Title: EPIDEMIOLOGICAL APPROACHES TO INDOOR AIR QUALITY
1EPIDEMIOLOGICAL APPROACHES TO INDOOR AIR QUALITY
- Michael Abramson PhD, FRACP
- Department of Epidemiology Preventive Medicine
2OBJECTIVES
- Following this session, you will be able to
- List the major chemical and biological
contaminants in indoor air - Know how available methods rank in the hierarchy
of exposure assessment - State the available epidemiological study designs
in order of methodological strength - Interpret the findings of epidemiological studies
of indoor air quality
3WHY STUDY INDOOR AIR?
- In developed countries, most of the population
spend most of their time indoors - Physical, chemical and biological characteristics
of indoor air are of major importance for
respiratory health - Indoor exposures may be responsible for most
cases of asthma, hypersensitivity pneumonitis and
respiratory infections
4INDOOR ENVIRONMENT
- Physical factors - temperature, humidity etc
- Chemical contaminants ? Formaldehyde
- Volatile Organic Compounds - paint
- Nitrogen dioxide - gas appliances
- Environmental Tobacco Smoke
- Biological contaminants
- Allergens - Dust mite, Cat, Cockroach etc
- Fungi - Alternaria, Cladosporium
- Bacteria Legionella, Gram negatives
5HIERARCHY OF INDOOR EXPOSURE ASSESSMENT
- Ecological
- Surrogates
- Fixed indoor sampling
- Activity diaries
- Personal sampling
- Passive badge dosimeters
- Active sampling from breathing zone
- Biomarkers
6ASSESSMENT OF INDOOR HCHO EXPOSURE
- Indoor environmental sampling
- Passive samplers - filter paper impregnated with
2,4 dinitrophenylhydrazine (DNPH) - 4 day indoor exposure ? HPLC for
dinitrophenylhydrazone assay - Personal sampling
- Dosimeter badge attached to collar over shift
- Sep-Pac DNPH silica cartridge
7ASSESSMENT OF INDOOR NO2 EXPOSURE
- Surrogates eg. gas cooker, gas heater
- Indoor environmental sampling
- Palmes tubes
- Filter paper impregnated with triethanolamine, 4
day indoor exposure, azo dye added, colour
development ? spectrophotometry - Personal sampling
- Passive diffusion badges
8ASSESSMENT OF INDOOR VOC EXPOSURE
- Occupational exposure mg/m3 eg. painting
- Indoor air mg/m3 - static passive badge samplers
can underestimate exposure - Adsorbents ? Activated charcoal solvent
extraction - Polymeric resins eg. Tenax GC (2,6
diphenyl-p-phenylethylene oxide) thermally
desorbed - Artefacts, Background VOC, Degradation of VOC
- Active sampling into 6l stainless steel canister
9ASSESSMENT OF INDOOR ALLERGEN EXPOSURES
- House Dust Mite counts /g fine dust
- House Dust Mite allergen (Der p1) level (mg/g
reservoir dust) by immunoassay - Der p1 has been detected in BAL fluid
- Nasal allergen sampling (Tovey et al)
- Cat allergen (Fel d1) in reservoir dust
- Airborne cat allergen levels
10NASAL ALLERGEN SAMPLER
Reproduced with the permission of Dr Euan Tovey
11ASSESSMENT OF FUNGAL EXPOSURES
- Total fungal spores - Burkard sampler
- Speciation of viable fungal spores (propagules)
- Andersen sampler ? sampling time too brief
- Culture identification to genera level
- Ergosterol ? cumulative fungal exposure
- Nasal sampling under development
- No standard assays for fungal allergens
12Two stage Andersen sampler
13CONCLUSIONS ABOUT INDOOR EXPOSURE ASSESSMENT
- Assessment of indoor air quality remains on a low
level of the exposure hierarchy - Personal sampling of chemical exposures is
feasible but rarely employed - Indoor allergen exposures are almost exclusively
assessed on reservoir dust levels - Fungal exposures suffer from sampling variation
and lack of standard allergen assays
14EPIDEMIOLOGICAL STUDY DESIGNS
- Cross-sectional studies (surveys)
- Gas appliance exposure in young adults
- Case control studies
- Wood heating and otitis media
- Cohort studies
- Children with asthma in the Latrobe valley
- Young adults with asthma in Melbourne
- Randomised controlled trials
- Effects of VOC free paint on asthmatics
- Encasement of bedding in mite allergy
- Systematic reviews meta-analysis
15GAS APPLIANCES RESPIRATORY SYMPTOMS
- Xsectional study n 1159 young adults
- Exposure defined by type of stove
- Respiratory symptoms significantly more common
in exposed women eg. wheeze adjusted OR 2.07,
nocturnal SOB 2.32, asthma attack 2.60 - No significant association between gas cooking
respiratory symptoms in men
16GAS APPLIANCES LUNG FUNCTION
- Use of both gas stove and open gas fire
associated with 3.2 reduction in FEV1 - 43 of asthma attacks could be prevented by not
cooking with gas - Women are more likely to be exposed to
significant concentrations of NO2 whilst cooking
than are men - (Jarvis et al Lancet 1996347426-31)
17INDOOR NO2 LEVELS RESPIRATORY SYMPTOMS
18CONCLUSIONS ABOUT NO2
- Unvented gas appliances associated with
unacceptably high indoor levels of NO2 - Such NO2 exposures associated with respiratory
symptoms in women children - NO2 can increase bronchial hyperreactivity
airway inflammation (features of asthma) - Domestic gas appliances should be well maintained
and vented externally
19EFFECTS ON ASTHMATICS OF EXPOSURE TO CONVENTIONAL
OR VOC FREE PAINT
- Beach J, Raven J, Ingram C, Bailey M, Johns D,
Walters EH, Abramson M. Eur Respir J
199710563-566
20RESEARCH QUESTIONS
- Is there any difference between VOC free and
conventional paint upon respiratory symptoms in
asthmatics? - Is there any difference between VOC free and
conventional paint in their effect upon lung
function and bronchial hyperreactivity (BHR) in
asthmatics?
21SUBJECTS
- 17 asthmatics with symptoms provoked by paint or
other strong odours - Age 18 65 years
- FEV1 gt 60 predicted
- No exacerbation within 6 weeks
- No pregnant or lactating women
22METHODS I
- Double blind cross-over design
- Each subject attended for 3 visits
- Visit 1. Check eligibility, consent, lung
function, Methacholine (MCh) challenge - Visit 2. Paint for 60 minutes, symptoms lung
function recorded every 15, MCh challenge when
completed - Visit 3. As for Visit 2, using other paint
23METHODS II
- Sequence of paint use was allocated randomly
- Painting was carried out in separate room
adjacent to the lab, with a member of staff
present throughout - Paint was applied to a board 2.7m2 using a brush
- All paint used was white
24RESULTS
25CONCLUSIONS
- VOC free paint was less likely to cause wheeze or
breathlessness in asthmatics - This appears to be due to a large difference
between paints in a few subjects - The absolute magnitude of change in symptoms
scores was generally small - Neither paint had an adverse effect on lung
function or BHR
26HCHO EXPOSURE ALLERGIES IN CHILDREN
27ETS CHILDHOOD MORBIDITY
28ETS CHILDHOOD MORBIDITY
29Adjusted OR for wheeze in young adults exposed to
ETS
Janson et al. Lancet 2001 358 210309
30WOOD HEATING
- Acute respiratory illness in young children
- ?Increased wheezing cough in children
- Shortness of breath cough in asthmatics
- Decline in FEV1 in forest fire fighters
- Acute lower respiratory tract infections in
Navajo children - Otitis media (Case control study)
31WOOD HEATING II
- Bronchiolitis obliterans (Case reports)
- Interstitial lung disease
- Methaemoglobinaemia
- ? Less hayfever, pollen sensitivity
- PAH Mutagenic genotoxic
- (Robinson Campbell 1998)
32- COHORT STUDY OF YOUNG ADULTS
- European Community Respiratory Health Survey
(ECRHS) subjects aged 20- 44, randomly drawn from
the south eastern suburbs of Melbourne in 1992 - Samples were invited for the second (laboratory)
stage in 1993 of whom 876 participated - A follow up of this cohort was carried out in
1996 in which 485 participated
Our study sample
33Risk of being sensitised to cats increased in the
top quartile of Fel d 1 (OR 95 CI)
10
8
6
Odds Ratio
4
2
1
0
Fel d 1-floor
Fel d 1-bed
plt0.05
34Risk of asthma increased in the top quartile of
Fel d 1 levels (OR 95 CI)
16
14
12
10
Odds Ratio
8
6
4
2
1
0
plt0.05
35RCT OF BEDDING ENCASEMENT
- 33 young adults with current asthma and house
dust mite allergy - Randomised to encasement of bedding wit
impermeable or cotton covers - Bed dust collected before, 3 6 months after
encasement - Clinical outcomes QoL, BHR, symptoms, peak flow
rates, medication
36HOUSE DUST MITE ALLERGEN
37QUALITY OF LIFE
38 OTHER CLINICAL OUTCOMES
39CONCLUSIONS
- Formaldehyde may be associated with allergic
sensitisation in children - Indoor particles have a wide variety of health
effects including asthma symptoms - Cat allergen exposure is associated with some
features of asthma in young adults - Simple physical methods do not reduce house dust
mite exposure sufficiently to produce clinical
benefits
40HOW TO INTERPRET EPIDEMIOLOGICAL FINDINGS
- Were there clearly identified comparison groups
that were similar with respect to important
determinants of outcome, other than the one of
interest? - Were the outcomes and exposures measured in the
same way for the groups being compared? - Was follow-up sufficiently long and complete?
- Is the temporal relationship correct?
41HOW TO INTERPRET EPIDEMIOLOGICAL FINDINGS
- Is there a dose-response gradient?
- How strong is the association between exposure
and outcome? - How precise is the estimate of risk?
- Are the results applicable to my practice?
- What is the magnitude of risk?
42ACKNOWLEDGMENTS
- Euan Tovey
- Maria Garrett
- Jerry Beach
- Shyamali Dharmage
- Dulux
- VicHealth
- Department of Human Services
43REFERENCES
- Beach JR, Raven J, Ingram C et al. The effects
on asthmatics of exposure to conventional water
based and a volatile organic compound free paint.
Eur Respir J 199710563-566 - Dharmage SC, Bailey M, Raven J et al. Current
indoor exposures to fungi and cats, but not house
dust mites influence allergy and asthma among
highly mite exposed adults. Am J. Respir Crit
Care Med 2001 164 65-71
44REFERENCES
- Di Franza JR Lew RA. Morbidity and mortality
in children associated with the use of tobacco
products by other people. Pediatrics 199697560
568 - Garrett MH, Hooper MA, Hooper BM, Abramson MJ.
Respiratory symptoms in children and indoor
exposure to nitrogen dioxide and gas stoves. Am
J Respir Crit Care Med 1998 158891-95
45REFERENCES
- Janson C et al. Effect of passive smoking on
respiratory symptoms, bronchial responsiveness,
lung function, and total serum IgE in the ECRHS.
Lancet 2001 358 210309 - Jarvis D et al Association of respiratory
symptoms and lung function in young adults with
use of domestic gas appliances. Lancet
1996347426-31 - Robinson DL Campbell EA. Published studies on
health effects of woodsmoke. Clean Air
19983237-41