QUESTIONS
1. A dinosaur extinction theory suggests that massive
heating of the Earth's atmosphere in the path of a
falling asteroid would have led to extremely acid rain,
killing the land vegetation and hence the dinosaurs'
food supply. What acid would have been involved?
POLLUTION & HEALTH
SOME DEFINITIONS…
MORBIDITY: refers to the state of being diseased or
unhealthful. Morbidity refers to the incidence of ill health in
a population
- expressed as a probability of illness or similar metric
MORTALITY: is the state of being mortal (having a finite
life). Mortality refers to the incidence of death in a
population
- expressed as number of deaths per 1000 individuals per year
SOME EFFECTS…
ACUTE: irritation to the eyes, nose and throat, and
upper respiratory infections such as bronchitis and
pneumonia, headaches, nausea, and allergic
reactions. Short-term air pollution can aggravate the
medical conditions of individuals with asthma and
emphysema
CHRONIC: respiratory disease, lung cancer, heart
disease, and damage to the brain, nerves, liver, or
kidneys. Continual exposure to air pollution affects
the lungs of growing children and may aggravate or
complicate medical conditions in the elderly.
COSTS: healthcare, lost productivity in the
workplace, and human welfare
bold = included in Lave and Seskin, 1970 study
WAYS THIS IS STUDIED…
EPIDIOLOGICAL STUDIES: mortality and morbidity rates (often from
governments), need to classify cause of death or control for other
variables (eg. smoking habits, occupational exposure, genetics, etc.)
 can fail to find significant relationships or find spurious ones due to
unmeasured variables
 must find a relationship that is so strong that it is extremely unlikely
that missing variables could be the cause
EPISODIC RELATIONSHIPS: relate daily/weekly mortality (or mobidity)
rates to coincident indices of air pollution
 problem: air pollution usually more subtle (someone killed during an air
pollution event likely gravely ill)
 also need to control for other factors (eg. absences from Monday during
an air pollution event might be related to weekend activities, not air
pollution health impacts)
Tools: statistical analysis, multiple regressions, thorough uncertainty
and significance analyses
HARVARD SIX CITIES STUDY
Cohort study: 8111 adults followed from 1974-1991 (annual surveys)
Associated fine-particulate pollution with excess mortality. No observable threshold
[Dockery et al., 1993, NEJM]
AMERICAN CANCER SOCIETY: PM EFFECTS
Cohort Study: 1.2M participants in American Cancer Society tracking 1982-1998
~1/2 linked with air pollution data for metropolitan areas in the U.S.
Mortality Relative Risk (RR) Ratio Associated With 10-μg/m3 Differences of PM2.5 Concentrations
Each 10-μg/m3 elevation in fine particulate air pollution was associated with
approximately a 6%, and 8% increased risk of cardiopulmonary, and lung cancer
mortality.
[Pope et al., 2002, JAMA]
REDUCED LIFE EXPECTANCY DUE TO PM
A decrease of 10 μg/m3 in the concentration of fine PM was associated with an
estimated increase in mean life expectancy of 0.61 years
[Pope et al., 2009, NEJM]
OZONE CORRELATED WITH RESPIRATORY
HOSPITAL ADMISSIONS
Episodic study: acute respiratory health effects at 168 hospitals in Ontario (1983-1988)
Adjusted admissions (binned by decades of ozone)
5% of respiratory hospital admissions in May-Aug associated with ozone
[Burnett et al., 1994, ER]
MAIN ISSUES WITH HEALTH-POLLUTION STUDIES
1. Controlling for other variables (intensive effort required to get
true picture of lifestyle and impacts)
2. Understanding cause of death (particularly how to get
information once someone in a cohort study has passed
away!)
3. Effort required for long-term cohort studies
4. Approximating exposure with ambient monitoring networks
 Working more on personal exposure monitoring
5. Getting detailed information on size, composition of particles
and how they affect health
6. Scaling up! Assuming all populations respond alike
(economically, environmentally, racially)
APPLICATION OF EPIDIOMIOLOGICAL STUDIES:
INVESTIGATING THE LINK BETWEEN RISING CO2
AND AIR POLLUTION MORTALITY
T leads to increases in O3
 H2O increases O3, except in low NOx conditions
Pre-industrial to present-day population weighted 8-hr O3 = 0.72 ppb
y= health effect change (death rate)
x=mixing ratio change
=fractional increase in risk per unit x
yo= baseline health effect rate
P=population exposed to a min threshold
[Ostro et al., 2006]
Found that pre-industrial to present day increase in T (~ 1K) and water vapour (~1
ppb) over US, led to an increase of 415 deaths/yr due to O3 exposure in the US
(8500 dealth/yr worldwide). Previous studies estimate up to 15,500 deaths/yr due
to 1 ppb change in O3
[Jacobson, 2008]
IMPACT OF BLACK CARBON EMISSION REDUCTIONS ON
HUMAN MORTALITY
Avoided deaths for halving emissions
AF=attributable factor
RR=relative risk
X=change in PM2.5
=concentration response factor
yo=baseline mortality rate
Estimate that halving global
anthropogenic BC emissions avoids
157 000 annual premature deaths
globally, mostly near the source region
(esp. Asia).
[Anenberg et al., 2011]
GLOBAL HEALTH INDICES FROM SATELLITE
OBSERVATIONS
Multipollutant Air Quality Health Index (AQHI): [Stieb et al., 2008]
AQHI = 0.09 x NO2 (ppb) + 0.05 x PM2.5 (ug/m3) + 0.05x O3 (ppb)
~ excess mortality risk (%)
NO2 and O3 from OMI, PM2.5 estimates from MODIS/MISR
[Randall Martin, Dalhousie]