacco smoke are well
documented as hazardous, the prevalence of population exposures is
very high, and there ts an increased incidence of respiratory tract
symptoms and functional decrements in children residing in home. with
Pokers, compared with those in bodes without smokers. Tbese
considerations and recent evidence of increased lung~cancer rates
among nonsmoking women living with smoking husbands have led us to
conclude that indoor exposure to tobacco Ike has adverse effects.
Coughing, beadacbe, nausea, and irritation of eyes, nose, and throat
are among the reported symptoms. Although many studies have measured
various components of tobacco smoke indoors, total exposure teas not
been determined. Passive exposure to tobacco smoke may constitute an
important exposure to respirable particles, such gaseous compounds as
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acrolein and fo~ldebyde, bencolalpyrene, and various trace metals.
Reduced ventilation increases concentrations of tobacco spoke. As an
energy~conserving compromiser spoking could be restricted to zones
that are well ventilated. public policy abould clearly articulate
that involuntary exposure to tobacco smoke teas adverse health effects
and ought to be minimized or avoided where possible. Under this
framework, the prohibition or restriction of poking in public
buildings, offices, etc., is a Control option to be considered with
ventilation and air~cleaning.
INDOOR COMBUSTION
When fuel combustion occurs indoors-~e.g.r for heating' ~king,
and power machinery, including suto~biles it gives rise to increased
concentrations of gases and particles. Unvented gas cooking is
probably responsible for a large portion of nitrogen dioxide exposures
in our population. In many bones, chronic exposures to nitrogen
dioxide indoors may exceed established national ~bient-air quality
Standards. Sborter-tera 1-h average concentrations indoors often
exceed the highest hourly concentrations Measured outdoors. Me
concentrations of nitrogen dioxide and carbon monoxide in residences
have not been fully documented. Bowever, ape studies have ~ rn an
association between gas cooking and the impairment of lung function in
children. Gas ~ King appliances are also sources of carbon monoxide,
carbon dioxide, formaldebyde, hydrogen cyanide, sulfate particles,
organic particulate matter, and organic vapors. m e problem of
chronic or even peak exposures to combustion products indoor e will be
accentuated with decreased ventilation and the increased use of
portable space heaters, wood- and coal-burning stoves, and indoor
venting of gas dryers. Carbon monoxide, nitrogen oxides, and
particles from automobile exhaust can produce increased concentration
in office buildings and public areas. Concentrations exceeding 1-h
carbon monoxide national ambient-air quality standards (NAAQS) by a
factor of 2-4 have been reported in several ice-akating rinks that use
gasoline~powered ice resurfacing Machinery. Office buildings and
apartment buildings with attached or underground garages can also have
sustained high concentrations of carbon monoxide inform. Secau"
both carbon Monoxide and nitrogen dioxide are odorless at iced
concentrations, the presence of increased and possibly hazardous
concentrations may go undetected.
Although confirmation te necessary, the available evidence
suggests that important population exposures to nitrogen dioxide and
carbon Monoxide can occur indoors and may constitute a sufficient
threat to the genera, public bealtb to Justify r_dis1 action.
Reducing exposure to those gases is relatively straightforward.
Source removal or direct venting of combustion sources abould be
considered.
Efforts to conserve energy present other potential problems
indoors. Effective energy~coneervation measures can result in an
overcapacity of existing heating equipment. Operation of such
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equipment at low load factors any decrease its overall combustion
efficiency and increase emission of the products of combustion.
MICPOORG~NISMS AND A~R~S
Microorganisms are present in the indoor environment and are
associated with human activity and the presence of domestic article.
The aicroorgani—e include bacteria, viruses, and fungi. Many
Microorganism such as spores, Molds, and fungi-~ultiply in the
presence of increased humidity. It is possible that reduced
ventilation arid the increased use of untreated recirculating air could
increase the concentrations of aicroorganisme. - ny of these
microorganism can produce infection, disease, or allergic reactions.
Respiratory viruses and bacteria can be trsnss~ltted fray person to
person in buildings and confined spaces. Certainly, respiratory
infections are an important cause of Morbidity that results in lost
earnings and discomfort. It is reasonable to assume that Come of the
incidence of respiratory disease results fro. airborne tran - lesion,
but it is not at all clear what effect ventilation, air-~nditioning.
Or air~cleaning will have on incidence. If the Win transmission is
between persons in contact with or close to each other, the mechanism
and efficiency of disease transfer will be relatively ineensitive to
ventilation rates and other operating conditions of tbe air handling
system. However, to the extent that infectious and allergenic
microorganisme remain viable and airborne, Substantial reduction in
Ventilation rates will tend to increase concentratior,~ and most likely
the probability of infection and allergy.
MOISTURE
Water vapor in confined spaces is a product of metabolic and
respiratory procesees, as well as of indoor combustion and evaporation
from clothes and dish~washing and bathroom functions. Condensation of
water indoors has been shown to increase corrosive effects of absorbed
gases. Decreases in ventilation tend to increase the indoor relative
humidity during the beating seasons. Access water vapor adsorbs or
condenses on drier or colder surfaces, and tot gives ri" to
increased deterioration or corrosion of building ~teriale,
furnishings, decorations, artwork, and other artifacts. Tncres~d
relative humidity may also promote the growth of molds, algae, and
fungi. Thus, humidity control may become an important component of
reduced-ventilation strategies. Some energy penalty easy result that
abould be considered in relation to the energy savings tot may be
obtained through reduced ventilation.
RBSPONSI8TLITI~;
The quality of the indoor environment ts not the responsibility
exclusively of any individual or government body. Even ~ single hose
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built in isolation (away fro. outdoor sources of cont~inante} teas the
potential to be con taming ted by its occupants, soil, outgassing from
piped~water use, building arteriole, cooking, space-heating, conquer
products, pesticides. molds, and fungi. Responsibility for the indoor
environment is on four levels: indi~ridualas arodilat aanufaetur~ra,
building designers, contractors, and ownerat and government.
—st sources of contamination are associated with human activity.
Individuals also exercise ace control over contamination sources and
ventilation. Bience, the individual can directly affect bis or her own
exposure, a. well as the exposure of those with wow the indoor space
is shared. rnis is also true, to a lesser extent, in the
nonindustrial workplace and in public buildings.
Building comers and operators are responsible for maintaining the
indoor environment and ensuring that at least minimal ventilation
standards are being set. It should be noted that there is little or
no enforcement of ventilation standards, once building plans are
approved. Architects, engineers, and contractors should treat indoor
environmental quality as a design objective. There are Many
opportunities in building design to separate people from the Sources
of contamination or to remove the sources entirely.
Manufacturers have the responsibility to warn the Consumer
adequately of the potential hazards of products. As evidence on
specific contaminants such as formaldebyde and nitrogen dioxide from
gas stoves--becomes available, less harmful substitutes can be
considered, and results of research on the control of the sources can
be made available.
Government Cores the responsibility to ensure that the indoor
environments to which the public has access are healthful. Clearly.
in the assessment of indoor concentrations, in instrument de~relop'sent,
and in the contrc>1 of health~directed research on indoor pollutants,
government can nerve the public interest. Government can establiab
ordinance. (regulations) to protect the general public from nuisances,
contamination, or direct health damages such ordinances may include
performance standards related to building materials and ventilatior~
codes for public and priorate buildings. In the same vein, go~rerns~ent
can require product certification in the case of know or potential
hazards. Furthermore, government can establiab concentration
standards or source~oontrol specifications. Radon, a naturally
occurring substance, is ~ clear example of con~minanto that would
require government attention, as opposed to that of industry or the
individual.
, ~ ~ ,
CONCLUSIONS
Definitive conclusions on the character of indoor sir are
prevented by the lack of systematic studies. The alterable data base
has been generated by a series of pilot studies and does not fully
characterize the variety of pollutants, indoor environments, and
occupancy cond$tione. Furthermore, the implementation of
energy~con~ervation measures and the introduction of new building
mater$ale have $ntene$f$ed the problem of indoor air contamination.
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Studies explicitly addressing both long-term and episodic events
have not been undertaken. Episodic release of contaminants in the
indoor environment may be rare, but can lead to short-term high
contaminant concentrations, which must be considered (in addition to
long-term low concentratione} in assessing the overall health risk of
indoor contaminants.
Measurement of indoor contaminants necessitates a sampling
protocol that considers the spatial and temporal profile of several
pollutants, as well as air diffusion and ventilation characteristics.
In addition, measurement techniques for assessing indoor
concentrations have to meet more rigorous requirements, particularly
with regard to sensitivity and interferences. Unfortunately, many of
the instruments required to characterize long-term and short-term
indoor pollutant concentrations do not exist.
From a practical viewpoint, it would be desirable to determine the
emission rate of an indoor pollutant by simple physical measurements
and to infer the dose received by a human inhabiting the trapdoor space.
But several intervening steps must be evaluated that involve degrees
of uncertainty ranging from good estimates to total ignorance. The
first process to be considered is the transport by diffusion and
convection; transport is influenced initially by the fluid motion of
the air near the source and throughout the indoor space. Cede modes
of transport depend on a number of factors and are usually spatially
and temporally variable. They lead to a concentration profile of the
contaminant as a function of position and time. Measuring such
profile" is virtually impossible, so the usual approach is to use
mathematical models of dispersion. The human receptor is not
stationary. Therefore, to obtain an exposure history, the spatial
history of the receptor ebould be specified or estimated. Inexact
knowledge of this function introduces a further degree of
uncertainty. Dose to the receptor is related to exposure through
deposition functions that express the fraction of the exposure that is
available to reach specific receptor sites and produce effects. These
deposition functions are themselves functions of several variables
that are usually Eagerly specified or unknown. Thus, several layers of
uncertainty are embedded between emission rate and receptor dose.
Indoor air pollutants generated or released indoors typically
occur in concentrations and mixtures that are often episodic and
generally vary over a wide range of time and from one space to
another. As a result, human exposures are difficult to assess for
individually or groups. If, in addition, the adverse health effects
are subtle, and especially if they are delayed, associations between
indoor air pollutants and disease or premature mortality are unlikely
to be discovered or demonstrated without a specific and substantial
effort. Thus, efforts to improve indoor air quality most likely will
have to be guided by information on the adverse health effects of
pollutants demonstrated and studied in other settings, such a. the
occupational environment.
For a limited number of air contaminants that can be found in
residential and public buildings, there is direct and circumstantial
evidence that human exposures are large enough and come-on enough to
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agent for subetantial morbidity and premature mortality. These
include radon progeny. sidestrea. tobacco poker formaldehyde, carbon
monoxide, nitrogen dioxide, aeropatbogene, and aeroallergene.
Bowever, our knowledge of the extent of the exposures and of the
exposure-reeponse relationships is inadequate to permit measurement or
even estimation of the resulting mortality and morbidity.
Furtber-~re, the kinds of health effects and the latent periods
between exposures and effects are quite varied. For exe pie, they
extend from acute intoxication from carbon monoxide and formaldehyde
to cancer that appears long after exposure to radon decay products and
as - ados.
In evaluating health ricks, it is reasonable to compare indoor
exposure with ambient air-quality standards for pollutants for which
there are suab standerde (carbon monoxide, sulfur dioxide, nitrogen
dioxide, ozone, lead, and total suspended particles). Depending on
bow the standards were developed, however, tbey may or may not
consider exposure of the aost sensitive population groups (the ill or
infirm or the very young). In addition, the composition of
particulate matter indoors, the potential synergistic interaction of
gaseous and particulate Batter, and the tine characteristics of
exposures can differ widely between the inshore and the ambient
environment. Bence, for cone pollutants, the ambient air-guality
standerde may actually underestimate the health risks.
Current knowledge would permit the establishment of defensible
indoor-air gusItty standards for only a few, if any, contaminants. In
any case, the establishment of such standards would not necessarily
lead to rational or enforceable con t role beyond ventilation codes for
dilution.-~Bcononica1 and reliable technigues for sampling and
anslyzing~tbe airborne oont~.inante of interest at very low
. Hi. . ~
concentrat-ione beve not been developed, nor have methods been
developed to relate spot samples fro. specific locations to integrated
doses.
He conclude tbst the best approach to the reduction of health
damage from exposure to indoor contaminants is to reduce the
population exposure to those oont~minante. Control strategies for
come pollutants would target the bigh-exposure groups. For other
pollutants, lowering the population~eighted wean exposure would, by
best estimates, reduce the bealth hazards.
8ecauee of the diversity of indoor pollutants and their sources
and because of the unpredictability of the distribution of such
points over tic and in different buildings, efforts to improve
indoor air quality s "uld ooncentrate on reducing the number and
strength of the sources by substitution of other asteris18.
Control strategies basal on the specifications of source Control
are preferred, ubenever feasible, because they are generally the most
dependable, with respect to tbeir extent and reliability of exposure
reduction. That suggests that reducing exposure through source
control or removal or through material substitution aunt be teared
by the practical realities of existing sources, which might not be
easy to eliminate, and by the unknown long-term toxicity of substitute
materials. When those strategies cannot achieve the desired degree of
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control at reasonable cost, they can be supplemented or replac" by
other engineering oontrole, such as dilution ventilation or
air~cleaning. however, it should be recognized that the cor~centration
reduction achieved through dilution may be less than that achievable
with source control or air~cleaning, whereas the effectiveness of
sir~cleaning devices usually depends on frequent and effective
application of maintenance procedures.
The specific source controls appropriate to each kind of
contaminant can be expected to crazy. For example, local exhaust
control is seost appropriate for nitrogen dioxide and carbon monoxide
from gas ranges, the sealing of walls and floors for radon control,
prohibition for asbestos~n~ining products, and specifications for
care of furniture, drapery, and carpeting materials prepared with
formaldehyde~containing subetances.
Air~conditioning systemize are generally designed to provide for all
or most of the thermal environmental requirements (i.e., heating,
cooling, and ventilating) of the occupied space. In the design of
tbese systems, it is necessary to select components that will ~ t the
particular requirements, such as heating coils or furnaces to beet
winter design temperatures, evaporator coils and condensing units to
meet summer design temperatures and humidities, and sir-cleanere or
ventilation air-flow rates to meet the sir-quality requirements of the
occupied space. The functional requirements of the space {i.e.,
residential, office, theater, etc.} also impose constraints on the
type of system that might be selected. Because of the wide variety of
functioned requirements of indoor environments and the other
constraints on design, a vast variety of control systems are used.
For instance, lighting and acoustic require'sents can influence the
size and location of the air~conditioning system, tbe location of air
supply and return devices, and air velocities in the air distribution
system. Available information suggests that this trend will continue.
Although the requirements may be described discretely and some
performance specifications are available for components of the system,
the effecti~renese of the system as ~ whole, including its impact on
indoor air quality, must be evaluated. Unfortunately, very few data
are available to indicate whether these systems, under actual loads,
perform in accordance with their designs.
R~ATIONS
1. A staged assessment of the exposures of the general population to
indoor pollutants and of the effects of such exposures on health and
welfare should be conducted by the federal government in both
residential and office buildings. Federal agencies with subetantia1
interests in definition of the indoor exposures i.e., the
Environsaental Protection Agency, the Department of Energy, the
Consumer Product Safety Mission, the Matione1 Institute for
Occupational Safety and Bealth, the Centers for Disease Control, the
National Inetitute of - 'riron~nte1 Bealth Sciences, the Pi and Drug
Administration, the National Center for Toxicological Re - arch, the
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Department of - I a" Urban "velo~nt. atc.-~ld "rtict~te
in the formulation of the study objectives and protocols and should
provide technical asaistance and financial support, as appropriate and
feasible. Congress should enunciate clearly its interest in healthful
and safe indoor environments.
2. Monitoring protocols and properly designed ~acn$toring instruments
must be developed to satisfy the special requirements involved in
investigating the indoor environment.
3. The indoor pollutants that should receive the initis1 Major focus
in investigation of sources, concentrations, dispersion, and referral
are radon and its progeny, tobacco smoke, for~ldebyde, nitrogen
dioxide, carbon monoxide, pesticides, water vapor, carbon dioxide, and
airborne contagion, including allergens.
4. The health effects that abould receive the initial major focus in
investigation are respiratory-infection rate. and respiratory
mechanical function in relation to nitrogen dioxide, tobacco~emake,
and airborne~contagion exposures s res~piratory-tract irritation and
potential carcinogenic effects in relation to formaldehyde, tobacco
smoke, asbestos, and alpha~emitting radon decay productat and Acute
intoxication, blood carboxybe~lobin, and cardio~rascular~dise~
aggravation in relation to carbon monoxide and nitrogen dioxide
exposures.
5. The low-le~rel acute and chronic complaints of malaise, headache,
stuffiness, and eye and throat irritation that are reported with
increasing frequency in large buildings deserve careful study.
6. me welfare and behavioral effects that should receive the initial
major focus in investigatior~ are material damage from mold formation
in relation to relative hum~ditys corrosion and surface deterioration
in relation to nitrogen dioxide' sulfur dioxide, and water vapors
fabric fading and deterioration in relation to solar radiation in
combination with nitrogen dioxide, sulfur dioxide, house dust, and
water vapor; soiling due to tobacco smokes and the lowering of work
productivity due to indoor air pollution and associated discomfort.
7. Responsibility for conducting a well~coordinated investigation of
the influence of building design and operational factors on the
concentrations of pollutants in both residential and co_rcia1
facilities should rest with the federal government, assisted by the
appropriate professional and scientific organizations.
8. The building factors that should receive the initial Moor focus
in investigation are as followas
a. The effects of reducing infiltration rates in existing
buildings on combustion efficiency of space-beating equipment and on
increases in relative humidity and concentration of indoor~generated
air pollutants and airborne contagion.
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b. The effects of materials of conetruction-and furnishings on
indoor-pollutant content--apecifically, there should be systematic
evaluations of outgassing and surface attrition of particleboard and
plywood (for formaldehyde and other organic subetances~s of wall and
floor coverings and fabrics {for organic substances); of masonry
products (for radon and dust) S of wallboard, pleater, and speckling
compounds (for dust and fibers) ~ and of the materials used for heat
storage in dry solar systems (for radon, dust, surface molds, etc.~.
c. The differences in air distribution, diffusion, mixing, etc.,
associated with the use of different climate-control systems, suab as
forced-air, baseboard, and radiant floor or ceiling systems.
d. The effectiveness of air-cleaning systems in capturing
pollutants in recirculating air--epecifically, this will require
in-place testing of systems, rather than test-stand evaluation of
components, and the effectiveness of a variety of commonly used
systems should be evaluated for radon and radon progeny, formaldehyde
and solvent vapors, and cigarette smoke.
9. The potential for consumer products to contaminate the indoor
environment needs to be evaluated. Hazardous components of these
products must be identified and tested. Adequate labeling, warning
users of bazards associated with product use and misuse in enclosed
spaces, should be required. Testing in homes is needed to assess the
extent of contamination, allergic reactions, and other health effects
of pesticides, residues, and consumer products.
Representative terms from entire chapter:
indoor pollutants
