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U.S. Environmental Protection Agency

U.S. Environmental Protection Agency

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U.S. Environmental Protection Agency

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  1. U.S. Environmental Protection Agency Using Contaminant Information in Evaluating Water Contamination Threats and Incidents

  2. Course Overview • This course is divided into ten parts • Part 1:Course Goals and Definitions • Part 2:Contaminants of Concern and Overview of Toxicology, • (Primarily as related to Chemical Contaminants) • Part 3:Characteristics and Properties of Chemicals as they • Relate to Water Systems Contamination • Part 4:Properties and Characteristics: Pathogens • Part 5:Properties and Characteristics: Radiochemical Agents • Part 6:Gathering and Managing Contaminant Information • Part 7:Data Use for Consequence Analysis • Part 8:Example Contamination Scenario • Part 9:Action Items and Learning Tools • Part 10:Appendix (Example Scenarios for other Contaminants) • Please click on the links above to go to that part of • the presentation

  3. Part 1: Course Goals and Definitions Return to Course Overview Slide

  4. Course Goal • Integrate existing water security knowledge, information, resources and tools into a training to provide for a more effective and efficient response to contamination threats and incidents Return to Course Overview Slide

  5. Course Goal • Gain a basic understanding of the following: • Basic toxicology • Contaminants of concern • Types of contaminant properties / characteristics • Understand the process involved in researching and analyzing contaminants of concern, including: • Identifying appropriate sources of information • Using data to assess potential threat and consequences to public health Return to Course Overview Slide

  6. Definitions • Routine Threats and Incidents • An actual occurrence in which hazards or threats result in a harmful, dangerous, or otherwise unwanted outcome • Hoaxes • Security breaches • September 11, 2001 • Anthrax-contaminated mail • National Special Security Events (NSSE) • A significant event or designated special event requiring security • Presidential Inauguration • State of the Union Address • National conventions • Olympics • International summit conferences Return to Course Overview Slide

  7. Part 2: Contaminants of Concern and Overview of Toxicology (Primarily as Related to Chemical Contaminants) Return to Course Overview Slide

  8. What are the Priority Drinking Water Contaminants? • More than 200 contaminants identified as posing a threat to drinking water systems, based on: • Health effects (toxicity or infectivity) • Ability to be dispersed through distribution system • Six main categories of contaminants • Inorganic chemicals (e.g., cyanide) • Organic chemicals (e.g., pesticides) • Schedule 1 Chemical Warfare Agents (e.g., sulfur mustard) • Biotoxins (e.g., ricin) • Pathogens (e.g., Bacillus anthracis [Anthrax]) • Radiochemicals (e.g., Cesium-137) Return to Course Overview Slide

  9. Toxicity Data • What is it? • A measure of the degree to which a substance can elicit a deleterious effect (including death) in a given organism • Why is it important? • Toxicity is directly related to the public health outcome of a threat • Many chemicals are more toxic via exposure routes other than ingestion • The public can be exposed to drinking water contaminants via showering (inhalation), bathing (dermal contact), as well as ingestion • Different types (acute, chronic) depending on chemical, concentration, and exposure route Basic tenet of toxicology: “Dosis facit venenum” The dose makes the poison (Paracelus) Return to Course Overview Slide

  10. Basic Toxicology • Acute, Sub-Acute • Immediate or almost immediate adverse health effects from exposure to a substance (for water contaminants, usually within a day) • Chronic, Sub-Chronic • Adverse health effects resulting from long-term or repeated (chronic, >10% of lifespan) exposure to a substance over a period of time • Can occur at low levels that have no ACUTE effects • Chronic health effects can be as severe as acute effects, but take much longer to manifest • Lethal, Sub-Lethal • Causes death immediately or over a short period of time • Sub-lethal is not quite lethal; less than lethal Return to Course Overview Slide

  11. Exposure Routes • Definition • The route through which a chemical, physical, or biological agent may enter the body • Dermal Route • Agent is absorbed directly through the skin • Inhalation Route • Agent enters through the respiratory tract or lungs • Oral Ingestion Route • Agent enters through the mouth and digestive system Return to Course Overview Slide

  12. Exposure Routes (cont.) • Other Routes • Ocular (through the eyes) • Mucous membranes • Direct entry into the bloodstream through cuts or open sores Return to Course Overview Slide

  13. Drinking Water and Exposure Routes • Drinking water use provides opportunities for exposure through all of these routes • Drinking and Cooking • Ingestion • Dermal • Bathing and Showering • Inhalation • Ocular • Mucus membranes • Maintenance and Recreation • Inhalation (Watering vegetable gardens) • Dermal, Inadvertent ingestion (Swimming and wading pools) • Direct entry through cuts or open sores • Inadvertent ingestion • Dermal Return to Course Overview Slide

  14. Toxicity Measures • Some toxicity measurements are more applicable than others in assessing the concentration at which a contaminant will have acute or immediate impacts, while others will have more chronic, long-term impacts • Assessing acute or immediate impacts of contaminant: • Lethal dose 50 (LD50), infectious dose 50 (ID50), or lethal concentration 50 (LC50) • No observed adverse effect level (NOAEL) • Lowest observed adverse effect level (LOAEL) • Assessing chronic, or long-term impacts of contaminant: • Maximum contaminant level (MCL) • Maximum contaminant level goal (MCLG) Return to Course Overview Slide

  15. Toxicity Measures (cont.) • Impacts will vary and may be based on acute or chronic levels • Health advisory (HA) • Reference dose (RfD) Return to Course Overview Slide

  16. MCLs and MCLGs • Maximum Contaminant Level (MCL) • The highest level of a contaminant that is allowed in drinking water • Only established for regulated contaminants • Enforceable standards • Based on lifetime exposure risk (typically for an end point, such as cancer) • Maximum Contaminant Level Goals (MCLGs) • Level of a contaminant in drinking water below which there is no known or expected risk to health • Allow for a margin of safety and are non-enforceable public health goals • The MCLG for some contaminants is zero, which means there is no safe level for the contaminant Return to Course Overview Slide

  17. Drinking Water Health Advisories (HAs) • Estimate of acceptable drinking water levels for a chemical substance based on health effects information • HAs are not a legally enforceable Federal standard, but serve as technical guidance to assist federal, state, and local officials • Developed for specific exposure durations • Developed by EPA’s Office of Water to provide guidance on non-regulated water contaminants and for emergency contamination events Return to Course Overview Slide

  18. Drinking Water Health Advisories (HAs) (cont.) • 1-Day HA • The concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for up to 1 day of exposure. The 1-day HA is normally designed to protect a 10-kg child consuming 1 L of water per day • 10-Day HA • The concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for up to 10 days of exposure. The 10-day HA is also normally designed to protect a 10-kg child consuming 1 L of water per day Return to Course Overview Slide

  19. Drinking Water Health Advisories (HAs) (cont.) • Lifetime HA • The concentration of a chemical in drinking water that is not expected to cause any adverse noncarcinogenic effects for a lifetime of exposure • Based on exposure of a 70-kg adult consuming 2L of water per day • The Lifetime HA for Group C carcinogens (i.e., possible human carcinogen) includes an adjustment for possible carcinogenicity • HAs are a concentration • They can be compared to the concentration of what was found in the contaminated water • HAs function as benchmark • If a contaminant is found in the water at a concentration higher than the HA, then people might suffer adverse health effects from drinking the contaminated water Return to Course Overview Slide

  20. Effect Levels • No Observable Adverse Effect Level (NOAEL) • Highest exposure level at which there are no biologically significant increases in the frequency or severity of adverse effect between the exposed population and its appropriate control • Some effects may be produced at this level, but they are not considered adverse or precursors of adverse effects • In short — concentrations below the NOAEL are generally considered safe, even when exposure is chronic • Lowest Observable Adverse Effect Level (LOAEL) • Lowest exposure level at which there are biologically significant increases in frequency or severity of adverse effects between the exposed population and its appropriate control group Return to Course Overview Slide

  21. Reference Dose (RfD) • Estimate of a daily exposure to the human population that is likely to be without an appreciable risk of deleterious effects during a lifetime. • Uncertainty may span an order of magnitude • Generally expressed in units of milligrams per kilogram of body weight per day (mg/kg/day) • Useful as a reference point from which to gauge the potential effects of the chemical at other doses. • Doses less than the RfD are not likely to be associated with adverse health risks Return to Course Overview Slide

  22. Reference Dose (RfD) (cont.) • As the frequency and/or magnitude of the exposures exceeding the RfD increase, the probability of adverse effects in a human population increases • However, all doses below the RfD may not be “acceptable” (or risk-free) and all doses in excess of the RfD may not be “unacceptable” (or result in adverse effects) Return to Course Overview Slide

  23. LD50, LC50, and ID50 • Lethal dose 50 (LD50) • Dose of a chemical required to kill 50% of the experimental subjects (e.g., rats, mice, cockroaches) • Standard measurement of acute toxicity for chemicals stated in milligrams (mg) of contaminant per kilogram (kg) of body weight • Applies to ingestion and dermal exposure routes Return to Course Overview Slide

  24. LD50, LC50, and ID50 (cont.) • Lethal concentration 50 (LC50) • Two types, depending on situation: • Human inhalation (also called LCt) measured in milligrams per cubic meter of air in a given time period (t) • Environmental exposure by aquatic organisms, measured in mg/L of water • Often human data are not available, and animal models are used • Infectious dose 50 (ID50) • Number of infectious pathogens required to produce infection or disease in 50% of the experimental subjects Return to Course Overview Slide

  25. LD50, LC50, and ID50 (cont.) • The lower the dose or concentration, the more toxic or infectious the contaminant • A contaminant with an LD50 value of 10 mg/kg is 10 times more toxic than one with an LD50 of 100 mg/kg • One limitation of animal models in determining what LD50, LC50, or ID50 of a human population may be that different animal species may have significantly different susceptibilities to certain contaminants than humans Return to Course Overview Slide

  26. LD50, LC50, and ID50 (cont.) • LD50, LC50, or ID50 are published for a variety of exposure routes, and only values for the same route are comparable • It is important to remember that the public can be exposed through all these routes (e.g. via showering (inhalation), bathing (dermal contact), as well as ingestion) Return to Course Overview Slide

  27. Related Acute Toxicity Measures • Other Lethal Doses (LDs) • Amount at which the contaminant is an LD to X percent of the population (e.g., LD10) • Lethal DoseLO (LDLO):The lowest published lethal dose of a chemical via a particular exposure route • The dose may greatly exceed the true lethal dose because it is often determined from a single individual and circumstance (e.g., an individual commits suicide by ingesting an entire can of poison; the LDLO is based on what they consumed, not the MINIMUM lethal dose) Return to Course Overview Slide

  28. Other Toxicity Measurements • Cell Death 50 (CD50) • The dose of a contaminant required to produce death in 50% of cells in study • Convulsive Dose 50 (CD50) • Median convulsive dose • Chronic Dose 50 (CD50) • Chronic dose resulting in chronic effects within 50% of the test population • Minimal Risk Levels (MRLs) • Estimate of the daily human exposure to a hazardous substance that is likely to be without appreciable risk of adverse non-cancer health effects over a specified duration of exposure Return to Course Overview Slide

  29. Toxicity Calculations • MCLs and MCLGs can be compared directly to drinking water concentrations to determine if there will be NO potential effect • The reverse is not necessarily true • Complex risk calculations are required to determine the extent of any potential effect • For other toxicity values, calculations must be performed to determine if the concentration level in water poses a threat Return to Course Overview Slide

  30. Toxicity Calculations (cont.) • Example: Comparison of an oral LD50 with the concentration of the contaminant in water: • C = concentration (activity for radionuclides) of contaminant in water • V = average volume of water consumed by an individual • W = average weight of individual consuming water • D = individual’s contaminant dose • The contaminant dose can be compared to the LD50 • If the calculated dose is higher than the LD50, health effects in the population could be severe and widespread • If the calculated does is lower than the LD50, comparisons to LOAEL and NOAEL should be made to determine if some effects may still occur; these risk calculations may be complex Return to Course Overview Slide

  31. Toxicity Measurements • Many assumptions about exposure are made when performing these types of calculations that may limit their usefulness • Average volume consumed may not reflect volumes actually consumed by an individual • Average weights do not reflectactual individual weights in a population; may be necessary to do calculations at multiple weights • Even if concentrations are below LD50; some adverse effects may occur • Common practice is to assume the exposure is to a 70kg human • May need to do perform calculations for sensitive populations (e.g. daycare center, or retirement facility, or hospital) Return to Course Overview Slide

  32. Part 3: Characteristics and Properties of Chemicals as they Relate to Water Systems Contamination Return to Course Overview Slide

  33. Chemical Contaminants Overview • Many potential chemical contaminants are widely available and vary greatly in their health effects (e.g., their acute toxicity) • Detecting some of these contaminants in water presents special challenges; detection of others is routine • Drinking water distribution systems may spread the contaminant over vast distances, although changes to the contaminated water may occur within the distribution system • Various physical and chemical properties of the contaminants affect their ability to efficiently contaminate and persist in water systems Return to Course Overview Slide

  34. Chemical Contaminants Overview (cont.) • Generally grouped into the following categories: • Inorganic chemicals (e.g., cyanide) • Organic chemicals (e.g., pesticides) • Schedule 1 Chemical Weapons (e.g., sulfur mustard) • Biotoxins (e.g., ricin) • Radiochemicals (e.g., Cesium-137) Return to Course Overview Slide

  35. Chemical Contaminants Overview (cont.) • Chemical Weapons (CW): defined in the Chemical Weapons Convention (www.cwc.gov); includes toxic chemicals covered by a listing known as Schedules, including their precursors • Schedule 1 contains chemicals that have been developed, produced, stockpiled, or used as CW or chemicals that are precursors (any chemical reactant that takes part at any stage in the production of a toxic chemical regardless of method); Schedule 1 chemicals have no large-scale industrial purpose • Schedule 2 contains chemicals that pose a significant risk to the objectives of the CWC or are CW precursors, and have no legitimate industrial use • Schedule 3 contains "dual-use" chemicals—chemicals that have been developed, produced, stockpiled, or used as CW or are CW precursors, but are produced in large quantities for legitimate (non-CW) uses Return to Course Overview Slide

  36. Chemical Contaminants Overview (cont.) • CW are popularly grouped into five categories: • Nerve (e.g., VX, Sarin) • Blister (e.g., distilled mustard, nitrogen mustard, sulfur mustard) • Choking (e.g., chlorine) • Blood (e.g., hydrogen cyanide) • Vomiting (e.g., adamsite) • Some generalities can be made: • Many are not stable in water • Many are difficult to obtain • Many are gases Return to Course Overview Slide

  37. Chemical Contaminants Overview (cont.) • Several Schedule 3 chemicals are found in water as a result of disinfection (e.g., chloropicrin, cyanogen chloride, etc.) • Water may not be the best delivery mechanism for CWs • Properties of CWs are evaluated like other chemicals Return to Course Overview Slide

  38. Chemical Contaminants Overview (cont.) • Biotoxin: A toxin naturally produced by a microorganism, plant, or animal • Examples: • Ricin – toxin that is derived from castor plant beans, Ricinus communis • Microcystins – toxins produced by blue-green algae • Some have very low lethal dose relative to most contaminants; however, some are less toxic than more common man-made organic chemicals • Although biotoxins may be used in an aerosol attack, they also represent a concern for food and water contamination • Properties evaluated like other chemicals • Biotoxins are also organic chemicals Return to Course Overview Slide

  39. Chemical Identity • Chemicals can be uniquely identified by their Chemical Abstract Registry Number, often called “CAS” • In finding properties of chemicals, the CAS is often helpful because many chemicals go by a lot of other names • CAS numbers can be in chemical catalogs, databases, and Material Safety Data Sheets (MSDS) • Illustration: The CAS for glyphosate is 1071-83-6 Return to Course Overview Slide

  40. Chemical Detection • The ability to detect a chemical contaminant in water is often an important step in the investigation of contamination • As used here, detection falls into two categories: • Sensory Perception • Chemical Analysis Return to Course Overview Slide

  41. Chemical Detection (cont.) • Sensory perception: usually occurs when the drinking water customer complains that the water looks, smells, and/or tastes unusual, but may or may not prevent the customer from drinking the water • Some contaminants may have distinctive odors or tastes, although perception of these by customers can vary dramatically • Is not always a sign of intentional contamination because some water systems are prone to complaints, particularly at certain times of year • NEVER INTENTIONALLY SMELL or TASTE a suspected sample • Example: A customer complains of an almond smell to the water • Hydrogen cyanide may smell like almonds • On closer inspection, the odor is determined to be a new almond scented shampoo Return to Course Overview Slide

  42. Chemical Detection (cont.) • Compliance monitoring for regulated chemical contaminants will most likely not detect the presence of many of the potential chemical agents; compliance monitoring for some chemicals is sometimes only required a few times a year • Water quality laboratories are often capable of analyzing water for many regulated chemicals of concern. Special techniques are required for confirming some Schedule 1 CW and biotoxins. • Early warning or rapid field detection is not available for many contaminants of concern • Changes in baseline water quality parameters (e.g., pH, turbidity, residual chlorine) may or may not indicate the presence of a chemical contaminant Return to Course Overview Slide

  43. Fate and Transport of a Chemical within a Drinking Water System • The fate of a chemical as it moves through a water system to the tap depends on the nature of the particular water system and also on properties of the contaminant • Predictions are often complicated and rely on: • - Accuracy of physical and chemical property data in the literature • Knowledge of the individual drinking water system Return to Course Overview Slide

  44. Drinking Water System Return to Course Overview Slide

  45. Portion of Drinking Water Distribution System • Understanding the behavior or water and contaminants in a distribution system is a complex task Return to Course Overview Slide

  46. Contaminant Properties • The next few slides will describe several contaminants properties: • Solubility • Detectability (of the contaminant in water) • Treatability (at the water treatment plant) • Stability (of the contaminant in the distribution system) • Along with a description of property, we’ll look at: • How does the property help assess the threat • What limitations about the property may be important • Illustration about the property’s relevance to a water system Return to Course Overview Slide

  47. Contaminant Property: Solubility • What is solubility? • The ability of a certain amount of chemical to dissolve in a certain amount of a given solvent • For example, one gram of sodium chloride dissolves in 2.8 mL of water at room temperature • How does this information help assess the threat? • Solubility must be compared to the concentration of concern in water (i.e., a highly toxic, less soluble chemical may be soluble enough to pose a health threat); low solubility does not automatically imply low threat • Some chemicals, which are soluble in water, need to be dispersed (e.g., by stirring) in order to dissolve • Some insoluble chemicals can still be effectively dispersed in water, although it presents a greater technical challenge (e.g., insoluble metals may need to be dissolved in acid and then added to water) Return to Course Overview Slide

  48. Contaminant Property: Solubility (cont.) • What limitations in solubility information should you be aware of? • Solubility data are based on pure chemicals and sometimes solubility is described using words such as “very”, “sparingly”, “slightly”, which is not very helpful, especially for highly toxic chemicals • Factors influenced by conditions in the distribution system affect solubility (e.g., temperature, pH, TDS concentration) • For contaminants added at high concentrations that exceed solubility, a layer of contaminant may be found on top or at the bottom of the water depending if the contaminant’s density (mass per unit volume) is less or more than water (e.g., oil floats on water) • The absence of a contaminant film on top (or bottom) of the water does not necessarily mean that no contamination is present, but that the contaminant is present but below its solubility limit Return to Course Overview Slide

  49. Contaminant Property: Solubility (cont.) • Illustration • Someone adds a 10 kg (10,000,000 mg) of a contaminant to a 1,000,000 L water tank • The LC50 of the liquid is 2000 mg/L to a water tank • Solubility data indicates the solubility is 0.1 mg/L • Where will the contaminant be (in the water or at the bottom of the tank)? • One source for solubility data says that a particular contaminant is “practically insoluble” • The LC50 of the contaminant is 30 mg/L • How does the toxicity compare with the solubility? Return to Course Overview Slide

  50. Contaminant Property: Treatability • What is treatability? • Ability of water treatment technologies (e.g., chlorination, sand filtration, activated carbon, etc.) to remove a contaminant or reduce its concentration in the water • How does this information help assess the threat? • The existing plant may be treating the water in such a way that contamination is removed or mitigated rapidly, resulting in fewer long term consequences • Also relevant to remediation in the case of contamination Return to Course Overview Slide