Human Health and the Human Health and the EnvironmentEnvironment

Molly Kile, ScDENVRE-115

Fall 2010

AnnouncementsAnnouncements

• More features added to the course website

http://isites.harvard.edu/icb/icb.do?keyword=k72216&pageid=icb.page350713

• Class participation is not graded but helps to build a sense of community.

• Assignment #1 is due today in your drop box

– Please check to the drop box to make sure the assignment has been uploaded

• Pedagogical goal of assignments is to foster critical thinking which involves comparing, contrasting and synthesizing what one has learned which requires being open to new knowledge and actively reflecting on its meaning.

Logistics of Distance EducationLogistics of Distance Education• Lecture is available as a live streaming feed during class period

and are also archived after processing (< 48 hrs)

• Chat room is only monitored during class

• If you live outside of the New England area you must arrange for proctored midterm and final exam a minimum of two weeks prior to scheduled exam dates– http://www.extension.harvard.edu/DistanceEd/how-it-works/polic

y.jsp

Economic LiteracyEconomic Literacy

• There is no formal (only suggested) economics prerequisite for this course

• Check your economic literacy and review concepts by taking the “Economic Literacy Self Assessment” on the course website. You should be familiar with these terms and concepts before the lecture on October 14.

• If you need or want to review economic terminology you can use any undergraduate economics textbook or the “Guidelines for Preparing Economic Analyses” by the US EPA.

– http://yosemite.epa.gov/ee/epa/eed.nsf/webpages/Guidelines.html

Agenda For TodayAgenda For Today

• Drivers of environmental issues

• Demographic and Epidemiological Transition

• Demographic dividend

• Linkage between human health and development

What influences human What influences human health?health?

Underlying PrincipleUnderlying Principle

Disease, illness and ill-health are not randomly distributed in a population

Behaviors

Genetics

Environment

General Environmental Health Definition:– The study of the health effects of all situation and risk

factors outside of genetic factors

Practical Environmental Health Definition:– The study of exogenous factors over which the

affected people have limited individual control

Tony Fletcher, London School of Hygiene

ENVIRONMENTAL QUALITY ENVIRONMENTAL QUALITY IMPACTS HUMAN HEALTHIMPACTS HUMAN HEALTH

Haiti DominicanRepublic

Ramifications of environmental Ramifications of environmental degradation degradation on health …on health …

SoilErosion

WatershedDegradation

FloodControl

ClimateChange

PopulationDisplacement

Lossof

Biodiversity

Deforestation

Hurricane Impact

Disaster Management

Water scarcity

Waterborne disease

Rural – Urban Migration

Social unrest

Malnutrition

Diminished crops

Loss of natural resources

Pharmaceutical/Agricultural

Vector-borne disease

Change in hydrological cycle

Life Expectancy at Birth Life Expectancy at Birth (2009)(2009)

Among the BestRank Country Year

1. Macau 84.4

2. Andorra 82.5

7. Australia 81.6

10. Sweden 80.8

28. Faroe Islands 79.4

50. United States 78.1

99. Dominican Rep. 73.7

113. Estonia 72.9

Among the WorstRank Country Year

159. The World 66.6

162. Russia 66.0

178. Botswana 61.9

181. Haiti 60.8

210. Afghanistan 43.34

206. Rwanda 42.73

223. Angola 38.2

224. Swaziland 31.8

Source: CIA, The World Factbook, https://www.cia.gov/library/publications/the-world-factbook/rankorder/2102rank.html

Drivers of Environmental Drivers of Environmental HealthHealth

A.D.2000

A.D.1000

A.D.1

1000B.C.

2000B.C.

3000B.C.

4000B.C.

5000B.C.

6000B.C.

7000B.C.

1+ million years

8

7

6

5

2

1

4

3

OldStoneAge New Stone Age

BronzeAge

IronAge

MiddleAges

ModernAge

Black Death —The Plague

9

10

11

12

A.D.3000

A.D.4000

A.D.5000

18001900

1950

1975

2000

2100

Future ?

Bil

lio

ns

Source: Population Reference Bureau; and United Nations, World Population Projections to 2100 (1998).

1. Population Growth1. Population Growth

~ 125 yrs

~ 50 yrs

~ ? yrs

2. Affluence2. Affluence

3. Technology3. Technology

Ehrlich IdentityEhrlich Identity

Environmental Impact = Population x Affluence x Technology

• The IPAT formulation arose from a dispute in the early 1970s among the most prominent environmental thinkers of the day about the sources of environmental impact

• Paul Ehrlich and John Holdren identified population size and growth as the most urgent IPAT factor

• Barry Commoner argued that post-World War II production technologies were the dominant reason for environmental degradation

• Provides a foundation for the analysis of environmental impacts per capita over time

(Ehrlich and Holdren, 1972):

Example: Lead (Pb)Example: Lead (Pb)

Ehrlich Identity: I=PATEhrlich Identity: I=PAT

• Environmental Impact is a multiplicative product from small changes in Population, Affluence and Technology

• Mathematically represented as:

(I + ΔI) = (P + ΔP)(A + ΔA)(T + ΔT)

Divide through by the identity

(1 + ΔI/I) = (1 + ΔP/P)(1 + ΔA/A)(1 + ΔT/T)

Where ΔI/I, ΔP/P, and ΔT/T is the percentage increase in impact, affluence and technology

Quantifying ImpactQuantifying Impact

• Example: Lead in gasoline from 1946 to 1968 in the US– Pop. increased 42%

– Vehicle mile per capita doubled

– Amount of lead per vehicle mile increased 81%

(I + ΔI/I) = (P + ΔP/P)(A + ΔA/A)(T + ΔT/T)

(1 + ΔI/I) = (1 + 0.42)(1 + 1.0)(1 + 0.81)

(1 + ΔI/I) = 5.14

ΔI/I = 5.14 – 1

=4.14

Or 414% increase in lead

Umbilical Cord Lead Levels and Umbilical Cord Lead Levels and IQIQ

The Port Pirie StudyThe Port Pirie Study

Baghurst et al., NEJM 1988Baghurst et al., NEJM 1988

Blood lead of 10 Blood lead of 10 μg/dL=IQ loss μg/dL=IQ loss of 3 ptsof 3 pts

(What’s the big deal)(What’s the big deal)

Population Impact Depends on Underlying Distribution

6.0 millionMentally Deficient

6.0 millionMentally Gifted

Public Health Impact of Subclinical Lead Toxicity

9.4 millionMentally Deficient

2.4 millionMentally Gifted

57% Increase inMentally Deficient

Population

SOURCE: http://www.epa.gov/bns/lead/Fig_01.gif

Impact of Lead Poisoning Prevention Policies on Reducing Children’s Blood Lead Levels

‘76 ‘80 ‘82 ‘84 ‘86 ‘88 ‘90 ‘92 ‘94 ‘96 ‘98

Year‘72

Blo

od

Le

ad L

eve

ls (µ

/dL

)

18

2

4

6

8

10

12

14

16

0

‘00‘74

Lead Gasoline Phase-out

(1973)

Lead-based Paint Poisoning Prevention Act

(1971)

‘78

Residential Lead Paint Ban (1978)

Lead Title X (1992)

Housing units with lead based paint

hazards reduced by 40% since 1990

Lead Contamination Control Act (1988)

Virtual Elimination of Lead in Gasoline

Ban on lead solder in food cans (1995)

Lead in Plumbing banned (1986)

‘02 ‘04

NHANES DATA - CDC

EnvironmentaEnvironmental Justicel Justice

US Children Aged 1-5 years with blood lead levels above 10 µg/dl*

• 11.2% African American• 2.3% Caucasian

* Bernard SM. Should the Centers for Disease Control and Prevention's Childhood Lead Poisoning Intervention level be lowered? AJPH. 93(8):1253-60, Aug 2003.

Photograph: Peter Essick for National Geographic

Underlying Ecological Underlying Ecological PrinciplesPrinciples

Carrying CapacityCarrying Capacity• Ecological definition:

– the number of individuals in a population that the resource of a habitat can support

• Other definitions:– Point at which the birth rate equals the death rate

– The number of individuals an environment can support without significant negative impacts

– The population size is constrained by whatever resource is in shortest supply (Malthus)

Tragedy of the [Unregulated] Tragedy of the [Unregulated] CommonsCommons

Garrett HardinGarrett Hardin

“Picture a pasture open to all. It is to be expected that each herdsman will try to keep as many cattle as possible on the commons. Such an arrangement may work reasonably satisfactorily for centuries because tribal wars, poaching, and disease keep the numbers of both man and beast well below the carrying capacity of the land.”

What are the consequences of adding one more animal to my herd?

• “The population problem has no technical solution; it requires a fundamental extension in morality.”

Science 1968

OvershootOvershoot

• A rapidly growing population can exceed (overshoot) the ecological carrying capacity due to the “momentum” of its growth.

• Indicators of Overshoot– Deterioration in renewable resources – Rising levels of pollution– Growing demands by military and industry to

secure resources– Investment in human capital postponed to

meet immediate consumption demands– Rising debt– Eroding goals for health and environment – Growing instability in natural ecosystems– Growing gap between rich and poor

Ecological EvidenceEcological Evidence

In 1944, 29 reindeer were introduced to St. Matthew Island.

In 1963, there were 6,000.

One winter later, there were less than 50.

By 1980, there were none.

Klein, 1968

Human Population GrowthHuman Population Growth

Factors that influence human population growth:

1. Fertility

2. Age structure of population

3. Mortality

1. Fertility1. Fertility

• Birth rate is defined as the number of live births per 1,000 women aged 15-49 in a given year

• Replacement level fertility– Net reproduction rate of 1

• Every woman of childbearing age has 1 daughter

– Total fertility rate of 2.1• Every woman of childbearing age has 2.1 children

Math Behind Exponential Math Behind Exponential GrowthGrowth

Consider a country with 100 people, growing at 7% per year. In 10 years, the population will double to 200 people, in another 10 years it will double again to 400 people, etc (see graph)

How long will it take this country to reach 1 million?

0.00200,000.00400,000.00600,000.00800,000.00

1,000,000.001,200,000.001,400,000.001,600,000.001,800,000.00

0 20 40 60 80 100 120 140

Years

Pop

ulat

ion

t = ln [N(t)/N(0)] / r

t = ln (1,000,000/100)/0.07t = ln (10,000)/0.07t = 9.2103/0.07t = 131.5 years

ExamplesExamples

1. How long would it take for a population to double if the growth rate is 3.5%?

Doubling Time

Time = 70/3.5 = 20 years

A special case is the doubling time, which is the time when N(t)/N(0) = 2.At that point rt = ln 2 = 0.69. If one knows the growth rate as a decimal fraction, then the Doubling Time = 0.69 / r.

This can be further simplified…the Rule of 70Where ,69/r is multiplied by 100 and rounded up to 70. This simplifies to:

Time for population to double = 70/rate expressed as a percentage

• US population is growing at a rate of 0.9% per year. How long will it take us to double our population from 307 Million?

Time = 70/0.9 = 77 years

Fertility Rates Are Fertility Rates Are DecliningDeclining

Average number of children per woman

5.75.25.4

6.46.4

8.5

5.3

3.3

6.2

3.1

2.4 2.1

4.3

2.5

Egypt India Indonesia Iran Pakistan Turkey Yemen

1970-1975 2000-2005

Source: United Nations, World Population Prospects: The 2004 Revision, 2005.

Factors that influence Factors that influence fertilityfertility

1. The proportion of women of childbearing age who are married or in a sexual union

2. The percent of women using contraception and the level of abortion

3. The proportion of women of childbearing age who currently are unable to conceive a child (usually from postpartum infecundity from breastfeeding)

4. Educational attainment of girls and women

Association Between Fertility and Association Between Fertility and Education of GirlsEducation of Girls

0

20

40

60

80

100

120

0 1 2 3 4 5 6 7 8

Percent of Girls Enrolled in Secondary School

Source: Population Reference Bureau, Population & Economic Development Linkages 2007 Data Sheet.

Total Fertility Rate

Association Between Fertility and Association Between Fertility and Female Labor Force ParticipationFemale Labor Force Participation

0

20

40

60

80

100

0 1 2 3 4 5 6 7 8

Female Labor Force Participation Rate 2004

Source: United Nations, World Population Prospects: The 2004 Revision, 2005; International Labor Organization, Yearbook of Labor Statistics 2006.

Total Fertility Rate 2000-2004

Association between fertility and Association between fertility and wealthwealth

6.4

4.9

4.1

4.9

3.2

2.42.8

2.4

1.4

Ghana 2003 Cambodia 2005 Colombia 2005

Poorest Quintile Middle Quintile Richest Quintile

Average Number of Children Born to a Woman During Her Lifetime

Source: ORC Macro, Demographic and Health Surveys.

2. Age Structure of a 2. Age Structure of a PopulationPopulation

• A large proportion of young people guarantees that population will continue to grow even with declining fertility

• Takes two or three generations (70-100 years) before each new birth is offset by a death

• Referred to as population momentum

Population MomentumPopulation MomentumThere is a growing population of women in their childbearing

years that will contribute to future world population growth even if fertility continues to decline

0.6

0.9

1.82.0 2.0

1.3

0

1

2

3

1950-1955 1970-1975 1990-1995 2010-2015 2030-2035 2045-2050

Bill

ion

s

0

1

2

3

4

5

6

Ch

ildre

n p

er

wo

ma

n

Women 15 to 49 Average number of children per woman

Source: United Nations, World Population Prospects: The 2004 Revision (medium scenario), 2005.

3. Mortality3. Mortality

• Death is the ultimate determinant of population growth

• Falling mortality precedes a decline in fertility

Death rate

Population growth rate

Birth rate

Time

Rat

e

How To Shift Causes of How To Shift Causes of MortalityMortality

• Improved sanitation and drinking water supplies

• Medical advances (vaccination, antibiotics)

• Social advances (improved nutrition, access to health care)

• Occupational Health & Safety (injury prevention, chemical safety)

• Infrastructure Improvements (roadways, housing, energy)

• Consumer Safety (injury prevention, chemical safety)

• Economic growth

Demographic TransitionDemographic Transitiondescribes population change over time

DemographicDemographicDividendDividend• Increase in the rate of

economic growth due to an increase in the proportion of working age people compared to non-working aged people

• Can occur late in the demographic transition when fertility rate falls and the youth dependency rate declines

Cover from the book by David Cork and Susan Lightstone:The Pig and the Python, How to Prosper from the Aging Baby Boom

http://www.iiasa.ac.at/Research/LUC/ChinaFood/data/anim/pop_ani.htm

Harnessing a Demographic Harnessing a Demographic DividendDividend

People’s Republic of China• 1952-1982: Invested in rural health care and education

– Infant mortality decreased from 200 to 34/1000 live births– Life expectancy rose from 35 years to 68 years– Fertility rates declined from 6 births/woman (1970) to 3 birth/woman(1979)

to “one child” policy in 1980– Universal primary education

• 1980s: Major policy reform – Economic deregulation and liberalization attracted foreign investment and

trade– Policies promoting gender equality

• Demographic dividend estimated to contribute 27% of China’s economic growth

Period of Potential Demographic BonusPeriod of Potential Demographic Bonus

• Countries with increasing numbers of working-age adults relative to dependent elderly and children have an opportunity to increase employment, investment, and savings

• Demographic bonus depends on economic policies and economic opportunities

1989 2011

1980 2008

1986 2050

1964 2024

1974 2047

1965 2014

1969 2037

1965 2013

2005 2050

1985 2048

2014 2050

1950 1975 2000 2025 2050

Chad

Ghana

Malawi

China

India

South Korea

Bolivia

Brazil

Guatemala

Czech Republic

Poland

Source: Population Reference Bureau, Population & Economic Development Linkages 2007 Data Sheet.

Epidemiological TransitionEpidemiological Transitionthe study of factors affecting the health and illness of

populations • Conceptually describes the interaction between causes

of mortality, life expectancy and developmentM

orta

lity

Rate

s

Infectiousdiseases

Epidemiological Transition

Non-communicablediseases

Systematic Shift in Disease

Systematic Shift In DiseaseSystematic Shift In DiseaseM

orta

lity

Rate

s

Infectiousdiseases

Socio-Economic Development

Trauma

Type 2Diabetes

CHDCancers

PremisePremise

• Fertility has a fixed upper limit but not mortality so mortality is the fundamental factor that controls population dynamics

• Diseases and injuries control mortality

• Investment in public health shifts the causes of death (Epidemiological Transition) and this will influence population structure where women and children benefit the most

• During the late phase of the demographic transition when fertility and dependency rates fall countries can harness the demographic dividend when output per capita rises

Stages in Epidemiological Stages in Epidemiological TransitionTransition

1. The Age of Pestilence and Famine– Mortality is high and fluctuating no sustained population growth– Life expectancy between 20-40 years

2. The Age of Receding Pandemics– Epidemics less frequent high population growth– Life expectancy between 30-50 years

3. The Age of Degenerative and Man-Made diseases– Mortality declines and stabilizes at a low level fertility rate

determines population growth– Life expectancy exceeds 50 years

Influence of Municipal Water on Influence of Municipal Water on MortalityMortality

Sewer system built & expanded

Reservoir/Aqueduct expansionsProtected watersheds

Public Health Benefits From Municipal Water Public Health Benefits From Municipal Water SupplySupply

• US from 1900-1940– Cholera and Typhoid Fever eliminated– Total mortality

140 to 20 per 100,000– Child mortality

130 to 60 per 1,000 live births – Life expectancy

16 years

• Cost-benefit analysis conducted by Cutler & Miller, 2005– 1:23 cost-benefit ratio – Every life saved cost $500* resulting in $11,500 gain

* 2002 US$

The Age of Receding PandemicsThe Age of Receding Pandemics

Morbidity and mortality associated with level of developmentMorbidity and mortality associated with level of development

http://www.nytimes.com/2007/11/26/nyregion/26manhole.html

Age of Degenerative & Man-Made diseasesAge of Degenerative & Man-Made diseases

LEADING CAUSES OF DEATH, US 20021. Heart disease 28.5%2. Cancer 22.8%3. Stroke 6.7%4. COPD 5.1%5. Accidental injury 4.4%6. Diabetes

3.0%7. Influenza/Pneumonia

3.7%8. Alzheimer’s disease

2.4%9. Kidney disease 1.7%

The Changing Built Environment•Rapid population growth•Urbanization•Sprawl•Traffic•Sedentary life style•Changing diet

Less Density = More Driving Less Density = More Driving

Miles per capita– more than Miles per capita– more than doubled in one generationdoubled in one generation

Miles per Capita: 1960 to 1995 From 4000 to 9200 VMT per person

Fine Food

Low Income-African American Neighborhoods:

2.4 fast-food restaurants/sq. mile

High Income – White Neighborhoods1.5 fast-food restaurants/sq. mileAmerican Journal of Preventive Medicine, October 2004

April 22, 2003

The result

Obesity* Trends Among U.S. AdultsObesity* Trends Among U.S. AdultsBRFSS, 2003BRFSS, 2003

(*BMI ≥30, or ~ 30 lbs overweight for 5’ 4” person)

No Data <10% 10%–14% 15%–19% 20%–24% ≥25%

ENVIRONMENTAL FACTORS ENVIRONMENTAL FACTORS INFLUENCE HUMAN HEALTH, INFLUENCE HUMAN HEALTH, HUMAN HEALTH INFLUENCES HUMAN HEALTH INFLUENCES ENVIRONMENTAL FACTORS … ENVIRONMENTAL FACTORS …

How significant is the impact of How significant is the impact of modifiable environmental factors on modifiable environmental factors on

global health?global health?

Environmental factors contribute to:

• 23% of all deaths

• 36% of deaths in children 0–14 yrs

• 24% of healthy life years lost

Examples of Modifiable Examples of Modifiable Environmental FactorsEnvironmental Factors

• Chemical or biological pollutants in air, water or soil• UV and ionizing radiation• Noise• Occupational risks• Built environments• Agricultural methods and irrigation schemes• Man-made climate and ecosystem change• Behavior related to the availability of safe water and sanitation

facilities

SummarySummary• Environmental Impact is a function of population, affluence and technology.

These drivers can have a neutral, positive or negative impact on the environment.

• Population growth is a central issue in sustainable development due to concerns about ecological carrying capacity of species and it is considered a problem with a non-technical solution

• Fertility has a fixed upper limit (and is controlled effectively by education of girls/women) but not mortality, so mortality ultimately controls population growth and demographics

• Causes of mortality are associated with level of development

• Investment in public health shifts the causes of death (Epidemiological Transition) and this will influence population structure (Demographic Transition) where women and children benefit the most

• When fertility and dependency rates fall countries can harness the demographic dividend when output per capita rises

Terminology and Concepts To Terminology and Concepts To ConsiderConsider

1. Erhlich Identity

2. Tragedy of the Commons

3. Carrying Capacity

4. Overshoot and Population Momentum

5. Doubling Time

6. How fertility, age structure, and mortality influence population growth (Demographic Transition)

7. How patterns of disease influence demographics (Epidemiological Transition)

8. Role of fertility, age structure and mortality in population growth

9. Population momentum can lead to demographic dividend

10. Environmental factors are modifiable and influence human health

ResourcesResources

• “Improving the health of the world's poor” BMJ No 7107 Volume 315

– http://www.bmj.com/archive/7107/7107e1.htm

• Population health in transition by John Caldwell

– http://whqlibdoc.who.int/bulletin/2001/issue2/79(2)159-170.pdf

• World Health Reports

– http://www.who.int/whr/en/

• Preventing disease through healthy environments: Towards an estimate of the environmental burden of disease

– http://www.who.int/quantifying_ehimpacts/publications/preventingdisease.pdf

• Health and Economic Growth: Findings and Policy Implications. Edited by G. López-Casasnovas, B. Rivera and L. Currais. MIT Press

– http://mitpress.mit.edu/catalog/item/default.asp?ttype=2&tid=10711

• Why Has China’s Economy Taken Off Faster than India’s? David E. Bloom, David Canning, Linlin Hu, Yuanli Liu, Ajay Mahal, and Winnie Yip

– http://www.hsph.harvard.edu/pgda/Bloom_Canning_China_India.pdf