SCand j work environ health 7 (1981) 95-100

Formaldehyde exposure in work and the

general.:environment

Occurrence and possibilities for prevention

by Raimo Niemela, MSc, Harri Vainio. MD'

NIEMELA R, VAINIO H. Formaldehyde exposure in work and the general environment:

Occurrence and possibilities for prevention. Scand j work environ health 7 (1981) 95-100.

Formaldehyde is extensively used for many different purposes. For this reason, serious concern has been expressed about the health hazards related to its potent irritating

and sensitizing properties. Recently published information about the potential car- cinogenicity of formaldehyde has generated further discussion of the potential health

hazards of this compound. This article briefly reviews the health hazards of

formaldehyde, the occurrence of formaldehyde in the environment, and general aspects of the prevention of existing hazards.

Key terms: asthmatic reactions, carcinogenicity, environmental exposure, occupational

exposure.

Formaldehyde and its possible health

hazards

Irritating and sensitizing properties

Forma'ldehyde, the simplest of tJhe aldehydes, is 'chemlcally more reacti'Ve Ithan its

higher homologues. It is used extensi'Vely

in a wide spectrum of commercial processes.

Exposure to low atmospheric concentrations of formaLdehyde Oa1l!SBS i>rritation,

especially of the eyes and respiratory tract

alt concentraJUODIs abov,e 0.3 cm3/m3 (0.38

mg/m3). A clear dose~respoiU'se relationship

has been observed (17). A conceni'l"atlion

as ,low as 0.5-1 cm3/m3 (0.63-1.25 mg/m3)

causes iniltaJtion of the mucOf\liS membT'anes

in some individuals. A!bout 17 Ofo of the

workers exposed to a concentration of 2

ems/ms (2.5 mg/m3) experiences moderate

to strong irritarfiion. A formaldehyde con1 Department of Industrial Hygiene and

Toxicology, Institute of Occupational Health,

Helsinki, Finland.

Reprint requests to: Mr Raimo Niemela,

Institute of Occupational Health, Laajaniityntie 1, SF-01620 Vantaa 62, Finland.

cellitraltian of 10 cm3/mS (12.5 mg/m3) is

tolerated on,ly wi1lh difficulty; expooure to

concentrations above this level caus,es

severe difficul:ty in breathing, burning of

the 'eyes, nose and 'trachea, intense l'acrimation, and severe coughing (14).

Direct contact wii1Jh so'lutions, solids, or

resins oonta:ilniJng free formaldehyde has

been shown to c,ause bo.th inflammatory

and allergic dermatitis (14). In Finland

more than 100 cases of occupational eczema

due to formaldehyde have been reported

from 1975 to 1979.

Most of ifue cases of eczema have

been allergic reactiJons. In addi'llion a few

oases of OCcupaitional asthma have annually

been reported in Finland. Asthmatic

symptoms may be due to allergiIC sensitiiIvity to formaldehyde, even at low concellitrations (2). The obstructive symptoms

may be of eiJther the acute or the delayed

type.

Carcinogenicity of formaldehyde

FormaMehyde is mutagenic in some

bacteria, fungi, yeast, and Drosophila (8).

furmaldehyde has been Shown to induce

0355-3140/81/020095-6
single-strand breaks in DNA (deoxyribonuCleic acid) of both prokaryotic a!Ild

eucaryotic cells (11, 16). Despite its wide

use and :lm0WlI'l genetic effects, only H'1Jtle

infornnation ilS available on its pdbeilibal

careinogeruidty. NClJSal carcinomas have

been found in 25 % of Sprague-Dawley

rats exposed to formaldehyde (14.6 cms/rns;

18.25 mg/mS), a!Ild hydrochloric acid (10.7

cm3/m3 ; 13.38 mg/m3) (18). Tumors were

suggested to be due to the formation of

bis(chloromethyl)ether, a known agent

causing nasal cancer (9). Others have

suggested, however, that the carcinogenic1ty of bis(chloromethyl)ether may be due

to hydrolysis to forma:ldehyde (19).

Just 'recently, the carcinogenic potential

of 'formaldehyde vapor was evaluated in

Fischer-344 rats and B6C3Fl miee exposed

in inhalaltion chambers to formaldehyde

concentraitions of 0, 2, 6 or 15 cm3/mS (0,

2.5, 7.5, or 18.75 mg/mS) 6 hid, 5 d/week

(20, 21). For each species, exposure groups

oorusilSted of 120 anima'Is per sex per exposure level. Ai six-monlth intervals (at 6, 12,

18 & 24 months) predetermined numbers

of animals of both species were killed

and dissected. Dose-related 'histological

changes were observed, including rhinitis,

epithelial hyperplasia, ~nd squamous

metaplasia. A total of 37 and 95 squamous

cell carcinomas were detected in rats exposed to a £ormaldehyde concentraltion of

15 Icm3/mS (18.75 mg/mS) by 18 and 24

montlls, 'respectively. 'I1hree rCllts exposed

to 6 cm3/m3 (7.5 mg/mS) hJad developed a

squamous cell carcinoma of the nose by

24 months.

Two neoplasms of the nasal turbinates

were identilfied in the mice at 15 cm3/m3

(18.75 mg/m3) exposure levels af,ter 24

months of exposure (WD Kerns, personal

c()lmmun~cation). No nasal cancers were

observed among the con'troil animals.

Whi'1ethe exposure levels used in the

experimental c8Jrdnogenidty studies have

been higher than those whioh occur at

workplaces (table 1) and Whi[e rodents, in

contrClJSt to :hurnans, breaJthe through !ffue

nose, the degree and site of carcinogeniciJty

may be modified in humans. As an example, biS'(chloromethyl)ether causes nasal

tumors in rats ~9), whereas oancers of the

lungs aTe found in humans (24). Quantitative hUJIIl·an riJsk assessmerut can be

a'ohieved oil'ly after careful and exrtensive

epidemiioilogiJC stud1es.

96

Formaldehyde in the work environment

Formaldehyde and its derivatives are used

in numerous industria:! oper,ations involving ,the 'manu£aiCture, formu:lartion,

commercial distribution, and production of

a variety of products. Formaldehyde is

used maittllyin phenoliJc, urea, melamine

and acetal resins. These l'e&lns are utilized

in llhe production of particle board, plywood, ftulation materials, adhesives,

paints, t€xtiles, the coatings of papers, etc.

The IMt.1tute of Occupational Health in

Finland has measured the level of airborne

formaldehyde iJn occupational and nonoccupa'tionalenv,ironments during the last

few yearn. The measurements have been

made either as a service based on the

ol'ders of employers or in conjunction with

resea'l'ch projeots. Ai'r samples were collected in midg,et impingers and analyzed

by the chromotl'opic add method (7). The

results of the measurements of formaldehyde concentratilons are summarized in

taMe 1. In Finlland the 1Jh~old limit

value (TLV) ooiJmg fur rthe work environment is 2 cm3/m3 (2.5 mg/m3) (12).

The textile industry uses synthetk resins

iJn permanent press f'abrics, in fireproofing,

and in dying. The concentrat1ons of formaldehyde used are lower than 1 cms/ms

(1.25 mg/m3).

In the tlannin'g and shoe manufaclJu['iJng

industry, Formalim® (an aqueous solution

of formaldehyde) is used in finishing operations ,to gllue substances toge1Jher. It is

sprayed onto the surface to be treated.

The ev.apO!I"ation of formaldehyde during

this operation 15 so great that the TLV for

fOI1maldehyde is oiften exceeded.

Synthetd.cresirrl's with £orma'ldehyde as

a componenJtare used in the manufac,turing of 'particle hoard and plywood. The

most commonly used are urea-rormaldehyde, melamine-formaldehyde and phenol-

£ormaldehyde resins. These resins aTe

sOiluble in water and always conta.i.n a

small ,amount Of free formaldehyde. Phenolic resin is nearly the only plywood

adhesive used in FmIanid. Particle boaros

are mainlly glued with urea resin, even

When melamine~urea-fol'ma}dehyde resin

is used in the manufacturing of moisture

resistarut particle board. Formaldehyde

does not evaporate from phenolic resins as

readily as from urea and melamine resins.
For this re-ason the formaldethyde problem

is more seriOU!s in the particle board induS/try than tn 1Jhe plywood industry.

In the proces!s of manufacturing particle

board, formaldehyde is relea'sed during

,the following stages: the mixj>ng of glue,

the forming stages, the hot pressin,g stage,

the cooling stage. The evaporation of

fo!rmaldehyde is especiaUy gl'ea:t during

the hot pressing and cooling stages. The

concentrations of formaldehyde measured

range from 0.1 to 4.9 cm/m3 (1.25 to 6.13

mg/m3 (13). A great amount of formaldehyde is clhemiJcally 'bound by the curing

process. NevertJheless, a small residue

remains in 'the free or loosely bound starte;

during 1Jhe 'course of time, this residue is

relea'sed in w,arlfuouses ,and even in dwellings.

The ,release of residues of free formaldehyde resulius in 'high concentra,tions during

the £1rst year or more. Due to the continuous depoJymerizaHon of formaldehydeurea resin, the release of residues decreases

exponentiaJ]ly to a steady concentr<lJtion

whidh is higher than th'e ,concentr,ation of

1Jhe natural !background. Grealter amounts

of free formaldehyde in boards result if

resins with a ,higher content of free formaldehyde are incorrectly applied or if the

resins are insufficiently cured during the

pressing stage.

The manufacturing of wooden furniture

I1equiresa wide rang,e of adhesives, lacquers, paints, and hardeners cOJltaining

formaldehyde as a component. Formaldehyde is r,eleased during the mixing, spreading, hOlt pressing and drying operations of

glue application. During painting, the

highest fOI1maldehyde exposure occurs

during \jjhe application and drying process.

The formaldehyde concentrations measured have been quite high; 18 Ofo of the

measuremenits obtained exceeded the

Finnish TLV of 2 em3/m3 (2.5 mg/m3). This

valJue was exceeded in an adhesive plant

during 'the manufacture of urea resins.

At present, many welding metals are

painted or treated with corrosion preventiNes cOJlltaining synthetic resins. The

product,s of ,thermal decamposirtion may

eontain 'formaldehyde. Painting is also a

typiJcal work operation in machine shops.

Forma;ldehyde exposure may occur if ~he

pai'!llts used contain forma1dehyde. The

formal1deihyc1e concentrations measured

have usually been below 2 em3/m:l (2.5

mg/m3).

In the manufacturing of elec1'rical machinery 'and apparatus, soldering and lacTable 1. Airborne formaldehyde concentration in occupational and nonoccupational environments.

Air samples were taken during 10 min - 2 h and analyzed with the chromotropic acid method.

Items

Textile plants

Shoe factories

Particle board plants

Plywood plants

Wooden furniture manufacturing plants

Adhesive plants

Foundries

Welding and machine shops

Workshops manufacturing

electrical machinery

Soldering

Lacquerng, treatment of plastic

Construction sites

Hospitals, policlinics

Offices, schools

Dwellings

Formaldehyde concentration

(cm'/m')"

Number of Source items',l Arithmetic Number of

Range measure- mean ments

2 (1977-1979) 0.2 0.1~.5 16 Finishing and dyeing

substances 1 (1977) 1.9 0.9-2.7 4 Formalin spraying 3 (1977-1979) 1.15 0.1--4.9 220 Urea and melamine resins 6 (1977-1979) 0.35 0.1-1,2 91 Phenolic and urea resins 19 (1977-1979) 1.35 0.1-5.4 134 Adhesives, lacquers, paints

1 (1977) 1.75 0.8-3.5 17 Urea-formaldehyde resin 10 (1972-1975) 2.7 43 Furan resin

(38% > TLV) 3 (1977-1979) 0.6 0.05-2.0 8 3 (1977-1980) 0.5 0.05-1.2 9 Plastic tape, paints,

corrosion preventive 10 (1977-1979) below 0.1 47 Solder 0.35 0.2-0.5 8 Lacquer, melamineformaldehyde plastic

7 (1974-1975) 2.8 0.5-70 10 Lacquer 7 (1977-1979) 0.7 0.05-3.5 25 Formaldehyde disinfectant 4 (1977-1980) 0.24 0.05~.77 12 Insulation foam, adhesive,

(1976--1980) lacquer 65 0.29 0.01~.93 186 Particle board, insulation

foam, glue of wall panel

a Year(s) of measurement in parentheses.

" 1 cm'/m' = 1.25 mg/m'.

97
quel"mg are common work operations. This

industry uses a great variety of plastic

produots. Many solders contain colophony

resins whose pyrolysis during 1lhe solderilng

operation produces formaLdehyde (3). The

formaldehyde concentrations measured

have been very low, below 0.1 em3/m3

(0.13 mg/m3). The formaldehyde concen~

tra'tJions measured were below 0.5 om3/m3

(0.63 mg/m3) during the preSJSing of melamine-fo:vma1dehyde plastics and the lacquering of transformers.

The cold-setting furan resins are used

in foundries as binding agents for sand,

mainly in the making of oo.res. Furan

binder.s contain either urea-formaldehyde

or phenol-formaldehyde resins. As a voLantle co,mponent in furan resin, formaldehyde is released into the ,air of the workroom when the sand is mixed and when

thecor,e boxes are filLed. According to a

study of Finn1sh foundries in 1972-1975,

38 Ofo of :the measurements obtained exceeded the TLV (23). Later measuremen.ts,

im 1977-1979, based on oJ:1ders from f<>U'llddes showed somewhat lower cc>ncentrations of formaldehyde.

In the construction industry, the hig'hreslt

formaldehy;de exposure was found during

the :lacquering of parqu,et floors (1). In

most cases, carbamide lacquer of two components was used for this purpose. Carbamide lacquer 'always contains some free

fol'maldehyde, which evaporaJtes dUTing

the application and drying of the lacquer.

The aVe1'age concentrati·on of formaldehyde was at the level of 2 em3/m3 (2.5

mg/m3); 40 Ofo of the measurements exceeded the present Finnish TLV. Momentary concentrations we,re found to be many

times greater than rthe average figure.

In hospitaLs, formaldehyde is used to

preserve tissue specimens and as an agent

of chemical sterilldzation. Momerutary forma1dehyde conceTIJtl'a'tions stemming from

autoclaves and disinfection have exceeded

the VJaliJd TLV, bUit the time-weighred

average 'has remained below 1 ems/ms

(1.25 mg/m3).

Even th<:mgh particle boaI1d is a COiIIlmOIl C·OIIlstruOtion malteri'al in offiices and

schools, the f.o:vmaldehy;de problems which

we have encounter·ed have occur.red only

in Ithe pr·eseIlJee of other s<>Urces orr. formaldehyde. Urea-fo:vmaldehyde foam, which

irs used for thermal insuJation, has caused

problems along with carpet adhesive or

98

parquet lacquer. The fact that particle

board has oawed iless complaints in offices

and schools than in dwellings is obviously

due ,to better veIliti1a1llon. Ul'ea-formaidehyde linsularlion foam may cause iong~term

releas€s of fomnaldehyde. Formaldehyde

evolves from earpet adhesives and lacquers

on!ly during short periods ofappJicaition

and drying. Evaporation for a few weeks,

howev·er, is possi:ble ifth·e composition of

lacquer and hardener is incorrect. The

measured concentrations have ranged from

0.05 to 0.77 ·cm3/m3 (0.06 to 0.96 mg/m3).

Formaldehyde in nonoccupational

environments

Formaldehyde commonly occurs in nonoccupa1:ional environments. It i,s fo:vmed

during 1Jhe :thermal decomposition. of many

organic substances. The concenwation of

aildcl1yde in tthe eX!haust fumes of combustion motors is usuaHy 10-30 em3/m3

(12.5-37.5 mg/m3). C~garette smoke contains even more fOI1IIlJaldehyde than the

preViaiEng TLV '(22). Some drugs used in

the treatment of urinary infections (methenamine mantdelJate and methenamine hippurate) are metabolized in a way that

fOI'maldehyde is released in the urinary

traot (10).

In dwellings, formaLdehyde evaporates

from 'construotion materials and :turniJtu.re.

The InsUtute of Occupational Health in

Finland has measul'ed the formaldehyde

concentration in 65 dwellings during the

last 4 a. PaI1tic1e boavd was the main

soU'oce of formaldehyde in 61 dwellings,

urea-formaLdehyde foam iIn 3, and the adhesive of a waH panel in 1. The highest

measured concentrat~on was 0.93 em3/m3

(1.16 mg/m3). In F.inland, no indoor air

standards for nonoccupational enIYhx>I1-

ments have heen set. An upper limit for

f.ormaldehyde concentration - 0.12 em3/m3

(0.15 mg/m3) - has lbeen suggeSited for the

indoor home environment in Denmark (6).

According 10 Da'IlJish investigatioll1S (4, 5),

the conceIlltmtion of formaldehyde in

dweNings depends on ,the sources of formaldehyde, :the age of the buiJdiIng, verutilation, air !temperature, and ak humidity

condiJtions.

The standaro proposal for minimum ventilaHon in dwellings put forwavd by the

Nordic Commi.1ltee for Buillding Codes is
0.5 air change/h (15). In some modern

dwellings today, however, it is as low

as 0.1 change/h. These low ventilation

rates cause an increase in indoor humidity; in periods when the sun shines

through the windows of well-insulated

dwellings, the hot-humid indoor environmern and the low rate of ven:ti'lation

may cause high indoor concentrations of

formaldehyde. 11herefore, the change in

building .teohnology caused by inoreases in

the cost of energy may aggravate the

hazards of formaldehyde.

Control and elimination of formaldehyde

hazards

Substituting a less toxic compound for

toxk malberial is :jjhe classic propo,sal for

reducing risk,s to workers' heaG.rtfu. Formaldehyde is an important and inexpensive

chemical it-hat iJs used in many ways, and it

is therefore not 'an easy task to find a substitute. However, it has been possvble to

reduce the airborne forma,Mehyde concentrations, eg, in the plywood and particle

board industries, by rearrang,ing ventilahon, Iby 'lliring new types of glues, and by

other simi'lar methods (13).

Any process including the 'hand-ling of

formaldehyde should the isolated as completely aJS possible. If total isolation is

impossi!ble, then art; least the strongest

sources of emission should be enclosed.

Spray booths or rooms, as well as drying

areas, should be equipped with exhaust

systems. In ca:ses of lesser sources of formaldehyde, it is possijble to remove vapors

with local exhaust ventilation. If formaldehyde evaporates from large sunEaces,

general ventilati'On should be effective

enough. In some ca\ses formaldehyde exposure is of short durati'On; i!t is then possible to reduce exposure by ,the use of

proper respirators.

The most sertous problems in dwe'llings

arise when residents move into a newly

constructed 'house wirth unfinished or pOOl"

quality 'partide boards. For the reduction

of formaldehyde hazards in dwellings, the

amount of free formaldehyde in boards

must be kept as low as possible. Effective

quality control of b(}ards is therefore necessary. The rate of air dhange shou1d be

sUlffideIlJt. Treatment with a formaldehyde~bsor:biJng paint can also reduce

evaporation (6).

References

1. Ahonen K, Engstrom B, Lehtinen PU. Rakennustyokartoitus. Institute of Occupational Health, Helsinki 1977. (Tyoolosuhteet

7).

2. Alanko K, Keskinen H, Saarinen L. Ammattiastma [Occupational asthma]. Duodecim 93 (1977) 306-318.

3. American Conference of Governmental Industrial Hygienists. Documentation of the

threshold limit values for substances in

workroom air. Cincinnati, OH 1976.

4. Andersen I, Lundqvist GR, Molhave L.

Formaldehyde indeluft i danske boliger.

Ugeskr laeg 136 (1974) 2133-2139.

5. Andersen I, Lundqvist GR, Molhave L.

Indoor air pollution due to chipboard used as a construction material. Atmos environ

9 (1975) 1121-1127.

6. Andersen I, Lundqvist GR, Molhave L.

Formaldehyde i boligluft. Ugeskr laeg 141

(1979) 966-971.

7. Finnish League for Standardization. Determination of formaldehyde in workplace

air with chromotropic acid method. Helsinki 1978. (SFS 3862).

8. Fishbein L. Pontential industrial carcinogens and mutagens. Elsevier, Amsterdam-axford-New York 1979, pp 142-147.

9. Kuschner M, Laskin S, Drew RT, Capiello

V, Nelson N. The inhalation carcinogenicity of alpha halo ethers: III. Lifetime and

limited period inhalation studies with

bis(chloromethyl)ether at 0.1 ppm. Arch

environ health 30 (1975) 73-77.

10. Laaketietokeskus. Pharmaca fennica 1980.

Oy Lansi-Suomi, Rauma 1979.

11. Magna-Schwencke N, Ekert B, Moustacchi

E. Biochemical analysis of damage induced

in yeast by formaldehyde: I. Induction of

single-strand breaks in DNA and their

repair. Mutation res 50 (1978) 181-193.

12. Ministry of Social Affairs and Health.

Tyopaikan ilman epapuhtauksien enimmaispitoisuudet. Institute of Occupational

Health, Helsinki 1972. (Sosiaali- ja terveysministerion vahvistamat teknilliset turvallisuusohjeet no 11).

13. Niemela R, Riipinen H, Aatola S, Kahko- nen E, Makela P, Vaha-Soyrinki A. Ilmanvaihto lastulevy- ja vaneritehtaissa. Institute of Occupational Health, Helsinki 1980.

(Tyoterveyslaitoksen tutkimuksia 164).

14. Nordiska expertgruppen fOr gransvardedokumentation. 1. Formaldehyd. Arbetarskyddsverket, Stockholm 1978. (Arbete oeh

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April 1980.

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Sinziniz BI. Possible mechanisms of lethal

and mutagenic action of formaldehyde.

Mutat res 27 (1975) 123-126.

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Eye irritation response at low concentrations of irritants. Arch environ health 13

(1966) 570-575.

99
18. Sellakumar AR, Albert RE, Rusch GM,

Katz GW, Nelson N, Kuschner M. Inhalation carcinogenicity of formaldehyde and

hydrogen chloride in rats. Proc am assoc

cancer res 21 (1980) 108.

19. Shooter IV. Assays for phosphotriester formation in the reaction of bacteriophage

R17 with a group of alkylating agents.

Chemio-biol interactions 11 (1975) 575-588.

20. Swenberg J, Kerns W, Pavkov K, Mitchell

R, Gralla EJ. Carcinogenicity of formaldehyde vapor: Interim findings in a longterm bioassay of rats and mice. In: Abstracts of the second international congress

of toxicology, Brussels, July 6-11, 1980.

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Received for publication: 3 December 1980

100

21. Swenberg JA, Kerns WD, Mitchell RI,

Gralla EJ, Pavkov KL. Induction of squamous cell carcinomas of the rat nasal

cavity by inhalation exposure to formaldehyde vapor. Cancer res 40 (1980) 3398-

3402.

22. Vainio H, Sorsa M, Hemminki K. Tupakoinnin mutaatioriskit. [Mutational risks

of smoking]. Duodecim 96 (1980) 620-627.

23. Virtamo M, Tossavainen A. Gases formed

from furan binding agents. Scand j work

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24. Weiss W, Moser RI, Auerbach O. Lung

cancer in chloromethyl ether workers. Am rev resp dis 120 (1979) 1031-1037.