EPIDEMIOLOGICAL APPROACHES TO INDOOR AIR QUALITY

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EPIDEMIOLOGICAL APPROACHES TO INDOOR AIR QUALITY

• Michael Abramson PhD, FRACP
• Department of Epidemiology Preventive Medicine

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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

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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

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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

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HIERARCHY OF INDOOR EXPOSURE ASSESSMENT

• Ecological
• Surrogates
• Fixed indoor sampling
• Activity diaries
• Personal sampling
• Passive badge dosimeters
• Active sampling from breathing zone
• Biomarkers

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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

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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

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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

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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

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NASAL ALLERGEN SAMPLER
Reproduced with the permission of Dr Euan Tovey
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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

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Two stage Andersen sampler
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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

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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

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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

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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)

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INDOOR NO2 LEVELS RESPIRATORY SYMPTOMS
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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

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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

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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?

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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

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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

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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

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RESULTS
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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

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

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WOOD HEATING II

• Bronchiolitis obliterans (Case reports)
• Interstitial lung disease
• Methaemoglobinaemia
• ? Less hayfever, pollen sensitivity
• PAH Mutagenic genotoxic
• (Robinson Campbell 1998)

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• 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
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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
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Risk of asthma increased in the top quartile of
Fel d 1 levels (OR 95 CI)

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14
12
10
Odds Ratio
8
6
4
2
1
0
plt0.05
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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

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HOUSE DUST MITE ALLERGEN
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QUALITY OF LIFE
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OTHER CLINICAL OUTCOMES
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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

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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?

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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?

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ACKNOWLEDGMENTS

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

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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

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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

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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