Effects of longterm exposure to outdoor air pollution

1
Effects of long-term exposure to outdoor air
pollution

• Gerard Hoek

2
Background

• Long-term annual average or multi-year averages
• Fewer studies on long-term exposures
• Public health impact even more important than of
  the short-term exposures

3
(No Transcript)
4
(No Transcript)
5
(No Transcript)
6
Ecological studies

• Used routine data as in the time series studies
• Health and exposure at the area level

7
Early ecological studies

• Risk Anal. 1987 Dec7(4)449-61. Associations
  between 1980 U.S. mortality rates and alternative
  measures of airborne particle concentration.
• We analyzed the 1980 U.S. vital statistics and
  available ambient air pollution data bases for
  sulfates and fine, inhalable, and total suspended
  particles. Using multiple regression analyses,
• we conducted a cross-sectional analysis of the
  association between various particle measures and
  total mortality. Results from the various
  analyses indicated the importance of considering
  particle size, composition, and source
  information in modeling of particle pollution
  health effects.
• Of the independent mortality predictors
  considered, particle exposure measures related to
  the respirable and/or toxic fraction of the
  aerosols, such as fine particles and sulfates,
  were most consistently and significantly
  associated with the reported SMSA-specific total
  annual mortality rates. On the other hand,
  particle mass measures that included coarse
  particles (e.g., total suspended particles and
  inhalable particles) were often found to be
  nonsignificant predictors of total mortality.
  Furthermore, based on the application of fine
  particle source apportionment, particles from
  industrial sources (e.g., from iron/steel
  emissions) and from coal combustion were
  suggested to be more significant contributors to
  human mortality than soil-derived particles.

8
Issues with ecological studies

• No individual confounders e.g. smoking
• Individualized exposure not possible
• Ecological fallacy
• Less convincing than in the case of time series
  studies where the major confounders are also
  available from routine databases

9
Mortality cohort studies
10
Harvard 6 cities study

• Dockery DW, Pope CA, Xu X, Spengler JD, Ware JH,
  Fay ME, Ferris BG, Speizer FE. N Engl J Med.
  19933291753-9.
• Prospective cohort study
• Individual confounders
• 9,000 subjects living in 6 U.S. cities
• Followed for 15 years
• Cities varied in long-term concentrations of
  sulfur oxides and particles

11
(No Transcript)
12
Dockery, NEJM 1993 329 1753-9
13
Pope, JAMA 2002
14
(No Transcript)
15
Spatial autocorrelation in ACS
16
Relative risk of long-term exposure to ambient
air pollution on mortality
17
(No Transcript)
18
Exposure variability within communities
19
(No Transcript)
20

• Assessed the ACS cohort (23,000 subjects) in Los
  Angeles area
• Spatial interpolation of monitoring data

21
(No Transcript)
22
Oslo mortality cohort studyRelative risk per 10
ug/m3 Nox obtained from a dispersion model
23
Lancet, 2002
24
(No Transcript)
25
Land use regression / regression mapping

• Dutch birth cohort (3000, spread over NL)
• Measurements impossible
• Measurements at 40 sites locations of NO2, PM2.5
  and soot. Four 2-week periods spread over one
  year.
• Geographic Information Systems information in
  specific circles around each site of
• Traffic intensity (r 50, 250 and 1000 m)
• Address density (r300, 1000, 5000 m)
• Population density (r300, 1000, 5000 m)

26
Land use regression

• Pollution concentrations at 40 sites linked to
  GIS predictors, using linear regression models
• Model was used to predict concentrations at the
  home address of the children

27
Prediction model PM2.5 (?g/m3) R2 0.73
28
Odds ratios for a 10 ?g/m3 change of PM2.5 for
symptoms at age four, adjusted for confounders
29
Cardiovascular disease
30
(No Transcript)
31
(No Transcript)
32
(No Transcript)
33
Respiratory disease
34
(No Transcript)
35
(No Transcript)
36
Truck traffic and respiratory symptoms Ciccone,
Occup Environ Med 199855771
Torino, Rome, Milano
Frequency of daily lorry transit
37
Living near a major road and wheeze. Venn. AJRCCM
20021642177-80.
38
Brunekreef, Epidemiology 1997 8 298-303
39
(No Transcript)
40
Conclusions

• Long-term exposure to outdoor air pollution is
  associated with
• increased mortality rates
• respiratory disease
• possibly cardiovascular disease
• (Traffic / combustion) PM important
• Developments in exposure assessment have
  strengthened long-term studies (GIS
  geostatistical methods land use regression)

41
Conclusions

• Uncertainties remain with respect to
• Causal agent(s)
• Biological mechanism
• Sensitive groups
• Differences between locations