1. Human Health Risk Assessment and Chemical Safety
AFCEE, 2002
Human Health Risk Assessment and Chemical Safety
Stephanie Simstad
The Ohio State University Extension
Clermont County
Source for AFCEE, 2002 photo:
Air Force Center for Environmental Excellence

2. Acknowledgements U.S. EPA risk assessment documents including:
Risk Assessment Guidance for Superfund
Presenter’s Manual for “Superfund Risk Assessment and How You Can Help”

3. What if . .
Ohio EPA
Your private water well has been sampled and results show that a commonly used pesticide is present in your drinking water. How would you determine whether this contaminant could be a health problem for your family?

4. Overview
Description of risk assessment and how it is used Use of human health risk assessment process to evaluate a contaminated family well Group exercise to identify source and pathways of pesticide into well Consideration of exposure pathway analysis to identify Best Management Practices for protection of drinking water sources

5. Human Health Risk Assessment
A formalized process to evaluate risk posed to humans from exposure to an identified hazard
Evaluation of both cancer and noncancer effects
Evaluation of risk to adult, child, or even prenatal populations
Note: The same process is used in ecological risk assessment. In ecological risk assessment, risk is evaluated for environmental receptors such as fish, animals or plants.

6. Hazard versus Risk Hazard Risk Potential to do harm
tornado
hazardous chemical
Risk
Likelihood of defined harm to occur from specific hazard
1 additional cancer per 10,000 people exposed
(OEPA)
The key point in this slide is to ensure that participants understand that the term risk is being used very specifically in a risk assessment. There are many hazards that we see everyday, but they carry with them differing levels of actual risk.
Another way to define risk is that it is “the potential for a harmful event, such as cancer, that carries with it a doubt about whether the harmful event will occur (US EPA, 2000) (Presenter’s Manual for “Superfund Risk Assessment and How You Can Help”).
(NOAA)
Individual
Lifetime Risk of
Developing
Melanoma is
1 in 75.
(NIH)

7. How is Risk Assessment Used?
To set drinking water standards for public water supplies Licensing and regulation of pesticides Identification and clean-up of hazardous waste sites Identification of special handling requirements for chemicals
Risk assessment is required by regulation as the basis for determination of many chemical standards that are in place through the Environmental Protection Agency and the Food and Drug Administration. Of interest to the PAT participants, risk assessment is used to determine acceptable pesticide residues in commercially sold produce as well as to determine special handling requirements for pesticides and other chemicals

8. Back to the Well . . .
You’ve found that the family well is contaminated and you use this water for drinking, cooking, and bathing. How would the risk to those who use water from the well be evaluated?

9. Risk Assessment is a 4-Part Process
Hazard Identification
What chemicals are present and are they likely to be toxic?
Exposure Assessment
Who is exposed, at what concentration, how often, and for how long?
Toxicity Assessment
How is it toxic and at what exposure levels?
Risk Characterization
What does the risk assessment tell us about this situation?
From: US EPA, (Presenter’s Manual for “Superfund Risk Assessment and How You Can Help”)

10. Risk Assessment Process (U.S. EPA)
Hazard Identification
Exposure Assessment
Toxicity Assessment
Source: U.S. EPA
It is important to note that both the exposure assessment (i.e., to how much a typical individual may be exposed) and the toxicity assessment (i.e., what are the health effects of that chemical at that dose) are used to determine the likelihood of harm from the situation being evaluated.
Risk Characterization

11. Step 1:Hazard Identification
Collect data on presence of chemical
Sampling
Modeling
Chemical fate and transport
Determine if chemical may be toxic
Develop model of how chemical may move through environment
Conceptual Site Model is used to organize information regarding chemicals and potential transport to people
AFCEE, 2002
The Hazard Identification step usually consists of sampling to see what chemicals may be present. Modeling is used to estimate chemical concentrations between actual sampling points or to determine degradation by-products or changes in the chemical as it moves through the environment. Chemical fate and transport describes how and where a chemical moves through the environment as well as what chemical form it may be expected to change to. It allows predictions to be made on the “fate” of the chemical in the environment. For example, the pesticide DDT is known to accumulate in living organisms both through sampling evidence and the fact that it is much more soluble in fat than water. You would expect to have relatively lower levels of DDT in a water body when compared with fish, even if the DDT were initially released to the water. DDT also changes chemical form to DDE as it is modified by the environment.
A conceptual site model (look ahead at the next few slides) is a way of determining where chemicals are likely to move in the environment and how they may come into contact with people. It organizes information and also is used to identify “gaps” in available data that can be filled by additional sampling or modeling. The next slide provides prompts of questions that are the beginning steps in the development of a conceptual site model. The picture slide (two slides later) is a graphic that shows how this information can be put together.
© Vermont DPS, 2000

12. Input for Conceptual Site Model Modified from Oak Ridge (2002)
How are
chemicals transported
to receptors?
How does
exposure change
through time?
Conceptual
Site Model
Who may be
exposed?
Source: Oak Ridge National Lab, 2002
What information
is missing?
How may
they be
exposed?

13. Modeling of Chemicals in the Environment
Chemical characteristics
More or less soluble in water?
Soil and connections to surface and ground water
Type of soil
Likely paths to and through water sources
General Concept
Based on knowledge of the chemical, the soils, and local water sources; predictions can be made about how that chemical will move through the environment.
Understanding the chemical being assessed, as well as the environment in which it is released, is critical to identifying where the chemical may move in the environment.
For example, PCB’s do not dissolve easily in water but are much more soluble in fat. They would be expected to be found in greater levels in fish or other animals than in the water, especially as time passes since the PCB entered the water body.
Why is all this important?
There are many ways that people can come into contact with chemical and many of these can occur a great distance or a significant amount of time after events such as a spill. Proper development of conceptual site model ensures that all potential paths by which the chemical can contact people are identified and assessed.

14. Conceptual Site Model (Oak Ridge National Lab, 2002)
This slide provides an opportunity to highlight:
Chemicals can move in the environment in many different ways when released. For example, it can move through soils to ground water and be picked up by a farm well. From that same set of chemical drums, some chemical can also be volatilized into the air and individuals may inhale it.
There are multiple ways that individuals can be exposed to chemicals when they are released. For example, the same farm family that may be drinking the contaminated ground water may also be in contact with soils contaminated from the waste pile spill.

15. Step #2: Exposure Assessment
Who is Exposed?
Adult, Child, Special Populations
How Are They Exposed?
Ingestion, Inhalation, Skin Contact
What is the Concentration of Chemical to Which They are Exposed?
ppm in Water or Soil
How Often Are They Exposed?
Days per year, Number of years
Exposure is contact with a chemical through either swallowing (ingestion), breathing, or direct contact on skin.

16. Path Traveled by Chemical
Exposure Pathway
Definition: The steps that a chemical takes from the source to an exposed individual
Exposure is contact with a chemical through either swallowing, breathing, or direct contact on skin
Individual
Using Well
Spilled
Container
Soil
Groundwater
Well
Definition source: U.S. EPA (2000) Presenter’s Manual for: “Superfund Risk Assessment and How You Can Help”.
Path Traveled by Chemical
Exposed
Individual
SOURCE

17. Exposure Pathway Diagram (ATSDR, 2002)
This slide can be used to discuss the multiple exposure pathways that can result from a release of chemicals at one specific location.
For example, a pile of drums can leak (source), this leak can contaminate soils (fate and transport), contaminated soils may have direct contact with someone who has access to them (point of exposure) or contaminated soils can travel to waterways and contaminate fish that someone may eat (another potential point of exposure). Contaminated soils that are used for family gardens can produce contaminated produce that people may ingest (another potential point of exposure).

18. Complete Exposure Pathways
Key to Risk Assessment is Identifying Complete Exposure Pathways
Individual must have contact with chemical for it to cause a health effect
Two key points for this slide:
Identifying correctly when chemicals are traveling or coming into contact with people is one of the most important aspects of the risk assessment process
For a health effect to occur from chemical exposure, the chemical must come into direct contact with receptor. There are many potential exposure pathways and not all are obvious. This last point is discussed a few slides after this one.
Contact
Chemical
Receptor

19. Complete Exposure Pathway
Steps in Complete Exposure Pathway
Source
Chemical Transport and Transformation
Exposure Point
Receptor and Exposure Route
Definitions:
Source: origin of chemical (e.g., leaking drums, contaminated soil, etc.)
Chemical Transport and Transformation: chemicals can move from the source location to other areas and media through erosion of soils, migration downward through soils, migration to ground water, etc. The chemical may also change form (e.g., speciation, chemical itself (DDT to DDE)) during that process.
Exposure Point: Place where people can be exposed to the chemical such as a drinking well
Exposure Route: Way a chemical enters the body, examples are ingestion, inhalation, or through the skin
Receptor: Person who is potentially exposed to chemical
Definition source: U.S. EPA (2000) Presenter’s Manual for: “Superfund Risk Assessment and How You Can Help”.
Individual
Drinks
Water
Spilled
Container
Soil
Groundwater
Well
RECEPTOR AND EXPOSURE ROUTE
EXPOSURE POINT
SOURCE
CHEMICAL TRANSPORT

20. Exposure Point and Exposure Route
Exposure Point defines the place that an individual comes into contact with the chemical
Home with lead-contaminated paint
Exposure Route describes the way a chemical enters the body
Ingestion (Eating and Drinking)
Inhalation (Breathing)
Dermal (Skin Contact)
Definition source: U.S. EPA (2000) Presenter’s Manual for: “Superfund Risk Assessment and How You Can Help”.

21. Exposure Pathways All exposure pathways are not obvious
Ingestion of contaminated soil
Children during play (200 mg soil /day)
Children who deliberately ingest soil (1 gram soil/day)
Incidental ingestion by adults (100 mg soil/day)
Inhalation of chemical vapors
During showering with contaminated water
Volatile chemicals will vaporize into the air from the shower water, they can then be inhaled by person showering
Vapor migration into homes from contaminated ground water or soil under homes
Note:
Ingestion of contaminated soil for children during play represents the soil and dust ingestion rate of a 6 month to 2 year child who still may mouth some toys or put hands in their mouth. This represents a soil ingestion rate expected from indoor play. For context, 200 mg. of soil is approximately the size of one regular-sized aspirin. Since children tend to spend more time in contact with soil and have more intensive contact with soil, they are likely to have a greater “exposure” to soil contaminants than adults who may come into contact with the same soils.

22. Identify Source and Potential Exposure Pathways
Release Mechanism is the same as chemical transport.
Exposure medium describes the medium (i.e., soil, air, water, groundwater, etc.) where the individual comes into contact with the chemical.
(Oak Ridge National Lab, 2002)

23. Back To Contaminated Well Example. . .
Who is exposed when family farm well is contaminated? What are their routes of exposure? ? ?
Drinking Water Well
Routes of Exposure
Answers:
Receptor would be anyone in the family who drinks the water, eats food cooked with the water, or showers or bathes with the water. They can also include visitors to the home or even the farm livestock if the same water well is also used for livestock during periods of the year. Additionally, if the well water is used for laundry or a dishwasher is present in the house, contamination from the water may volatilize (evaporate) into the air and family members may be exposed by breathing the air.
Routes of exposure: ingestion for water used for drinking and cooking, dermal for water used for bathing or showering, and inhalation for water used for bathing, showering, or other household uses if chemical is volatile.
Receptors

24. Exposure Assessment
Purpose is to calculate dose that individual receives
Dose represents a daily average intake per unit of body weight
Use information from conceptual site model and sampling to identify complete exposure pathways
Calculate dose for each exposure pathway by using exposure assumptions
Sum goes across all pathways to get total dose
The exposure assessment step identifies the “amount” that individuals are expected to come into contact with as a result of their normal activities in the area where the contamination is or comes to be present through chemical transport.

25. Exposure Assumptions
Answer “how much” and “how often” people may be exposed to chemical in air, water, soil or dust
Examples
How much water does an adult drink in one day?
How many days per year is someone at their home?
How many years does someone live in the same house?

26. Why Calculate Dose? Paracelsus (15th century scientist)
“Dose makes the poison”
For most chemicals, there is a threshold below which health effects are unlikely to occur
HOWEVER for some cancer-causing chemicals, a threshold is not assumed to exist
Toxicity data can then be compared with dose to determine if health effect likely to occur
Courtesy of the National Library of Medicine

27. Dose-Response Curve Dose – Chemical concentration per unit body weight
Response – Level of measured adverse effect
This is a dose – response curve for a non-carcinogen or a carcinogen with a threshold. A threshold is the lowest amount of chemical (dose) that can elicit an effect, doses below the threshold do not pose a threat of an adverse health effect. A typical dose could be expressed as 10 milligrams chemical per kilogram body weight per day. Types of typical adverse effects measured could be tumors, liver or kidney dysfunction, nervous system effects, changes in blood chemistry, or death.
Graphic Source:

28. Putting it all together. . .
Intake Equation for Drinking Water Example
C= Chemical Concentration (Obtain from sampling)
CR= Contact Rate (2 liters water/day)
EF= Exposure Frequency (350 days/year)
ED= Exposure Duration (30 years)
BW=Body Weight (70 kg.)
AT= Averaging Time (10,950 days)
These are typical exposure assumptions for exposures to chemicals when the source is contaminated drinking water used at a residence. They are for an adult. Child-specific exposure assumptions can also be developed and will take into account the lower contact rate (i.e., how much water per day an individual drinks) as well as a lower body weight.

29. Special Concerns During Exposure Assessment
Children
Children will often have a higher dose than adults when exposed to the same chemical concentration in the environment
Differences in children’s activities
Playing in dirt, infant mouthing of toys, formula-dominated diet of young infants
Water, food, and air intake per pound of body weight can be higher for children than adults
Children are often referred to as a “sensitive subpopulation” in risk assessment. To ensure that risk assessments are protective for both children and adults, child-specific exposure assumptions are often used.

30. Step #3: Toxicity Assessment
What toxicity data are available?
Acute or chronic effect? Or both?
Cancer or noncancer effect? Or both?
Consider effects of multiple chemicals
Similar to “Mode of Action” concept in pesticides but broader since multiple nonlethal effects can still have an adverse impact on human health
Consider route of exposure
Effects can be route of exposure specific
Effects from multiple chemical exposures (i.e., exposures to more than one chemical at one time) are considered in the risk assessment. For example, different chemicals can act on the same body system and cause effects that are additive. The relationship between this concept and the mode of action that most applicators are more familiar with is that chemicals often exert their effects on specific systems in the body, much like an herbicide that disrupts specific pathways in plant systems.
An example of a route of exposure specific effect could be lung cancer from asbestos exposure. If an individual drinks asbestos contaminated water, they will not develop lung cancer.

31. Sensitive Subpopulations
Children
Rapid development and differing physiologies of young children can result in potentially greater sensitivity to contaminants
Lead exposure and the developing brain
Exposure to lead during prenatal or early childhood can cause irreversible intelligence losses
What are potential sources on the farm for lead exposure to children?
Answer:
Potential sources of lead include: paint chips and dust from old paint that contains lead, drinking water contaminated with lead from old pipes in the home, previous spills of leaded gasoline, etc.

32. Sensitive Subpopulations
Children or adults with health problems
Compromised immune systems
Undergoing chemotherapy
Organ transplant patients
Diseases affecting immune system
Other diseases that affect body system that chemical exposure may target
Children or adults with “hidden” sensitivities
Genes can increase or decrease susceptibility to environmental factors and can therefore modify risk
Compromised immune systems are relevant for carcinogen exposures because of the role the immune system plays in identifying and attacking early stage cancers.
The presence of other diseases that may affect the same body system that the chemical may target may also place individuals at a higher risk when exposed to chemicals.
Genes control enzyme levels in the body as well as the vigor of repair mechanisms in the body. Many chemicals are detoxified by enzymes once they enter the body. If an individual had relatively low levels of an enzyme needed to detoxify chemical exposures, they could also be at greater risk. Likewise, some chemicals have the potential to be “toxified” when they come into contact with certain enzymes. If an individual had relatively higher levels of this enzyme, they could also be at greater risk. This is a rapidly developing area of risk assessment practice and it is not often explicitly evaluated.

33. Distinction between Cancer and Noncancer Effects
Calculation of dose and some exposure assumptions differ
Large number of carcinogenic contaminants are assumed to have no threshold
What would dose-response curve look like if we did not assume a threshold existed?
Hint: An effect would be seen at any dose level.
The dose for carcinogens is averaged over an individual’s lifetime, this is due to the way that cancer toxicity data are generated.
Answer: the dose-response curve would begin at the origin of the graph and there would be a effect at the lowest dose tested. An example, could be drawing the curve at a 45 degree angle to the origin.

34. Step #4: Risk Characterization
The risk characterization combines the information obtained on toxicity with the calculated exposure to provide an estimate of risk.
Purdue, Pesticides and Ecological Risk Assessment: History, Science, and Process. PPP-41.
Purdue, 1997

35. Risk Characterization Answers
What is the likelihood of harm following exposure to this chemical in this specific situation?
Provides a numerical estimate of risk
Identifies key uncertainties in this estimate
Compares numerical estimate of risk with a previously determined risk goal
The identification of uncertainties is an important aspect of the risk characterization. It provides information on whether there were key data that were not available or were estimated, the likelihood that the risk estimate is an under or overestimation of risk and in what areas the assessment is less certain. It can sometimes identify areas of further study that could be used to refine the estimate of risk.
The risk goal is defined and discussed on the next slide.

36. Risk Goal
Most environmental programs have a specified risk goal which has gone through review
Risk goal is a policy determination
Risk goal is numerical estimate of acceptable risk for cancer or noncancer effects.
1 in 1,000,000 for cancer or the level of reference dose (threshold + uncertainty factor) for noncancer effect.
Compare numerical estimate of risk with risk goal
If risk goal is exceeded, risk management decision necessary
Risk management is distinct from risk assessment. It is the decisionmaking process used to determine if and how to address the identified risk.

37. Risk Assessment is One Part of Decisionmaking Process to Manage Hazards
Science determines likelihood of effect but risk management determines whether and how the risk should be addressed
Policy decision
As noted in the graphic, risk management involves considering the benefits of addressing the risk, the costs, the technical feasibility of risk management actions, legal and policy requirements, etc.

38. What Does Risk Assessment Not Tell Us?
Whether risk is “acceptable” Whether risk is equitably distributed across population Predictions regarding personal or individual risk

39. Summary
Risk assessment is a 4-part process to evaluate risk from suspected hazards.
Hazard Identification
Exposure Assessment
Toxicity Assessment
Risk Characterization
For a hazard to have an adverse impact on health, there must be contact between the receptor and the hazard. Exposure must occur.
Children and other sensitive subpopulations can have greater exposure and toxicity to the same environmental conditions than other adults.

40. Summary contd.
Risk goals are used as a comparison point with calculated risk values. These are policy, or nonscientific, determinations.
Risk characterization
defines the risk relative to the risk goal,
identifies uncertainties, and
identifies receptors and exposure pathways of most concern.

41. Summary contd.
Risk management is the decisionmaking process to determine whether to take action for an identified risk.

42. Case Study Scenario

43. Case Study Review Working back from the contaminated well
What are some possible sources and associated pathways?
Which source and pathway do you believe to be the most likely cause? Why?
See the completed answer sheet in the instructor materials

44. BMP’s to Prevent Potential Well Contamination?
Pesticide Selection? Pesticide Storage? Pesticide Application Practices? Well Placement? Well Maintenance? Well Abandonment?
The participants should help to provide these answers. To help steer their answers, see the “Suggested Wrap Ideas for the Activity” in the Group Activity file. For additional information on well placement, maintenance, and abandonment, see the Take Home Reference information provided in the Farm-A-Syst sheets and the Ohio Department of Natural Resources sheets on “Well Abandonment”.

45. And How Can You Use Your New Risk Assessment Knowledge?
Think about the possible ways that chemicals stored or used at your farm could reach receptors, especially through drinking water pathways.
The take home lessons for this presentation which can be reinforced through the next series of slides:
Chemicals often travel far from their original application area and may contact people or environmental receptors who are not near the original source of chemicals.
Pathway analysis can be used to identify and mitigate potential pathways that chemicals may travel from sources to people. Chemical sources on the farm can include chemical storage sheds where spills may occur, application to crop land, fires in storage area, floods, etc. An awareness of chemical transport and exposure pathways is the first step in being able to evaluate these hazards on a farm-specific basis. X

46. Consider Drinking Water Sources
Be aware of drinking water sources that could be affected by your use of agricultural chemicals
Private family wells? Public Water Supply wells?
Nearby reservoirs used as public water sources?
Drinking water intakes in rivers or streams?
Take necessary steps to protect them

47. Consider Local Conditions When Selecting Pesticides
Be aware of geologic and hydrologic conditions when selecting pesticides
Type of soils
Sand versus clay?
Location of surface water bodies and runoff pattern of surface water
Location and depth of ground water
Answer to question posed:
Pesticides that are highly water soluble would be expected to be very mobile in sandy soils and move with the water through the soil column. The soil would not be expected to absorb much of the chemical.
Think:
If you have shallow groundwater and sand/gravel soils, what should you be concerned about if you choose to apply a highly water soluble pesticide?

48. Consider Local Surface Water Quality Conditions
OEPA
Be aware of local water quality conditions when selecting pesticides
Are there any identified problems with pesticides in water, sediment or fish in local streams or rivers?
See Ohio EPA’s web site and associated reports
Join your local watershed group!
Most watersheds in the state have a watershed coordinator and group working to improve water quality

49. Consider and Use Appropriate BMPs
University of Arizona
Be aware of BMPs when storing and applying pesticides
Store properly and be prepared for spills
Read and follow the label!
Drinking and surface water advisories (e.g., Atrazine)
Use buffer strips and maintain streamside areas in natural state
U.S. EPA
NRCS