Environmental Health Perspectives Vol. 94, pp. 91-94, 1991



# Irritant Effects of 

# Formaldehyde Exposure 

# in 

# Mobile Homes by

# Kai-Shen Liu,* Fan-Yen 

# Huang,* Steven B. 

# Hayward,* Jerome 

# Wesolowski,* and Ken Sextont

This paper reports the irritant effects associatedwith formaldehyde exposures inmobile homes. Week-long, integrated fomakldehy concentratioas were nm red uingpaivemonitors insummer andwinterwhile themobilehome residents continued their normal activities. Information on acute healthproblems, chronic respiratory/allergic illnesses, smoking behavior, de v , and time spent athome was obtnedonover 1000 individualsduringthesampling period. Measured formaldehyde concentrations varied fromunder the limit ofdetection (0.01 ppm) toOA6 ppm. Formaldehyde exposure was estiated foreach individual bymultiplying theconcentrationmeasured inhis orher home by the time he

or she spent at home. Irritant effects were found to be associated with formaldehyde exposure after controlling for age, sex, smoking status, and chronic illnesses using a logistic procedure. Some of the interaction terms found to be significant indicated that there were synergistic effects between formaldehyde exposure and chronic health problems.


# Introduction

Acute 

### health effects caused 

### by low-level exposures to for

### maldehyde (HCHO) have been demonstrated in controlled studies of humans and animals and have also been observed in 

### occupational and residential environments 

### (1). Human 

### subjects have 

### experienced eye irritation at 0.5 ppm in an 

### experimental chamber 

### (2). Irritation effects in the upper 

### respiratory tract

### begin
at 0.1 ppmandbecome more common at 0.2 ppm 

### (3). Symptoms in the lower 

### airways such as 

### cough, chest 

### tightness, andwheeze

are observed at 

### higher levels 

### (> 5 

### ppm), but may occur in the

presence of fine 

### particles at lower 

### (0.07 ppm) concentrations 

### (4,5). Electroencephalogram (EEG) changes havebeen found in human 

### subjects exposed to 0.04 ppm ofHCHO 

### (6 ). 

### Headache,

nausea, 

### vomiting, anddiarrheahavebeen 

### reported by

### people ex

### posed to concentrations 

### ranging from 0.02 to 4.15 ppm in residential environments 

### (7). Neurobehavioral 

### effects, such as 

### headache, dizziness, nausea, memory 

### loss, and 

### sleeping problem were also observed 

### amoi1t histology technicians 

### exposed
to concentrations between 0.2 and 1.9 ppm 

### (8). Approximately 1 to 

### 7% of

### dermatologicpatients show

### positive

responses to

### patch tests with 

### 2% HCHO 

### (9). While it is clear that HCHO can 

### produce hypersensitivity reactions 

### by the dermal route, it is less certainthat it can induce

### hypersensitivity reactions 

### by inhalation 

### (bronchial asthma). Occupational studies have

*California Indoor Air Quality Program, Air and Industrial Hygiene Laboratory, California Departmntof Health Services, 2151 BerkeleyWay, Berkeley, CA 94704-9980. tOffice of Health Research, RD-683, United States Environmental Ptection Agency, Washington, DC 20460. Address reprint requests to K. -S. Liu, California IndoorAirQuality Program, Air and Industrial Hygiene Laboratory, California Department of Health Services, 2151 Berkeley Way, Berkeley, CA 94704-9980. 

### shown that bronchial asthma is 

### related to 

### repeated exposure to HCHO at 

### levels lower than 1 

### ppm, even though chamber studies have 

### failed to

### produce 

### asthma attacks in

### nonasthmatic people, or
even on 

### asthma

### patients at 

### higher levels 

### (10,11). The reason 

### for the 

### discrepancy between the 

### occupational finding and 

### the results of 

### chamber studies is not known. 

### Since 

### formaldahyde is an 

### irritant chemical that also causes 

### hypersensitivity reactions, it is possible that it might produce

more 

### symptoms among

### people with chronic 

### respiratory illnesses and

### allergyproblems. But 

### aside fromthe 

### investigations of

### asthma 

### patients mentioned 

### above, there are no 

### systematic studies on 

### HCHO's effects on

### people with chronic 

### respiratory diseases or 

### allergy problems. HCHO is a 

### widely used chemical. Billions of 

### pounds of HCHO 

### are

### produced in the United States 

### annually, 

### ofwhich ap

### proximately one-half is used 

### in the wood 

### products industry. 

### Plywood and

### particle board, commonlyused in

### construction, are 

### the

### major sources 

### ofHCHO in 

### residential environments. Mobile 

### homes, because of their 

### air-tight structures, extensive use of 

### pressed wood

### products, and 

### relatively small 

### volumes are more 

### likely to 

### have 

### elevated HCHO 

### concentrations than conventional homes. HCHO-related health 

### complaints in

### mobilehomes have 

### been 

### reported in several states 

### (12), and several 

### investigations have 

### been carried out to 

### study such 

### complaints. A random sam

### ple of 

### mobile homes has been 

### investigated in 

### only one study, 

### namely, a 

### pilot study of 65 noncomplaint mobile homes in 

### Wisconsin. In 

### that 

### study, a 

### positive relationship was 

### found between 

### HCHO 

### concentration and eye 

### irritation (13). However, due to 

### the small 

### sample 

### size, only one 

### of 

### many 

### potential con

### founders, age, was 

### adjusted for in 

### the statistical 

### analysis. In 

### 1984-1985, the California State IndoorAir 

### Quality Program 

### carried out a 

### random 

### survey

### ofHCHO in

### mobilehomes. 

### Thema

### jorhypothesis to

### be testedwas 

### that irritant 

### effects are

### positivelyLIUETAL.



### associated with HCHO 

### exposures. To test the 

### hypothesis, the 

### survey was 

### designed to a) 

### obtain the 

### distribution of 

### HCHO 

### concentrations from randomly selected 

### noncomplaint mobile 

### homes, b) 

### estimate HCHO 

### exposures for 

### residents of mobile homes using 

### the 

### concentrationdata and time activity

### patterns for 

### occupants, and 

### c) test the 

### association

### between HCHO 

### exposures and 

### physical symptoms by 

### controlling major 

### potential confounders. 

### The survey was also 

### used to determine the 

### important 

### factors 

### affecting HCHO concentrations. 

### This paper 

### addresses mainly the 

### health effects of 

### HCHO, while previous papers discussed other 

### aspects of 

### the 

### study 

### (14-17). 

# Methods

An 

### age-stratified random 

### sampling scheme was used in 

### this 

### survey for the selection of mobile 

### homes. A 

### list of 

### randomly selected mobile homes with 

### approximately 60% of the 

### homes 

### manufactured after 1980 was 

### provided by the 

### California Department 

### of

### Housing and 

### Community Development. Atotal 

### of2203 letters were mailed to 

### recruit

### participants. Forty-fourpercent of 

### the 

### recipients responded 

### positively to 

### the request, and 

### the age 

### distribution oftheir 

### residences was 

### similar to 

### that ofthe original list. The survey 

### consistedof 

### two phases. The summerphase was 

### carried out 

### during July andAugust, 

### 1984, and 

### the winterphase 

### during February and 

### March, 1985. A

### total of

### 663 mobile homes with 1394 residents 

### completed the summer

### phase and 

### 523 homes with 

### 1096 

### residents finished the winter phase of the 

### survey. A detailed 

### description of

### the 

### study

### design can

### be 

### found ina

### previous 

### publication 

### (14). The 

### large sample size of the 

### participants (over 1000 in

### dividuals) allowed for control of

### potential confounders such as 

### age, sex, 

### smoking status, and 

### time spent at

### home without the loss 

### ofstatistical 

### power. It 

### also 

### allowed the 

### investigation ofthe effects of HCHO on 

### people with 

### chronic 

### respiratory illnesses and 

### allergy problems. 

### This survey was 

### carried out

### by

### mail, 

### although 

### approximately 20% ofthe residences were 

### visited in the 

### summer, and an 

### addi

### tional 

### 14% were 

### visited in 

### the winter. 

### Passive HCHO 

### monitors, along with a cover 

### letter, instructions, 

### logging 

### forms, a

### questionnaire, and a return

### envelope were 

### mailed to 

### the

### participants. They
were 

### instructed to 

### uncap themonitors and

### put one in 

### the 

### kitchen and one in 

### the master 

### bedroom. 

### After 7 

### days of 

### exposure, 

### monitors and 

### completed 

### questionnaire were 

### mailed 

### back. The residents carried out 

### their normal 

### daily activities 

### during the 

### monitoring period. HCHO 

### concentrations were 

### measured

### using the 

### chromatrophic acid method. The survey 

### questionnaire consisted of 

### questions on 

### housing characteristics, household 

### activities, and occupant 

### information. Itwas 

### filled out 

### by an 

### adult in

### each

### participatinghousehold. Occupant 

### information was 

### obtained 

### forall residents. It 

### includedper

### sonal 

### data, 

### presence or 

### absence of 6 

### respiratory/allergy 

### diseases, and 16

### physical symptoms. Personal 

### data

### requested were 

### name, age, sex, 

### occupation, 

### smoking status, and 

### the average number of 

### hours 

### spent at 

### home 

### per 

### day 

### during the 

### 1-week 

### monitoring period. Individual exposure was 

### obtained 

### by 

### multiplying the average 

### HCHO concentration 

### by the time spent in 

### the mobile home. 

### The 6 chronic conditions were 

### asthma, 

### hay 

### fever, em

### physema, 

### rashes, chronic 

### bronchitis, and

### allergies. The 16 symptoms were asthma 

### attacks, 

### wheezing or

### difficult

### breathing, chest 

### pain, 

### stinging or 

### burning 

### skin, 

### burning or 

### tearing eyes, sore 

### throat, running nose, 

### cough, rashes, headache, sleeping 

### prob

### lems, dizziness, nausea or 

### vomiting, unusual 

### fatigue or 

### drowsiness, abdominal pain, anddiarrhea. Occurrences of

### these symptoms were reported 

### for the 2 weeks prior to the end of 

### the 

### monitoring period. Variables related with symptoms were 

### first identified 

### using univariate 

### analyses. The effects of HCHO on symptoms were 

### then 

### evaluated 

### using logistic regression to 

### control 

### potential confounders. 

# Results

HCHO 

### concentrations measured in this study 

### varied from 

### below the 

### limit of detection 

### (0.01 ppm) to 

### 0.46 ppm. Since no 

### significant differences were 

### found 

### between the kitchen and 

### bedroommeasurements, 

### the two values were averaged to represent 

### the 

### whole-house concentration. The 

### mean of the whole

### house HCHO concentrations 

### ofall 

### monitoredmobile 

### homes was 

### 0.089 ppm 

### inthe summer

### and 0.088 ppm

### in the

### winter. The week

### ly 

### HCHO exposure for

### each 

### individual was 

### obtainedbymultiply

### ing the 

### whole-house concentration by the total number 

### ofhours spent at 

### home during the

### monitoring week. 

### Weekly HCHO exposures 

### varied from 0 (several residents didnot 

### stayat

### home dur

### ing the sampling

### week) to 

### 53.4 ppm-hr in the summer and 

### from 0 to 

### 40.9 ppm-hr 

### in the winter. 

### The average 

### exposures were 

### 9.8 ppm-hr and 9.9 ppm-hr, 

### respectively. Based on 

### the returned 

### questionnaires, there were 1394 individuals included in 

### the summer

### phase and 

### 1096 individuals included in 

### thewinter

### phase ofthe 

### study. The 

### characteristics of

### the 

### participants are shown in 

### Table 1. 

### Fifty-three percent were 

### females and 

### 47% were

### males. One-thirdwere 

### 65 years 

### ofage or 

### older, and one-quarter were 

### smokers. 

### Thirty-three percent 

### reported having 

### chronic 

### respiratory disease and/or 

### allergy problems. The symptoms 

### reported 

### in this survey were 

### found to 

### be statistically 

### significantly related with 

### gender, age, 

### smoking status, 

### andpresence 

### ofchronic 

### respiratory/allergyproblems. As
can 

### be seen in Tables 2 and 

### 3, the 

### percentage of

### people having various symptoms was 

### generally higher for females, 

### smokers, and 

### persons with chronic 

### respiratory/allergy problems. 

### However, the 

### reported symptoms didnot 

### vary 

### linearlywith age. When 

### the

### prevalence of

### the 16 

### symptoms was 

### compared among three age groups 

### (5-19, 

### 20-64, 65+), reported 

### symptoms did not 

### always increase with 

### age. For 

### eight symptoms in 

### the summer and six 

### symptoms in 

### the 

### winter, 

### highestprevalence rates were found 

### among the 

### people between the 

### age of 20 

### and 64 

### years. 

### Age, gender and 

### smoking status are 

### usually controlled in 

### epidemiologic studies as 

### potential confounders to evaluate the 

### relationships betweenhealth effects and

### exposures. 

### However, in this 

### study, the close associationbetween the 

### reported symptoms and 

### thepresence of

### chronic 

### respiratory/allergy conditions made it 

### neccessary that these 

### conditions be controlled as 

### well. The 

### strong association is 

### indicated inTables 2 and 3. Prevalence rates of 

### symptoms among the

### people with chronic diseases are 

### higher than 

### those 

### among females or 

### smokers. 

### Furthermore, all 

### the differences between the

### people with andwithout chronic conditions 

### (except forthe symptomofnausea 

### in the 

### summer) are 

### statistically significant. Due to 

### the nonlinear 

### relationship between age 

### and symptoms, the

### procedure of 

### linear 

### logistic regression was 

### carried out on the 92IRRITANTEFFECUS OF FORMALDEHYDE

Table 1. Characteristics of participants in the California HCHO study.

No. ofparticipants (%)
Parameter Summer Winter Gender Male Female Age 4 5-19 20-64 2 65 Smoking Yes No Respiratory/allergy conditions Yes No Allergy Yes No Asthma Yes No Chronic bronchitis Yes No Emphysema Yes No Hayfever Yes No Rashes Yes No HCHO concentration

< 0.05 ppm 0.05-0.1 ppm
> 0.1 ppm HCHO exposures, ppm-hr

< 7.0 7.0-12.0

> 12.0 645 (46.5) 743 (53.5)

46 (3.4) 135 (9.8) 739 (53.9) 452 (32.9)

372 (26.9) 1011 (73.1)

464 (33.3) 928 (66.7)

297 (21.3) 1095 (78.7)

59 (4.2) 1333 (95.8)

71 (5.1) 1321 (94.9)

42 (3.0) 1350 (97.0)

175 (12.6) 1217 (87.4)

86 (6.2) 1306 (93.8)

429 (30.8) 552 (39.7) 411 (29.5)

631 (46.7) 357 (26.4) 364 (26.9) 518 (47.4)

575 (52.6)

39 (3.6) 90 (8.3) 587 (54.0) 371 (34.1)

256 (23.4) 836 (76.6)

356 (33.5) 707 (66.5)

209 (19.7) 854 (80.3)

53 (5.0) 1010 (95.0)

77 (7.2) 986 (92.8)

34 (3.2) 1029 (96.8)

115 (10.8) 948 (89.2)

51 (4.8) 1012 (95.2)

220 (20.4) 535 (49.6) 323 (30.0)

406 (39.6) 337 (32.9) 282 (27.5)

Table 2. Percentage of participants with symptoms by gender, 

### smoking status, and respiratory/allergy diseases in summer phase.

Gender Smoker Respiratory/allergy Symptom Female Male Yes No Yes No Abdominal pain 7.0 2.8* 5.1 5.0 9.1 3.0* Asthma attack 0.8 0.9 0.3 1.1 2.6 0.0* Burning eyes 16.2 11.5* 17.0 13.0 25.9 8.1* Burning skin 3.9 2.2 4.0 2.8 6.9 1.2* Chest pain 5.8 3.1* 5.4 4.3 6.7 3.5* Cough 19.8 14.3* 25.9 14.1* 28.5 11.5* Diarrhea 9.7 6.5* 10.5 7.4 12.5 6.0* Dizziness 8.1 4.0* 5.4 6.5 8.6 5.0* Fatigue 15.2 11.2* 15.6 12.6 19.8 10.0* Headache 26.2 14.9* 24.3 19.8 32.3 15.1* Nausea 5.8 2.6* 4.3 4.4 5.6 3.7 Sleeping problems 19.4 12.7* 17.8 15.6 24.4 12.2* Rashes 5.5 3.4 4.9 4.4 12.3 0.7* Running nose 19.4 16.1 19.1 17.4 29.7 11.9* Sore throat 11.7 7.1* 10.0 9.4 15.7 6.5* Wheezing 8.1 7.0 11.3 6.2* 16.4 3.1* *Significant result from x2 test withp-value less than 0.05.

age group with the 

### largest sample size 

### (age 20-64). In addition
to the 

### independent variables of

### gender, smoking status, chronic 

### respiratory/allergy diseases, and HCHO exposure, an interaction Table 3. Percentage of participants with symptoms by gender, smoking status, and respiratory/allergy diseases in winter phase.

Gender Smoker Respiratory/allergy Symptom Female Male Yes No Yes No Abdominal pain 4.5 2.0* 4.0 3.1 5.3 2.3* Asthma attack 1.6 1.0 0.4 1.6 3.9 0.0* Burning eyes 14.8 10.8 13.3 12.8 22.2 8.2* Burning skin 2.5 2.2 3.2 2.1 3.7 1.7* Chest pain 6.1 3.2* 7.2 4.0* 9.0 2.6* Cough 24.6 21.2 31.7 20.2* 34.8 17.0* Diarrhea 6.4 3.4* 6.4 4.6 8.7 3.1 * Dizziness 7.3 4.0* 5.2 5.9 8.4 4.4* Fatigue 11.2 6.6* 14.1 7.5* 12.1 7.5* Headache 25.5 14.4* 24.1 19.1 33.4 13.6* Nausea 5.9 1.8* 3.2 4.1 7.6 2.1* Sleeping problems 16.6 10.0* 12.9 13.4 21.1 9.6* Rashes 3.4 5.0 4.4 4.1 9.3 1.6* Running nose 22.5 20.6 24.1 20.7 30.6 17.0* Sore throat 14.1 11.4 11.7 13.1 17.7 10.3* Wheezing 7.8 6.4 11.2 5.9* 16.6 2.4* *Significant result from x2 test withp-value less than 0.05.



### term ofHCHO 

### exposure and chronic 

### diseases was 

### also included in 

### the 

### logistic model. The 

### logistic model can

### be 

### expressed as 

### the 

### following function:


### ln(P/(1-P)) = a + 

### b1X1 + 

### b2X2 + 

### b3X3 + 

### b4X4 + 

### cX3X4

where P = 

### the probability of 

### having a 

### given symptom; 

### XI = 

### gender; X2 = 

### smoking status; 

### X3 = 

### chronic 

### respiratory/allergy disease 

### status; X4 = 

### HCHO 

### exposure; and 

### X3X4 = 

### chronic disease x 

### HCHO exposure. 

### The results 

### ofthe 

### logistic regression on 

### 16 symptoms forboth
seasons are 

### shown in 

### Table 4. As can 

### be seen 

### from 

### this 

### table, complaints of 

### burning/tearing eyes, 

### stinging/burning 

### skin, fatigue, and 

### sleepingproblems in the summer and

### burning/tearing eyes, chest 

### pain, 

### dizziness, sleeping problems, and sore 

### throat in 

### thewinterwere 

### significantly associatedwith HCHO ex

### posure after all the 

### important 

### potential confounders were con

### trolled. HCHO acted 

### sometimes 

### independently and sometimes 

### jointlywithchronic diseases 

### (as an 

### interaction

### term) to 

### affect the 

### irritant 

### effects. The fact that some 

### interaction terms 

### reached the 0.05 

### significance level 

### indicates a

### highprobability that 

### there were 

### synergistic effects between HCHO 

### exposure and 

### chronic diseases. 

### Since 

### burning/tearing eyes were 

### associated with HCHO ex

### posure for 

### both seasons, an 

### attempt was 

### made to 

### establish the 

### relationship between HCHO 

### exposures and

### percentages ofpeo

### plewith eye symptoms 

### by

### dividing subjects into three ranges of 

### exposure. The exposure-response 

### relationship is shown in

### Figure 1. For 

### the three ranges 

### of HCHO exposure, 

### the percentage of 

### people with

### burning/tearing eyes in the summer 

### increased from 

### 13.3% (<7.0 ppm-hr) to 

### 17.1% (7.0-12.0 ppm-hr) and then to 

### 21.4% (>12.0 ppm-hr). In

### the

### winter, the increases are 

### from 10.8 to 

### 14.7% and 

### then to 

### 20.6%. 

# Discussion

Because this 

### study was a 

### random 

### survey, 

### which covered the 

### entire State 

### of

### Californiaand 

### includedmobile

### homes ofall 

### ages, 

### the average

### measured HCHO 

### concentrations were 

### expected to 

### be lower than 

### those from surveys 

### of homes 

### where occupants 9394 LIUETAL.

Table 4. Variables 

### significantly related with health symptoms for the

participants between 20 and 64 years of age.'

Significant independent variables Symptom Summer (n = 726) Winter (n = 544) Abdominal pain Gender Asthma attack

- Burning eyes Gender, HCHO, chronic HCHO, chronic Burning skin HCHO, smoker, chronic

- Chest pain Gender HCHO, smoker, chronic Cough Smoker Smoker, chronic Diarrhea Dizziness Gender Gender, HCHO Fatigue HCHO*chronicb Smoker Headache Gender Gender Nausea Gender Gender Sleeping problems Gender, HCHO*chronicb Gender, HCHO Rashes Chronic Running nose Chronic Sore throat Gender, chronic HCHO*chronic Wheezing Smoker, chronic Smoker aThe variables listed in this table are those entered into the linear logistic regression function withp-values less than 0.05. bHCHO*chronic indicates an interaction between these two variables.

25

---0 Summer 

### -+I Wlnter

20

p
e r C e n t

a 10 g e

5

0 0-7.0 7.0-12.0 >12.0



### HCHO Exposure 

### (ppm x hrs)

FIGURE 1. Percentage ofparticipants between 20 and 64 years having burning/tearing eyes by three ranges of HCHO exposures. 

### complained of symptoms. For 

### these 

### noncomplaint 

### participants chronically exposed to 

### relatively low 

### levels of

### HCHO, 

### positive associationswere

### foundbetweenweek-longaverageHCHOexposures 

### and irritant effects. Both in the 

### winter

### phase and summer 

### phase, several irritant 

### symptoms were

### relatedtoHCHOexposures 

### when the

### potential confounders ofage, 

### gender, smoking status, andstatus

### of

### chronic

### respiratory/allergyproblems were

### controlled. This indicatesthat

### HCHO-relatedirritant symptoms 

### existamong 

### residents ofmobilehomeswhohavenot 

### formally 

### complainedto 

### government 

### agencies, suggesting that 

### effects occur at 

### lower HCHO 

### levels than

### previously thought. Another 

### significant finding

### ofthis studywas 

### the 

### synergistic effect between HCHO exposure 

### and 

### chronic respiratory/allergy problems. For 

### persons 

### with such chronic health 

### problems, 

### the prevalenceratesofirritant 

### symptoms were

### generallyhigherthan 

### forthosewithout chronicproblems. Further, for some 

### symptoms, theserateswereeven

### higherthanwouldbe

### expectediftheeffectsof 

### HCHO exposureand

### chronichealth

### problemwereonly

### additive. A

### positive

### exposure-responseassociationwas 

### observed in 

### this study for

### burning/tearing eyes over 

### the exposure ranges 

### studied. 

### Further, responses were 

### found at exposure 

### levels as low as 7 

### ppm-hr. For a 

### person who 

### spends 

### 60% of the time 

### inside his or 

### her own 

### home, a 

### weekly HCHO 

### exposure of 7 

### ppm-hr can 

### be 

### translated into a 

### weekly average HCHO concentration of 

### 0.07 ppm. It 

### is not 

### uncommon to 

### find HCHO concentrations at 

### this 

### level in

### mobile homes 

### (14). 

### The fact that 

### approximately 10,000 mobile homes are 

### sold 

### annually in 

### California alone 

### implies that the 

### affected 

### population may be 

### substantial.

Technical andadministrative support forthis studyprovidedbyB. Chang, G. Kulasingam, E. Kothny, M. Petreas, L. Pierce, andL. Webber is greatlyappreciated.

REFERENCES

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