Date post: | 22-Jan-2018 |
Category: |
Documents |
Upload: | davidkbkim |
View: | 630 times |
Download: | 1 times |
PREVENTING THE CAUSES OF DISEASE
David Kim, PhD
Vestergaard Frandsen West Africa
18 March 2011
BIRTH DEATH
HEALTH
DISEASE
The Workplace
Mine
Busy Street
Farm
The Environment
Indoor Cooking
Swimming Pools
Vehicular Emissions
Prevention
The act of hinderingMerriam-Webter’s dictionary
Prevention of Disease Requires…
1. Hazard identification
2. Dose-response assessment
3. Exposure assessment
4. Risk characterization
Hazard Identification
Group Exercise:
You are part of a public health team that has been sent
to a neighbourhood of a city where parents have been
complaining of their children experiencing coughing,
runny noses, and fevers that won’t go away. The
number of children with these symptoms is growing
every year; the numbers are 4 times larger than
expected. With your team, discuss the possible causes
of these symptoms.
Childhood Leukaemia in Woburn
• A 1981 Department of Public Health study confirmed a childhood leukaemia cluster in Woburn, MA. The number of cases was 4 times higher than the national average.
• Woburn has a 130-year industrial history that resulted in significant local deposition of chemical manufacturing waste.
Epidemiology
• Epidemiology is the basic science of public health.
• Purpose is to study (1) the distribution of disease in a population, and (2) the determinants of that disease.
• Concerned with person, place, and time.
Person
Place
• Family
• Village
• City
• Country
• Continent
• Global
Time
• Hour
• Day
• Week
• Month
• Year
• Decade
• Century
Unit of Measure
1000 people living in Accracontracted the flu last year. Whatis the incidence rate?
Relative Risk
The IR of swine flu when flying with Deltais 2 cases per 1000 people each week. TheIR of swine flu on all airlines is 1 case per1000 each week. What is the RR of gettingswine flu when flying with Delta?
Woburn MA: person
• Child diagnosed with leukaemia before 19th
birthday.
• Diagnosed between 1969 and 1989.
• A resident of Woburn MA at the time of diagnosis.
Woburn MA: place
Woburn MA: time
Woburn MA: Relative Risk
RR = 9
For those living near contaminatedwell water relative to all residentsof Woburn. Is there a reason forconcern?
Summary of Epidemiology Studies
Advantages
• Study human populations.
• Can examine adverse effects associated with exposures to risk factors in real time.
• Convincing data if studies are conducted correctly.
Disadvantages
• Long time to execute
• Costly
• Difficult to establish causality
Dose-Response Assessment
• Determine whether the causative agent can damage human cells/tissues/organs.
• Studies are typically conducted in laboratories.
• Fundamental science is toxicology
Toxicology
Paracelsus, the father of
toxicology
“The dose makes the poison”
Toxicokinetics
• What the body does to the chemical.
• Defined by absorption, distribution, metabolism, and excretion (ADME).
• Establishes the DOSE in dose-response.
Toxicodynamics
• What the chemical does to the body.
• Defined by cellular damage, DNA modifications, protein concentration changes, etc.
• Establishes the RESPONSE in dose-response.
Decreased dopamine levels in Parkinson’s disease patients
In Vivo Experiments
In Vitro Experiments
In Silico Experiments
Dose-Response Curves
• NOAEL: No Observed Adverse Effect Level
• LOAEL: Lowest Observed Adverse Effect Level
Dose-Response Curve for Cr(VI)
Summary of Toxicology Studies
Advantages
• Highly controlled.
• Fast results.
• Can better establish causal relationship between dose and effect.
Disadvantages
• Laboratory conditions
• Extensive use of animals
• Questionable relevance to humans
Exposure Assessment
Study of contaminant levels in:
– Air
– Water
– Soil
– Biological Samples
– Food
Objectives of Exposure Assessment
• Measure the amount of contaminant in the environment.
• Record how often humans come into contact with the contaminant.
• Identify who comes into contact with the contaminant.
Air Monitoring
Water Monitoring
Spoil Monitoring
Biological Monitoring
Summary of Exposure Studies
Advantages
• Quantitative
• Real-world values
Disadvantages
• High cost of conducting studies (i.e., analytical chemistry)
• Small number of samples due to intensive nature of studies
Risk Characterization
• Final phase of a risk assessment.
• Integrates information collected from EPIDEMIOLOGY, TOXICOLOGY, and EXPOSURE ASSESSMENT studies.
• Qualitative and quantitative conclusions.
• Synthesizes all the information and recommends actions to prevent diseases from spreading.
Risk Characterization for Cr(VI)
• Clearly there is an association between leukaemia and living where Cr(VI) levels are high.
• Toxicological studies demonstrate a positive dose-response, suggesting a causal relationship.
• Exposure studies have measured presence of Cr(VI) levels in drinking water that exceed health standards.
• All evidence seems to point to the need to reduce Cr(VI) levels in order to prevent childhood leukaemia from occurring.
Final Group Exercise
• Small-scale mining in Ghana.• Mercury is used to clean gold
nuggets.• Mercury is associated with skin
cancer and other deadly ailments later in life.
• Environmental contamination has made water undrinkable.
• Biological monitoring shows that people are exposed to dangerous levels of mercury.
What evidence do you need to evaluate whether or not preventive action should be taken?