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AFCEE, 2002 Human Health Risk Assessment and Chemical Safety Stephanie Simstad The Ohio State University Extension Clermont County 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” 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? 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 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 Hazard versus Risk • Hazard (OEPA) – 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 (NOAA) Individual Lifetime Risk of Developing Melanoma is 1 in 75. (NIH) 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 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? 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? Risk Assessment Process (U.S. EPA) Hazard Identification Exposure Assessment Toxicity Assessment Risk Characterization 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 AFCEE, 2002 may move through environment – Conceptual Site Model is used to organize information regarding chemicals and potential transport to people © Vermont DPS, 2000 Input for Conceptual Site Model Modified from Oak Ridge (2002) How are chemicals transported to receptors? Who may be exposed? How may they be exposed? How does exposure change through time? Conceptual Site Model What information is missing? 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. Conceptual Site Model (Oak Ridge National Lab, 2002) 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 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 Spilled Container Soil Groundwater Well Path Traveled by Chemical SOURCE Individual Using Well Exposed Individual Exposure Pathway Diagram (ATSDR, 2002) 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 Chemical Contact Receptor Complete Exposure Pathway • Steps in Complete Exposure Pathway – Source – Chemical Transport and Transformation – Exposure Point – Receptor and Exposure Route Spilled Container SOURCE Soil Groundwater CHEMICAL TRANSPORT Well EXPOSURE POINT Individual Drinks Water RECEPTOR AND EXPOSURE ROUTE 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) 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 Identify Source and Potential Exposure Pathways (Oak Ridge National Lab, 2002) Back To Contaminated Well Example. . . • Who is exposed when family farm well is contaminated? • What are their routes of exposure? Drinking Water Well ? Receptors ? Routes of Exposure 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 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? Why Calculate Dose? • Paracelsus (15th century scientist) Courtesy of the National Library of Medicine – “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 Dose-Response Curve Dose – Chemical concentration per unit body weight Response – Level of measured adverse effect Putting it all together. . . C CR EF ED Intake Dose (mg/kg day ) BW AT • 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) 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, formuladominated diet of young infants • Water, food, and air intake per pound of body weight can be higher for children than adults 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 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? 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 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 doseresponse curve look like if we did not assume a threshold existed? Hint: An effect would be seen at any dose level. Step #4: Risk Characterization The risk characterization combines the information obtained on toxicity with the calculated exposure to provide an estimate of risk. Purdue, 1997 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 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 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 What Does Risk Assessment Not Tell Us? • Whether risk is “acceptable” • Whether risk is equitably distributed across population • Predictions regarding personal or individual risk 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. 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. Summary contd. • Risk management is the decisionmaking process to determine whether to take action for an identified risk. Case Study Scenario • Smith family well was found to have “herbex” contamination • Both neighboring farms have used or stored herbex • Handouts – – – – Risk Assessment Case Study Map Pesticide Application Worksheet Participant worksheet to complete Herbex label Case Study Map Pictures of Storage Sheds Mr. Ulright’s Shed Mr. Sorong’s Shed Hints • Examine map closely • Environmental information from herbex label • Review Pesticide Application Worksheets • Complete participant worksheet to aid in identifying all parts of exposure pathway Case Study Answers • 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? BMP’s to Prevent Potential Well Contamination? • Pesticide Selection? • Pesticide Storage? • Pesticide Application Practices? • Well Placement? • Well Maintenance? • Well Abandonment? 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. X 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 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 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? Consider Local Surface Water Quality Conditions • 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 OEPA 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 U.S. EPA advisories (e.g., Atrazine) – Use buffer strips and maintain streamside areas in natural state NRCS