Air Pollution and Health –unanswered questions - IAPSC

Air Pollution and Health
–unanswered questions
Jon Ayres
Department of Environmental &
Occupational Medicine
University of Aberdeen

Air Pollution and Health –unanswered
questions
• What is the dose to the individual
– susceptibility
• Acute cardiac effects
• Which particle metric
• Chronic effects
– Does air pollution cause asthma
– How much life is lost
• Interventions
– Changes in emissions

Acute cardiac effects

Air pollution and cardiovascular mortality
% increase /10 ìg/m 3 Increase in PM 10
8
Respiratory
% Change in Daily Mortality
6
4
2
0
-2
Total
Cardiovascular
Santa Clara
Philadelphia
Utah Valey
Birmingham
Cincinnatti
Six Cities
Santa Clara
Philadelphia
Utah Valey
Birmingham
Cincinnatti
Six Cities
Santa Clara
Philadelphia
Utah Valey
Birmingham
Cincinnatti
Six Cities

PM 10 and Cardiac Admissions
• Daily hospital
admissions of elderly
(65+ yrs) for 1986-89
(Detroit)
• 32 ìg/m 3 (IQR)
increase in PM 10
associated with:
+1.8% 1IHD
+2.4% IHeart Failure
+1.9% IDysrhythmias
Admissions/Day
Ischemic Heart Disease
46
45
44
43
42
0 25 50 75 100
PM 10
(m g/m 3 )
Schwartz & Morris, Am J Epi 1995

Air Pollution and Arrhythmia
PM 2.5 lag 2 days
OR for ICD Discharge
1.8
1.6
1.4
1.2
1.0
0.8
0 10 20 30
PM 2.5
(m g/m 3 )
Peters et al 2000

Pollution Pollutant Exposure
exposure
Pulmonary
Injury
Effect on airway
receptors
Thrombosis and
inflammation
Impairment of
cardiac vagal
control
Plaque rupture
and coronary
occlusion
Myocardial
Ischaemia
CVS
Death

Cardiac effects - what we don’t (fully)
know
• The susceptible sub-groups
• How these effects occur (mechanisms)
• The degree of loss of life

Which particle metric
• PM 2.5
• PM 10
• Numbers
– surface area
– surface constituents
• NO 2

Chronic effects

Asthma and air pollution
• Does air pollution make asthma worse on
a day-to-day basis
• Does air pollution make asthma worse
over time
• Does air pollution cause asthma in the
first place

Asthma and air pollution in Children of 12
communities of Southern California
(McConnell et al 2002)
• Asthma incidence: increased in high ozone
areas (median 8-hr 57ppb) among children
playing three or more outdoor sports (8% of
all children)
• Asthma prevalence: no association
• Asthma incidence: no association

Prevalence of Asthma symptoms and proximity
to traffic. 60,000 children in Nottingham UK.
Venn et al 2000
Primary schools
Secondary schools

ISAAC UK: prevalence of wheezing in urban and
non urban children aged 12-14 yrs. N= 27,000.
Kaur et al 1998
Urban
Non Urban
60
50
Percentage
40
30
20
10
0
Ever
wheezed
Wheeze
past 12
months
>4
episodes
Daily
activities
affected
Speech
limiting
attacks

Asthma and air pollution
• Does air pollution make asthma worse on
a day-to-day basis - YES
• Does air pollution make asthma worse
over time – DON’T KNOW
• Does air pollution cause asthma in the
first place – PROBABLY NOT

Life expectancy and chronic effects of air
pollution -
estimated effect of reducing PM 2.5 by 1ìg/m 3
COMEAP 2001.
• On average around 2.5d/person/lifetime
– ca. 0.35m life years for the whole UK population
• But if this applies only to a susceptible proportion the
improvement would be greater
– if 10% population susceptible would amount to around 1 month
per susceptible person
– if 1% susceptible would amount to around 1 year per person
• For a birth cohort born in 2000 the average individual
benefit would be between 0.5 and 4.5 weeks

Chronic effects – what we don’t know
• Whether all the population is at risk from air
pollution exposure
• In those who are susceptible to what extent they
are affected
– Loss of life
– Worsening disease
• Whether air pollution causes asthma
• What the cost-benefits would be of reducing air
pollution, in health terms

Interventions

Changes in pollutants and mortality in
Dublin – 1984-97
Clancy et al Lancet 2002;360:1210-4]

Changes in pollutants and mortality in
Dublin – 1984-97
• 35.6ìg/m 3 (70%) decline in black smoke
• Adjusted non-trauma deaths fell by 5.7%
• Respiratory deaths fell by 15.5%
• Cardiovascular deaths fell by 10.3%
• This represents about 116 fewer respiratory and
243 cardiovascular deaths pa
Clancy et al Lancet 2002;360:1210-4]

Cardiorespiratory and all cause changes in
mortality after reduced sulphur emissions in
Hong Kong
• 2.1% fall in all cause deaths
• 3.9% fall in respiratory deaths
• 2.0% fall in cardiovascular deaths
• Mostly occurring in the first 2 years post intervention
• Average gain in life expectancy per year of exposure was
20 days (f) and 40 days (m)
• More recently, suggested this could be due to changes in
health care delivery over the same period
Hedley et al Lancet 2002;360:1646-52]

Air Pollution and Health –unanswered
questions
• Cardiac effects
– Who are the susceptible sub-groups
– How do these effects occur (mechanisms)
• Chronic effects
– Is all the population at risk from air pollution
– What is the size of the effect
– Does air pollution cause asthma
– What would the cost-benefits be of reducing air
pollution, in health terms
• Interventions
– Are they of short or long term benefit or both
– What pollutants should be targeted