Current Topics in Environemental Epidemiology: Whats in the news this week

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Current Topics in Environemental Epidemiology
Whats in the news this week?

• PH 2610
• November 6, 2002
• Lowell E. Sever, Ph.D.

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Overview

• Background Concerns of the public
• Historical concerns in environmental epidemiology
• Current concerns in environmental epidemiology
• Environmental agents and pathways of exposure
• Electric and magnetic fields and cancer

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Overview

• Hazardous waste sites and health effects
• Congenital malformations and hazardous waste
  sites Issues of exposure estimation and risk
• Clusters and concerns about environmental causes
• Woburn (A Civil Action)
• Brownsville

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Aims of Epidemiology

• Describe
• Explain
• Predict
• Prevent

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Common Public Perceptions of Risk

• Stuff in the environment
• Bad things happen to people

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Environmental Epidemiology What do people worry
about with respect to health effects?

• Getting cancer themselves carcinogenesis
• Their children having birth defects
  teratogenesis
• Their grandchildren having genetic diseases -
  mutagenesis

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Environmental Exposures

• To put it simply, if someone is not inhaling,
  ingesting, or absorbing the pollutant, there is
  no exposure and hence no adverse health effect is
  possible.

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• PATHWAYS
• EXPOSURE OF RECEPTOR POPULATION
• DOSE

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Assessing the Risks of Environmental Exposures

• Pollutant sources
• Transport of pollutants from sources to humans
• Exposure of humans to pollutants
• Doses received
• Adverse health effects resulting from the doses

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Exposure Pathways

• Most frequent pathways
• Ground water
• Subsurface soil
• Sediment
• Surface water
• Lead, trichlorethylene, or both are identified
• as hazards at 50 of sites where people are
  exposed.

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Approaches to Assessing Exposure in Human Studies

• Ambient environmental studies population level
  based on geographic location
• History of applications/releases
• Environmental monitoring
• Environmental modeling

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Approaches to Assessing Exposure in Human Studies

• Ambient environmental studies individual level
• Questionnaires
• Biomonitoring
• Biological markers

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Some Common Problems with Human Exposure Data

• Long lead times between exposures and outcomes
  for substances that are stored in the body
• Synergy between agents and mixed exposures

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Some Common Problems with Human Exposure Data

• Questions of what to measure
• Peak exposures vs. time-weighted average
• High correlation between agents
• High variability of human exposure
• Time to time
• Person to person

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Some Common Problems with Human Exposure Data

• Sample-to-sample variation
• High laboratory or analysis costs
• Often small numbers of samples
• Incomplete and inaccurate monitoring systems
• Ambient vs. Indoor vs. Personal Monitors

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Exposure Issues

• Low dose exposure
• Biological issues related to timing of exposure
• Exposure timing and embryologic development
• Latency/induction period
• Immediacy of effects
• Retrospective exposure assessment and biologic
  markers

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A Current of Fear"

• Issues in cluster investigations
• Publication bias
• Media interpretation
• Strengths and limitations of epidemiology
• Importance of complimentary lab studies
• Comparative risk
• Definition and ascertainment of exposure

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A Current of Fear"

• Guidelines for causation
• Strength of association
• Dose-response relationship
• Temporal sequence
• Consistency
• Specificity
• Biological plausibility
• Animal model
• Intervention effect

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Studies of EMF and Cancer - Background

• Original study published in 1979 reported
  association between wiring configurations outside
  of homes and risks of childhood cancers
  particularly leukemia.
• This has been followed by numerous studies of
  potential associations between both childhood
  cancers and adult cancers and EMF exposure, both
  occupational and residential.

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Studies of EMF and Cancer - Background

• Media often categorizes EMF with radar,
  microwave, cell phones, and video display
  terminals really dealing with extremely low
  fields (ELF) power frequency fields.
• Three general categories of exposure
• Occupational
• Residential due to power transmission and
  distribution lines
• Residential due to electric appliances

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ATSDR Priority Health Conditions

• Birth defects and reproductive disorders
• Cancer (selected anatomic sites)
• Immune function disorders
• Kidney dysfunction
• Liver dysfunction
• Lung and respiratory diseases
• Neurotoxic disorders

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Barry Johnson, Ph.D., Assistant Administrator of
ATSDR, May 23, 1995

• Although epidemiologic findings are still
  unfolding, when evaluated in aggregate (i.e., by
  combining health data from many Superfund sites),
  proximity to hazardous waste sites seems to be
  associated with a small to moderate increased
  risk of some kinds of birth defects and, less
  well documented, some specific cancers.

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Barry Johnson, Ph.D., Assistant Administrator of
ATSDR, May 23, 1995

• Health investigations of communities around some
  individual hazardous waste sites have found
  increases in the risk of birth defects,
  neurotoxic disorders, dermatitis, leukemia,
  cardiovascular abnormalities, respiratory
  dysfunction, and immune disorders.

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Issues in Epidemiologic Studies of Hazardous
Waste Sites

• Completed exposure pathways with evidence of
  exposure
• Surrogates of exposure residential location
• The use of environmental databases
• Heterogenity of exposure mixtures of substances
  at most sites
• Aggregation of sites

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Avenues of Exposure for a Child through its
Parents

• Mothers Exposure
• Pregnancy
• Nursing

• Fathers Exposure
• Contaminated Clothing
• Exhaled Vapor
• Tracking Things Home
• Germinal Effects

CHILD
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Hazardous Waste Sites - New York (Geschwind et
al. 1992)

• 9313 cases from NY State Congenital Malformations
  Registry and 17,802 births without malformations
  from 20 counties in Upstate NY with 590
  uncontrolled hazardous waste sites.
• Exposure risk index calculated for mothers
  residence at delivery based on hazard ranking
  score for each site and presence of a waste site
  within a radius of one mile of the residence.

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Hazardous Waste Sites - New York (Geschwind et
al. 1992)

• Maternal proximity to a hazardous waste site was
  associated with an increased risk of all types of
  malformations (OR 1.12, CI 1.06-1.18).
• Risks for malformations of the integument,
  musculoskeletal, and nervous systems, as well as
  oral facial clefts were increased significantly
  among mothers living in proximity to hazardous
  waste sites.

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Hazardous Waste Sites - California(Croen et al.
1997)

• Exposure based on proximity to hazardous waste
  sites
• Presence of hazardous waste site in census tract
  of residence
• Residence within one mile of hazardous waste site

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Hazardous Waste Sites - California(Croen et al.
1997)

• Increased risks were reported for both neural
  tube defects and conotruncal heart defects
  associated with proximity to NPL sites, using
  both measures, but these were not statistically
  significant.
• Neural tube defects
• NPL site in Census Tract OR 1.4 (CI 0.7-2.7)
• NPL site within 1/4 mile OR 2.1 (CI 0.6-7.6)
• Conotruncal heart defects
• NPL site in Census Tract OR 1.3 (CI 0.6-3.0)
• NPL site within 1/4 mile OR 4.2 (CI 0.7-26.5)

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