The Role of Epidemiology in Air

Quality Public Policy Decision-making

Ronald White, M.S.T.Department of Epidemiology

Johns Hopkins Bloomberg School of Public HealthNorthern Transportation and Air Quality Summit

August 14, 2008

Air Pollution: Evidence and Policy

Policy

Population Impact

Health Risks (risk assessment)

Health Hazard

Epidemiology Clinical Studies Toxicology

ExposureAssessment

How Do We Investigate the Relationship Between

Environment and Health?

ObservationCross-sectional

Case-control

Cohort• “Panel”• Long-term

– Prospective– Retrospective

ExperimentClinical Studies

Animal (In vivo) Studies

Cellular (In vitro)Studies

hypotheses

mechanisms

ExtrapolationCause-effect mechanism of response

Biochemical systems

Threshold of human response?

Rapid acquisition of Data

Cells

Realistic models of human disease?

Maximal dose-response data

AnimalsToxicology

Public acceptanceCause-effect

HazardsVulnerable persons

Acute effects onlyFew covariates

Artificial ExposureControlled exposureExperimental Healthy or Diseased Subjects

Clinical Studies

Association versus causation

Long-term, low-level effects

Minimal dose-response data

Susceptible Groups

Many covariates and confounders

No ExtrapolationsDiseased Groups

Difficulty of Quantifying Exposure

Natural ExposureCommunitiesEpidemiology

WeaknessesStrengthsPopulationDiscipline

Three Disciplinary Approaches for Obtaining Health Information

(modified from Vallero, Fundamentals of Air Pollution, 4th ed.)

Air Pollution Health Study Methodologies

Epidemiologic Research on Air Pollution Health Effects

Strengths

▪ Actual exposures

▪ Susceptibility range

▪ Combined effects

▪ Public health relevance

Weaknesses

▪ Exposure misclassification

▪ Specificity of outcomes

▪ Feasibility

▪ Costs

▪ Imprecision

Key Epidemiologic Study Designs For Air Pollution Health Effects

• Ecological designs– Compares population-level exposures to health outcomes– Multi-community – Time-series

• Surveys or cross-sectional designs– “Snapshot” of exposure and health effects relationship at one point in time

– Multi-community

– Roadway proximity & health studies

• Cohort designs– “Panel” or short-term studies– Long-term studies (e.g., ACS-II, Six-Cities)

• Case-control designs– Compares exposure for cases of disease vs. those without disease (i.e.

controls)– Used primarily in air pollution cancer-related studies

e.g., NMMAPS

Potential Confounders in Epidemiological Studies of Air Pollution

Confounding factor: Associated with health outcome and exposure factor (but not caused by exposure)

• Active and passive smoking

• Socioeconomic status

• Demographic characteristics

• Occupational exposures

• Access to medical care

• Nutrition

Potential Effect Modifiers inEpidemiological Studies of Air Pollution

• Active cigarette smoking

• Airways responsiveness

• Symptom status

• Other environmental exposures

• Other host factors

What Do Regulators Want From Epidemiologic Research?

• Evidence of effects based on “actual human exposures”

• Determination of hazard

• Quantification of risk

• Magnitude of effects on “susceptible” or “sensitive” persons

• Evidence of improved health from interventions (Accountability)

Application of EpidemiologicalEvidence to Air Pollution Policy

• NAAQS Reviews; Risk Assessments based on epi studies:– 2005 PM: total, CV, respiratory, C-P, lung cancer mortality; C-P hospital

admissions; respiratory symptoms– 2007 Ozone: total, respiratory, C-P mortality; respiratory hospital admissions;

symptoms in asthmatic children– 2007 Lead: neurological, hematological and immune effects in children;

neurological, hematological, renal and CV effects in adults

• ∆ Air Quality Studies– Six Cities– Atlanta Olympics

• Regulatory Intervention Studies– Dublin– Hong Kong

• Roadway Proximity and Health Studies– Policy applications

Air Quality Improvement StudiesSix Cities Follow-up Study

• 8,000+ white adults

• Portage, WI; Topeka, KS; Louisville, KY; Kingston, TN; Watertown, MA; Steubenville, OH.

• Extended 1993 Dockery et al. study: 1974 – 1989 (period 1) to 1990 – 1998 (period 2)

• Ability to examine effect of fine PM reductions over study period

Laden et al., AJRCCM, 2006

Six Cities Cohort Follow-up

0.70.80.91.01.11.21.31.4

0 5 10 15 20 25 30 35

PM2.5 (μg/m3)

Mor

talit

y R

isk

Rat

io

SteubenvilleTopeka

Watertown

Kingston

St. Louis

Portage

(Laden et al, AJRCCM, 2006)

Orange = Period 1Yellow = Period 2

Air Quality Improvement Studies1996 Atlanta Olympics Study

– Downtown Atlanta closed to traffic; 24-hr public transit; 1,000 extra park & ride buses provided; altered downtown delivery schedule; flex and telecommute work

– Daily peak ozone levels < ~28% compared to pre and post-Olympics period (one month each); daily traffic counts <22.5%

– Acute care childhood asthma events• < 42% Medicaid• < 44% HMO• < 11% Pediatric ER• < 19% Hospitalizations

Freidman et al., JAMA, 2001

Regulatory Intervention StudiesDublin Coal Study

– Coal use banned September 1990

– Compared daily air pollution, weather, and deaths for 6 year period before and after the ban

– Avg. reductions: BS = ~36µg/m3 (71%)SO2 = ~11µg/m3 (34%)

– Reductions in mortality rates:• total non-trauma deaths - ~ 6%• respiratory deaths - 15.5%• cardiovascular deaths - ~10%• but not for accidental deaths

Clancy et al., Lancet, 2002

Regulatory Intervention StudiesHong Kong Fuel Sulfur Study

– July 1990: Sulfur in fuel limit of 0.5%

– Immediate reductions in SO2 (80%) and Sulfate PM10(41%) for most highly polluted areas. Avg. 45% reduction in ambient SO2 levels over 5 years

– 2 years post intervention: reductions in chronic bronchitis symptoms and bronchial hyper-responsiveness in children

– Reductions in all cause (2%), respiratory (~4%), and cardiovascular (2%), but not neoplasm (cancer) deaths

Hedley et al., Lancet, 2002

Roadway Traffic Proximityand Health Studies

• Growing body of studies assessing exposures and health effects associated with close residential proximity to high traffic roadways

• Epidemiological health studies conducted in Europe, Japan and Scandinavian countries, with increasing number in U.S.

• Risk gradients in a 0-200 meter buffer– Distance from roadway (traffic volumes)– Traffic density in proximity buffer – Traffic density with neighborhood background matching– NO2 home/outdoor levels (assuming distance is fixed)

Roadway Proximity/Traffic Density and Health Study Outcomes

– Respiratory symptoms– Asthma outcomes– Allergic sensitization– Immunologic effects– Respiratory function– Respiratory disease– Adult and childhood cancers– Cardiovascular outcomes– Birth outcomes– Mortality

Traffic-related ExposuresAsthma and Respiratory Symptoms/Lung Disease

Type Local TrafficIncidence +

Exacerbation/Prevalence +

Acute Care Visits +

ED Visits/Hospitalization +/-

Medication Use +/-

Respiratory Symptoms + CoughPhlegmWheezeShortness of Breath

COPD + (women)

Traffic-related ExposuresCardiovascular Effects

Type

Blood Pressure

Acute MI

Atherosclorosis

CHD prevalence

ED Visits/Hospitalizations

Cardiac Function

Local Traffic

+

+

+

+

+

+/-

Traffic-related Exposures Growth and Development

Type Local Traffic

Low birth weight +/-

Pre-term birth +

Lung Function +

Neurodevelopment +BC

Traffic-related ExposuresCancer

Type Local Traffic

Childhood +/-- All cancers- Leukemia- Central Nervous

System- Lymphomas- Brain

Lung +

Mesothelioma +

Traffic-related ExposuresMortality

Type

Total Mortality

Cardiopulmonary Mortality

Stroke Mortality

Local Traffic

+

+

+

Potential Issues in Near RoadwayStudy Interpretation

• Proximity: proxy for what pollutant(s) ?

• Subjective exposure and/or outcomes

• Self-selection of residence

• Exposure Assessment– Measurement error - temporal and spatial

• street canyons, wind– Complex mixture - local and regional input

• Confounding– Social and demographic factors– Roadway-associated exposures

• noise, power lines

• Susceptible populations– Age, Sex, Asthma, SES, Diet, Genetic

Policy Applications – School Siting

CA school siting law (SB352, 2004)

• Prohibits siting of new schools within 500ft of freeway or major traffic corridor unless negative short and long-term air pollution health risk determination

• Negative health risk determination required for sites after identification of sources of hazardous pollutants (including freeways and major traffic corridors) within ¼ mile of school site

AADT = Avg. Annual Daily Traffic

Policy Applications –Sensitive Uses Siting Guidelines

• CARB Land Use and Air Quality Handbook: A Community Health Perspective (2005 Land Use Handbook)

– guidance on siting sensitive land uses in proximity to sources of air toxics (e.g., diesel PM from freeways & high traffic roads)

– sensitive land uses include residential communities, schools and school yards, day care centers, parks and playgrounds, hospitals and medical facilities

– recommends that sensitive land uses be sited no closer than 500 feet from a freeway or other high traffic roadway

• Sacramento Metropolitan Air Quality Management District “Recommended Protocol for Evaluating the Location of Sensitive Land Uses Adjacent to Major Roadways (Draft - June 2008)”

– assists local land use jurisdictions in assessing the potential cancer risk of siting sensitive land uses adjacent to major roadways (health risk assessment)

– potential mitigation measures

Emerging Traffic and Health IssuesIntelligence Effects

Increases in Black Carbon (traffic pollution marker) associated with3-4 point lower IQ and cognitive function test scores

Suglia et al., AJE, 2008

Emerging Traffic and Health IssuesMental Health Effects

Traffic, Air Pollution and Schizophrenia

Pedersen et al; Schizophr Res. 2004 Jan 1;66(1):83-5.

Traffic-related Exposuresand Mortality

Netherlands Cohort Study

Exposure CR non-CR/non-LC All-cause2

NO2 background 1.54 (0.81-2.92) 1.07 (0.61-1.90) 1.09 (0.70-1.69)

Major road1 1.94 (1.08-3.48) 1.04 (0.54-1.97) 1.53 (1.01-2.32)

1) within 100m of HWY or 50m of major urban road2) Individuals living ≥ 10 years at enrollment address

489 death out of 4492 subjects, 55-69Follow-up: 1986-1994

Hoek et al; Lancet 2002; 360(9341):1203-09

Traffic Proximity and Respiratory Symptoms

Parent-reported wheeze in secondary school children (150 meter distance buffer)

Venn et al. AJRCCM 2001

Traffic Proximity and Respiratory Symptoms

Odds of symptoms in last year among children (0-15yrs) living within 50m of a street with 10,000-30,000 vehicles per day compared with children living on a close by “quiet“ street (adjusted for local background)

Outcome boys (n ~ 110) girls (n ~ 135)

• Wheeze 0.7 (0.2-2.5) 5.3 (1.1-25.0)

• Attack of dysp 0.4 (0.1-2.6) 15.8 (1.4-174.4)+ wheeze

• Respir. medication 1.7 (0.6-5.1) 2.9 (1.1-7.9)

Oosterlee et al, Occup Env Med 1996

Traffic and Asthma

• LA & San Diego Cos.

• “Poorly controlled asthma” – weekly asthma symptoms or hospitalization during past year

Meng et al., AAAI, 2007

Traffic Proximity and Lung Development

• So. CA. Children’s Health Study (12 communities)

• Actual v. predicted lung function

• Changes likely permanent with long-term health implications

Gauderman et al., Lancet, 2007

Traffic-related Exposures and Growth and Development

Wilhelm M and Ritz B; EHP, 2003

More Information• EPA Control of Hazardous Air Pollutants from Mobile

Sources (2007); Regulatory Impact Analysis; Chapter 3, Section 3.5. http://www.epa.gov/otaq/regs/toxics/420r07002.pdf.

• JHU Workshop on Traffic, Health & Infrastructure Planning (2004)

– Background information documents http://www.jhsph.edu/RiskSciences/Research/TrafficProximity.html

– White RH, Spengler JD, Dilwali KM, Barry BE, Samet JM; Report of Workshop on Traffic, Health and Infrastructure Planning; Archives of Environmental and Occupational Health, 60: 2, 2005.

Additional References

• Boothe V and Shendell D; Potential health effects associated with residential proximity to freeways and primary roads: review of scientific literature, 1999-2006. J Environ Health, 2008 Apr; 70(8): 33-41.

• Meng Y-Y et al.; Living Near Heavy Traffic Increases Asthma Severity. UCLA Health Policy Research Brief. 2006.

• Salam M, Islam T, and Gilliland F; Recent evidence for adverse effects of residential proximity to traffic sources on asthma. Curr Opin Pulm Med; 2008 Jan; 14:3-8.

• Samet J; Traffic, Air Pollution, and Health. Inhal Tox, 2007 Sept; 19:12, 1021-1027.