U.S. Environmental Protection Agency

1
U.S. Environmental Protection Agency

• Using Contaminant Information in Evaluating Water
  Contamination Threats and Incidents

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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

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Part 1 Course Goals and Definitions
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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

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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

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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

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Part 2 Contaminants of Concern and Overview of
Toxicology (Primarily as Related to Chemical
Contaminants)
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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)

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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)

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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, gt10 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

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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

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Exposure Routes (cont.)

• Other Routes
• Ocular (through the eyes)
• Mucous membranes
• Direct entry into the bloodstream through cuts or
  open sores

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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

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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)

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Toxicity Measures (cont.)

• Impacts will vary and may be based on acute or
  chronic levels
• Health advisory (HA)
• Reference dose (RfD)

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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

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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 EPAs Office of Water to provide
  guidance on non-regulated water contaminants and
  for emergency contamination events

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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

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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

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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

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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

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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)

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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

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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

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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

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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)

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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)

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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

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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

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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 individuals 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

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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 reflect actual 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)

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Part 3 Characteristics and Properties of
Chemicals as they Relate to Water Systems
Contamination
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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

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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)

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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" chemicalschemicals
  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

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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

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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

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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

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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

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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

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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

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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

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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

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Drinking Water System
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45
Portion of Drinking Water Distribution System

• Understanding the behavior or water and
  contaminants in a distribution system is a
  complex task

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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, well look
  at
• How does the property help assess the threat
• What limitations about the property may be
  important
• Illustration about the propertys relevance to a
  water system

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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)

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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 contaminants 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

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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?

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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

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Contaminant Property Treatability (cont.)

• What limitations in this information should you
  be aware of?
• Efficacy of a particular process for a particular
  contaminant depends on the treatment technologies
  conditions at the plant
• Treatment data may be unavailable for many
  contaminants
• Literature has inconsistent data for some
  contaminants-possibly due to difference in
  treatment conditions
• Applies generally to contamination added to the
  system before the treatment plant. However,
  water treatment plants add residual disinfectant
  before the water leaves the plant and enters the
  distribution system
• Illustration
• Someone adds a quantity of a particular pesticide
  to the source water of the treatment plant
• The treatment plant uses activated carbon, which
  the literature indicates effectively removes the
  contaminant

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Contaminant Property Stability

• What is stability?
• The ability of a contaminant to withstand
  degradation, which can reduce the toxicity or
  infectivity of a contaminant
• With the distribution system, primarily a
  function of processes such as hydrolysis,
  volatilization, reactivity, adsorption
• Biodegradation (degradation of the contaminant by
  microorganisms) may be important in the source
  water
• How does this information help assess the threat?
• When available, degradation rate data may be used
  to estimate the half-life of a contaminant in a
  water system half-life is the time is takes for
  half of the contaminant to degrade
• A chemical with a short half-life in a drinking
  water system may not persist long enough to have
  significant effects on the public
• A chemical with a longer half-life in a drinking
  water system may persist for sufficient time to
  have significant effects on the public

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53
Contaminant Properties Stability (cont.)

• What limitations in this information should you
  be aware of?
• Stability data are based on pure chemicals, and
  depending on the stability process, the data may
  not be available for the chemical dissolved in
  water.
• For instance, reactivity data are sometimes given
  for the undissolved compound, which can differ
  markedly from the compounds behavior in water
• Estimates of half-life are not available for some
  contaminants
• Environmental fate and transport predictions rely
  on the accuracy of physical and chemical property
  data in the literature
• Due to the complexity of drinking water
  distribution systems, the amount of time that
  contaminated water can remain in the distribution
  system varies tremendously by location, even
  within the same distribution system it can be an
  extremely complex task to apply degradation rates
  when trying to estimate how much contaminant the
  public has been exposed to

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Stability Related Process Hydrolysis

• What is hydrolysis?
• A reaction that occurs between a chemical and the
  water itself, often resulting in permanent
  degradation of the original chemical
• How does this information help assess the threat?
• Hydrolysis may produce byproducts that are less
  toxic than the parent chemical, thus, hydrolysis
  sometimes, but not always, greatly reduces the
  toxicity of contaminated water
• Contaminants, especially highly toxic ones, that
  are resistant to hydrolysis may be of greater
  concern due to their persistence in water
• What limitations in this information should you
  be aware of?
• Hydrolysis rate is pH and temperature dependent
• Hydrolysis rate data are not available for all
  contaminants or are not available for pHs and
  temperatures of interest

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Stability Related Properties Hydrolysis (cont.)

• Illustration
• The half-life of a certain pesticide is listed as
  2 days
• This means that after two days, the concentration
  of the contaminant will by 1/2, but will still be
  present
• The half-life of a particular chemical weapon is
  around 8 minutes at room temperature
• Within an hour or two, the concentration is
  reduced to essentially zero

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Stability Related Process Volatilization

• What is volatilization from water?
• The process through which a contaminant dissolved
  in the water enters the gas phase (i.e., the air
  above the water)
• Henrys Law constants are essentially determined
  from the equilibrium ratio of the concentration
  in the air to the concentration in the water
• Vapor density is the density of a gas relative to
  air
• How does this information help assess the threat?
• Henrys Law constants provide an indication of
  whether the chemical is likely to move from an
  aqueous phase into gas phase (e.g., contaminated
  water to the air)
• Vapor density provides an indication of how
  quickly a contaminant could dissipate
• May help predict risk due to inhalation

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Stability Related Properties Volatilization
(cont.)

• What limitations in this information should you
  be aware of?
• Henrys Law Constant assume equilibrium
  conditions, but volatilization is not an
  equilibrium process
• Applies to small concentrations
• Temperature dependent
• In water under specific conditions (e.g., pH),
  some contaminants may co-exist in both volatile
  and non-volatile forms, which affects the amount
  of volatile contaminant
• Illustration
• The dimensionless Henrys Law constant for
  benzene is 0.25
• This means that concentration in the water is 4
  times in the air.
• At drinking water pHs, sodium cyanide is present
  as hydrogen cyanide, which can volatilize from
  the water

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58
Stability Related Process Reactivity

• What is reactivity?
• Reaction between a contaminant and another
  substance
• For water systems, a principal reaction of
  interest occurs between an oxidant and the
  contaminant of concern
• One oxidant frequently found in finished drinking
  water is chlorine
• How does this information help assess the threat?
• The oxidation of a chemical contaminant
  frequently, but not always, decreases the
  toxicity of the water
• Reaction rates for different contaminants can
  vary dramatically from instantaneous to nearly
  imperceptible
• What limitations in this information should you
  be aware of?
• Oxidation is dependent on temperature and pH
• The presence and concentration of other
  substances in the water may significantly affect
  the oxidation rate

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59
Stability Related Process Reactivity(cont.)

• Illustration
• A certain pesticide is known to react rapidly
  with chlorine
• You measure the chlorine residual at a tap and
  find there is a large one
• It is less likely that the pesticide is present
  at that tap
• Contamination with a chlorine sensitive
  contaminant is suspected, so you measure the
  chlorine residual at a tap
• You find very little
• Does this indicate contamination?
• Maybe notsome parts of the distribution system
  have far less residual than was added at the
  plant due to natural chlorine decay
• In arsenic treatment of water systems, oxidation
  changes the chemical form of arsenic, and is
  known to frequently reduce toxicity and ease of
  removal

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60
Stability Related Properties Adsorption

• What is adsorption?
• A measure of the tendency of a chemical to
  partition out of the water into a substance with
  an organic-like phase (e.g., certain sediments,
  some water system pipes and components, etc.)
• The octanol-water partition coefficient (KOW) may
  be an indicator. KOW is the concentration of the
  contaminant in octanol divided by the
  concentration in water after the contaminant
  equilibrates between the two solvents
• How does this information help assess the threat?
• Related to the fate of a chemical in the water
  system
• May provide an indication of the chemicals
  persistence in the water system (e.g., need for
  remediation of the system)
• A compound with a higher KOW may be more likely
  to persistently contaminate drinking water system
  components than a contaminant with a lower one.
  A slow release of the contaminant from the water
  system components could taint the water until
  enough water has passed through for sufficient
  desorption of the contaminant.

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Stability Related Properties Adsorption (cont.)

• What limitations in this information should you
  be aware of?
• The reliability of KOW as a predictor is highly
  dependent on both the chemical and the material
  to which the chemical is partitioning. Not all
  materials have an organic-like phase that behaves
  like octanol.
• This dependency may be unknown (e.g., given the
  wide variety of pipe materials in use)
• Temperature-dependent
• Valid only under equilibrium conditions
• Illustration
• Hydrogen cyanide has a KOW of 0.5. An organic
  pesticide has a KOW of 1.3. Which is more likely
  to persist in the pipes, leading to a slow
  release in the water over time?
• Information gathered revealed that the pipes in
  that part of town were made of a material to
  which neither contaminant measurably adsorbed.

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Part 4 Properties and Characteristics Pathogens

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63
Pathogens Overview

• Disease-causing organisms that may result in
  illness or death
• May be referred to as bioterrorism agents,
  replicating agents, select agents, pathogens,
  microorganisms, microbes
• Large quantities may be grown from small initial
  cultures
• Unique ability to multiply in the body over time
  and increase their effect
• May be referred to by disease or by organism
  name
• Salmonella typhi is the causative agent for
  typhoid fever
• Vibrio cholerae is the causative agent for
  cholera
• Yersinia pestis is the causative agent for plague

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64
Pathogens Overview (cont.)

• Classified (for our purposes) into three
  categories
• Bacteria (including rickettsia and
  rickettsia-like organisms)
• Viruses
• Protozoa

Escherichia coli bacteria
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65
Bacteria

• Single-celled, prokaryotic (non-nucleated)
• Relatively easy to grow, may not require host
  cells for growth growth media often simple
• 0.1 - 10Fm in size
• Some are easily disinfected by chlorination,
  certain species produce spores that are stable in
  some environmental matrices for weeks or longer
  also some may propagate in a water system

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66
Bacteria (cont.)

• Organisms may be susceptible to antibiotics
• Examples
• Bacillus anthracis (anthrax)
• Burkholderia pseudomallei (melioidosis)
• Yersinia pestis (plague)
• E. coli O157H7 (hemorrhagic colitis)

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67
Viruses

• Obligate intracellular parasites containing
  either DNA or RNA with a protein coat. May also
  have a lipid envelope
• Unable to replicate or metabolize without a host
  cell
• Grown in cell cultures, embryonated eggs, or
  animals
• 0.01 - 0.1Fm in size
• Stability is estimated at less than a day to
  weeks for some, unknown for others
• Antibiotics have no effect
• Examples
• Variola (smallpox)
• Caliciviruses (e.g., Norwalkvirus)
• Hepatitis viruses (e.g., Hepatitis A)

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68
Protozoa

• Single-celled, eukaryotic (containing a nucleus),
  organisms 0.8 - 70Fm in size
• Protozoa of concern are parasites. There are
  other non-protozoan parasites, some of which may
  be of concern
• Some produce cysts (or oocysts) that are very
  stable
• May be susceptible to specialized antibiotics
  (e.g., Nitazoxanide)
• Examples
• Cryptosporidium parvum (cryptosporidiosis)
• Toxoplasma gondii (toxoplasmosis)
• Entamoeba histolytica (amebic dysentery)

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Fate and Transport and Health Effects

• Fate and Transport
• Many pathogens are stable in water long enough to
  pose a threat
• In suspension in water, rather than in solution
• Exposure routes may include ingestion,
  inhalation, and/or dermal contact
• Health Effects
• Small volumes of infectious material can
  potentially infect large numbers of people
• May not cause immediate symptoms due to
  incubation period in host
• Symptoms may be vague/ambiguous (e.g., flu-like
  symptoms), delaying diagnosis

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Other Properties Infectivity

• What is infectivity?
• A measure of the ability of a microorganism to
  establish itself in a host species and begin to
  multiply
• May be expressed as an ID50 value (the number of
  organisms needed to infect 50 percent of the
  exposed hosts in a given time period)
• How does this information help assess the threat?
• Introduction of pathogen with a low ID50 value
  may be a significant threat, even when low levels
  or concentrations are present
• Introduction of pathogen with very high ID50
  value may require high concentration of organisms
  to have the same impact

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71
Other Properties Infectivity (cont.)

• What are the limitations of infectious dose
  information?
• Knowledge of the source of the estimate is
  crucial to understanding the significance of this
  number
• ID50 values may be derived from estimates made at
  outbreaks, or from animal models (rather than
  human dosing studies).
• Variation in reported and actual ID50 may also
  arise from strain, culture conditions, host
  factors, etc.
• ID50 values should include information on the
  route of infection. ID50 values for ingestion and
  inhalation may differ by several orders of
  magnitude
• Doses lower than the ID50 may cause illness, and
  this relationship may not be linear
• Some studies report the Minimum Infectious
  Dose, which may vary greatly from the ID50
• Many pathogen detection methods do not provide
  information on infectivity

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Other Properties Incubation Period

• What is incubation period?
• The time between exposure and the appearance of
  symptoms
• How does this information help assess the threat?
• Pathogens with longer incubation times may no
  longer be viable or present in the water system
  at or after the onset of symptoms
• If there is a continuous source of a pathogen,
  then a longer incubation period may allow more
  individuals to be exposed
• What limitations in this information should you
  be aware of?
• Actual incubation period will depend on the
  following conditions
• Initial dose
• Virulence of the organism (severity of disease
  produced)
• Rate of replication of the organism
• Health of the host (e.g., immunocompromised)

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Other Properties Virulence

• What is virulence?
• Virulence is a measure of the ability of an
  organism to cause severe disease or death
• One measure of virulence is the mortality rate.
  This is generally calculated as the number of
  deaths per thousand.
• How does this information help assess the threat?
  
• Diseases with higher mortality rates may be of
  greater consequence to homeland security
• What limitations in this information should you
  be aware of?
• Medical treatment may affect the mortality rate,
  so mortality may be reported with both treated
  and untreated rates
• Mortality rates are dependant on correctly
  identifying underlying cases, so the case
  definition used in generating the mortality rate
  will be highly significant

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Other Properties Communicability

• What is communicability?
• Transmission of disease from person to person
  the property of being contagious
• How does this information help assess the threat?
• Even though stop-use notices to public may
  prevent new infections for non-communicable
  diseases, new infections may continue to occur
  for communicable pathogens via secondary
  transmission
• What limitations in this information should you
  be aware of?
• Degree of communicability may depend on the
  strain of organism released
• Good sanitation practices can prevent the spread
  of many communicable diseases

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Other Properties Stability

• What is stability?
• An assessment of the organisms susceptibility to
  various environmental factors while in the
  distribution system, including
• Temperature, pH
• Osmotic pressure caused by differences in
  chemical concentrations inside and outside the
  pathogen
• Residual chlorine
• How does this information help assess the threat?
• Stable organisms with environmentally resistant
  life stages (such as anthrax spores and
  Cryptosporidium spp. oocysts) may survive longer
  in the distribution system
• Some organisms may be more susceptible to
  residual chlorine levels or osmotic pressure,
  reducing the possibility of transmission

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Other Properties Stability (cont.)

• What limitations in this information should you
  be aware of?
• Data on organism stability may result from
  studies using different organism strains or
  system conditions than are present any specific
  distribution system

Salmonella typhi
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77
Other Properties Treatability

• What is treatability?
• Assessment of removal or inactivation of an
  organism by various treatment processes
• How does this information help assess the threat?
• Determination of effectiveness of treatment at
  the water treatment plant during event if
  organism is added to source water
• Determination of chlorine residual effectiveness
  in distribution system during event if organism
  is added after treatment
• Evaluate the effectiveness of various options to
  decontaminate the system
• What limitations in this information should you
  be aware of?
• Data on organism treatability may result from
  studies using different strains or conditions

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Challenges for Detection

• Most pathogens of concern will not be detected
  during monitoring for routine contaminants or
  indicators (e.g., total coliforms)
• Analytical results may not be indicative of
  virulence or infectivity
• Water concentration techniques can be used prior
  to analysis but overall analytical sensitivity
  may be below the concentration of concern for
  some contaminants
• Most onsite drinking water utility laboratories
  are currently capable of monitoring for indicator
  organisms, some of these laboratories can
  conduct assays for some common waterborne
  pathogens however, capability and capacity for
  many specific pathogens must be expanded

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Challenges for Detection (cont.)

• The Select Agent Program (SAP) limits
  confirmatory analysis for a list of Select
  Agent pathogens (e.g., Bacillus anthracis) to
  approved labs. Failure to comply with the SAP
  can result in lengthy jail terms or heavy fines.
• Many of the SAP approved labs conducting
  confirmatory testing of Select Agent samples are
  part of Laboratory Response Network (LRN)

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Part 5Properties and CharacteristicsRadiochem
ical Agents
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81
Radiochemical Agents Overview

• Two general types
• Naturally occurring (e.g., radium, uranium and
  thorium)
• Man-made produced exclusively by nuclear
  reactors, accelerators, cyclotrons, or nuclear
  weapons
• Neutron capture products in nuclear fuel rod
  assemblies, such as plutonium-239 (239 Pu) and
  americium-241 (241Am)
• Fission products that accumulate in fuel rod
  assemblies or produced by nuclear detonations,
  such as cesium-137 (137Cs), and strontium-90
  (90Sr) or corrosion/wear product activation such
  as cobalt-60 (60Co)
• Accelerator produced medical radioisotopes, such
  as iodine-123 (123I) or cobalt-57 (57Co)

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Radiochemical Agents Overview (cont.)

• Can be categorized by the type of radiation an
  unstable isotope emits
• Alpha radiation Particle emitted from the
  nucleus of an atom consisting of two neutrons and
  two protons (same as a helium atom nucleus)
• Beta radiation Particle emitted from the nucleus
  of an atom consisting of an electron or positron
• Gamma radiation Emission from the nucleus of an
  atom consisting of a high energy photon (gamma
  photon)

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Radiochemical Agents Overview (cont.)

• Radiochemical agents may fall into one or
  multiple radiation categories
• 90Sr is a beta emitter
• 137Cs and 60Co are both beta and gamma emitters
• 235U and 239Pu are both alpha and gamma emitters
• Sources of radiochemical agents
• Oil exploration equipment
• Mining and milling sites for uranium, and rare
  earth ores
• Power generation equipment
• Weapons production, maintenance and disposal
• Food and medical irradiators
• Industrial radiography

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Radiochemical Agents Overview (cont.)

• Small quantities widely used in many activities
• Medical
• Food industry
• Laboratory/scientific research

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Fate and Transport and Health Effects

• Fate and transport
• Most will remain in solution
• Many are highly absorbable into biologic systems
  (e.g., 90Sr, uranium, tritium)
• Concentrations will likely be uniform in the
  distribution system
• Health effects
• If exposure is at low levels but for a long
  duration, or is at a high, but non-fatal level
  for a short duration, the general long-term
  health effect is induction of cancers
• However, extremely high doses in short-term
  exposure events cause cellular damage that may be
  significant enough to result in death

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Fate and Transport and Health Effects (cont.)

• Health effects, cont.
• Many radioactive agents are organ-specific
• Iodine-129 129I uptake in the thyroid gland
• Uranium uptake and toxicity in kidneys

• For contaminated water, the most significant
  health risk is ingestion water can significantly
  attenuate (shield) alpha and beta radiation (but
  only minimally attenuate gamma radiation),
  reducing the threat of direct exposure

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Other Properties Toxicity

• What is toxicity?
• How poisonous or harmful a substance is in
  specified amounts
• How does this information help assess the threat?
• Some radioisotopes may result in both chemical-
  and radiation-induced toxicity
• Chemical toxicity often is of greater concern
  (e.g., uranium)
• LD50 much higher than MCLs (for the regulated
  analytes)
• However, a single alpha particle may induce a
  mutational event
• What limitations in this information should you
  be aware of?
• Toxicity studies for radiochemical contaminants
  may not cover all chemical species
• Most radiation exposure limits are based on
  dosimetric models combined with radiation
  dose-response models, rather than empirical
  studies

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Other Properties Speciation

• What is speciation?
• The types of chemical compounds in which a
  radioactive contaminant may occur, such as a
  salt, oxide, hydroxide, or organometallic
  complex, etc.
• How does this information help assess the threat?
• Can identify forms of radioactive species that
  may be in solution
• Different species will have different properties
  relevant to chemical fate and transport and
  health effects
• What limitations in this information should you
  be aware of?
• Can be used only to estimate the actual threat of
  the contaminant of concern

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89
Other Properties Solubility

• What is solubility?
• The amount of a solid that can be dissolved in a
  solvent (water)
• How does this information help assess the threat?
• Can be used to assess the exposure risk
• Radiochemical compounds with relatively high
  solubility may be more of a