PB HLTH 150B Lecture Notes - Lecture 3: Exposure Assessment, Public Health, Exposure Science

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History of exposure assessment:
1920's - physicians and engineers/chemists collaborated to discover causes of
occupational diseases
Methods were developed to measure toxic chemicals in the air of mines and
factories
1950's to 1970: Initially focused on toxic chemicals and particulate matter in
urban air and, somewhat later, in drinking and indoor air
1970's to present: Major U.S. legislation established
OSHA: Occupational Safety and Health Admin
Environmental Protection Agency (EPA)
Chemicals in ambient air and water
§
Important policies include TSCA, FIFRA, and Superfund
§
Divide between occupational sources (industrial hygiene) and ambient and
indoor sources (exposure science)
Shift from understanding causes of disease to risk assessment and compliance
Environmental epidemiology continues to mature as key public health science
Exposure: Contact between a chemical and a person or organ
Dose: Amount of chemical that enters a person or organ after crossing an exposure surface
Endogenous: (Internal exposure) hormones, reactive oxygen species, lipid peroxidation, gut
flora, etc甲醛
Exogenous: (external exposure) air, water, diet, skin
Routes and pathways of exogenous exposure:
Ingestion
Inhalation
Dermal
Across the placenta
Exposure assessment:
Quantitative estimation of exposure received by population over a period of time
Classification of exposure status relative to other members of a population (high low)
Units of laboratory measurements
Air: mass/volume (mg chemical/m^3 air)
1 ppm=1 mL chemical/m^3 air= 1 uL chemical/L air1uL chemical/L air
1 ppb= 1/1000 of a ppm
Water, food, soil, and dust: mass/mass basis
Biological chemical concentrations: mass/volume
Surfaces: chemical loading: Mass/Area
Standard Exposure equation:
D=C*IR*AF*EF/BW
D = exposure dose
C = contaminant concentration
IR = intake rate of contaminated medium
AF = bioavailability factor (assume 1 in this class)
EF = exposure factor
BW = body weight
EF = (F * ED)/AT
F = frequency of exposure (days/year) [if it is in week we need to multiple by 52]
ED = exposure duration (years)
AT = averaging time (ED * 365 days/year)
GPS: Overlaying time-varying locations on the corresponding pollution levels allows estimation of
cumulative exposures
Biological monitoring: Levels of chemicals or their products (metabolites) in biological samples
Biological: A quantifiable biological response in proportion to exposure (e.g, DNA adduct)
Effect: A quantifiable biological response due to toxicant (toxin) exposure
Biomarkers of exposure
Urine
Blood
Breast milk
Saliva
Hair
Meconium
Biomonitoring in health:
Exposure trends
Exposure classification for epidemiologic studies
Dose reconstruction/ Risk Assessment biomonitoring equivalents
Advantages:
Direct measure of exposure
Likely closer to disease/effects
Integrates all routes
Can damp variability
Problems:
Invasive
Laboratory methods may not be available
High variability of non-persistent compounds can limit utility
Kinetics: Residence time of a toxicant in the body determines its utility as an exposure biomarker
Lecture 3
Wednesday, September 5, 2018
4:33 PM
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§
§
Exposure: Contact between a chemical and a person or organ
Dose: Amount of chemical that enters a person or organ after crossing an exposure surface
Endogenous: (Internal exposure) hormones, reactive oxygen species, lipid peroxidation, gut
flora, etc甲醛
Exogenous: (external exposure) air, water, diet, skin
Routes and pathways of exogenous exposure:
Ingestion
Inhalation
Dermal
Across the placenta
Exposure assessment:
Quantitative estimation of exposure received by population over a period of time
Classification of exposure status relative to other members of a population (high low)
Units of laboratory measurements
Air: mass/volume (mg chemical/m^3 air)
1 ppm=1 mL chemical/m^3 air= 1 uL chemical/L air1uL chemical/L air
1 ppb= 1/1000 of a ppm
Water, food, soil, and dust: mass/mass basis
Biological chemical concentrations: mass/volume
Surfaces: chemical loading: Mass/Area
Standard Exposure equation:
D=C*IR*AF*EF/BW
D = exposure dose
C = contaminant concentration
IR = intake rate of contaminated medium
AF = bioavailability factor (assume 1 in this class)
EF = exposure factor
BW = body weight
EF = (F * ED)/AT
F = frequency of exposure (days/year) [if it is in week we need to multiple by 52]
ED = exposure duration (years)
AT = averaging time (ED * 365 days/year)
GPS: Overlaying time-varying locations on the corresponding pollution levels allows estimation of
cumulative exposures
Biological monitoring: Levels of chemicals or their products (metabolites) in biological samples
Biological: A quantifiable biological response in proportion to exposure (e.g, DNA adduct)
Effect: A quantifiable biological response due to toxicant (toxin) exposure
Biomarkers of exposure
Urine
Blood
Breast milk
Saliva
Hair
Meconium
Biomonitoring in health:
Exposure trends
Exposure classification for epidemiologic studies
Dose reconstruction/ Risk Assessment biomonitoring equivalents
Advantages:
Direct measure of exposure
Likely closer to disease/effects
Integrates all routes
Can damp variability
Problems:
Invasive
Laboratory methods may not be available
High variability of non-persistent compounds can limit utility
Kinetics: Residence time of a toxicant in the body determines its utility as an exposure biomarker
Lecture 3
Wednesday, September 5, 2018
4:33 PM
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 6 pages and 3 million more documents.

Already have an account? Log in

Document Summary

1920"s - physicians and engineers/chemists collaborated to discover causes of occupational diseases. Methods were developed to measure toxic chemicals in the air of mines and factories. 1950"s to 1970: initially focused on toxic chemicals and particulate matter in urban air and, somewhat later, in drinking and indoor air. Divide between occupational sources (industrial hygiene) and ambient and indoor sources (exposure science) Shift from understanding causes of disease to risk assessment and compliance. Environmental epidemiology continues to mature as key public health science. Exposure: contact between a chemical and a person or organ. Dose: amount of chemical that enters a person or organ after crossing an exposure surf. Endogenous: (internal exposure) hormones, reactive oxygen species, lipid peroxidation, flora, etc . Quantitative estimation of exposure received by population over a period of time surface ation, gut time. Quantitative estimation of exposure received by population over a period of time. Classification of exposure status relative to other members of a population (high l.

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