Burning Issues

Formaldehyde - Our Homes and Health, Department of Natural Resources, Ball State University

[Wood smoke has formaldehyde in it.]

Indoor Air Quality Notes:

No. 1, 2nd Ed., Summer, 1989
Thad Godish, Ph.D., Director
Indoor Air Quality Research Laboratory

There is increasing scientific evidence to suggest that
formaldehyde contamination of residential and nonresiden-
tial indoor environments may be responsible for a variety of
irritating symptoms which appear to be building related.
Recognition that formaldehyde exposure can cause irritating
symptoms in sensitive individuals has prompted govern-
ments in Denmark, Sweden, the Netherlands, Italy, Finland,
West Germany, and Canada to adopt or propose the adop-
tion of indoor air quality standards for formaldehyde to limit
exposures. Concerns about acute health effects associated
with urea-formaldehyde foam insulation, as well as a poten-
tial cancer risk, has resulted in bans on the use of urea-
formaldehyde foam insulation for residential applications in
the United States (subsequently voided) and Canada.

The Nature of the Health Problem
Formaldehyde is a potent eye, upper respiratory and skin
irritant. Evidence from several studies also indicates that it
causes central nervous system effects, including headaches,
fatigue, and depression. It also has the potential for caus-
ing asthma and inducing asthmatic attacks as a nonspecific
irritant. Additionally, animal studies suggest that formalde-
hyde is a potential human carcinogen.

Recent epidemiological studies of occupationally-exposed
individuals suggest that formaldehyde causes human
cancer. Studies of residents of mobile homes exposed to
formaldehyde above 0. 1 0 ppm for 1 0 + years indicate a
significantly increased risk of throat cancer. This increased
risk is approximately 2 in 10,000.

Although cancer concerns have received the major share
of public and regulatory attention, investigations of consumer
complaints and epidemiological studies indicate that the
acute irritating symptoms which are associated with residen-
tial formaldehyde exposures are a very significant public
health problem.

Presumptive Evidence for a Causal Relationship
Presumptive evidence for a cause/effect relationship be-
tween reported health problems and the indoor environment
of an individual's home includes: (1) Symptoms commonly
occur in more than one family member. (2) Symptoms are
often most severe in the individuals) who spend the most
time at home, e.g., homemakers, infants, retirees. Such
individuals have the longest formaldehyde exposure dura-
tion. (3) Symptoms often diminish in severity when affected
individuals are away from the home environment. Extended
absences usually result in marked improvement. Note: When
this is not the case, the new environment may also have
significant formaldehyde contamination. (4) Symptoms
diminish in severity when home environment is provided
significant continuous ventilation by opening windows and/o,
doors. (5) Symptoms show a distinct seasonal pattern. Onset
can be related to a) the beginning of the heating season, b)
increased indoor relative humidity, or c) change in daily
activities which result in more time spent indoors. Diminish-
ed symptom severity may be associated with a) cold dry out-
door weather and b) summertime ventilation of home. (6)
Symptom onset may be associated in time to a) moving into
a new home (conventional or mobile), b) recent house
remodeling, c) acquisition of new furnishings, d) insulating
home with urea-formaldehyde foam, e) a change in activity
level. (7) Symptoms reported by visitors to affected home

Presumptive evidence for a cause/effect relationship be-
tween reported building-related illness symptoms and formal-
dehyde contamination of an individual's home includes: (1)
Symptoms are similar to those reported by workers who are
occupationally exposed. (2) Short-term human exposure
studies have shown irritation of eyes, nose and throat at con-
centrations as low as 0.10 ppm. (3) Symptoms can be related
to indoor humidity levels. Symptoms are most severe when
humidity levels are 50% or greater. When humidity is less
than 35%, symptoms diminish in severity. (4) Symptom onset
may occur in nonresidential environments where elevated
formaldehyde levels are common, e.g. furniture stores.
clothing stores, clothing sections of department stores. (5)
Presence of potent formaldehyde sources such as par-
ticleboard subflooring, urea-formaldehyde foam, extensive
quantities of either particleboard or hardwood plywood panel-
ing, cabinets and furniture. (6) Peak formaldehyde levels of
circa 0.06 ppm or higher. (7) Symptom severity increases
with formaldehyde concentrations. (8) Symptoms most
severe in new conventional or mobile homes.

Although apparent formaldehyde/building-related illness
symptoms may be similar to other common ailments such
as colds, they may be distinguished by their persistence,
recurrence, and distinct association with certain indoor envi-
ronments. In addition, several symptoms appear to be uni-
que to formaldehyde/building-related health problems. These
include unusual fatigue and unusual thirst. The former is par-
ticularly notable.

Evidence for Causation
Recent scientific studies indicate that formaldehyde ex-
posures are capable of causing symptoms in sensitive indi-
viduals at concentrations that are commonly found in a wide
variety of American homes.

At formaldehyde levels typical of many mobile and modular
homes. (0.35 ppm), Danish workers have reported a
significantly high prevalence of the following symptoms (as
compared to a control population): eye, nose, and throat
irritation, headache, abnormal tiredness, menstrual irregu-
larities, and unnatural thirst. Canadian studies of residents
of urea-formaldehyde foam-insulated (UFFI) houses have
indicated a dose-response relationship between the formal-
dehyde concentrations in UFFI houses and the following
symptoms: dizziness, diarrhea, eye irritation, nosebleed,
cough and sputum production. The average formaldehyde
concentration of the UFFI houses surveyed was a very low
0.045 ppm. Interestingly, UFFI residency was associated with
a significant increase in the objective symptoms, nasal air-
way resistance, and auquamous metaplasia of nasal
epithelial cells. The latter is considered to be a response to

Studies have been conducted at Ball State University
which have demonstrated a dose-response relationship be-
tween the level of formaldehyde present in residential envi-
ronments such as mobile homes and homes with par-
ticleboard subflooring and the severity of 16 different symp-
toms. These include: eye irritation, dry/sore throat, runny
nose, cough, sinus irritation, sinus infection, headaches,
unusual fatigue, depression, difficulty sleeping, rashes,
bloody nose, nausea, diarrhea, chest pain, and abdominal
pain. These significant relationships were observed at an
average concentration of 0.09 ppm. These studies suggest
that low-level formaldehyde exposures (less than 0. 1 0 ppm)
common to many homes in the U.S. are sufficient to exacer-
bate existing symptoms or to cause them directly.

Menstrual Disorders
Several studies have reported that menstrual irregulari-
ties/disorders may be related to occupational and/or residen-
tial formaldehyde exposures. This relationship apparently is
unknown to physicians treating gynecological problems in
this country. The implications of a formaldehyde link to
menstrual irregularities is significant since some treating
physicians recommend a hysterectomy as a means of
treating severe menstrual problems. Because a hysterec-
tomy has significant reproductive implications, it is impor-
tant that formaldehyde exposure be seriously evaluated as
an etiological factor by gynecologists and other treating
physicians and those affected. It is particularly likely to be
a factor where formaldehyde levels are high such as in
mobile or modular homes and in residences with particle-
board subflooring. Absence from the elevated formaldehyde
environment for a month or more should provide an indica-
tion whether the menstrual disorder may be associated with
formaldehyde exposure.

Formaldehyde--Sources and Levels
Although formaldehyde is used in a large variety of con-
sumer products, only a few release quantities of free formal-
dehyde sufficiently to significantly contaminate indoor air.
Problem products which may include particleboard sub-
flooring, paneling, cabinetry, furniture, hardwood plywood
paneling, use urea-formaldehyde (U-F) resins in their
manufacture. For wood products these resins are used as
interior-grade adhesives.

U-F resins are chemically unstable. They may release free
formaldehyde from the volatilizable, unreacted formaldehyde
trapped in the resin and from the hydrolytic decomposition
of the resin polymer itself. It is the release of the unreacted
formaldehyde fraction which is primarily responsible for the
high initial indoor formaldehyde levels associated with the
new mobile homes, conventional homes with particleboard
subflooring and homes recently insulated with urea-
formaldehyde foam.

The release of most of the unreacted formaldehyde may
occur in approximately 6 months depending on sources pre-
sent. After most of the volatile formaldehyde is released,
indoor levels may only be a fraction of those when the pro-
ducts were new. A 50 + percent decline is common.

Although a significant decline can be expected, the pro-
blem does not go away as commonly believed. Significant
continuous formaldehyde release can be expected as the
resin polymer undergoes hydrolytic decomposition. Because
of this, release of free formaldehyde from U-F products can
be expected to continue for an indefinite period.

Formaldehyde-releasing products differ in their emission
potential. Consequently, indoor formaldehyde levels will be
determined to a considerable degree by the nature of form-
aldehyde sources present. Additionally, they will also be
determined by the quantity of source material used in the
building interior. Despite common belief that indoor levels
are due to the additive emissions of all sources present,
laboratory studies show that major formaldehyde sources
interact. This interaction results in a number of outcomes
from source suppression to slight augmentation to complete

Most homes have measurable formaldehyde levels.
Homes in which formaldehyde contamination appears to be
associated with relatively low-level sources such as furniture,
one paneled room, etc. measured formaldehyde levels in the
range of 0.02 to 0.07 ppm with peak levels typically 0.05 to
0.06 ppm. Homes insulated with U-F foam (1 or more years
after installation) will have formaldehyde levels in the range
of 0.03 to 0.13 ppm with peak levels in individual homes in
the range of 0.07 to 0.13 ppm. Although U-F foam-insulated
homes have received the most notoriety and, of course,
regulatory attention, it must be pointed out that peak formal-
dehyde levels in such homes are relatively low. On the other
hand, conventional homes with particleboard subflooring will
have measured levels of formaldehyde in the range of 0.06
to 0.15 ppm with peak levels in the range of 0.10 - 0.15 ppm.
It is the mobile home, however, that exposes its residents
to the highest formaldehyde levels. Typically, peak formal-
dehyde levels in mobile homes have been in the range of
0.20 - 0.50 ppm with values as high as 1-2 ppm reported for
mobile homes manufactured before 1980. In most new
mobile homes formaldehyde levels are usually less than 0.40
ppm and are typically in the range of 0.10 to 0.30 ppm.

Cabinetry & Furniture
Two of the most overlooked problems of residential form-
aldehyde contamination and building-related symptoms have
been those associated with cabinets and furniture. Kitchen
and bathroom cabinets alone have the potential for causing
residential formaldehyde to rise to levels of 0.10 ppm or
higher. particularly when they are new. Almost all hardwood
cabinets, including solid wood, can be expected to release
significant quantities of free formaldehyde into living spaces
of homes. Typical materials used in cabinet manufacture
include particleboard, medium-density fiberboard, and hard-
wood plywood. Medium-density fiberboard is the most potent
source of formaldehyde found in residences. It is commonly
used in cabinet manufacture as a core material overlain by
hardwood plys. It is typically 5/8 inches thick and looks like
a thick hardboard. However, hardboards such as Masonite
are usually 1/4 inch and do not use U-F adhesives. Particle-
board is often used as shelving, as core material for hard-
wood plys, and as countertops. In countertops, the bottom
surface is not covered by barriers such as Formica and is
considered to be a potent source of formaldehyde. It is not
uncommon for cabinets to be made of good quality hardwood
plywood. Even such cabinets are seen to be potent sources
of formaldehyde, but less so than those constructed of par-
ticleboard and/or medium density fiberboard. It is not unusual
for cabinets to be constructed of all 3 materials-
particleboard, medium-density fiberboard, and hardwood

Most wood furniture available commercially is constructed
of wood products using urea-formaldehyde resins. Particu-
larly significant are those using medium-density fiberboard
and particleboard. These typically serve as core materials
overlain by hardwood plys, or in the case of inexpensive fur-
niture, a paper-based or plastic laminate.

Cabinets made from hardwood plywood or from solid
wood, as well as solid wood furniture, may be significant
sources of formaldehyde. The formaldehyde source is an
acid-catalyzed wood finish containing urea-formaldehyde,
particularly in the first six months after application. These
acid-catalyzed finishes are almost universally applied to hard-
wood plywood cabinets manufactured in the U.S., and their
use is widespread on solid wood and hardwood plywood
household furniture. Such finishes are commonly applied to
hardwood floors and prefinished wood materials.

Environmental Factors
Levels of formaldehyde inside a residence or other type
of building structure depend not only on the potency and
quantity of sources present but also on environmental con-
ditions which exist both on the inside and outside. Particularly
significant is the inside temperature and relative humidity.
As a general rule in the temperature range of 65 to 86 degrees F,
a temperature increase of 10 degrees F will result in an approximate
two-fold increase in formaldehyde levels. Conversely, a
decrease of 10 degrees F will result in a 5O% reduction in levels. Less
significant, but nevertheless important, is the effect of humid-
ity. An increase in relative humidity from 30-70% can be
expected to result in an approximate 40% increase in form-
aldehyde levels.

Low relative humidities during the winter period in many
northern residences are in part a major cause of the
significantly lower formaldehyde levels reported for homes
under winter conditions. The effect of low humidity is par-
ticularly significant in UFFI homes.

In addition to low humidity, lower wintertime formaldehyde
levels are due to increased infiltration rates which lower
formaldehyde levels by dilution. Increased infiltration rates
are associated with large indoor/outdoor temperature dif-
ferences and higher wind speeds. The greater the
temperature differential between the inside and outside of
a building, the lower the formaldehyde level. Conversely, the
smaller the temperature differential the higher the for-
maldehyde concentration. In the latter case, such
temperature conditions are common in spring and fall
months. Formaldehyde levels can be standardized to a given
indoor/outdoor temperature differential using the following
equation: Cs = Cm + 0.0016 delta-T where Cs = standardiz-
ed formaldehyde concentration, Cm = measured formalde-
hyde concentration, and delta-T = the indoor/outdoor
temperature difference at the time of testing.

Maximum formaldehyde values in general occur under
warm, humid conditions, particularly when the residence is
closed. Elevated formaldehyde can be expected in northern
residences in the spring and fall if home ventilation by open-
ing windows is practiced in the summer months and in the
spring, summer, and autumn months when air conditioning
is used. In warm, humid climates such as those experienced
in Florida and southeastern Texas, elevated formaldehyde
levels can be expected throughout most of the year. In the
drier climates of the West, formaldehyde levels and expos-
ures will be typically lower than in other areas of the country.

Formaldehyde concentrations decrease rapidly with time.
Significant decreases can be expected. The decrease time
or decay rate will depend on the potency of source materials,
their quantity relative to the air volume in the building, and
evironmental factors such as ventilation, temperature, and
relative humidity. The more potent the source and greater
the extent of its use, the longer it will take for formaldehyde
levels to decrease by a given percentage with time. The
higher the temperature and relative humidity and the higher
the ventilation rate, the more the formaldehyde level will
decrease with time. The decrease is initially very rapid follow-
ed by extended, much slower decreases. The release of
formaldehyde from source materials will never completely

New Products
Since 1978 there has been a significant improvement in
wood products bonded with urea-formaldehyde resins in
respect to formaldehyde emissions. Low emission par-
ticleboards and hardwood plywood paneling dominate the
present market for such wood products. Emissions of form-
aldehyde from low-emission products are only a fraction of
what they were prior to 1978. Despite this, the best grades
of particleboard applied as subflooring produce formalde-
hyde at levels that are typical of peak levels in UFFI houses
which can still be described as problem houses. Products
have improved, but yet remain sufficiently potent in their
formaldehyde releasing potential to cause a variety of irri-
tating symptoms.

Formaldehyde Standards
What level of formaldehyde exposure in a residence is
safe? There appears to be no lower level that is safe for
everyone. However, the lower the concentration, the lower
the risk of adverse health effects.

A variety of official and recommended standards have
been applied to formaldehyde exposures. For individuals
occupationally exposed, the Occupational Safety and Health
Administration (OHSA) permits exposures up to an average
of 1 ppm 8 hrs./day, 5 days a week, with a requirement of
medical surveillance for employees exposed to concentra-
tions greater than 0.5 ppm.

Occupational standards cannot, however, be validly used
to determine the safety of residential exposures. Such stan-
dards are designed to provide a relative measure of protec-
tion to nominally healthy workers age 18 to 65 for an 8-hour
day/5 day work week. Occupational standards cannot eas-
ily be extrapolated to residential exposures which may range
from 14-24 hours/day, 7 days per week. Exposed individuals
in residential environments not only include nominally
healthy adults, but also the very young, the old and those
with existing ailments. These subpopulations may be expec-
ted to be at greater health risk to formaldehyde exposures
than occupationally-exposed workers.

In response to reported building-related illness health pro-
blems associated with residential formaldehyde exposures,
several West European countries have proposed or pro-
mulgated indoor air quality standards for formaldehyde. For
West Germany and the Netherlands this standard is 0.10
ppm maximun concentration; for Denmark 0.12 ppm.
Although no residential indoor air quality standards have
been established in the United States, the American Soci-
ety of Heating Refrigerating and Air Conditioning Engineers
(ASHRAE) has recommended a voluntary standard of 0.10
ppm, maximum concentration. NASA has had a similar
standard for manned space travel of .10 ppm since 1967.

Canada has recently recommended an action level of 0.10
ppm for residential exposures with a target level of 0.05 ppm.
This means that the Canadian government has concluded
that levels of 0. 1 0 ppm and above are not safe and that the
homeowner act to reduce levels. This is in marked contrast
to the Department of Housing and Urban Development's
target level of 0.40 ppm for new mobile homes. This target
level in essence says that HUD believes that human ex-
posures of 0.40 ppm in residential environments are safe.
OSHA on the other hand says that exposures to 0.50 ppm
over as little as an 8-hour period requires medical surveil-
lance. The HUD target level reflects the ability of wood pro-
duct manufacturers to make products which do not exceed
the target level. The target level does not protect public
health. Rather than protecting consumers, it provides
regulatory sanction for the manufacture of defective products
which are a significant threat to public health.

Building-Related Illness Checklists
Checklists have been developed and presented here to
assist individuals, public health practitioners, and physicians
in evaluating the potential relationship between an individ-
ual's health problems and the indoor environment of his/her
residence or place of employment.

The household symptom checklist summarizes a variety
of symptoms or health problems which, although they may
be nonspecific, have been associated with formaldehyde
exposures. These symptom/health problems usually are per-
sistent or recurring and generally do not have an easily
recognizable etiology. The checklist in itself may suggest a
building-related illness health problem since it may show a
pattern of household or family illness which may not be
recognized in the normal practice of medicine.

Confirmation of Building-Related Illness
An evaluation of responses to the attached checklists may
help to identify a building-related health problem. A strong
association between the reported illness and the indoor
environment is suggested with increasing frequency of
positive responses.

Particularly significant are responses to items which in-
dicate that symptom severity decreases with absence from
the home or with significant home ventilation. The former,
however, should be viewed with some caution. Removing
an individual from his/her home not only changes exposures
to air contaminants such as formaldehyde, but it also may
change lifestyle patterns, type of food consumed, etc. Addi-
tionally, one must also assume that the new environment has
less contamination than the existing one. In many cases the
new environment itself may also pose a building-related
health problem. To minimize changes in lifestyle factors,
eating habits, etc. a confirmation protocol based on providing
significant ventilation to the home environment is

Note #2 - Residential Formaldehyde Control available on
request. Please send a self-addressed, stamped envelope
for each request.


For each item respond by Checking yes, no, don't know or not applicable,
in the adjacent column.

Yes No Know N/A
1. Symptoms reported by more than one family member.
2. Irritating symptoms most severe in family member who spends
most time at home.
3. Symptoms severe in infants or very young children.
4. Symptoms become less severe when individual is absent from
home with longer periods showing marked improvement.
5. Symptoms diminish in severity when home is provided
significant continuous ventilation.
6. Symptoms exhibit a seasonal pattern.
7. Onset of symptoms can be associated in time with:
a. moving into a new conventional or mobile home
b. recent house remodeling
c. acquisition of new furnishings
d. insulating home with urea-formaldehyde foam
8. Symptoms reported in visitors to individual's home.



Yes No Know N/A
1. Symptoms most severe during warm humid weather.
2. Symptoms least severe on cold dry winter days (in colder
3. Symptoms of eyes, upper respiratory and central nervous
system (eye, upper respiratory and CNS effects).
4. Peak formaldehyde levels of circa 0.06 ppm or higher.
5. Symptom onset in environments where elevated formaldehyde
levels are common, e.g. clothing stores, clothing sections of
department stores, furniture stores, etc.
6. Presence of major formaldehyde sources.
a. particleboard subflocring
b. paneling - hardwood plywood, particleboard
c. cabinets - particleboard, medium density fiberboard,
hardwood plywood
d. wood furniture - particle board, medium density fiberboard,
hardwood plywood
e. urea-formaldehyde foam insulation
f. acid-catalyzed finished wood materials - cabinets, furniture,
hardwood floors
7. Symptoms very severe in residents of mobile homes or new
homes with particleboard subflooring.
8. Symptoms associated with one area of house where potent
sources of formaldehyde are located (i.e. closed bedroom)-



For each resident indicate with a check persistent or recurring
symptoms/health problems which cannot be associated with any readily
diagnosed illness such as cold, flu, etc.

Occupant's Name:


Eye irritation
Eye infection
Dry/sore throat
Excessive phlegm production
Runny nose
Sinus congestion
Sinus infection
Bronchial pneumonia
Shortness of breath
Asthmatic attacks
Disturbed concentration
Unusual fatigue
Difficulty in sleeping
Nasal Sores
Diarrhea/loose stool
Chest pain
Abdominal pain
Menstrual problems
Unusual thirst

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