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OCR for page 30
IT
SUMMARY AND CONCLUSIONS
CHARACTERIZATION OF I~R AIR PORTION
The air quality of the indoor environment has been characterized in
a limited number of pilot studies. Because of the large variety of
distinct indoor environments- - ingle and multifamily residence-,
of f ices, hospitals, restaurants, schools, recreational facilities,
transportation facilities, etc.--there is a major difficulty in
characterizing The indoor air environment.. Moreover, even within one
indoor environment differences in structure, in the operation and
strength of emission sources, and in hogan acti~rittes add to the
complexity of characterizing air quality. The available data, mostly
from the residential environment, amply demonstrate the diversity of
characteristics of indoor air and help in identifying subjects that
warrant further research.
RADIOACTIVITY
(pp ~ 58-82 )
The data base on sources and source strengths of indoor radon is
just beginning to be es~cablished. Initial attention focused on
building materials and groundwa~cer. Recent evidence from regional
studies in the United States points to ground soils {under buildings)
as perhaps the major source of radon. Only a small number of buildings
in the United States have been measured for radon and radon progeny.
Indoor concentrations are affected by various factors, including
ventilation rate, deposition of radon progeny on indoor surfaces, and
interactions of radon progeny with fine particles from various sources
(e.g., tobacco smoke and house dust).
Data from severed studies indicate that indoor radon-222
concentrations vary by at least two orders of magnitude, with average
values of about 1 nCi/~3. Such a large range is not surprising,
inasmuch as the studies included -various types of buildings, building
materials, underlying materials, and ventilation rates and used many
different measurement techniques. Radon progeny concentrations are
often given as potential alpha-energy concentration. (PA]3C), expressed
30
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31
in working levels (WL). Limited measurements indicate that typical
average radon progeny concentrations in residential buildings range
from 0.004 to 0.02 WL in some houses. Concentrations are muab higher
indoors than outdoors.
ALDEHYDES (pp. 82-100)
AIdebyde concentrations are almost always higher indoors than
outdoors. Formaldehyde is the most important aldebyde. Sources of
aldebydes include building materials (particleboard and plywood},
urea-formaldehyde (UF) insulation, and, to a lesser extent, combustion
appliances, tobacco smoke, and other consumer products. Variation" in
indoor aldehyde concentrations are not well understood, and emanation
rater from the various sources are not well quantified. Owing to the
time spent inside residences (including mobile bones}, offices, and
other indoor environments, human exposures to indoor formaldehyde are
markedly higher than exposures to outdoor formaldehyde.
Typical indoor formaldehyde concentrations in buildings with
products containing urea-formaldehyde resins range between O.OS and 0.3
ppm, although in some unusual instances concentrations of a few parts
per million have been measured in bosses with OF foam insulation. In
residences with sources of high rates of emission of formaldehyde-
containing products, the concentration typically range from 0.01 to 1
PP~
CONSUMER PRODUCTS
-
(pp. 100-111)
Many consumer products may emit gaseous and particulate
contaminants into tbe indoor environment during their use or even
during storage. Moat of the chemicals in these gases and particles may
be known or can be identified, but the chemical products resulting from
mixtures and interactions of them are not known. Likely exposures and
durations are poorly understood, even for cases in which the products
are used as directed. Willful abuse of aerosols or careless use of
solvents in enclosed spaces have resulted in acute and delayed
disorders and in death. The carcinogenicity of some compounds. such as
benzene and vinyl chloride, teas led to voluntary removal from consumer
products, but many chemicals with potentially toxic effects are still
in wide use. The use of insecticides, pesticides, and herbicides is
widespread. Even when applied outdoors, some compound. have been
measured indoors and have persisted over a considerable time.
.
ASBESTOS AND OTHER FIBERS
(pp. 111-128)
Asbestos is a widespread component of the structural environment in
schools, homes, and private and other public buildings. Its release in
the indoor environment depends on the cohesiveness of the
a~bestos~containing material and the intensity of the disturbing
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force. - at contamination is episodic, activity-related, and local.
Fiber counts and ~~s concentrations of fibers have been aessured and
shown to exceed those outdoors, and on occasion they may approximate
the occupational limit of 2 fibers per cubic centimeter. Fortunately,
during normal use, buildings containing asbestos have not shown indoor
fiber counts higher than outdoor counts. Current data are very limited
and apply mostly to schools and ~ few office buildings, but it appears
that the general public exposure to asbestos fibers is exceedingly low
in public buildings. A systematic and comprehensive survey of indoor
asbestos fiber contamination is needed and wil3. require reliable,
portable, and continuous monitors. Asbestos control technologies have
been applied in various indoor environments. Asbestos removed requires
a complex protocol to be carefully applied. because the very activity
of removal may cause severe asbestos contamination.
INDOOR COMBUSTION
(pp. 134-149 )
Unvented combustion appliance., especially gas stoves, are major
sources of indoor sir pollution. Although emission rates from a appall
number of gas alcoves have been determined for several pollutants, the
data base is very limited. Indoor concentrations of carbon monoxide
and nitrogen dioxide associated with incomplete combustion have been
observed to exceed current ambient-air quality standards. Carbon
dioxide emission from Invented combustion appliances may build up to
concentrations in the range of occupational air quality standards.
Local exhaust ventilation appears to be the most effective control
strategy for reducing pollutants from combustion. Improved combustion
efficiency and source elimination (lee., adsorbers or ~ change to the
use of electric ranges} are two additional Control approaches.
Residential wood and coal stoves are also potential sources of indoor
contamination. Attached and underground garages can contribute to
indoor carbon monoxide, nitrogen dioxide, and particle concentrations.
.
Carbon Monoxide
Indoor carbon monoxide concentrations are often higher than
corresponding outdoor concentrations. High indoor concentrations may
be attributed to emission from such sources as gas cooking facilities,
attached garages, faulty furnaces, and cigarette-~aoking. Typical
average indoor carbon monoxide concentrations in residences very
between 0.S and 5 ppm; observed E - ak values reach 25 ppe. In public
buildinqs, the indoor concentrations are usually lower than observed
residential concentrations, except under conditions of exceptionally
heavy smoking, as in bars, or in office buildings with underground
garages and improperly designed or malfunctioning ILIAC Myers.
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33
Carbon Dioxide
The indoor-to~outdoor ratio is greater than 1 for at least 90S of
the total monitored hours. Hourly indoor carbon dioxide concentrations
often exceed 2,000 ppm. Observed typical outdoor carbon dioxide
concentrations are approximately 400 ppm. The principal sources of
indoor carbon dioxide are the metabolic activity of occupants and
Invented combustion appliances.
Nitrogen Oxides
Emission from cooking appliances and emission from unrented heaters
are the principal contributors of oxides of nitrogen in the indoor
environment. The range of observed hourly indoor (residential} nitric
oxide concentrations is 30-300 ppb, with a maximum of about 500 ppb.
Indoor hourly concentrations of nitrogen dioxide '.rary between 50 and
500 ppbs indoor peaks of 700 ppb have been measured. Typical weekly
indoor concentrations of nitrogen dioxide range from 20 to 100 ppb.
The upper values in all the ranges just noted are associated with
Invented Gas appliances.
SHORING (ppe 149 - 168 )
Passive exposure of many nonsmoker" to the contaminants in tobacco
smoke occurs repeatedly. The indoor concentrations of tobacco~smoke
compounds that have other sources exceed the concentration. found
outdoors. For many people, the main or sole exposure to numerous
gaseous and particulate compounds results from passive exposure to
tobacco Ike. Children of Inking parents are among the largest
identifiable groups in this category. For the most part, however, the
specific contribution of tobacco combustion products to personal
exposures has not been documented. Most nonchamber measurements have
been of the survey type; many have measured ~ single component of amok e
without reference to outdoor concentrations, ventilation, or air
dispersion.
Smoking is the major source of indoor particles, but other human
activities (e.g., cooking and vacuum cleaning} also contribute indoor
particles. Particulate matter has variable composition, and the data
base indicates that there are no constant ratios of indoor to outdoor
concentrations. The ratio of observed daily indoor concentrations of
total suspended particles (TSP) to corresponding outdoor TSP
concentrations varies from 0.3 to 4. Residences occupied by families
with pre-achool-age children and smokers often have higher indoor than
outdoor concentrations. The TSP 24-h ambient-air quality standard,
which must not be exceeded more than once a year, is 260 ~g/m3.
The typical range of obeer~red indoor residential 24-h TSP
concentrations is 30-100 ug/m3, with an obeer~red maximum of 600
~/m3.
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34
Concentrations of fine particles (diameter, less than 2.5 - }
range from 10 to more than 260 W/~3 for a 24-h sample. The higher
concentrations are a~st always associated with smoking.
Concentrations in bars, offices, and cars with smoking can be higher
than 500 ),g/m3.
ODORS (pp. 168-202)
Odor. arising from occupant. and their activities figure in
indoor-air quality issues predominantly on the basis of comfort, rather
than health. Such routine indoor activities as cooking, Smoking,
bathroom use, and maintenance give rise to odors that are often
disagreeable and in some cases offensive. To a varying degree, almost
all building materials and furnishings are sources of odor. We
determination of odor attributes--such as intensity, character
(pleasantness/unpleasantness), duration, and perceptual threshold--is
complex, but can be effectively accomplished with ~ combination of
instrumentation and the use of panels of human.obeervere. Odor
controls increase in complexity from good housekeeping to ventilation
to masking and, finally, to air-cleaning.
OTHER CHEMICAL POLLUTANTS (pp. 82-111, 134-149)
Nonmethane BYdrocar bon
The ratio of indoor to outdoor total nonaethane hydrocarbon (NMHC)
concentrations is greater than 1 for about 90% of the total monitored
hours; that is, the SAC concentrations observed in the residential
environment are ale - at always higher than the outdoor concentrations.
Fluctuations in the indoor concentrations may be associated with
cooking, cleaning, and other activities. Typical concentrations in
residential buildings vary between 0 and 8.0 ppe, whereas typical
outdoor concentrations are between 0 and 3.5 pp~. Measured ~HC
concentrations in new office buildings often exceed 10 ppm and reach as
high as 50 ppm; this may be attributed to the extenel~re use of
synthetic organic building materials and furnishings in new office
buildings, as well as cleaning solvents and maintenance materials.
Ozone
Indoor ozone concentrations are generally lower than outdoor.
Unless there is an indoor generation source of ozone from electric
arcing or ultraviolet radiation {such as an electrostatic precipitator
or a document copier), the ratio of corresponding hourly indoor to
outdoor concentrations is almost always less than 1. ozone is
primarily a product of outdoor photochemical reactions. Precursor
pollutants leading to the formation of ozone are primarily of
automotive origin, but other sources include the combustion of fuels
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35
for heat and electricity, the burning of refuse, the evaporation of
petroleum products, and the handling and use of organic solvents.
Ozone is highly reactive and decays rapidly by absorption on indoor
surfaces. Indoor ozone has been measured at up to 120 ppb; typical
concentrations are between O and 20 ppb.
Sulf ur Dioxide
Indoor sulfur dioxide concentrations are usually lower than
corresponding outdoor concentrations. Sulfur dioxide emission indoors
is usually small, and, because it is a relatively reactive contaminant.
it is absorbed by indoor surfaces. Indoor hourly sulfur dioxide
concentrations are typically below 20 ppb.
Particulate Chemical Composition
There is very limited information on the chemical composition of
indoor particles. Measured lead concentrations in residences are
commonly iow--often below 0.5 ug/m3. Lead concentrations as high
as 2 vg/m have been measured in residences with wall paints that
contain lead compounds or in residences that are near major roads.
Indoor residential concentrations of nitrates are quite low and are
driven mainly by the outdoor concentrations. Observed daily indoor
concentration" of nitrates do not vary widely--between 1.0 and 5
ug/m3, with typical values at the lower end of the range.
The data base on sulfates shows that the indoor 24-h sulfate
concentration is usually lower than the corresponding outdoor
concentration. The type of fuel used for cooking and heating is
important in determining the indoor~outdoor relationship; houses with
gas appliances have a slightly higher indoor/outdoor ratio than houses
without gas appliances. Sulfor-containing compounds are added to
residential gas for detecting leaks of the otherwise odorless fuel.
Indoor daily sulfate Concentrations range between 2.0 and 15.0
~g/~3, with typical values at the lower end of the range.
AIDE MIC~R~ISMS AD DEGAS (pp . 394-417 1
For indoor biogenic pollutants' the sparseness of satisfactory
measurement methods and the resulting lack of an adequate quantitative
data bare constitute serious problems. In contrast with other indoor
pollutants, biogenic pollutants bear complex and varied organic
structures that defy automatic chemical assay. Biogenic agents exhibit
limited direct toxicity, more often provoking infection or allergic
responses. Bacterial and viral agents can produce infections in
humans; however, the indoor transmission of these agents i. not fully
understood. A broad array of fungi, algae, actinomycetes, arthropod
fragments, and dusts have been confirmed as airborne antigen sources
that evoke human allergic responses. Indoor biologic pollutants--most
`-~e
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36
notably bacteria and fungi--also play important roles in the
deterioration of surfaces and spoilage of stored materials.
MONI=d~NG AND MOD4=I~ OF I~R PQ==TON
.
Indoor air quality Monitoring, in addition to pollutant sampling,
must involve ventilation-rate measurements and daily activity logs of
occupants. in addition, meteorologic data and outdoor pollution
measurements may also be needed for the monitoring and assessment of
indoor pollution.
Most indoor monitoring studies have relied on instrumentation
developed for monitoring workplace or ambient air. The use of
conventional monitoring instrumentation is frequently awkward,
expensive, and suitable only for a limited number of comprehensive
indoor air quality studies. Owing to the special requirements,
instruments and sampling strategies are being developed specifically
for indoor residential and office environments. The advent of personal
monitors ha. permitted, in a few cases, the startup of monitoring and
exposure studies for specific pollutan~--nitrogen dioxide and radon.
Personal and portable monitors are being developed for carbon monoxide,
formaldehyde, and particulate matter. Monitoring the indoor
environment, either with fixed-location sampling devices or with
personal monitors, requires special protocols addressing pollutant
sampling, instrument calibration, source operations, and occupant
activity. When indoor monitoring takes place under normal occupancy
conditions, the protocol must ensure that the act of monitoring itself
avoids influencing those occupancy conditions.
Indoor-air pollution simulation model. provide a theoretical
framework for relating outdoor pollutant concentrations, meteorologic
factors, building factors, ventilation rates, and indoor source and
sink dimensions with indoor pollutant concentrations. Most
importantly, a validated simulation model must accurately predict a
desired concentration for conditions other than those tested
experimentally. Depending on ventilation conditions and the geometry
~ ~ . · .
of the structure, a single room, a Floor, or a whole outsang may De
adequately approximated as a single air-quality compartment (entity).
However, if sources and sinks are not uniformly distributed and if the
indoor environment is large, pollutant stratification occurs within a
building and a multicompartment numerical model is required to simulate
the indoor-air pollution concentrations. Almost all numerical models
are mass-balance equations that simulate the dynamic relationships
among indoor pollutant concentrations, outdoor concentrations, indoor
sources, and sinks ~ including ventilation) .
FACTORS MAT AFFECT EXPOSURE TO INDOOR POLLUTION
Exposure is ~ dynamic concept that is defined as Me joint
occurrence of two perhaps independent events: the presence of ~ person
in ~ specific environment and the presence of a pollutant at a specific
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37
concentration in the same environment. Because both human activities
and air pollutant concentrations vary spatially and temporally,
pollutant concentrations obtained from outdoor monitoring networks arc
inadequate for determining haven exposure. Bumen activities are among
the factors that must be addressed in assessing exposure to air
pollutant". They have been studied by many researchers, mostly
sociologists, to determine population mobility patterns and time
budgets. The results indicate that, on the average, employed Americana
spend 90% of the day indoors, whereas homemakers and retired people
spend up to 95S of their time indoors. General sociologic studies may
be used in air-pollution research, but do not address specific topics
of interest for the assessment of human exposure to air pollutants.
The exact indoor location (or environmental Cadet its of paramount
importance in exposure studies. Of all environmental types, the
in-transit mode has been studied more extensively than any other
microenvironment.
Indoor air quality, and therefore exposure to pollutants, varies
geographically as a function of outdoor regional air quality and as a
function of the rural, urban, or suburban character of the location of
the indoor environment in question. In rainy residences, the indoor sir
quality does not vary substantially. In larger buildings with many
ventilation zones, indoor sir quality pay very in accordance with the
f unction {utility) of each zone. Building factors that influence
exposure include the site condition., such as microclimate and
proximity to major outdoor pollution sources, building design (age,
size, ventilation systems), occupancy, and building operations. she
exact nature of the cause-and-effect relationships between these
factors and indoor air quality has not been established.
Hl3AI.TE EATS OF I~R FO"=ION
Several classes of pollutants with major indoor sources were
identified as having important known or reasonably likely effects on
human health: sidestream cigarette smoke, radon and radon progeny,
mineral and vitreous fibers, formaldehyde, indoor combustion products,
agents of indoor contagion and allergens, and, to a lesser extent.
temperature and humidity extremes, noise, and odors.
Other classes of indoor pollutants may have impacts on human
health, such as consumer-product aerosols and pollutants from hobby,
interior~decorating, and maintenance activities (e.g., solvent and
pigments). Because the evidence of their effects on health is meager,
the Committee could not determine whether specific effects were
attributable to them and concluded that effective review at an
appropriate depth was not feasible. Many airborne solvents, pigments,
mineral dusts, and other products used in hobbies and interior
decoration are present in the indoor air. The best data base on the
effect. of exposure to those substances is that drawn from studies of
the industrial workplace, and the reader is therefore referred to the
occupational-health l iterature .
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38
INVOLUNTARY SHORING
-
(pp. 364-382 )
Tobacco smoke is a major source of both gaseous and particulate
pollution in the indoor environment, and the nonsmoker absorbs
measurable amounts of carbon monoxide and nicotine, as well as s~11
Bunts of other smoke constituents, owing to involuntary smoking. The
carbon monoxide absorbed varies from negligible in well-ventilated
office buildings to Bunts that raise the carboxyhemoglobin (COlIb)
concentration by 2-31 in an exposure of 1-2 h.
The Comb produced by tone most severe Involun~ry-s~king ensure
likely to occur in everyday living is capable of reducing the maxi - 1
exercise capacity of normal healthy adults, but does not measurably
affect submaximal exercise capacity. Carbon monoxide has been shown in
one study to reduce the amount of exercise that pa~cients with hypoxia
chronic obstructive lung disease can perform before the onset of
dyspnea .
Patients with angina pectori" have a reduced exercise tolerance
After involuntary smoking that may be a combination of paychologic
stress and a carbon monoxide induced decrease in oxygen delivery to the
yocardz~. Carbon monoxide clearly reduces the Bunt of exercise
possible before the onset of angina in patients with angina pectoris.
Sell changes in visual and auditory vigilance have been
demonstrated at COMb concentrations that can be produced by involuntary
smoking, but no change in tests of complex function has been
demonstrated. Involuntary smoking has not been shown to produce acute
change. in lung volumes or in a number of small-airway resistance
measurements in normal healthy aduL - .
Long-term exposure to cigarette
Bake has been related to small-airway dysfunction in healthy
nonsmok ing adults .
Children whose parents smoke have been shown in some studies to be
more likely to have respiratory symptoms, bronchitis, and pneumonia as
infants. This relationship has been found in some studies to be
independent of parental symptoms, socioeconomic class, and the smoking
habits of other children in the household. It abows, in those studies,
a dose-response relationabip with the number of cigarettes smoked per
day by the parents. To the extent that these associations may be due
to cigarette smoke, it is reasonable to assume that the particle mass
or a specific compound contained therein, rather than nitrogen dioxide
or carbon monoxide, is responsible.
A twofold risk of cancer mortality in nonsmoking women has been
associated (in a Japanese study} with having husbands who Bake.
Apparently, the risk is proportional to the amount of passive smoking.
RADON AND RADON PRO
-
(pp. 307-322)
The radon gas that diffuses out of radium-bearing building
materisIs, subsurface soil beneath buildings, and well water into the
indoor air undergoes radioactive decay. As a result, the indoor sir
contains both radon gas and alpha~emitting decay nuclides in
particulate form, herein referred to as credos progeny..
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The health effects of radon and radon progeny are well established
from studies of workers. Exposure to radon and its progeny at high
concentrations has resulted in several hundred excess cases of lung
cancer among uranium miners in tbe western United States. The health
effects of much smaller amounts of radon progeny from indoor exposures
can be estimated on the basis of a linear, no-threshold dose model,
which yields upper-limit estimates of excess cancer in populations
exposed to various indoor concentrations of radon and radon progeny.
Lifetime cumulative exposures to radon progeny that result from current
indoor exposures are lower by approximately a factor of 100-10,000 than
those received by the U.S. uranium miners who have been studied.
The reliability with which the uranium-miner lung-cancer experience
can be extrapolated to the effects of indoor exposure. to radon progeny
among the general population i. limited by several important
difference. between the populations and by uncertainty about the extent
of the effect of cigarette-~moking on the incidence and latent period
for lung cancer related to radon progeny. The population differences
include: (1) an adult, male, healthy working population versus a
general population that includes the very old, the very young, and the
chronically ill; {2) coexposures to relatively high concentrations of
silica duct and diesel exhaust among the miners versus coexposure" to
relatively low concentrations of household pollutants and conewmer
products among the general populations and {3) differences in the
ethnic and social backgrounds and smoking histories Wang the different
populations.
ASBESTOS AND OTEI13R FIBERS
tPP. 339-350 )
The inhalation of asbestos fibers can lead, many years later, to
pulmonary fibrosis, lung cancer, and mesothelioma of the pleura and
peritoneum. All these diseases have been seen in humans who had
chronic occupational exposures to airborne asbestos fibers, and they
have all been reproduced in animals. Lung cancer and mesotbelio~a have
also been seen in humans who bad no occupational exposures, but who
lived either in the same households as asbestos~worker. or in
neighborboods where the ambient air had increased asbesto--fiber
concentrations resulting from proximity to an asbestos-related industry
or a geologic anomaly that acted as a source of airborne fiber.
Asbestos and asbestos~containing products such as ceiling tiles,
floor tiles, pipe insulation, and speckling compounds were widely used
in bonnet and public buildings because of their excellent thermal and
acoustic insulation and structural properties. When these materials
and products are displaced or disturbed by abrasion of deteriorating
surfaces during housekeeping and maintenance operations, renovations,
redecorating, or, especially in public building-, malicious mischief,
asbestos fibers can be released into the sir. Concern about the
inhalation of fibers that can result "e led to extensive and expensive
programs to remove asbestos, under controlled conditions, from
accessible regions of public buildings, such as saboole and libraries.
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do
Fibrous ~teriale used as substitutes for asbestos include glass
fiber, rock ~ol, and slag wool. They have been abase, in aniaa1
injection and implantation studies, to be capable of producing lung
fibrosis and aesotbelio~a. Bowever, they are wah lees important in
this regard than asbestos, and there is no corresponding buman-healtb
evidence associated with the forms in which they are used in industrial
and consumer products. Thus' their substitution for asbestos appears
to be beneficial, inasmuch as sueb substitution reduces the risk
associated with asbestos exposure.
~ RMALDERYDE
(pp. 322-338)
Formaldehyde teas been the subject of numerous complaints regarding
irritation of the eyes and respiratory tract, nausea, beadach*, rash,
tiredness, and thirst. These sy~pta" bare been reported Mainly by
residents of mobile and conventional ~es in which
formaldebyde~yielding products have been identified. Documented cases
of bronabial asthma due specifically to formaldehyde are few, More
commonly, asthma is aggravated by the irritating properties of
form Idebyde.
Aqueous solutions of formaldehyde damage the eye and irritate the
skin on direct Contact. Repeated exposure to dilute solutions any lead
to allergic contact dermatitis. Poisoning from ingestion is uncommon,
because the irritancy of formaldehyde makes ingestion unlikely.
A preliminary report from the Chemical Industry Institute of
Toxicology teas about that formaldehyde induces nasal cancer in
laboratory rats and in some of the laboratory mice similarly e^pveed at
the high dose. Nass1 cancer tree developed in the group of rats exposed
at 15 ppm and 6 ppm, and dose-related histologic changes of the nasal
mucosa in rats exposed at 2 and 6 ppm. Although the human mutagenic
and teratogenic potential of formaldehyde is not known, it has
exhibited mutagenic activity in a wide variety of organism.
Data on the health effects of otber environmental factors and their
interactione--such as cigarette-emoking history, variability of health
status, age, and genetic predisposition Which may modify responses to
formaldebyde} --have not been adequately evaluated. That saskes it
difficult to assess accurately the bealth risks attributable to
exposure to formaldehyde. However, the complaints of residents of
homes with formaldebyde-containing products are similar to complaints
made by persons studied in the [aboratory.~t similes formaldehyde
concentrations' hence, these health complaints may be related to
foraaidebyde exposure in the home. Accordingly, ~ subetantial
proportion of the U.S. population may be likely to develop sy~ptona as
a result of exposure to formaldehyde at low Concentration It has
been estimated, on the basis of laboratory tests a" various kinds of
population surveys, that perhaps 10-208 of the general population may
be susceptible to the irritant properties of formaldehyde at extremely
low concentrations. For exe - le. cove persons report mild eye, nose,
and throat irritation and other sy~ptosas at concentrations lese than
0.5 ppse, and come note sy.}?toas at concentrations as low as 0.25 ppe.
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~1
These concentrations could also cause bronchooonstriction and asthmatic
symptom in some susceptible persons, and chronic exposure to low
concentrations can result in sensitization. mere appears to be ~ wide
range of individual susceptibility to formaldehyde exposure. We cannot
determine Me exact numbers of susceptible people residing in indoor
environments where exposure to formaldehyde could produce adverse
responses. On the basis of estimates of the number of susceptible
persons among the geners1 population and the estimate that about 11
million persons in the United States now reside in mobile homes of
varied age, construction, and quality, it Day be concluded that ~
substantial number of persons are at risk of developing adverse health
effects associated with formaldehyde.
I NDOOR COMBUSTION
(pp. 3S0-364)
The combustion of fossil fuels in air results in the generation of
effluent stream. containing carbon monoxide, nitric oxide, nitrogen
dioxide, formaldehyde, carbonaceous particle-, and other products of
incomplete combustion, as well as the products of complete
combu~tion--carbon dioxide, water, and sulfur dioxide. When the
effluents are not vented to the outside, as in the cane of most gas
ranges and some space-heaters, the effluents are mixed into the indoor
air .
The percentage increase in the indoor concentration of the
combustion effluents resulting from such indoor sources is generally
greatest for nitric oxide and nitrogen dioxide. For homes with gas
ranges, indoor nitrogen dioxide concentrations are frequently twice a.
h igh as outdoor concentrations . The long-term integrated
concentrations can exceed thy national annual ambient-air quality
standard (MAAQS) of 100 ~/m (0.05 ppm) in some houses. Although
chronic animal inhalation studies and community air-pollution
epidemiology studier using central ~sonitorinq-station data have not
established that exposures at or near the NhAQS for nitrogen dioxide
produce measurable health effects, several recent studies of the health
statue of children living in homes with gas ranges have shown that they
had more respiratory illness and poorer respiratory function than
children living in comparable homes with electric ranges.
Increases in carbon monoxide sufficient to cause measurable health
effects are usually associated with improperly operated flames or
especially prolonged use of unrented space-heatere. Both carbon
monoxide and nitric oxide bind with hemoglobin and reduce tissue
oxygenation. Carbon monoxide from indoor combu8tio~ sources and
sidestream cigarette smoke can be shown to cause measurable increases
in Comb of exposed persons, but the health implications of such
i ncreases remain speculative. The Importance of increased carbon
monoxide and formaldehyde concentrations in indoor air was discussed
above.
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42
INDOOR AGENTS OF CONTAGION AND Air
(pp. 382-417 )
There is considerable evidence that a number of contagious~disease
organisms--including those associated with influenza, Legionnaires'
disease, tuberculosis, measles, mumps, and chicken pox--are capable of
airborne transmission in the indoor cnviron~nt. Other respiratory
diseases, such as the con cold and pulmonary infections, involve
airborne transmission. Because of the important role of respiratory
diseases in overall acute morbidity, airborne transmission of
contagious agents is important in the indoor environment.
The droplet-nucleu. theory--whereby liquid particles emitted from
the human respiratory tract evaporate to ~ particle size that can
remain airborne for a period sufficient to be carried by natural air
currents or convective ventilation flows and later deposited in the
human airways--is generally accepted and used as a basis for
transmission models. The effect of reduced ventilation in residences
and off ices on the incidence of infections is unknown.
Only a few airborne allergens are found in enclosed spaces. Their
health effects are difficult to estimate, although their impact is
sometimes appreciable.
EFFECTS OF I~R POLLUTION ON B~ ~F~
-
Effects on human welfare are taken to include loss of productivity,
human discomfort, and effects on Materials, primarily soiling and
corrosion of exposed surfaces.
SOCIOECONOMIC STATUS
(pp. 419-421)
Members of low income classes are more likely to live in pearly
insulated housing with higher air-exchange rates. Several reports have
indicated that gas Stoves or unrented gas or kerosene heaters are used
for supplemental space-heating in northern cities. The percentage of
homes with smokers appears to be inversely related to parental
educational level. Lead intoxication in children occurs
disproportionately in lower-inco~e urban populations; higher ambient
airborne-lead concentrations may contribute. Bowever, sooe potential
sources of indoor pollution may occur More frequently in the middle and
upper income brackets. Many consumer products, as well as oral and
wood stoves, exemplify such sources. Although the distributions of
these and other factors nary be functions of socioeconomic status that
cause some segments of society to be more or less disadvantaged winch
respect to a hazardous indoor environment, We available data allow
little more than speculation.
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43
PRODUCTIVITY
(pp. 431-437 )
There is a growing recognition of the difficulties in clearly
demonstrating the linkage between environmental quality and
productivity. Perhaps as a result of these difficulties, there appears
to be a slackening of research in this subject. Anecdotal or
observational evidence can be found to support the conclusion thee
improving air quality should improve productivity, but objective
documentation does not appear to exist or to be readily available. The
most promising avenues for research appear to be tbose which
demonstrate direct health effects of the various pollutants.
Nevertheless, under the modern, broad definition of ~productivity,. a
reduction in productivity is an almost certain consequence of pollution
itself .
SOILING ~ corset
(pp. 437-445)
Reduced indoor environmental quality can result in degradation and
deterioration of indoor materials, furnishings, and artifacts. As
efforts required for maintenance and housekeeping increase, the costs
of owning or operating a building increase. To protect property or
reduce costs of operation, more stringent control of indoor
environmental quality may be required than may be indicated for
protection of the health of occupants.
DISCOMFORT
,-
(pp e 4 21—4 31 )
Control of indoor environments in nonindustrial facilities is
designed to provide a degree of comfort acceptable to the occupants.
When a stimulus (whether odor, temperature, humidity, noise, or air
pollution) is changed beyond an acceptance threshold, there can be
adverse effects. This kind of environmental control may be difficult
to provide. However, the comfort-discomfort relationship may be one of
the more important aspects to consider in evaluating the performance of
indoor environmental control systems.
CONTROL OF INDOOR POLLUTION
CONTROI, STRATEGIES
(pp e 488—498 )
Three basic strategies have been identified: source removal.
dilution, and air-cleaning. In each of these classifications, methods
can be selected that will reduce exposure. The appropriate strategic.
to be used, either separately or in combination, must be selected with
respect to other and interacting factors--thermal, acoustic,
energy-conservation, and economic.
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44
CODES AND STANDARDS
_
(pp. 451-465 S Ap - - ix A)
Minimal requirements of acceptability are often stated in building
codes and standards in terms of air-exchange rules, temperature limits,
and so forth. These documents tend to cause minimal requirements to be
established for such direct effects as temperature, humidity, and
odors, but may not be sufficient to provide for other effects, such as
sir pollution or noise. Nor do these codes consider the interactions
that can occur awns these factors and other system features such as
lighting, thermal load O and spatial requirements .
. .
. ~
AIR DIFFUSION COrr=L
. . .
(pp. 465-471)
Indoor air quality is most Only Controlled by fore - -air
systems. Bowever, if diffusion control is designed without considering
possible stratification of air within a room or a building, there may
be local violations of thermal, humidity, or air~quality criteria for
acceptability, and occupants may be exposed to conditions other than
expected from the design.
. .
INDOOR ENVIRON CONTROL SYSTEM
.~7
(pp. 465-471 )
Control methods::.for indoor environments require specification of
environmental criteria and definition of the control variables. The
environmental criteria that are identified in this document are health,
comfort, welfare, energy consumption, and costs. The control variables
identified are spatial requirements, lighting factors, thermal factors,
air quality, and acoustic factors. Although environmental criteria and
control variables can be identified and described, the capability of
sensing the appropriate variables and controlling the system to meet
the specified criteria is severely limited. Moreover, most indoor
environmental control systems must attempt to respond activity or
passively to all five of the Control variables simultaneously.
Residentis1 air-oonditioning systems are conventionally designed to
respond to spatial, thermal, and air-quality variables And, to a
limited extent, acoustic variables. For larger facilities, such as
offices and schools, air-conditioning systems must also respond to
variations in occupancy and lighting loads, in addition to spatial,
thermal, air-quality, and acoustic factors. For other functional
spaces (e.g., concert auditoriums, art galleries, museums, and
hospitele}, some or all of the verishles must be controlled with
additional precision.
For many years, air-conditioning systems were designed to meet the
required environmental criteria (primarily thermal) at ainDeal first
cost. Operating costs were not considered important as first costs,
because energy was relatively inexpensive, compared with labor and
material. However, as the costs of energy increased rapidly during the
last decade, operating costs became a major factor in environmental
control. Energy-conservation measures were implemented in many
OCR for page 45
~5
buildings to reduce operating costs. Soac of these measure {e.~.,
improved system efficiency through better esintenance) had no is pact on
environmental control, but others {e.g., reduced ventilation, heat, and
lighting) had potentially adverse effects. One reason for the
occurrence of adverse effects was lack of understanding' by building
operators and owners, of the interrelationships axons ventilation
rates, lighting, and health responses.
. ~ ~ ~ ~ ~ ~ . . ~ ~ .
As an example, changes in
Gong can arrect tnerma~ comas, which affect ventilation rates.
Conversely, results of come energy~oonservation measures have indicated
that indoor environmenta1 quality not not be degraded and, in fact,
may be enhanced by these changes {e.g., reduced stratification within
occupied spaces). Thus, two general conclusions can be drawn: control
methods may not be capable of adequately responding to environmental
changes as energy-conser~ra~cion measures and cost contraints are
applied; and the quality of the indoor environment need not be
degraded, but can be enhanced if care is exercised in the selection and
implementation of the energy and cost oonatrainta.
AIR~CLEANING EQUIPMENT
(pp. 471-488 )
Air~cleaning equipment for residential. and commercial applications
is generally limited to particle filtration. Some gas and vapor
removal equipment is available, primarily for commercial applications.
Methods of rating or evaluating the performance of the gas and vapor
removal systems are not yet available. Methods are available for
rating and evaluating particle removal equipment, but they are
simplistic and outdated. Moreover, in-place methods of system
evaluation are available only for special cases, such ss hospitals and
laboratories.
COST m.F~:TIVENESS
..
(Appendix B)
Several economic models are available that can be used to evaluate
the costs associated with various control strategies.
Cost-effectiveness models that incorporate life~cycle costing are
needed for decision-ouking.
An approach to estimating the tact of residential
energy~conser~ration Measures on air quality is discussed in Appendix B.
The approach has not been validated or put into practical use, but is
presented for illustration and discussion.
Representative terms from entire chapter:
indoor environment
