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EPIDEMIOLOGICAL APPROACHES TO INDOOR AIR QUALITY

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List the major chemical and biological contaminants in indoor air ... Allergens - Dust mite, Cat, Cockroach etc. Fungi - Alternaria, Cladosporium ... – PowerPoint PPT presentation

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Title: EPIDEMIOLOGICAL APPROACHES TO INDOOR AIR QUALITY


1
EPIDEMIOLOGICAL APPROACHES TO INDOOR AIR QUALITY
  • Michael Abramson PhD, FRACP
  • Department of Epidemiology Preventive Medicine

2
OBJECTIVES
  • 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

3
WHY 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

4
INDOOR 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

5
HIERARCHY OF INDOOR EXPOSURE ASSESSMENT
  • Ecological
  • Surrogates
  • Fixed indoor sampling
  • Activity diaries
  • Personal sampling
  • Passive badge dosimeters
  • Active sampling from breathing zone
  • Biomarkers

6
ASSESSMENT 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

7
ASSESSMENT 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

8
ASSESSMENT 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

9
ASSESSMENT 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

10
NASAL ALLERGEN SAMPLER
Reproduced with the permission of Dr Euan Tovey
11
ASSESSMENT 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

12
Two stage Andersen sampler
13
CONCLUSIONS 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

14
EPIDEMIOLOGICAL 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

15
GAS 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

16
GAS 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)

17
INDOOR NO2 LEVELS RESPIRATORY SYMPTOMS
18
CONCLUSIONS 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

19
EFFECTS 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

20
RESEARCH 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?

21
SUBJECTS
  • 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

22
METHODS 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

23
METHODS 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

24
RESULTS
25
CONCLUSIONS
  • 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

26
HCHO EXPOSURE ALLERGIES IN CHILDREN
27
ETS CHILDHOOD MORBIDITY
28
ETS CHILDHOOD MORBIDITY
29
Adjusted OR for wheeze in young adults exposed to
ETS
Janson et al. Lancet 2001 358 210309
30
WOOD 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)

31
WOOD 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
33
Risk 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
34
Risk 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
35
RCT 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

36
HOUSE DUST MITE ALLERGEN
37
QUALITY OF LIFE
38

OTHER CLINICAL OUTCOMES
39
CONCLUSIONS
  • 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

40
HOW 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?

41
HOW 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?

42
ACKNOWLEDGMENTS
  • Euan Tovey
  • Maria Garrett
  • Jerry Beach
  • Shyamali Dharmage
  • Dulux
  • VicHealth
  • Department of Human Services

43
REFERENCES
  • 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

44
REFERENCES
  • 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

45
REFERENCES
  • 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
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