Exposure Assessment,
Conceptual Modeling,
Biomonitoring and
Environmental Regulations
Conrad (Dan) Volz, DrPH, MPH
Assistant Professor
Department of Environmental and Occupational
Health
Co –Director for Exposure Assessment, University of Pittsburgh Cancer Institute, Center for
Environmental Oncology

Occupational/Environmental Exposure
Definition
Contact over time and space between a receptor (human or ecological) and a biological, chemical or physical hazard.

Components of Environmental and
Occupational Health Exposure Pathways

Source (s)—Often with unique fingerprint(s).

Rate(s) of contaminant emissions.

Transport route(s) through environmental media.

Route(s) of exposure.

Exposure concentration(s).


The duration, frequency and intensity of contact with the contaminant.
How Long/Often and Much?

Identification of individual activity patterns, population distributions and susceptible populations.


Air

Surface Water

Groundwater

Sediment

Soil

Subsurface area

Food Chain


A written and/or pictorial representation of an environmental system and the biological, physical and chemical processes that determine the transport and fate of contaminants through environmental media to environmental receptors.


Sources of contaminants (can be multiple sources as well as species on a site).

Pathways of environmental transport.

Indications of any barriers or remedies that exist or are proposed.

Pathways to ecological and human receptors.


Pull together technical data concerning a site from numerous sources.

Support the selection of sampling locations to establish background concentrations of identified contaminants.

Identify data needs and gaps.

Describe and integrate the processes that determine contaminant release, migration and receptor exposure.


Determine exposure routes (inhalation, ingestion and/or dermal absorption).

Identify uncertainties in the model that need further study.

Preliminarily evaluate the risk to human and ecological receptors (CERCLA NPL status is based on a significant risk to human health or the environment).


Facilitate the selection of remedial alternatives and evaluate the effectiveness of remedial actions to reduce exposure.

For use a a communication tool in the decision-making process involving experts from exposure assessment, human and ecological health, remediation engineers etc.

As a risk communication tool for the public.

Conceptual Site Model for a Former Manufactured
Gas Plant
Required Component of CERCLA Site Assessment

Modeling –Mercury in New Jersey Wells

 “Biomonitoring” is the analytical measurement of biomarkers in specified units of tissues or body products (blood, urine, etc.)
(Environmental Health Perspectives-
November, 2006).
 “Biomarkers” are any substances, structures, or processes so measured that indicate an exposure or susceptibility or that predict the incidence or outcome of disease (Toniolo et al. 1997).

 National Health and Nutrition
Examination Survey (NHANES)-
Centers for Disease Control and
Prevention
 CDC National Environmental Public
Health Tracking Program, UPACE –
Center of Excellence
 Interagency National Children’s Study
 Farm Family Exposure Study
(University of Minnesota)

Examples of Human Biomonitoring for Exposure Assessment
 Phthalates
 The organophosphorus pesticides are malathion and chlorpyrifos.


Can sample in a naturalistic environment, without
IRB clearances (retains ecosystem complexity).

Initially test hypothesis regarding conceptual models of contaminant fate and transport.

Establish a baseline of contaminants in biomass as part of an ongoing monitoring program (important for assessing the need for or failure of site remediation ie, Superfund, RCRA, DOE-NNSA).


Establish the exposure and thus risk to humans from consumption of contaminated foodsespecially fish (incredibly important to tribal groups and vulnerable sub-populations- Amish, immigrant Asians, African Americans).

To establish the efficacy of and use aquatic and other species as sentinels for human health effects.

To determine population risk from contaminant exposure to a species or an ecosystem.


Microbial Oxidation of Anthropogenic Compounds-
Biotransformation, Biodegradation, Mineralization
- Tremendous variety of microorganisms that have the ability to use pollutants such as alcohols, fuels and solvents as well as natural organic detritus as a source of energy.
- The rate of microbial degradation decreases for contaminants with;
 Increasing molecular weight.

Lower solubility in water.

Increasing number of aromatic rings.

Increasing numbers of branches.

The number of halogen atoms in their make-up (chlorine, fluorine, bromide etc.)


Increasing concentrations of contaminants in sediments and water leads to bioconcentration and accumulation in aquatic organisms.
-
Bioconcentration – The process of aquatic organisms accumulating chemicals from water only.
-Bioaccumulation - The process of aquatic organisms accumulating chemicals from both water and food.
Bioconcentration Factor- (BCF) – The ratio of the concentration of a chemical in an organism to the concentration of that chemical in seawater, freshwater or brackish water.
Thereforemg of chemical/kg of organism
__________________________ = Liter/kg mg of chemical in solution/Liter


BCF can be an observed ratio or be the prediction of a partitioning model.
- ModelingAssumptions
 1.
Pollutant chemicals partition in passive way between water and the organism.
 2.
Chemical equilibrium exists.
These assumptions are most valid for lipophilic
(hydrophobic) chemicals- they are more rapidly exchanged between the water and organism than they are excreted or biodegradated by the organism.

Bioconcentration and accumulation modeling-continued

1.
2.
Fish Model- Fish is a bag of oil and tissue water.Chemical partitions between the bag and surrounding water according to:
K ow which is the reciprocal of the chemicals water solubility.
The lipid content of the fish.
--log BCF = 2.791 – 0.564 log S where S is Water Solubility in ppm This formula has been determined using Brook and Rainbow Trout,
Sunfish, Flathead Catfish

Bioaccumulation Models are Kinetic and depend on the dynamics of intake, storage, metabolic transformation and excretion of specific chemicals in specific organisms .
-Use a first order kinetic model to estimate the depuration
(cleansing) or partial removal of a contaminant from a fish given a specific contaminant concentration so
- C = C o e -kt Where C is the concentration at any time t, C o is the initial concentration, k is the first order rate constant and t is the time.

White Bass-Hg in Filet, ppm-95% CI
.16
.14
.12
.10
.08
.06
.04
.02
N = 45
Pittsburgh Pool
Pittsburgh Pool vs Other
10
Storebought

Barium in White Bass fillet in ppm, 95% CI
.08
.06
.04
.02
.14
.12
.10
0.00
-.02
N = 45
Pittsburgh Pool
Pittsburgh Pool vs Other
10
Storebought

Channel Catfish, Hg in fillet, 95% CI
.4
TYPE_FIS: 1 Channel Catfish
.3
.2
.1
0.0
-.1
N = 39
Pittsburgh Pool
Pittsburgh Pool vs Other
11
Storebought
13
Kittanning

Occupational and Environmental
Health Legislation

Occupational Safety and Health Act of 1970-
Adopted the 1968 American Conference of
Governmental Industrial Hygienists (ACGIG),
Threshold Limit Values (TLV’s) for airborne contaminants.
- A TLV is an exposure concentration that most workers can be exposed to 8 hours/day, 40 hours/week over a working lifetime with no adverse effect.

Occupational and Environmental
Health Legislation

Comprehensive Environmental Response,
Compensation and Liability Act of 1980
(CERCLA)- commonly called Superfund
-To provide for remediation of sites not cleaned-up by the responsible party.
-To establish priorities for the clean-up of the nation
’ s worst toxic and radiological waste sites.

Conduct human and ecological risk assessments through the Agency for Toxic
Substances and Disease Registry (ATSDR).
Conduct remedial investigation and feasibility studies.

Occupational and Environmental
Health Legislation

Resource Conservation and Recovery Act of
1976 (RCRA)
- Creates cradle to grave regulatory scheme to manage, store, transport and dispose of hazardous waste.
- Designed to prevent current hazardous waste disposal from causing future environmental health problems.