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Drinking Water Contamination. AOEC Teaching Module 2007.

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drinking water contamination

Drinking Water Contamination

AOEC Teaching Module



This educational module was produced by Michael Greenberg, MD, MPH, Arthur Frank, MD, PhD, and John Curtis, MD for The University of Texas Health Science Center at San Antonio (UTHSCSA) Environmental Medicine Education Program and South Texas Environmental Education and Research Program (STEER-San Antonio/Laredo/Harlingen,Texas)Administrative support was provided by the Association of Occupational and Environmental Clinics through funding to UTHSCSA by the Agency forToxic Substances and Disease Registry (ATSDR), U.S. Department of Health and Human Services.Use of this program must include acknowledgement of the authors,UTHSCSA and the funding support.For information about other educational modules contact the UTHSCSA STEER office, Mail Code 7796, 7703 Floyd Curl Drive, San Antonio,Texas 78229-3900,(210)567-7407.

  • 2 Introductory case studies
  • Examples of specific toxicants
    • Farm chemicals
    • Perchlorate
    • Heavy Metals
    • Biologicals
  • Clinical problem solving
  • After completion of this module, the student will be able to:
    • Describe the importance of the water supply as it relates to epidemic illness
    • Identify issues related to water purity as related to the use of industrial and agricultural chemicals
    • Demonstrate ability to evaluate illness due to biological contamination of water
case study 1 introduction to the problem
Case Study #1Introduction to the Problem
  • From March 23rd to April 5th, 1993 two water treatment facilities in Milwaukee reported record setting turbulence in intake water
  • April 5th the Department of Health reported an outbreak of gastrointestinal illness

Maximal Turbidity of Treated Water in the Northern and Southern Water-Treatment Plants of the Milwaukee Water Works from March 1 through April 28, 1993

Mac Kenzie W et al. N Engl J Med 1994;331:161-167

mystery gi illness
Mystery GI Illness
  • 50% of the population served by the southernmost plant and 25% of those served by the northern plant become ill
    • Over 400,000 (26% of population) estimated to be affected
  • GI illness:
    • Watery diarrhea lasting approximately 9 days
    • Low grade fever
    • Average 10 lbs. weight loss
  • Cryptosporidium was identified in over 600 stool samples (30% of those tested)
  • No other causative organisms found in greater than 2% of samples
  • Later, Cryptosporidium was also found in ice made from water during that period
cryptosporidium in water
Cryptosporidium in water
  • Disease transmitted by oocysts
  • Not destroyed by chlorine or chloramine
  • Difficult to identify and not normally screened for by water treatment facilities
  • Disease is usually self-limited in immunocompetent hosts
illustrative points
Illustrative Points
  • Importance of evaluating air, water, and food supply in epidemic illness
  • Relevant history regarding event
  • Symptoms, evaluations of patients
  • Impact on water-quality standards
  • Impact on U.S. public health including impact on HIV/AIDS awareness
case study 2
Case Study #2
  • In January of 2003, a resident of Hebbronville, TX contacted the Texas Department of Health concerned about elevated arsenic (As) levels in drinking water

Hebbronville Library

  • Agency for Toxic Substances and Disease Registry (ATSDR) conducted an evaluation of local residents and water supply
  • Water supply:
    • Arsenic levels in the drinking water ranged from 43.7 to 52.1 µg/L
    • Prior to 2006, the maximum contaminant level for As was 50 µg/L

Home of the Hebbronville Longhorns

evaluation of population
Evaluation of Population
  • 2/3 of the 140 people sampled had urinary inorganic As concentrations > reference concentration of 10 µg/L
  • Drinkers of tap water had higher-than-reference range levels
  • Drinkers of bottled water had substantially lower levels.

Hebbronville Courthouse

evaluation of population16
Evaluation of Population
  • According to the ATSDR 91% of the population described themselves as Hispanic
  • Typical regional diet included rice and beans cooked in water - potentially increasing arsenic consumption:
    • 8-9 µg As per serving of rice
    • 20-24 µg As per serving of beans

(if cooked in water containing 50 µg/L)

actions recommended in hebronnville
Actions Recommended in Hebronnville
  • Those with inorganic As levels > 20 µg/g of creatinine to be retested
  • Individuals encouraged to discuss their results with a personal health care provider
  • Evaluation of other (dietary) sources of As
  • Efforts to reduce As levels in the public water system.
  • Unclear what, if any, health effects would be expected
  • Possible parallels to areas such as Taiwan and Bangladesh that have experienced high levels of environmental arsenic
  • Borders India and Burma
  • Local water wells were commonly contaminated with disease-causing microorganisms
bangladesh water supply
Bangladesh Water Supply
  • UNICEF and other international organizations promote the use of “tube wells” for safer water supply in the 1970’s and 1980’s
    • Thin tubes sunk in ground; usually < 200 meters in depth
    • Resulted in high levels of arsenic in soil leached into water, first confirmed in 1993
quantification of arsenic exposure
Quantification of Arsenic Exposure
  • In 1980’s first reports of arsenic-related dermatologic disease
  • Analysis of water in British Geological Survey showed that >35% of wells contained

> 50 g As/L

    • In some districts >80% of wells contained greater than 50 g As/L
    • 8% had As concentrations of

> 300 g/L

chronic arsenic toxicity
Chronic Arsenic Toxicity
  • Approximately 125 million residents drawing from water supply
  • In some studies 30-50% of patients had skin lesions due to arsenic
    • Skin lesions typically develop after latency of 10 years
public health implications
Public Health Implications
  • Other potential long-term effects of arsenic exposure:
      • Cancers, including skin, bladder, kidney and lung
      • Neurological effects
      • Hypertension, vascular disease
      • Pulmonary disease
      • Diabetes

Environmental Health Perspectives Volume 110, Number 2, February 2002

public health issues bangladesh
Public Health Issues - Bangladesh
  • How to treat the millions of exposed patients?
    • Nutritional supplementation?
    • Infected hyperkeratotic lesions?
  • What about tremendous predicted expense from excess cancer morbidity/mortality?
toxicological and environmental specifics
  • Farm chemicals
  • Perchlorates
  • Solvents
  • Arsenic
  • Microbiological Agents
occurrence of nitrite nitrate
Occurrence of Nitrite/Nitrate
  • Naturally occurring inorganic ions
    • Enter groundwater from fertilizer use, including anhydrous ammonia
    • Releases totaled over 110 million pounds
    • Contamination from septic systems
  • Chemical characteristics lead to migration to ground water
  • Groundwater supplies 20% of nitrate intake, but can be higher in the setting of water contamination
  • MCL for nitrates has been set at 10 ppm, and for nitrites at 1 ppm
    • US Geological survey in 1995 showed >8,000 wells had levels exceeding 10 ppm
    • 1-2% of population estimated to be exposed to excessive levels of nitrates
  • >600,000 homes draw from contaminated wells and rural wells are not routinely tested
health effects
Health Effects
  • Nitrites and nitrates cause oxidation
  • Nitrates are converted in vivo to nitrites
    • More potent oxidizers
  • Oxidation of iron in hemoglobin results in methemoglobinemia
  • Oxidized hemoglobin unable to carry oxygen effectively
  • Infants at risk due to:
    • Increased levels of fetal hemoglobin
    • Reduced levels of methemoglobin reductase
  • One cause of infantile cyanosis or “Blue-baby syndrome”
  • Has resulted in numerous infant deaths
methemoglobinemia treatment
Methemoglobinemia Treatment
  • Supportive care
  • Removal from exposure
  • Reducing agents such as methylene blue
  • Antioxidants such as vitamin C
toxicological and environmental specifics32
  • Farm chemicals
  • Perchlorates
  • Solvents
  • Arsenic
  • Microbiological Agents
  • Naturally occurring (e.g. in saltpeter deposits)
  • Magnesium, potassium, sodium, lithium, ammonium perchlorate are manufactured in large amounts
    • Uses include: solid rocket fuel, ammonium perchlorate, explosives
  • Perchlorates are the primary oxidizers in solid rocket fuel
  • Perchlorates are also very stable in water
  • EPA reports that 40 of 1547 National Priority Sites contain perchlorates
    • Leaves soil to enter water
      • May persist for years
    • No proven method for removal from water
  • Exposure pathways may include:
    • Drinking contaminated water
    • Also may occur through tobacco use
    • Proximity to industrial use of perchlorates
perchlorate contamination
Perchlorate Contamination
  • In 1997 perchlorates were discovered in drinking water
  • Primarily affects Western States

Environmental Science and Technology/News May 1, 1998

health effects38
Health Effects
  • Perchlorates effect the thyroid
    • Interferes with the thyroid’s ability to take up iodide
    • Clinical relevance is unclear
    • Human studies generally report insufficient evidence to determine risk of carcinogenesis
toxicological and environmental specifics39
  • Farm chemicals
  • Perchlorates
  • Solvents
  • Arsenic
  • Microbiological Agents
solvents including mtbe
Solvents - including MTBE
  • Methyl-t-butyl-ether
    • Manufactured by reaction of methanol and isobutylene
    • Flammable liquid with disagreeable odor
    • Evaporates quickly
    • Added (like ethanol) to gasoline as an oxygenator to decrease carbon monoxide emissions.
potential exposure pathways
Potential Exposure Pathways
  • Possible ingestion of MTBE in water
    • Concentration dependant
  • Dermal exposure while showering or swimming
    • Medically important systemic absorption is unlikely
mtbe possible health effects
MTBE - possible health effects
  • Any adverse effects are expected to be a function of exposure and dose
  • Vapor exposure (at high concentration for prolonged periods) may have mild but reversible effects
  • Ingestion
    • Potential cancer risk is unproven
      • Not classified by the IARC
      • Only weak evidence of carcinogenicity in some animal studies
water purity standards
Water Purity Standards
  • EPA recommends < 4 mg MTBE/Liter
  • State-specific limits exist
  • Taste/odor threshold is 20-40 ppb
toxicological and environmental specifics44
  • Farm chemicals
  • Perchlorates
  • Solvents
  • Arsenic/Heavy Metals
  • Microbiological Agents
heavy metal occurrence
Heavy Metal Occurrence
  • Mostly natural
    • Mineral deposits
    • Natural soil constituents
  • Increased levels may exist at some industrial sites
potential exposure pathways46
Potential Exposure Pathways
  • Contaminated water supply
  • Food grown in contaminated soil or with contaminated water
potential health effects arsenic
Potential Health Effects - Arsenic
  • Acute
    • Possible GI illness, neuropathy
    • Uncommon from environmental exposure
    • Intentional exposures
      • Suicidal
      • Homicidal
  • Chronic
    • Dermatologic, vascular and malignant disease
    • Environmental exposure
      • Bangladesh
treatment for arsenic metals
Treatment for Arsenic/Metals
  • For chronic exposure the treatment is REMOVAL FROM EXPOSURE
  • For acute exposure, consultation with a Poison Control Center or medical toxicologist is advisable
    • Chelation may be considered in some extreme cases
toxicological and environmental specifics49
  • Farm chemicals
  • Perchlorates
  • Solvents
  • Arsenic
  • Microbiological Agents
microbiological water contamination
Microbiological Water Contamination
  • Several broad categories, including:
    • Bacterial
    • Protozoa
    • Viruses
bacterial contamination
Bacterial Contamination
  • Traveller’s diarrhea
    • Up to 50% of international travelers may be afflicted depending on region
      • Approximately 10 million people
    • High-risk areas
      • Latin/Central America
      • Africa
      • Middle-East
      • Asia
traveller s diarrhea
Traveller’s Diarrhea
  • Caused by infectious agents
    • Primarily Escherichia coli
      • Produces enterotoxins
    • Watery diarrhea lasting several days

E.coli 0157:H7

traveller s diarrhea53
Traveller’s Diarrhea
  • Prevention:
    • Avoidance of local waters and ice
    • Bottled water for consumption
    • Daily bismuth (e.g.Pepto-Bismol) preparations
    • Avoidance of strong antacids (PPIs)
    • Possibly prophylactic antibiotics for select patients
  • Usually self-limited
  • Only symptomatic treatment usually required
  • Antibiotics (sulfa drugs, quinolones) may slightly reduce duration of illness
  • Enteroinvasive disease caused by any of several organisms
    • Salmonella, Shigella, Campylobacter
  • Bloody mucoid diarrhea with fever, fecal leukocytes
  • Antibiotic treatment recommended

Salmonella infantis

protozoal infections
Protozoal Infections
  • Common cause of endemic diarrheal illness
  • Typically spread through fecal-oral transmission
  • Common types include
    • Cryptosporidium
    • Giardia
cryptosporidium parvum
Cryptosporidium parvum
  • Worldwide presence in water supply
    • Not effectively killed by chemical purification methods
  • Prevention through
    • Boiling of drinking water
    • Water filtration with 1 micron pores

Life Cycle of Cryptosporidium and Infection of Host Epithelial Cells

Chen X et al. N Engl J Med 2002;346:1723-1731

cryptosporidium health effects
Cryptosporidium - Health Effects
  • Watery diarrhea lasting 1-2 weeks in normal hosts
  • May result in dehydration, weight-loss
  • Usually self-limited, but may be severe in immunocompromised hosts
    • Treatment includes anti-retrovirals for those with HIV
    • Possible role for nitrazoxanide
giardia lamblia
Giardia Lamblia
  • Very common parasitic disease
  • More common in warmer climates
  • Prevention is similar to measures for cryptosporidium
    • Boiling of water
    • Filtration
      • Reverse osmosis
      • 1 micron pores
viral diseases
Viral Diseases
  • Multiple viral pathogens
    • Rotaviruses
    • Hepatitis A
    • Enteroviruses
  • Most common epidemic (not endemic) diarrheal illnesses
  • No specific treatment
norwalk virus
Norwalk Virus
  • Common cause of epidemic diarrheal illness
  • Responsible for recent outbreaks on cruise ships
  • Hygiene
    • Reduce fecal-oral transmission
    • Hand-washing
    • Sanitization of surfaces
  • Vaccination
    • Effective for hepatitis A prevention

Reported Cases of Hepatitis A, United States

1995: Vaccine Licensed

1996: ACIP recommendations

1999 ACIP recommendations

Source: NNDSS, CDC


States with Hepatitis A Rates > 10/100,000 1987-97

Rate > 20/100,000

Rate 10-20/100,000

Rate < 10/100,000

Number of years that Reported Incidence of

Hepatitis A Exceeded 10 Cases per 100,000,

by County, 1987-1997


Rate per 100,000

> = 20

10 - 19

5 - 9

0 - 4

Hepatitis A Incidence, United States

1987-97 average incidence

2002 incidence


Approach to the Evaluation and Management of Infectious Diarrhea

Thielman N and Guerrant R. N Engl J Med 2004;350:38-47

water as a terrorist target
Water as a Terrorist Target
  • Watersheds and reservoirs contain a centralized depot of an essential resource for large numbers of people
  • Often inadequately protected
  • Impossible to monitor for all possible pathogens at all times
prevention of water terrorism
Prevention of Water Terrorism
  • Certain chemical properties of water are monitored continuously
  • Very large volume of water
    • Would require very large amounts of toxins to reach harmful levels
    • Attractive terrorism agents would have to be extraordinarily potent to be effective (such as botulinum toxin)
clinical problem solving
Clinical Problem Solving
  • 40 patients present over a 2-3 day period with GI illness
    • Watery diarrhea
    • Crampy abdominal pain
    • No fever/vomiting
  • No occupational, social, or family connection between most patients
key physician actions
Key Physician Actions
  • Recognize cluster of illnesses
  • Try to find shared exposure
    • Attendance at a gathering
      • Family/workplace picnic etc.
    • Eating at same restaurant or similar unusual foods
    • Face-to-face contact (same school, workplace)
  • Some hospitals receive many more patients than others
  • Most patients come from same geographic area
  • No particular meals, restaurants, or workplaces occur with greater than expected frequency
  • Comparing geographical distribution of patients to water distribution plans reveals that areas affected all receive water from same reservoir and treatment plant.
role of community physician
Role of Community Physician
  • Physicians are on the “front-line”
  • They are the interface between the public and the public health agencies
  • Therefore, physicians must treat not only individual patients, but be vigilant to protect and treat their entire community
key physician actions77
Key Physician Actions
  • Recognition of illness cluster
  • Recognition of probable environmental illness
  • Development of rational evaluation and treatment options
  • Reporting responsibilities
    • Contact the CDC and local public health officials
treatment and disposition of patients
Treatment and Disposition of Patients
  • Evaluate and resuscitate as necessary
    • Identify and treat dehydration
    • Check stool for blood and/or fecal leukocytes to screen for enteroinvasive disease (dysentery)
    • Symptomatic treatment
  • Obtain stool cultures, send stool for evaluation for ova and parasites
  • http://www.atsdr.cdc.gov/hac/pha/hebbronville/hae_p1.html#sum
  • Agency for Toxic Substances and Disease Registry. 2001. Case studies in environmental medicine: taking an exposure history. Atlanta: US Department of Health and Human Services
  • American Academy of Pediatrics. 1970. Policy statement. Infant methemoglobinemia: the role of dietary nitrate. Pediatrics 46(3):475-8
  • U.S. EPA. Integrated Risk Information System: Perchlorate and Perchlorate Salts. 2/18/2005
  • U.S. EPA. Assessment Guidance for Perchlorate. January 26, 2006
  • Chen X.-M. et al. Current Concepts: Cryptosporidiosis. N Engl J Med 2002; 346:1723-1731, May 30, 2002.
  • Thielman NM, Guerrant RL. Acute Infectious Diarrhea. N Engl J Med 2004; 350:38-47, Jan 1, 2004