Water Quality and the Safe Drinking Water Act

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Water Quality and the Safe Drinking Water Act
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Topics

• Water quality introduction
• Drinking water treatment history
• Safe Drinking Water Act
• Risk assessments for setting standards
• Benefit analyses

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What do we mean by water quality?

• Water as the solvent
• Solutes and contaminants
• salinity
• Suspended sediments
• Microbiologic constituents

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Common dissolved solids (99)

• Cations
• Sodium
• Potassium
• Calcium
• Magnesium

• Anions
• Chloride
• Sulfate
• Bicarbonate

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Some other things we measure in Water...

• TDS (Total dissolved solids)
• EC (Electrical Conductivity)
• Hardness (concentration of Ca and Mg salts)
• pH (acidity of the water)

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Water Quality for What?

• Earliest Records of Drinking Water Treatment
• Earliest record of methods to improve the taste
  and odor of drinking water date to 4000 BC
• Alum used by Egyptians for clarifying water
  1500 BC
• Hippocrates advised people to boil and strain
  water 400 BC

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Earliest Association of Diseases with Drinking
Water

• Dr. John Snow demonstrated in 1854 that cholera
  in London was spread through drinking
• 1856 Darcy first uses sand filtration in Dijon
• In the 1890s, studies in Lawrence, Massachusetts,
  demonstrated a reduction in typhoid fever
  incidence with drinking water filtration

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Water Treatment in U.S.
1871 First slow sand filter in U.S. 1896
First rapid sand filter in U.S. 1908 First use
of chlorine as a primary disinfectant 1920s Filt
ration and chlorination used widely in large
cities
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Water Treatment in the U.S.
1940s Treatment for inorganic contaminants 1970s
Treatment for organic contaminants 1980s Advan
ced water treatment methods
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Success in Early Drinking Water Protection

• Cancer 129

Typhoid Deaths Per 100,000 People

• Car Accidents 16

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Treatment Effectiveness in Reducing Typhoid Deaths
Detroit, Michigan
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The Safe Drinking Water Act

• SDWA enacted in 1974
• Two major SDWA amendments
• 1986
• 1996

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Key Terminology

• National Primary Drinking Water Regulation
• Sets legally enforceable standards
• Limits levels of specific contaminants that can
  adversely affect public health
• Maximum Contaminant Level or Treatment Technique
• National Secondary Drinking Water Regulation
• Nonenforceable guideline
• Covers contaminants that may cause cosmetic or
  aesthetic effects

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Key Terminology

• Maximum Contaminant Level Goal (MCLG)
• 1412(b)(4)(A) level at which no known or
  anticipated adverse effectsoccur and which
  allows for an adequate margin of safety.
• Not enforceable
• Maximum Contaminant Level (MCL)
• 1412(b)(4)(B) levelwhich is as close to
  the maximum contaminant level goal as is
  feasible.
• Enforceable

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Contaminant Effects

• Adverse health effects from acute exposure
• Adverse health effects from chronic exposure
• Adverse health effects from exposure during
  critical periods

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Carcinogenicity

• Category I compounds are carcinogens
• Category II compounds exhibit carcinogenic as
  well as noncarcinogenic endpoints
• Category III compounds are noncarcinogenic

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Types of Contaminants

• Chemicals
• Naturally occurring
• Man-made
• Microbiological
• Disinfection byproducts

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Chemical Contaminants

• Volatile organic chemicals (VOCs)
• Synthetic organic chemicals (SOCs)
• Inorganic chemicals (IOCs)
• Radionuclides
• Disinfection byproducts (DBPs)

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Microbiological

• Viruses
• Bacteria
• Total coliforms, fecal coliforms
• Others
• Protozoa
• Giardia and Cryptosporidium

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Disinfection Byproducts

• Naturally occurring organic compounds in source
  water react with disinfectants to form byproducts
• DBPs in chlorinated surface water may be linked
  to increased risks of cancer, reproductive and
  developmental effects

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Sensitive Sub-Populations

• Infants and children
• Elderly people
• Immuno-compromised individuals
• Highly exposed individuals

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What is an Adverse Health Effect?

• EPA definition
• any biological, physiological, anatomical,
  pathological, and/or behavioral change that may
  affect the performance of the whole organism or
  reduce the ability of the organism to respond to
  additional challenges.

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Toxicology Study Methods

• Some animals subjected to high doses of chemicals
• Necessary to observe statistically significant
  rates of disease
• Other animals exposed to lower doses of chemicals
• Necessary to provide data inputs for a
  dose-response curve

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Strengths and Limits of Toxicology Studies

• Environmental factors, such as exposure to other
  contaminants, can be controlled
• Facilitates interpretation of results

• Uncertainty associated with extrapolating
• From high doses tested to environmentally
  relevant doses
• From effects on animals to effects on humans

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Epidemiological Studies

• Studies based on human exposure
• Epidemiologists seek to identify
• Risk factors associated with the occurrence of
  disease
• Protective factors that reduce the risk of disease

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Strengths and Limits of Epidemiological Studies

• Less effective in determining the causes of
  common diseases in large populations
• Difficulties correlating data across geographic
  areas
• Cannot definitively prove cause and effect

• Especially useful where high rates of rare
  diseases occur in small populations
• Provide data on the actual incidence of disease
• Dose-response and exposure estimates not needed

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Non-carcinogens

• Non-threshold type
• Lead
• Neurological and cognitive effects in young
  children
• Microorganisms
• Cryptosporidium, Giardia, Legionella, total
  coliforms, viruses

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Carcinogens

• The MCLG is traditionally set at zero for all
  carcinogens
• Assumed to be genotoxic
• No threshold
• Non-zero MCLGs are possible, reflecting
  non-genotoxic effect

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Maximum Contaminant Levels

• An MCL is an enforceable standard
• Set as close to the MCLG as feasible
• SDWA provides guidance on what is feasible
• Requires determination of whether benefits
  justify costs (1996 Amendments)

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Benefit and Cost Analyses

• Benefits of MCL must balance costs of compliance
• Cost of compliance is an explicit concern

Benefits
Costs
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Regulations Currently Being Developed

• Disinfection by-products
• Enhanced Surface Water Treatment Rule
• Ground Water Rule
• Radon
• Total Coliform / Distribution System Rule

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Summary

• Standards ensure baseline of water quality in
  public water supply systems
• Based on risk assessments and cost benefit
  analyses
• Designed to minimize potential for acute and
  chronic illness associated with water
• Continually being reviewed and revised