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IT]
"CO~TIONS
The Committee on Indoor Pollutants recognizes that decisions
affecting the quality of the indoor environment are being made by
manufacturers, government agencies, builder-, building operators,
professional organizations, and private individual.. The decisions
encompass a broad range of activities in our society, with important
and long-term consequences. Federal agencies are planning
energy-conservation programs in buildings, contemplating the banning
of some products, and esti~ting the health risk associated with
indoor pollutant exposures. State and local government units are
considering revisions of building codes, ordinances to prohibit
smoking in public buildings, and requirements that asbestos insulation
be removed from schools. It can be presumed that there are similar
examples of decision-making at various levels in the private sector
that affect indoor environmental quality. In view of the possible
impact of these decisions, the Committee is concerned that policy,
research, and economic decisions be formulated with proper
understanding of their implications for the quality of the indoor
environment. For specific indoor contaminants, two basic inadequacies
in the available data must be resolved rapidly: poor definition of
population exposures and lack of understanding of the health and
welfare consequences of exposure to contaminants in the indoor
environment. This chapter presents the Committee'. general and
specif to recommendations for remedying these inadequacies .
We have observed that the existing cats base is, for the most
part, derived from pilot studies or anecdotal reports. The results of
the pilot studies reveal the complexity and diversity of the
information that must be looked at in evaluating the quality of indoor
environments. In some cares, the potential health significance of
exposure to indoor contaminants has been alluded to; but the full
extent of a potential problem with respect to types of contaminants,
concentrations, and numbers of people exposed has not been determined.
We believe that the research problem is large and requires
national coordination. A national coordinated research program would
have the following advantages:
46
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~7
· It would provide reasonable allocation of research efforts
among various federal agencies, national laboratories, and academic
institutions.
· It would provide standards for study design and quality
assurance that are sufficient for various decision-making purposes.
· It would provide integration of research activities and
dissemination of the information derived.
· It would provide maximal effectivenss of available funding.
!
The objectives of such a research program should be these:
· To determine the various sources and distribution of selected
pollutants, to measure their ranges of concentrations, and to identify
populations at r isk .
· To understand how the contaminants move inside buildings, how
they nix and react, and the rate at which they are repoured or
dissipated under various conditions.
· To characterize indoor pollutant emission source strengths
under actual conditions.
· To develop and test the effectiveness of control technologies.
· To determine the effects of energy-conservation measures on
indoor sir quality.
To meet some of these objectives, there must be research aimed at
developing improved instruments and at strategies for using them in
the study of indoor pollutants. Instruments used to characterize
indoor air quality reflect the early stages of this scientific
endeavor. The sampling devices used in indoor studies were originally
designed for sampling outdoor or industrial air. Many commercially
available ambient-air monitors are bulky, noisy, and expensive and
have not been tested for interferences that may be encountered
indoors. These devices have mostly been judged to be inadequate for
investigating indoor air quality, because their sensitivity, accura Q ,
and precision are not sufficient for the measurement of pollutants in
the small volumes of air in indoor spaces. The Committee recognizes
the importance of recent developments in the field of personal
monitors; but it also recongizes the need for a simultaneous effort
devoted to the development of air sampling devices designed
specifically for indoor environments. The new instruments must be
designed to record ~hort-term peaks in concentrations.
Instrumentation alone is not sufficient for characterizing the
indoor environment. Numerous variables indoors (perhaps more than
outdoors) must be considered: some sources of pollutants are peculiar
to some indoor environments; there are differences in structure type,
ventilation, and other characteristics that affect pollutant
concentration-; and activity patterns and time budgets of occupants
vary. Human activity patterns and time budgets, which are essential
in determining total exposures to air pollutants, are now derived from
population surveys. These survey" do not require (and therefore do
not obtain} information relevant specifically to indoor air quality.
The Committee sees the need for analysis of these variables and their
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~8
effects and reco_nds the development of ~1 strategies lfor
sampling, etc.) or protocols as guidance for future research. (=e
formulation of model sampling 8tr.~te8, for exile, is not want to
stifle innovation in sapling designs, but rather to establish the
model to be used for poppa ring data obtained by researchers whose
objectives differ.) The Committee reca~ende the formulation of
strategies and protocols for measuring the strength of Serious indoor
pollu~nt-emitting sources and for 888e88inq the effectiveness of
control devices and procedures in abating pollution.
The Committee recommends the formulation of a standard foldout for
reporting data and the develoF~nt of protocols for standardized
statistical approaches that will require only clinic analysis to be
used in validating numerical models. These wa,ld help to reduce
difficulties in comparing existing data and facilitate the development
of valid conclusions' conclusions now are often based on exceedingly
s~11 Apples.
, _,
Even comprehensive information about the quality of the indoor
environment would not permit determination of tote1 pollutant
exposure. It must be recognized that people are exposed to many of
the Awe pollutants outdoors, in transit, in the occupational-
industrial environment, and elsewhere. The relative i~itance of
each kind of enviroDent can be established and priorities can be set-
if and only if pollution ensures in all distinct environments are
characterized. I - Ok of a complete assessment guy lead to inefficient
allocation of scientific effort and control funds in each kind of
environment. me Committee believes that Me research efforts to
characterize indoor air pollution and human exposures indoors aunt
continue and intensify, if we are to determine total human exposure to
pollutants and understand environmental contamination and its effects
on health and the quality of life.
The remainder of this chapter presents specific recommendations
for research, grouped by class of indoor contaminant discussed in the
body of the report, and discusses the need for increased understanding
of indoor pollutants in general and the need for consumer protection.
RADON
,-
Nstionally coordinated investigations on radon ~nd its progeny
should take place on two levels. A well-funded and coordinated
national survey of radon concentrations in ~ representative apple of
residential buildings ts necessary to activate the exposure of the
total population to radon and radon progeny. Mbnitore that use the
track-etch plastic chip may be adequate for integrated measurements
for such national surveys, because they are inexpensive and are
specific to radon. Bowever, the performance of these and other
passive devices needs to be carefully evaluated. Inexpensive
instruments for measuring radon concentrations on a short-tare basis
need to be developed. mese instruments should be available to local
health agencies and others for spot surveys. On another level,
research on the transport and transformation of radon inside buildings
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49
deserves special attention. Rates of emanation of radon from various
sources, building materiale, soil, and qroundwater should be evaluated
in a variety of on-site and controlled conditions. the effectivences
of strategies for abating or eliminating indoor radon ~ including the
use of material sealants and fine~aerosol collection devices) must be
evaluated.
There is an urgent need to study the health effects of radon and
radon progeny. On the basis of known effects in miners exposed to
radon and radon progeny at relatively high cor~centrations, a plausible
case can be made that ~ substantial fraction of the lung~ncer
incidence in nonsmokers is due to the alpha-rad$ation dose to the
respiratory tract epithel$um from inhaled and deposited radon progeny
particles. It is urgent that this obeer~rat$on be examined
quantitatively by studies of appropriate human populations already
know to be exposed at below 100 WHIM and preferably in the range of
20-50 WLM. It is known that in Bone geographic area. large
populations are being exposed to radon gas and radon progeny particles
in their residences at concentrations that, although much lower than
those in uranium mines, are substantially higher than those in most
residences. Epidemiologic studies of populations exposed to radon and
radon progeny are reasonable and can provide the information necessary
for the establishment of realistic and needed ex~sure-response
relationships. These research studies should include examinations to
determine early pathologic change. other than tumors (e.g., changes in
sputum cytology and chromosomes aberrations), with 8"ci81 attention
to the possibility of a relationship of those changes to the eventual
development of lung cancer. Such studies should be performed as soon
as possible.
FOR M ALD1 3 " DE
Simple and reliable passive monitors that would easily satisfy the
requirements of large surveys of bu$1dinge for formaldehyde emission
do not exist. Monitoring formaldehyde is extremely difficult, because
of the influence. of temperature, humidity, and some analytic problems
that affect its detection. Both continuous and passive monitors are
needed with sensitivities in the range of 10-30 parts per billion. A
national survey for indoor formaldehyde exposures is not needed. but
systematic study of formaldehyde concentrations In a variety of indoor
locations is needed to estimate potential exposure of humans. "is
study would also identify sources of indoor formaldehyde by type of
building and decorative materials and would evaluate the effects of
ventilation rates and other variables on Me ooncentratior~. Regular
measurements over specified periods would help to identify
formaldehyde emission rates of insulating building materials and
furnishings as functions of temperature, humidity, ventilation rate,
and material age.
Formaldehyde emitted from buildings and conquer products has
resul~ced in complaints of adverse health effects by people in some
mobile homes and in some conventional residences and other buildings.
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so
Some of thee emission occurs oared long periods. Thus, long-tere
effects in Duane continuously exposed to for~aaldebyde at low
concentrations need to be studied. There is a particular need to
aseese the carcinogenic potential in the concentration ranges of human
exposures, inasmuch as one study in one strain each of rats and mice
hes shown that long-term exposure (~eating 24 ao) caused nasal
cancer. Humans have been and are now being exposed to formaldehyde in
several types of Pupations and in a variety of structures.
Epidemiologic investigations are needed to assess the human health
effects of formaldehyde, the magnitude and duration of exposure, and
the influence of cigarette-~aoking habits and the presence of other
contaminants. The mutagenic, ~bryotoxic, and teratogenic effects
must be included in the epideaio10gic and animal studies. In humans
exposed to formaldehyde, the aechani - s of airway and target cell
responses must be evaluated and characterized as to sensitization and
adverse effects in susceptible population groups, such as asthmatics
and persons with chronic obstructive lung disease. Bxposure-effect
relations and the mechanism involved in the biologic effects require
further animal toxico10gic research. For~aldebyde abould be
restricted to the extent that Ixweehold conquer products and building
products in normal use will not release potentially hazardous or
irritating Punts of formaldehyde into indoor air.
TOBACCO SMOKE
.
Tobacco smoke has abown so~ evidence of being a major cont~nt
in many indoor environments. Involuntary exposure to tobacco ~..~;
should be assessed to identify locations and populations with been
exposure and to determine the factors that contribute to high
exposures indoors. physical and biologic evaluation of tobacco~eaoke
constituents abould be continued. Tobacco-~moke constituents should
be test" for their toxic effects, their ability deco act as mutagens or
pr~otere of carcinogenesis, and their effects in combination with
other indoor pollutants. In addition, such properties of tobacco
Make as suse and age, chemical composition, irritation factors, and
odor cooponente should be examined to learn how they are affected by
ventilation rate, occupancy, extent of wok ing, air~cleaning . and
other control strategies.
The extent to which pismire exposure to sidestre~ tobacco Pike
produces respiratory tract symptoms and functional decrements in
non~okere, especially children, needs further documentation and
measurement. prospective studies of children in hales with Here
would be especially desirable to determine rates of lung Maturation
and illness frequency during childhood and adolescence.
Inforeation on the potential health effects of exposure of
nonsmokers to tobacco Poke should be widely.disseminated. He
~energy~cost penalty. of providing adequate ventilation in indoor
environments that permit Eking should be analyzed in a variety of
public buildings. Increased cigarette taxation as a a'ec~ni" of
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51
reimbursement for the cost of the additional air-conditioning needed
to remove tobacco smoke should be explored by governments at all
levels.
ASBESTOS AND ASBESTIFORM FIBERS
. .
A systematic survey is needed for the evaluation of the
distribution, integrity, and concentrations of asbestos in buildings
that contain or are thought to contain asbestos material. Bowever,
before this survey can be conducted, there is a need to develop new
instruments to record fiber counts continuously, with ~ ice
determination and possibly asbestiform-fiber identification, because
current sampling and analytic.techniques are inadequate.
Synergistic and interactive toxic effects of asbestos fibers in
combination with other air pollutants, particularly organic vapors,
should be examined in animal toxicologic and mutagenicity studies.
Although come asbestiform fibers tbemselves do not appear to
constitute an immediate health concern, their role as initiators or
promoters in various disease processes should be studied. The
incidence of mesothelioma in humans should be monitored via a registry
and appropriate surveillance methods, to detect cases associated with
substantial nonindustrial exposure to asbestiform fibers.
Guidelines should be developed for the control of exposure to
airborne asbestos fibers during maintenance, renovation, and
reconstruction in buildings that contain asbestos and asbestos-bearing
shingles, tiles, planter, etc.
COMBUSTION
Indoor combustion produces a number of contaminants. Among the
contaminants that deserve special attention are nitrogen dioxide,
carbon monoxide, respirable particles, nitrosamines, and ~ ~
aromatic hydrocarbon-.
indoor combustion have not been adequately evaluated. The Committee
recommends that controlled chamber experiments be conducted to
determine the products and their rates of emission from various types
of combustion under various conditions. These experiments should
focus principally on gas and electric cooking appliances and
supplemental heating systems, such as natural-gas, propane, and
kerosene heaters and coal- and wood-burning stoves. Air-venting and
air-cleaning systems should be studied as means of reducing indoor
concentrations of contaminants.
Indoor concentrations of combustion products have only recently
been surveyed. Combustion products are present in many indoor
polynuclear
The rates of their emission from sources of
powered equipment.
locations, such as restaurants, cafeterias, homes, hotels, buildings
with attached garages, and recreational facilities that use gasoline-
More comprehensive and systematic surveys are
needed to identify the range of c~mhustion-product concentrations
encountered indoors and the numbers of people exposed to them. These
.
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52
studies should determine the population exposure to nitrogen dioxide
over both the short and the long term. In addition, the applicability
of a~hient-air fixed-location monitors for recording nitrogen dioxide
and carbon monoxide concentrations indoors and for assessing
individual exposures should be studied.
Chemical reactions and rates of renal of emitted gases should be
determined. Nitrogen dioxide formation and removal should be examined
in detail. This will in~rol~re the simultaneous measureacnt of other
gaseous compounds. me effects of reduced air-exchange rates, zone
ventilation, and source Edification on pollutant reactions should be
assessed. As with other indoor contaminants, there is a general need
to improve instrumentation. Both nitrogen dioxide and carbon monoxide
monitors are available for passive integrating sapling and for
continuous monitoring. Bowever, for indoor use, they need to be
evaluated with respect to interferences. To evaluate short-term
personal exposures, lightweight continuous monitors for oxides of
nitrogen need to be developed. Evaluation of personal exposures to
re~pirable particles is currently limited to integrated samples.
Lightweight portable samplers or direct-reading monitors that can
measure mass concentration over shorter periods are needed.
Nitrosamines can be for~d during cooking and Poking. forever,
very few detailed investigatione of the concentrations, aeebanisas of
formation, and potential control methods have been done.
The polynuclear aromatic hydrocarbons can be forced during
high-temperature combustion of organic Batter. Some of them have been
found indoors as a result of emission from self-cleaninq ovens and
fireplaces. Pilot studies should be initiated to evaluate the extent
of emission of polynuclear aromatic hydrocarbons and their indoor
concentrations .
The magnitude and prevalence of decreases in pulmonary function
and increases in respiratory tract infection rates among children
living in homes with gas ranges and homes with electric ranges need to
be determined more accurately, and there are several related issues
that require clarifications
· Whether the effects are due entirely to the increased
nitrogen dioxide concentration in the gas-stove homes or are
influenced by the presence of other combustion effluents from the
Stoves, such as carbon monoxide, formaldehyde, and particles.
· Whether the effects can be related Sore closely to peak
concentrations or to long-term average exposures.
· Whether the effects of exposures to sideatream cigarette
spoke and to nitrogen dioxide are additive or synergistic.
· Whether exposure-response relationships can be developed and,
if so, whether they indicate an effective threshold concentration for
peak or average exposures.
The influence of reductions in air infiltration rates in existing
buildings on indoor Concentrations of combustion products needs to be
determined. Among the potentially serious health consequences of
reductions in infiltration are:
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53
.
Creation of greater pressure differentials between the
indoors and the outdoors, which could reduce the effectiveness of the
venting of combustion sources, e.g., furnaces and water-heatere.
Problems in proper venting could cause substantial exposures to carbon
monoxide (which could lead to severe intoxication and fatalities), as
well as greater exposures to carbon dioxide, ni~crogen dioxide,
formaldehyde, and particles.
· Increase in chronic exposure. to carbon monoxide, nitrogen
dioxide, formaldehyde, and particles at low concentrations frae
unvented combustion sources; this could lead to increases in
respiratory infections in children and decreases in their lung
function .
CONSUMER PRODUCTS
The use of some consumer products can lead to the release of
aerosols and gases indoors. The gaseous compounds of concern are
mostly organic vapors. Among the compounds of principal concern are
aldehydes and polynuclear aromatic hydrocarbons that evolve from
plasticizers; nitrosamines and hydrocines from rubber products,
combustion products, and cleaning agents' polychlorinated biphenyle
(PCBe) from burnt-out ballasts in fluorescent lighter and a variety of
other middle- and higher-molecular~weight organic subetances from
pesticides. A few studies have noted the presence of many of these
compounds indoors. However, no systematic survey has been done. With
regard to the evolution of organic Molecules from pesticides,
organochlorinated pesticides should be examined first, including
aldrin, dieldrin, endrin, benzene hexachloride, pentachlorophenol,
depone, chlordane, and DOT. The emphasis should be on the
determination of body burdens of these compounds and specifically the
relative contributions of inhalation, ingestion, and absorption to
body burdens e
The contents of consumer products should be investigated, and the
chemical constituents should be tested for their toxic, mutagenic,
carcinogenic, and teratogenic properties. In particular, there should
be toxicologic studies of solvents, vapors, aerosols, and particulate
compounds present in these products. Their synergistic and
interactive effects with other indoor pollutants should be tested.
Consumer products whose use involves the release of gaseous and
particulate materials to the indoor atmosphere should be so labeled,
with their components. Warning labels for consumer products that can
seriously pollute the indoors should state that they are to be used
only in area- with adequate ventilation and should stipulate the
possible consequences of their use when there is inadequate
ventilation.
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54
A~PA=OG=S AND IS
Little is known about the sources, concentrations, and survival
rates of many seropathogens in hods and other buildings.
Relationships among the incidence of respiratory infections,
concentrations of aeropathogens. and air~exchange rates in buildings
must be examined. The urgency arises from the recent modifications in
building ventilation codes that recommend reduced ventilation rates I
residential and commercial structures. A sample of co~ercinI,
institutional, and residential build_nge should be evaluated for the
types and concentrations of aeropathogens under ~ variety of
conditions of occupancy, human activity, ventilation, humidity,
temperature, and contaminant control.
Special attention should be
given to the newer energy-efficient buildings and buildings with
drastically reduced ventilation. me potential for infectious
contamination from air-cleaning filters, air heat-exchangers, air
humidifying systems, and air-conditioning systems deserves special
attention.
Other agents in the indoor environment known to produce allergic
responses include pollens, household mites, molds, animal dander and
excrete, and bacterial spores. Further work is needed to characterize
the size distribution of allergen aerosols, their sources, and the
conditions that are conducive to their generation. The airborne
concentration of allergens in the indoor environment has been
determined in only a few instances, and the relationship between
indoor concentration and response is poorly understc~d.
Case~control
epidemiologic and immunologic studies are needed to clarify
exposure-effect relationships. Such studies will require improved
instrumental and analytic techniques to facilitate characterization of
concentrations of allergens and of the variety of microorganisms in
the indoor environment. Synergic of biO\ - iC and nonbiol~ic agents
should be explored in animal toxicology studies.
Some acute allergic responses, such as ~h~idifier fever,. are of
unknown etiology. me pathologic agents in immunologic and cese-
control epidemiologic studice need to be identified. The pathogenic
process by which repeated small exposures to soot allergens often lead
to irreversible fibrotic lesions, as in bird-fancter's disease, should
be elucidated, and the potential of other, acre ca~n inner
pollutants to produce such disease states should be evaluated.
VENTILATION STANDARDS AND COST - L STRA1~GIBS
, . .
Knowledge of ventilation rates is of priory importance in studies
of indoor contaminant concentrations. Given the variety of
residential living units and other public and private facilities, it
i. not surprising that very little information exists to characterize
air-exchange rate.. Studies should begin to characterize air-exchange
rates in existing buildings by building type, geographic location,
occupant life styles, building operation, and observed average
pollutant concentrations during the different seasons. Smaller-ecale
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55
studies over a considerable period are recommended to characterize sir
exchange and its effects on occupant babavior in a representative
number of buildings. This information would help to show the
relationships among air-exchange rates, pollutant concentrations,
pollutant generation, occupant behavior, and physiologic effects, an
well as the effects of energy-con~ervation programs aimed at reducing
air inf titration rates.
With the objective of maintaining indoor air quality, while not
adversely affecting heating and cooling cost., there is a need for
engineering studies to determine alternative strategies for air
dilution of pollutants. Case studies of specific buildings may be
useful in determining the efficiency of selected filtration-
ventilation Schemes. For example. it may be economically preferable
to filter (or scrub) recirculated air or a mixture of recirculated and
makeup air to maintain indoor air quality. Studies should be done on
the effectiveness and energy-conservation implications of pollutant
sensors used to activate air-dilution or air-cleaning system.
Engineering studies on both air handling and air treatment systems are
encouraged. Although specific buildings may be studied in detail, the
application of the findings should be generic; i.e., the lessons
learned should be applicable to other buildings.
Standard methods should be developed and applied to evaluate the
performance of in-place environmental control systems and components.
Improved methods of providing acceptable and eff icient air diffusion
for thermal and contaminant control should be developed. Life~cycle
cost evaluations should be made on the basis of current and projected
energy costs to characterize these costs for future use in alternative
designs of residences and large buildings. Air-conditioning, heating,
and ventilation systems especially should be evaluated, in connection
with other building characteristics.
EXPOSURE STtlDIES
Proper assessment of indoor contamination needs a perspective that
only total-exposure studier can provide. The relative contributions
to individual and population exposures of the contaminants encountered
indoors, with both indoor and outdoor sources, must be evaluated. For
contaminants with multiple entry. routes, the contribution of
inhalation of indoor.ppllutants must be compared with all other
contributions to body Ardent. Only with this evidence can research
and control efforts be prudently allocated. Under current conditions,
studies of total exposure to many contaminants are limited by the
available instrumentation and, to a lesser extent, by analytic
methods. Such efforts are expensive. The extrapolation of their
results is constrained by the smallness and often the
unrepresentativeness of the samples of participants, by the inadequacy
of the information on activity patterns in the population at large,
and by lack of understanding of the distribution of indoor and outdoor
pollutant sources and the pathways that contribute to body burdens.
However, studies of total exposure and an understanding of
At,
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56
activity-related concentration date will eventually advance our
knowledge of pollutant exposure. This knowledge is a prerequisite to
rational allocation of resources for warranted reductions in
population exposures.
The Committee urges investigation in the behe~riora1 aspects of
indoor environments, apecif $cally the relationships one performance,
sense of well-being. contaminant concentrations, and stress.
Temperatures, odors, and noise outside preferred ranges can reduce
productivity, especially in self-pacing tasks . The relationship
between productivity and the quality of the indoor environment needs
to be determined. It is recognized that rela~cionships between the
behavioral variables and pollutant concentrations soy be difficult to
establish. Simultaneous aeas~:ements of trace organic vapors,
water-vapor content, conductivity, noise, light, temperature, and sir
exchange rates should be pursued.
EDUCATION
Public education offers an effective way of reducing exposure of
the population to many contaminants encountered indoors. People
informed about the potential for exposure to pollutants from Consumer
products, tobacco spoke, combustion products, etc., w$11 exercise sooe
Control to reduce the pollutant concentrations in their environments.
For the most part, their option. for controlling these pollutants are
limited to source maintenance, ventilation control, and, to some
extent, air~cleaning. Information about mainlining a clean indoor
en~rironacnt and assessing indoor spaces for potential contamination
before purchasing or renting ~ structure and ~ variety of suggestions
could be disseminated through health-~intenance organizations,
regional health-planning agencies, public~affaire off ices, the
Environmen"1 Protection Agency, the Department of Housing and Urban
Development, the Depar men t of Energy, the Consumer Product Safety
Commission, and a variety of other federal and state agencies. Me
General Services Administration, the armed forces, and the Department
of Bousing and Urban Development are responsible for many residences
and other buildings. Through certification of m$nt~1 acceptable
occupancy standards, these federal-organizations could develop
strategies to ensure Ant indoor spaces under their Jurisdiction are
free from hazardous concentratione of oontaminants.
Professional and trade associations could be instrumented in
developinq and disseminating information. These associstione are
encouraged to catabliSh standards for acceptable practice, with
respect to manufacturing, designing, building, and using products,
equipment, and structures that influence the quality of the indoor air.
Representative terms from entire chapter:
nitrogen dioxide
