Urban Sprawl and Public Health - Detailed Notes

Urban Sprawl and Public Health

Historical Context and Definition

The advent of regular steam ferry service between Brooklyn and Manhattan in 1814 facilitated the first commuter suburb.
Suburban development progressed gradually in the 19th and early 20th centuries due to:
- Transportation advancements (commuter trains, streetcars).
- Real estate developers' innovations.
- Desire for peaceful, rural living.
Automobile ownership, becoming widespread in the 1920s, further spurred suburban growth, which accelerated in the late 20th century.
Currently, half of all Americans reside in suburbs.
Urban Sprawl: Rapid metropolitan expansion involving intricate land use, transportation, and socioeconomic development patterns.
Cities expand into rural areas with fragmented, low-density development.
Land uses (housing, retail, offices, industry, recreation, parks) are separated by custom and zoning.
Extensive road construction is necessary, making car travel essential for most trips.
New suburbs exhibit homogeneity in architecture and demographics, contrasting with the diversity of traditional urban or small-town settings.
Capital investment and economic opportunities shift from urban centers to suburban peripheries.
Regional planning and coordination tend to be weak.
Suburbanization reflects a lifestyle preference for many Americans.
Demographic and environmental shifts are expected to have both positive and negative health implications.
Public health concerns related to sprawl:
- Reliance on automobiles: air pollution, car crashes, pedestrian injuries.
- Land use patterns: sedentary lifestyles, water quality and quantity issues, urban heat island effect.
- Social dimensions: mental health and social capital effects.
While individual health effects are recognized, the comprehensive phenomenon of sprawl has been primarily addressed by engineers and planners, with limited public health framework or policy guidance.
Historically, public health and urban design shared overlapping concerns in the 19th and early 20th centuries.

Direct Effects of Reliance on Automobiles

Sprawl is directly linked to increased automobile travel due to lower density development.
Example: Atlanta, sprawling metropolitan area, has an average of 34.1 miles traveled per person per day by car.
Densely populated areas have lower per capita daily driving distances:
- Philadelphia: 16.9 miles.
- Chicago: 19.9 miles.
- San Francisco: 21.2 miles.
Vehicle miles traveled increase as neighborhood density decreases in metropolitan areas like Los Angeles, San Francisco, and Chicago.
While offering mobility, automobile use poses health risks:
- Air pollution.
- Motor vehicle crashes.
- Pedestrian injuries and fatalities.

Air Pollution

Motor vehicles are major contributors to air pollution.
Despite engine improvements, high vehicle miles traveled result in substantial emissions of harmful substances:
- Carbon monoxide (CO).
- Carbon dioxide ( $CO_2$ ).
- Particulate matter.
- Nitrogen oxides ( $NO_x$ ).
- Hydrocarbons.
Nitrogen oxides and hydrocarbons, under sunlight, create ozone ( $O_3$ ).
Mobile sources (cars, trucks) contribute significantly to national emissions:
- 30% of nitrogen oxides.
- 30% of hydrocarbon emissions.
In car-dependent areas, these proportions can be higher.
- Atlanta: On-road vehicles produce 58% of nitrogen oxides and 47% of hydrocarbon emissions.
Pollutants from vehicles (nitrogen oxides, hydrocarbons, ozone, particulate matter) significantly contribute to urban air pollution.
Air pollution may be highest downwind from the source due to regional transport.
Health hazards of air pollution:
- Ozone is an airways irritant, increasing respiratory symptoms, reducing lung function, and causing emergency room visits, hospitalizations, medication use, and absenteeism.
- Asthma and respiratory disease sufferers are particularly vulnerable.
- Particulate matter causes respiratory effects and elevated mortality.
- The elderly, young children, and individuals with cardiopulmonary conditions are more susceptible.
Carbon dioxide, produced from burning fossil fuels, is a major greenhouse gas, responsible for about 80% of emissions with global warming potential.
Motor vehicles are significant sources of other greenhouse gases (methane, nitrogen oxides, volatile organic compounds).
Automobile traffic contributes approximately 26% of U.S. greenhouse gas emissions.
Mobile source greenhouse gases increased by 18% in the 1990s due to increased vehicle miles traveled.
Global climate change impacts:
- Direct effects from heat.
- Increased formation of certain air pollutants.
- Higher prevalence of some infectious diseases.
Link between sprawl and respiratory health:
- Sprawl leads to high driving levels.
- Driving causes air pollution.
- Air pollution results in morbidity and mortality.
In car-dependent cities, air pollution reaches hazardous levels, with driving being a major emission source.
Research focuses on prevention, including:
- Developing low-emission vehicles.
- Identifying land use and transportation approaches to reduce car travel.
- Motivating less-polluting travel behaviors (walking, carpooling, efficient vehicles).

Motor Vehicle Crashes

Automobile crashes cause over 40,000 deaths annually in the U.S.
Fatality and injury rates per driver and mile have decreased due to safer cars and roads, seat belt use, and anti-drunk driving laws, but the total number of crashes remains high.
Car crashes are:
- Leading cause of death for people aged 1-24.
- Cause of 3.4 million nonfatal injuries annually.
- Cost an estimated $$200 billion annually.
More driving increases exposure to crash risks.
Suburban roads, particularly commercial thoroughfares and feeder roads, can be hazardous due to high speeds, traffic volume, and curb cuts.
Denser cities with public transport have lower fatality rates compared to sprawling cities.
- Examples of lower rates: San Francisco (2.45), New York (2.30), Portland (3.21).
- Examples of higher rates: Houston (10.08), Tampa (16.15), Atlanta (12.72).
Traffic crashes are seen as predictable and preventable.
Primary prevention involves decreasing driving exposure.

Pedestrian Injuries and Fatalities

Automobiles cause approximately 6,000 pedestrian deaths and 110,000 injuries each year in the U.S.
Pedestrians represent about one in eight automobile-related fatalities.
Atlanta saw pedestrian fatality rate increase with sprawl, even as the national rate decreased.
Dangerous roads are characterized by:
- Multiple lanes.
- High speeds.
- No sidewalks.
- Long distances between intersections.
- Roadways with commercial establishments and apartment blocks.
Denser cities show lower pedestrian fatality rates compared to sprawling cities.
- Examples of lower rates: Portland (1.89), New York (2.22), Chicago (2.52).
- Examples of higher rates: Dallas (3.03), Atlanta (3.61), Phoenix (4.08), Tampa (6.60).
High-speed, pedestrian-hostile roads in sprawling areas contribute significantly to pedestrian fatalities.
Safe and attractive sidewalks and footpaths are crucial for pedestrian safety.

Effects of Land Use Decisions

Land use and travel patterns are closely related.
Separation of land uses and greater distances increase driving while decreasing walking and bicycling.
In the U.S., only 1% of trips are by bicycle and 9% are on foot.
In comparison:
- Netherlands: 30% of trips by bicycle, 18% on foot.
- England: 8% by bicycle, 12% on foot.
Approximately 25% of all trips in the U.S. are shorter than one mile, yet 75% of those trips are made by car.

Physical Activity

Sprawl (characterized by low residential density, low employment density, and low connectivity) is associated with less walking and bicycling and more driving.
Low physical activity levels directly and indirectly threaten health.
Sedentary lifestyles are risk factors for:
- Cardiovascular disease.
- Stroke.
- All-cause mortality.
Physical activity prolongs life.
Men with the lowest physical fitness levels have a 2-3 times higher risk of overall mortality and a 3-5 times higher risk of cardiovascular mortality, compared to fitter men.
Walking 10 blocks daily is associated with a 33% lower risk of cardiovascular disease in women.
Poor physical fitness risk is comparable to hypertension, high cholesterol, diabetes, and even smoking.
Physical activity protects against cancer.
Lack of physical activity contributes to being overweight.
Overweight prevalence in the U.S.:
- 1960: 24% (Body Mass Index ≥ 25 kg/m²).
- 1990: 33%.
Obesity prevalence nearly doubled between 1960 and 1990.
Obesity increased from 12.0% in 1991 to 17.9% in 1998.
Being overweight is a risk factor for:
- Ischemic heart disease (increases risk up to fourfold in the 30-44 age group).
- Hypertension.
- Stroke.
- Dyslipidemia.
- Osteoarthritis.
- Gall bladder disease.
- Some cancers.
Overweight individuals have a 2.5 times higher mortality rate.
Being overweight increases Type 2 diabetes risk up to fivefold, correlating with the diabetes epidemic.
Sprawl contributes to physical inactivity, overweight, and related health issues.

Water Quantity and Quality

Water supply development improved public health in the first half of the 20th century.
Sprawl threatens water quantity and quality.
Clearing forest cover and constructing impervious surfaces decreases rainfall absorption and groundwater recharge.
Stormwater runoff increases.
One study found 4% rainfall runoff on grassland vs. 15% on suburban land.
Higher density development reduces peak flows and runoff volumes.
Communities using groundwater for drinking water (one-third of U.S.) may face shortages.
Water quality is affected by non-point source pollution.
Non-point source pollution occurs as rainfall or snowmelt picks up contaminants and deposits them into water sources.
Contaminants include:
- Fertilizers, herbicides, and insecticides from agriculture.
- Oil, grease, and chemicals from roadways.
- Sediment from construction sites and eroding stream banks.
Suburban development is associated with high loading of polycyclic aromatic hydrocarbons, zinc, and organic waste in surface water.

The Heat Island Effect

Urban areas can be 6°–8° F warmer than surrounding areas due to the urban heat island effect.
Causes:
- Dark surfaces absorbing and reradiating heat.
- Lack of vegetation for shade and cooling via evapotranspiration.
The heat island effect expands with sprawl and is aggravated by cutting trees and building roads.
Metropolitan expansion contributes to the effect.
More automobile travel from sprawling areas increases carbon dioxide production, contributing to global climate change, which intensifies the heat island effect.
Extreme heat events are increasing in U.S. cities.
Heat is a health hazard, causing:
- Heat syncope (fainting).
- Heat edema (swelling).
- Heat tetany (hyperventilation).
- Heat cramps (muscle spasms).
- Heat exhaustion (nausea, vomiting, weakness).
- Heat stroke (body's failure to dissipate heat, core body temperature exceeding 104°F), which carries a high fatality rate.
Risk factors for heat stroke:
- Being elderly, bedridden, homebound, or socially isolated.
- Having certain diseases or using certain medications.
- Living on an upper floor.
- Poverty and minority race/ethnicity.
Heat indirectly affects health via air pollution.
Increased energy demand for air conditioners raises power plant output, which results in:
- Higher emissions of pollutants.
- Enhanced ozone formation.

Social Aspects of Sprawl

Mental Health

Suburban migration was initially motivated by access to nature, which benefits mental and physical health.
Suburban refuge offers peace and restoration.
However, commuting may negatively impact mental health.
Automobile commuting is linked to:
- Stress.
- Stress-related health problems.
- Back pain.
- Cardiovascular disease.
Road rage: angry or impatient drivers attempting to harm others after traffic disputes.
Long delays on crowded roads are likely contributing factors.
Aggressive driving behavior is widespread.
Leading reasons for aggressive driving:
- Being rushed or behind schedule (23%).
- Increased traffic or congestion (22%).
Commuting stress affects well-being and social relationships, which may threaten mental health.

Social Capital

Suburban living has been linked to social isolation and loneliness.
Erosion of civic engagement and mutual trust (