Public Health and  Ecological  Interconnectivity:
  A  Conditional Probability Approach  Associating
      Degradation  of  Streams  and  Infant  Mortality
                            John F. Paul, Michael E. McDonald, Steven F. Hedtke
                              U.S. EPA, Office of Research  and Development,
      National Health and Environmental Effects Research Laboratory, Research Triangle Park, NC 27711
    Public Health Goal

    Major improvements in
  public health by reductions
    in pervasive diseases
  Pump linked to cholera outbreak
   Problem was viewed as health
   effect (mortality from cholera
        in population)
   Tracked back to water pump as
     likely source of exposure
    Current Approach
  linical exposure-based studies on
  individuals determine causation,
    but there are thousands of
       exposure agents.
    This implies possible large
  expenditure of funds on studies
   with no adverse health effects
  Possible Improvement
  Use Snow's large-scale approach
  as a screen and then follow with
  appropriately designed individual-
        based studies
      Death Records
    Demographic barometer of
     community health since
         19lh century

  Mortality and morbidity data still
  collected and publicly available in
     CDC national data bases
             Suggested Approach
                              Explore associations between
                            infant mortality and environmental
                              conditions (look for patterns in
                              associations) for more effective
                               public health intervention
                Infant Mortality

             Major health status indicator of
             populations and available at the
              county level of aggregation
           (Environmental Condition)
               Health of bottom-dwelling
               communities in streams is
            | integrative of recent water quality
              degradation and reflective of
               environmental condition
           (intent of This Research!

              Explore possible relationship
           | between environmental condition
                 and infant mortality
             Indicator of Public Health:
            probability of infant mortality rate
              (IMR) greater than 8.2/1000
              (national norm for 1989-98)

              Indicator of E-Condition:
            percent of stream miles degraded
              (low score for benthic index)
                            MD counties with > 60%
                                        For Maryland counties, is there a
                                         relationship between degraded
                                          stream condition and infant

                                          Formulate and test as null
Conditional Probabilit
Probability of something occurring
when something else has occurred
 Example: Probability of IMR in a
 county > 8.2 per 1000 if at least
  half of streams in county are
   degraded, P ( Y | X > 50%)
                                           Empirical conditional
                                            probability curve
     There is a real

  (but it is not cause-effect)
 Make the association quantitative
   by trying to disprove null
    Null Hypothesis


  conditional probability equals
   unconditional probability
 Result of bootstrap
   Less than 2 % chance that
   P ( Y | X > 78%) = P ( Y )
 could have occurred randomly
 Null hypothesis disproven!
                                                                                    Results Expressed as Relative Risk
                                                                                   Similar Shape for PA and WVJ *  
                                                                                       *V**      if | a M_
                                                                                       ^\HHtJr | f a-
 What would you conclude
 from these results? What
   are the next steps?
  Please share your thoughts
   with us on post-it notes.
  Our Conclusions and Next
   Steps are on handout.
A quantitative relationship exists
between environmental condition
  and public health outcome.
 If we protect the environment,
  can we also protect human
                                                                   If we understood the link (eco-
                                                                   human web), then management
                                                                     action could protect both
                                                                                     Confirm with additional data
                                                                                      sets and in other areas
                John F. Paul, Ph.D.
                Rr-w*rih (-IT. iriionifntjl S.K"
                Njtioiul rtrtlth Jnd Environ
                R*arch Ubor-turv ORD
                                                  Your Health  Your Environment  Your Future