Exposure Assessment.txt

Contact with a chemical, biological, or physical agent (sum total of exposure - integrated/aggregate/cumulative exposure via all routes of exposure) at the boundary of the body over a specified time period.

• 1. outer boundary (skin, openings into the body)
• 2. boundaries which agent must cross to be absorbed into the body resulting in internal dose (skin, lungs, GI tract)

How a substance contacts body and results in internal dose (inhalation, ingestion, dermal penetration).

Measures magnitude, frequency, duration, & route of exposure of animals, materials, ecological components to substances in the environment.

Describes size & nature of exposed population.

Determines sources, environmental transport & modification, & fate of pollutants & contaminants (and result of being exposed to contaminants).

Biological, physical, chemical

Natural & synthetic

Inhalation, dermal, ingestion

Potential dose is amt of chemical that's ingested/inhaled/applied to skin, but not yet in body (?).

• Applied dose is subset of potential dose.
• - amt of chemical available at the absorption barrier (skin, lung, GI tract).

Amt of chemical that's been absorbed & is available for interaction w/ biologically significant receptors.

Amt transported to an organ/tissue/fluid of interest.

Amt that reaches cells/sites/membranes where adverse effects occur.

The best for predicting adverse effects.

Potential --> applied --> internal --> delivered --> biologically effective

exposure = concentration*period of time

dose = absorption rate * time

usually mg/m^3

• Total dose = mass / body wt
• TWA dose = mg / (kg*day)

• Acute exposure: generally 1 contact w/ the chemical; usually < 1 day / short term.
• Chronic exposure: exposure takes place over substantial portion of lifetime
• Subchronic exposure: exposures of intermediate duration, e.g. usually in temp. job

• - monitor general environment
• - monitor microenvironments
• - personal exposure monitoring
• - questionnaires
• - biological monitoring
• - modeling

• Most accurate
• - biomarkers, biological monitoring
• - personal measurements
• - area/ambient monitoring in workplace, home & outdoors
• - surrogate of exposure (e.g. drinking water use)
• - distance fm industrial site & duration of residence
• - residence/employment by proximity to industrial site
• residence/employment in geographic area w/ site
• Least Accurate

• - designed for initial investigations as screening tool, and for risk-based corrective actions.
• - general criterion is conservatism as it often estimates exposure to most-exposed individual (higher concentration)
• - use generic parameters
• - often criticized as overly conservative
• - often used in prospective risk assessments

• - designed to assess actual exposure to pop'n for use in epid, dose-response studies
• - uses reasonable case scenario
• - requires demographic info
• - requires site-specific parameters

Uncertainty represents lack of knowledge abt factors affecting exposure/risk, and can lead to inaccurate/biased estimates.

Variability arises fm true heterogeneity across ppl/places/time, and can affect precision of estimates & degree which they can be generalized.

It is uncertainty analysis, which accounts for uncertainty in select parameters evaluating the range & probability of plausible exposure levels.

V*C*B

volume in L/day * concentration in ug/L * bioavailability

• - Environmental & occupational epid
• - risk assessment
• - risk management
• - dx & tx of diseases

X ppm = (Y mg/m3)(24.45) / (molecular weight)

• - specification/knowledge of target organ
• - mechanisms of toxicity
• - physical properties of contaminant

absorbed dose (which is the quantity entering the bloodstream available for distribution to other body compartments)

ADD = (C*IR*D*B) / W

B isn't stable in calculation of inhalational exposure

• ADD = mg/kg*day
• C = ug/m^3
• IR = m^3/day
• D = day

Age, gender, wt, hlth status, level of physical activity

when agents depositing in the respiratory exchange region (alveoli & respiratory bronchioles)

Highly h20 soluble chemicals tend to give upper respiratory tract effects with good warning properties

Low h20 soluble chemicals tend to give deep lung/alveoli effects that have poor warning properties

• 1. Gases & vapors: reach all regions of respiratory tract; absorption/toxicity depend on chemical properties
• 2. Aerosols: toxicity depends on chemical & physical properties

dust: irregular solid produced fm disintegration of parent material by crushing, grinding, etc.

fiber: dust particle but with aspect ratio L/W > = 3

smoke: produced fm combustion of organic matter (spherical particles)

fume: produced fm condensation of vapor/gaseous combustion product (spherical particles), very small when produced, tend to agglomerate; e.g. fm welding, brazing

mist: liquid particle formed fm condensation/atomization

• fog: visible mist
• smog: smoke & fog; photochemical rxn products

Most IMP

• Size - most IMP determinant of aerosol behavior
• Density
• Shape
• Diameter - IMP for descriptor, determined by microscope & aerodynamic

* particle size (aerodynamic diameter) critical in determining pattern of respiratory deposition that's IMP for regional toxic effects & systemic absorption

Monodisperse: very rare; not in industrial processes; all particles 'same size'/narrow distribution; e.g. pollens, spores

Polydisperse: typical for industrial processes; range of sizes

Gaussian/normal distri. usually doesn't describe well distributions of aerosols generated fm industrial processes.

• 1. Aerodynamics (respiratory tract deposition, design/operation of samplers)
• 2. Forces acting on aerosols (gravitational/sedimentational, inertial, diffusional, electrostatic, thermal)

NP, tracheobroncial, gas exchange region.

• NP
• Agents: allergens, inorganic dust, salts, etc.
• Effects: Rhinitis, ulceration, nasal cancer

• TB:
• Agents: inorganic acids & bases, cotton dust, grain dust, allergens, etc.
• Effects: broncho constriction & bronchitis, bronchial carcinoma

• GER
• Agents: molds, etc.
• effects: pulmonary inflammation, pulmonary carcinoma, pulmonary fibrosis

Gas is in gaseous state when 25 degrees Celcius, 1 atm

Vapor is gas phase of a substance that's liquid or solid at 25 degrees Celcius, 1 atm

C max = vapor pressure / atmospheric pressure * 10^6

atmospheric pressure = 760 usually when it's rm temp.

• Assume:
• 1. closed system
• 2. saturation conditions

B = [(fraction remaining in lower respiratory tract) * (resp. tract absorption efficiency) + (fraction ultimately swallowed) * (GI tract absorption efficiency)]

• fraction remaining in lower resp. tract
• = 1 * (alveolar fraction) + 0.5 * (bronchial fraction)
• = 1 * [(fraction of total particulate mass)*(alveolar deposition fraction)] + 0.5 * (fraction of total particulate mass)*(bronchial deposition fraction)]