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).

Factors Influencing Human Exposure 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.

Definition of Environmental Media - Air Surface Water Groundwater Sediment Soil Subsurface area Food Chain

What is a Conceptual Site Model? 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.

Components of a Complete Conceptual Site Model 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.

Why develop a Conceptual Site Model? 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.

Why develop a Conceptual Site Model (continued)? 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).

Why develop a Conceptual Site Model (continued)? 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”and “Biomarkers” -Definitions “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).

Examples of National Biomonitoring Programs 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.

Reasons for Biomonitoring Non-Human Species 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).

Reasons for Biomonitoring Non-Human Species-Continued Establish the exposure and thus risk to humans

from consumption of contaminated foods-especially 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.

The Basis for Biomonitoring Ecological Receptors 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.)

The Basis for Biomonitoring Ecological Receptors-Continued 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.

Therefore- mg of chemical/kg of organism __________________________ = Liter/kg mg of chemical in solution/Liter

Bioconcentration and accumulation modeling 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 Fish Model- Fish is a bag of oil and tissue water.Chemical partitions

between the bag and surrounding water according to:

1. Kow which is the reciprocal of the chemicals water solubility.2. 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 = Co e-kt Where C is the concentration at any time t, Co is the initial

concentration, k is the first order rate constant and t is the time.

1045N =

Pittsburgh Pool vs Other

StoreboughtPittsburgh Pool

95

% C

I H

g p

pm

.16

.14

.12

.10

.08

.06

.04

.02

White Bass-Hg in Filet, ppm-95% CI

1045N =

Pittsburgh Pool vs Other

StoreboughtPittsburgh Pool

95

% C

I B

a p

pm

.14

.12

.10

.08

.06

.04

.02

0.00

-.02

Barium in White Bass fillet in ppm, 95% CI

131139N =

TYPE_FIS: 1 Channel Catfish

Pittsburgh Pool vs Other

KittanningStoreboughtPittsburgh Pool

95

% C

I H

g p

pm

.4

.3

.2

.1

0.0

-.1

Channel Catfish, Hg in fillet, 95% CI

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.

CERCLA continued.

- 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.