Mite Antigen Concentrations in House Dust and the Occurrence of Wheezing in Children with Dust Mite Allergy

E PA/600/At- 93/082
MITE ANTIGEN CONCENTRATIONS IN HOUSE DUST AND THE
OCCURRENCE OF WHEEZING IN CHILDREN WITH DUST MITE
ALLERGY
Henderson, Frederick W.,' Lindstrom, Andrew B.,2 Beck, Melinda A.,1
Barnes, David M.,1 and Henry, Marianna M.1
1 The Department of Pediatrics, University of North Carolina Chapel Hill, N.C.
27599-8180 USA
2 U.S.E.P.A. Atmospheric Research and Exposure Assessment Laboratory, MD-56
Research Triangle Park, N.C. 27711 USA
ABSTRACT
We studied the relationship between dust mite antigen concentrations in house dust
samples and the occurrence and frequency of wheezing in 58 children with dust mite
allergy (wheal >_ 4 mm. mean diameter in response to a prick test with either D. farinae
or D. pteronvssinus antigen). According to their parents, 15 subjects had never
experienced recurrent wheezing, 8 had a history of past recurrent wheezing but no recent
wheezing, and 35 had a history of recent wheezing. Spirometry data were obtained with a
water seal spirometer and a limited dose methacholine challenge (total cumulative dose =
6.4 micromoles) was performed. Dust samples were obtained from 6 sites in each home:
the child's mattress, blanket, pillow, bedroom floor, and the recreation room couch and
floor. Per fl antigen concentrations were assayed using a monoclonal antibody based
ELISA and expressed as ng/gm sieved dust. Concentrations of Per fl were _> 10,000
ng/gm in at least one microenvironment in the bedrooms of 86% of subjects. Mean
concentrations of mite antigen in different micro-environments did not differ significantly
for dust mite allergic children with and without histories of recent wheezing. Among
children who had experienced recent wheezing, mean concentrations of mite antigen
tended to be higher in dust samples from homes of the 19 children who had experienced
> 5 episodes of recent wheeze than in samples from the homes of 16 children who had
experienced fewer episodes of recent wheezing; however, differences in mean
concentrations of Per fl in the microenvironments sampled were not statistically
significant. Similarly, Per fl levels in dust samples were not related to spirometry, or to
methacholine responsiveness. In this study, differences in the degree of home
environmental contamination with mite antigen did not account for differences in the
occurrence or frequency of wheezing, bronchial hyperreactivity, or lung function among
children with dust mite allergy.
This paper has been reviewed in accordance with the U.S. Environmental Protection
Agency's peer and administrative review policies and approved for presentation and
publication. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.

-------
INTRODUCTION
The prevalence of physician diagnosed asthma in school age children is approximately
3-5% while an additional 5-7% of school children experience recurrent wheezing which
has not been diagnosed as asthma. Asthma has been an important cause of school absence
and hospitalization among school age children for many years, and recent data suggest that
its prevalence may be gradually increasing. We recently conducted an epidemiologic
investigation designed to define more precisely factors associated with recurrent wheezing
in childhood. In that study of 454 children, allergic sensitization to dust mite antigens
was demonstrated in 67% of children with recent recurrent wheezing, and in 26% of
children without wheezing. In this report we describe an investigation of mite antigen
concentrations in house dust as a potential correlate of wheezing among children with dust
mite allergy.
METHODS
Subjects for the epidemiologic project were recruited from a general pediatric practice in
Raleigh, N.C. In the initial characterization of the population, 176 children with positive
dust mite skin tests were identified. A subset of 58 children of these children was
selected for the current study; the sample included mite allergic children with and without
histories of wheezing. Mite allergy was defined by immediate hypersensitivity skin testing
with epicutaneous application of D. farinae (10,000 AU/ml; Grier Laboratories) and
D. pteronvssinus (30,000 AU/ml; Holister-Steir) antigens. A wheal with a mean
diameter >_ 4 mm 15 minutes after skin test application was considered positive. Recent
wheeze history was obtained from the child's parent using a self-completion questionnaire
which included all symptom questions from the ATS-DLD children's respiratory health
questionnaire.
Spirometry was performed using a water-seal spirometer interfaced with a microcomputer
(Survey III, Warren E. Collins Inc.). Four replicate spirograms were obtained; reference
data of Polgar (1) were used to obtain predicted values from the spirogram with the
highest sum of FVC and FEV-1.
Methacholine challenge: Following a saline trial, serial two-fold increasing doses of
methacholine (Provocholine) beginning at 0.03 micromoles were administered using a
hand activated DeVilbiss nebulizer, model #40. The challenge was terminated when
FEV-1 had declined to 80% of the post-saline FEV-1 or when a cumulative dose of 6.4
micromoles of methacholine had been administered. Spirometry was performed 45 and 90
seconds following each dose of methacholine and sequential doses of methacholine were
administered every two minutes.
House dust samples were obtained between 12-1-91 and 3-15-92 with a vacuuming device
which collected samples on 0.3 micron pore size glass fiber filters using a flow rate of 28
cfm. Separate samples were obtained from 6 locations in each home: the pillow, blanket,
and mattress of the child's bed, the floor in the child's bedroom, the couch in the family
room, and the floor in the family room.

-------
Concentrations of Per fl. the major group I allergen of D. farinae. in dust samples were
determined using a monoclonal antibody based ELISA (2) and expressed as
nanograms/gram sieved dust.
Analysis: The natural logarithms of Per fl antigen concentrations were used in analysis.
T-tests were used to compare mean antigen levels in different microenvironments in the
homes of mite allergic children in different clinical categories.
RESULTS
Geometric mean concentrations of Per fl ranged from 2829 ng/gm in pillow dust to
11,978 ng/gm in bedroom carpet dust. The proportions of samples with Per fl
concentrations _> 10,000 ng/gm ranged from 31% of pillow samples to 61% of bedroom
floor samples. At least one sample from the child's bed containedJ> 10,000 ng/gm Per fl
antigen in 66% of study homes. Concentrations of Per fl < 2000 ng/gm in all three
bedding samples were observed in only 20% of homes.
To determine whether concentrations of Per fl in dust from different microenvironments
in the home were related to clinical status in study children, subjects were categorized into
four groups based on lifetime wheezing experience as reported by parents. Analysis
groups consisted of children who had experienced: 1) 5 or more episodes of recent
wheezing (in the two years before dust sampling; n = 19), 2) recent wheezing but less than
5 episodes (n = 16), 3) past wheezing (n = 8), and 4) children who had never experienced
wheezing (n = 15). Methacholine challenge data supported the clinical categorization of
study subjects. Seventy-four percent of children who had experienced 5 or more episodes
of recent wheezing responded to _< 3.2 micromoles of methacholine compared to 38% of
children with milder recent wheezing, and 19% of children who had never experienced
wheezing.
Figure 1 shows the distribution of maximum Per fl concentrations observed among the
three dust samples obtained from each child's bed by clinical status. At least 50% of
children in all clinical categories slept in beds contaminated with _> 10,000 ng/gm of
Per fl antigen; the proportion of children with dust mite allergy and recent wheezing who
slept in beds with high levels of Per fl contamination (60%) was slightly less than, but
similar to, the proportion of children with mite allergy but without wheezing who slept in
highly contaminated beds (76%). Among children with any recent wheezing (groups 1
and 2), children who had experienced less frequent wheezing tended to live in homes with
lower concentrations of Per fl in dust samples. However, geometric mean levels of mite
antigen did not differ significantly in any microenvironment sampled when children with
frequent recent wheezing were compared to children with less frequent wheezing. The
maximum difference in mean mite antigen concentrations was observed when the mattress
dust samples obtained from the homes of children with 5 + episodes of recent wheezing
(geometric mean = 12,110 ng/gm) were compared with the similar dust samples from the
homes of children with histories 1-4 episodes of recent wheezing (geometric mean =
2,581 ng/gm; p = 0.06). When children with any recent wheeze were categorized into
those with FEF 25-75 _
-------
MAXIMUM BEDDING DUST DER Fl ANTIGEN LEVELS
IN CHILDREN WITH DIFFERENT HISTORIES OF WHEEZING
LOGe NG/G
14
12
10
A A
A A
A a A
% A A
&
A
A 2 a
$
"A"
A
A
A
A
A
£ 10,000 NG/G
A
2,000 NG/G
RECENT 5+ RECENT <5 PAST NONE
N= 1 9 N= 16 N=7 N* 14
WHEEZING GROUP
Figure 1. Maximum bedding dust Per fl antigen concentrations in samples from homes of
children with different histories of wheezing.
DISCUSSION
Dust samples obtained during the winter months from homes of mite allergic children in
central North Carolina frequently yielded high concentrations (_> 10,000 ng/gm) of the
major group I allergen of D. farinae. Per fl. We identified no significant differences in
the distributions of Fl levels in dust samples from six different sites within the home
when data from the homes of mite allergic children with and without wheezing were
compared. Furthermore, we found no significant differences in the distributions of mite
antigen concentrations in dust samples from homes of children experiencing frequent
wheezing compared to children experiencing less frequent wheezing. In addition, neither
lung function nor methacholine response data provided evidence that mite allergic children
with more severe airway dysfunction resided in homes with higher levels of mite antigen
in bedding, furnishings, or carpeting.
The observation that more than 75% of mite allergic children who had not experienced
wheezing slept in beds contaminated with high concentrations of Per fl. indicates that
-------
certain mite allergic children are resistant to mite allergy-associated wheezing and
bronchial hyperreactivity even when mite antigen exposure is high. It is possible that we
studied too few homes with low levels of mite antigen contamination to demonstrate a
relationship between level of mite antigen contamination and severity of lower respiratory
disease among children who manifested both mite allergy and wheezing. Therefore, these
data should not be construed to suggest that protection of mite allergic children from mite
antigen exposure would not be associated with amelioration of the severity of clinical
disease.
REFERENCES
1. Polgar G, and Promadhat V. Pulmonary Function Testing in Children: Techniques
and Standards. 1971.
2. Chapman MD, Heymann PW, Wilkins SR, et al. Monoclonal immunoassays for
major dust mite (Dermatophagoides') allergens, Per pi and Per fl. and quantitative
analysis of the allergen content of mite and house dust extracts. J Allergy Clin
Immunol 1987;80:184-94.
-------
TECHNICAL REPORT DATA
(Pleese read Instructions on the reverse before complet'
1. REPORT NO. 2.
EPA/600/A-93/082
3
4 Jv?iIe lAigen concenfrations in house
dust and the occurrence of wheezing in children
with dust mite allergy
5 REPORT DATE
6. PERFORMING ORGANIZATION CODE
7 A^enclc%. Henderson, Andrew B. Lindstrom, Melinda A. Beck,
David M. Barnes, and Man anna M. Henry,
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
The Department of Pediatrics
University of North Carolina
Chapel Hill, NC 27599-8180 USA
10 PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
Atmospheric Research and Exposure Assessment Laboratory
Exposure Assessment Research Division
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA/600/09
15. SUPPLEMENTARY NOTES
16. ABSTRACT _
We studied the relationship between dust mite antigen concentrations in house dust samples and the occurrence and frequenc)
of wheezing in 58 children with dust mite allergy (wheal >_ 4 mm. mean diameter in response to a prick test with either D.
farinae or D pteronyssinus antigen). According to their parents, 15 subjects had never experienced recurrent wheezing, 8
had a history of past recurrent wheezing but no recent wheezing, and 35 had a history of recent wheezing. Spirometry data
were obtained with a water seal spirometer and a limited dose methacholine challenge (total cumulative dose = 6.4
micromoles) was performed. Dust samples were obtained from 6 sites in each home: the child's mattress, blanket, pillow,
bedroom floor, and the recreation room couch and floor. Der fl antigen concentrations were assayed ming a m<->nn<-lr>na)
antibody based ELISA and expressed as ng/gm sieved dust. Concentrations of Der fl were > 10,000 ng/gm id at least one
microenvironment in the bedrooms of 86% of subjects. Mean concentrations of mite antigen in different micro-environments
did not differ significantly for dust mite allergic children with and without histories of recent wheezing. Among children
who had experienced recent wheezing, mean concentrations of mite antigen tended to be higher in dust samples from homes
of the 19 children who had experienced J> 5 episodes of recent wheeze than in samples from the homes of 16 children who
had experienced fewer episodes of recent wheezing; however, differences in mean concentrations of Der fl in the
microenvironments sampled were not statistically significant. Similarly, Der fl levels in dust samples were not re\ateA m
spirometry, or to methacholine responsiveness* In this study, differences in the degree of home environmental contamination
wjth mite antigen did not account for differences in the occurrence or frequency of wheezing, bronchial hyperreactivity, or
lung function among children with dust mite allergy.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b IDENTIFIERS-OPEN ENDED TERMS
c COSATi I leld.'Group
Indoor Air Pollution
House Dust Mites
Asthma
Bioaerosols

16. DISTRIBUTION STATEMENT
Conference Proceedings
19 SECURITY CLASS /Tim Report:
21 NO OF PAGES
6
20 SECURITY CLASS iTtm page,
22. PRICE
EPA Fotm 2220-1
-------