week 5 mph 605 water & health part i

Dr. Sylvia Hood Washington, PhD ,ND S, MSE MPH

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MPH 605 Environmental Health Week 5

Part I: Water and Health

Dr. Sylvia Hood Washington, PhD,ND, MSE MPH

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The Hydrologic Cycle1. Over 97 percent of the world’s water is

salty, found in the oceans and in inland seas and saltwater lakes.

2. The remaining 3 percent is freshwater but over two thirds of this is locked in

the Antarctic and Arctic ice caps.

3. The available freshwater is in rivers, lakes, atmosphere and within the

ground and only makes up less than 1 percent of the world’s water.

4. Water is in a continuous motion among these locations in a so-called

hydrologic cycle.

5. Without the continuous evaporation from the oceans, precipitation on land

and runoff back to the oceans, no surface or groundwater recharge can take place and we would eventually exhaust our freshwater supplies.


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Definitions

Surface Water: All H2O naturally open to the atmosphere

Rivers, lakes, reservoirs

Ponds, streams, impoundments

Seas, oceans and estuaries

Groundwater: H2O found underneath

earth’s surface

Aquifers.

GWUDI: Groundwater Under the Direct Influence of Surface Water. Any water beneath surface of Earth characterized by:

Significant levels of insects

or other microorganisms

Significant and rapidly changing characteristics

Temperature Conductivity pH


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Ideal Characteristics of Drinking/Source Water•natural

filtration of rainwater through percolation through soil

•Reduced risk of contaminationIdeally

groundwater


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Freshwater

Even though the percentage of the population who live without access to potable water declined in the 1990s, rapid population growth meant that in terms of actual numbers, more people than before lacked clean water.

At the close of the 20th century an estimated 1.2 billion people lacked clean water, compared to about 1 billion in 1990.


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Water Scarcity

Nonrenewable

• Available only in finite quantities

Non Sustainable

• Is extracted faster than it is replenished


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Water Stress in 2025

27% of nations will face water stress (water levels at or below 1,700 m3 per person per year)

Occurs when population growth is higher than expected

Zero per capita availability in

• West Bank

• Seychelles


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Americans ---Profligate Water Users

Supply is ~ 10, 527 m3 per person per

year

~ per capita withdrawal is 1,654 m3

• 13% used in homes = 590 liters per person per day• Less than 0.2% used for

required drinking water• EPA estimate of daily

ingestion of water = 926 mL

• Advanced sanitation systems requires large amounts of water


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Somalia

Supply is ~ 1,787 m3

per person per year

~ per capita withdrawal is 401 m3

• 0.5% used in homes

• 99.5% used for agriculture


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Aquifer Recharge

In arid regions, recharge rate is very low

Deep aquifers created by countless ice ages

Ogallala Aquifer• Underlies 175,000 squares miles in 8 states. South Dakota

to Texas• Consists of fossil water• Provides ~ 30% of all groundwater used for irrigation in the

USA• Allowed for the transformation of the dustbowl into an

agriculturally rich region• Estimated depletion in the next 20 to 30 years.


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Agriculture and Water Scarcity

1. On a global scale, agriculture use of water represents almost 70 percent of the water withdrawal.

2. It is estimated that 6800 gallons of water is needed to grow a day’s food for a family of four.

3. Agricultural uses of water are the greatest global contributors to water scarcity and depletion of aquifers.


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Climate Change and Water Availability

Changes to the climate such as warming global temperatures will cause :

1. increased evaporation from the oceans

2. an increase in water vapor in the atmosphere

3. Increase in precipitation, involving more severe weather events.

More water vapor in the atmosphere will exacerbate the greenhouse effect :

4. precipitation may increase in some regions and

5. decrease in others shifting the water scarcity burden.


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Human Impacts

Hydrodynamics: the way water moves is dramatically

Dams, levies and canals

Channelization,

concretization and extraction

Eutrophication: high nutrient loads stimulate

blooms of algae in water, stimulating microbial

activity

Oxygen depletion

Fish kills


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Biological ContaminantsKnow pp. 509-510, Table 15.5

Bacteria

Viruses

Protozoa


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Microbiological Contaminants

•Biological contaminants can occur from point sources such as leaking septic systems or nonpoint sources such as runoffs from city streets.

•Most but not all of biological contaminants result from human or animal wastes and therefore waste management practices play a major role in water contamination.


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Exposure Routes

Ingestion of contaminated water

Breathing contaminated aerosols from:•Showers, toilet flushing, dishwashing

•Garden hoses, fountains, waterfalls and cooling towers

Exposure through recreational use•Unintended ingestion•Skin abrasions or alternate portals (eye, ear, anal)

•Hot tubs and whirlpool spas


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Deposition, Storage and Bioaccumulation of Pathogens

Concentrated fecal wastes in shellfish, crustacea• Hepatitis A• Norovirus• Campylobacteriosis• Salmonellis• Cryptosporidiosis• cholera

Filter feeding shellfish—oysters and clams have been found to have concentrated• Planktonic algae• Viruses• Bacteria• Protozoa


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Environmental Transformation of

PathogensIncrease an organism’s

virulence

Adaptation of to intracellular survival and growth

Can resist chlorine and grow within protozoan hosts• Legionella• Citrobacter• Klebsiella• Salmonella• Shigella• Campylobacter


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Waterborne Diseases

1. Vector-Borne Diseases

Some of the most prevalent and deadly infectious diseases are transmitted by vector that are related to the water.

2. Pathogens

While a wide range of diseases are caused by waterborne pathogens, the most common outcome from such pathogens is acute gastrointestinal infection (AGI).

Water Related Diseases and Climate Changes

Waterborne Diseases are likely to become a greater problem as the climate changes and the hydrologic cycle is affected.

Runoff from heavy rainfalls or melting snow can contaminate recreational water (higher levels of bacteria) and therefore increase human illness.


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Traditional Indicator—Microbial Contamination: Coliform Why? Supposedly offers the overall microbial content

1900s: nutrient agar plate at 37 degrees C

More recently enumerated in selective liquid culture media---most probable number method

Membrane filtration technique

Enzyme specific assays

Challenged lately because…

• Human pathogens can survive for extended periods

• Fate is very much organism specific


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Famous Outbreaks

1993 Milwaukee, Wisconsin:

Cryptosporidiosis

Largest documented waterborne disease outbreak in the USA

400, 000 became ill

50 associated deaths

Root cause was the large number of

parvum oocysts being washed into source

water close to intake channels

farms Sewage treatment Unidentified sources

Routine coagulation, sedimentation,

chlorination and rapid sand filtration

Operational lapses were identified

Poor mixing during coagulation

Restarting of dirty filters without backwashing


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Safe Drinking WaterThe safety of drinking water extends from the source to the faucet.

1. Source Protection: To protect human health as it relates to water supply, source water must be protected through maintaining generous buffers, limiting access for recreational purposes and preventing agricultural and industrial uses.

2. Water Treatment: Water treatment is essential for not only poor quality water sources but also for high quality source water. The steps of water treatment involve: coarse filtration, coagulation, precipitation, filtration and finally post filtration disinfection.

3. Water Distribution: Distribution is a critical step and in many cases of water contamination and waterborne disease outbreaks has been identified as the cause.

4. Point of Use Treatment and Bottled Water: As an alternative to tap water consumption, consumers are turning to point of use treatment or bottled water. While these are viable options, there is a compelling argument that if the money spent on these options were invested in municipal treatment and distribution many health risks could be mitigated.

27Dr. Sylvia Hood Washington, PhD ,ND , MSE MPH

Chemical Contaminants: Chemical contaminants can occur from point sources or nonpoint sources.

1. A point source is a stationary location or fixed facility from which pollutants are discharged; any single identifiable source of pollution; for example, a pipe, ditch, shop, ore pit, factory smokestack.

2. Nonpoint sources diffuse pollution sources (that is, the pollutants do not have a single point of origin or are not introduce into a receiving stream from a specific outlet; for example, they are pollutants carried off the land by storm water).

3. Common nonpoint sources are agriculture, forestry, urban, mining, construction, dams, channels, land disposal, saltwater intrusion and city streets.


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Point Source Discharges

Types of Discharges


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Nonpoint Source Discharges


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Regulatory Framework

1. Safe Drinking Water Act: This act was passed in 1974 and amended in 1986 and 1996; it mandates that the EPA must regulate contaminants in drinking water that might post a risk to human health.

2. Total Coliform Rule: Finalized in 1989 by the EPA, the Total Coliform Rule is the driving force behind drinking water safety and frequently serves as the first indication of potential contamination. The rule requires a water system to establish a regular coliform sampling plan, with sample sites that accurately represent water quality throughout the distribution system.

3. Consumer Confidence Reports: The Amendment of 1996 to the Safe Drinking Water Act requires Consumer Confidence Reports to be provided so that Americans can make practical, knowledgeable decisions about health and their environment.


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EPA Water Contaminants

For detailed information go to:

http://www.epa.gov/safewater/contaminants/index.html

week 5 mph 605 water & health part i

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