Transcript Water Contamination - AOEC

Drinking Water Contamination
AOEC Teaching Module
2007
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 for
Toxic 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.
Outline
• 2 Introductory case
studies
• Examples of specific
toxicants
–
–
–
–
Farm chemicals
Perchlorate
Heavy Metals
Biologicals
• Clinical problem solving
Objectives
• 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
• 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
Southern Water Treatment Plant
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
• 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
Investigation
• 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
• 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 selflimited in immunocompetent
hosts
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
• 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
Hebbronville, TX
Hebbronville
• 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
• 2/3 of the 140 people
sampled had urinary
inorganic As
concentrations >
reference concentration
of 10 µg/L
• Drinkers of tap water
had higher-thanreference range levels
• Drinkers of bottled
water had substantially
lower levels.
Hebbronville Courthouse
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
• 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.
Implications
• 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
Bangladesh
• Borders India and Burma
• Local water wells were
commonly contaminated
with disease-causing
microorganisms
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
• 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
% of Field-tests positive for As
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
• Other potential longterm 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
• 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
• 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
Exposure
• 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
• Nitrites and nitrates cause
oxidation
• Nitrates are converted in
vivo to nitrites
– More potent oxidizers
• Oxidation of iron in
hemoglobin results in
methemoglobinemia
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
• Supportive care
• Removal from exposure
• Reducing agents such
as methylene blue
• Antioxidants such as
vitamin C
TOXICOLOGICAL AND
ENVIRONMENTAL
SPECIFICS
•
•
•
•
•
Farm chemicals
Perchlorates
Solvents
Arsenic
Microbiological
Agents
Perchlorates
• 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
• Perchlorates are the
primary oxidizers in
solid rocket fuel
• Perchlorates are
also very stable in
water
Exposure
• 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
• Exposure pathways
may include:
– Drinking
contaminated water
– Also may occur
through tobacco use
– Proximity to
industrial use of
perchlorates
Perchlorate Contamination
• In 1997
perchlorates
were
discovered
in drinking
water
• Primarily
affects
Western
States
Environmental Science and Technology/News May 1, 1998
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
SPECIFICS
•
•
•
•
•
Farm chemicals
Perchlorates
Solvents
Arsenic
Microbiological Agents
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
• Possible ingestion of MTBE in water
• Concentration dependant
• Dermal exposure while showering or swimming
– Medically important systemic absorption is unlikely
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
• EPA recommends < 4 mg MTBE/Liter
• State-specific limits exist
• Taste/odor threshold is 20-40 ppb
TOXICOLOGICAL AND
ENVIRONMENTAL
SPECIFICS
•
•
•
•
•
Farm chemicals
Perchlorates
Solvents
Arsenic/Heavy Metals
Microbiological Agents
Heavy Metal Occurrence
• Mostly natural
– Mineral deposits
– Natural soil constituents
• Increased levels may exist at some
industrial sites
Potential Exposure Pathways
• Contaminated water supply
• Food grown in contaminated soil or with
contaminated water
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
• 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
SPECIFICS
•
•
•
•
•
Farm chemicals
Perchlorates
Solvents
Arsenic
Microbiological Agents
Microbiological Water
Contamination
• Several broad categories, including:
– Bacterial
– Protozoa
– Viruses
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
• Caused by
infectious agents
– Primarily Escherichia
coli
• Produces
enterotoxins
– Watery diarrhea
lasting several days
E.coli 0157:H7
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
Treatment
• Usually self-limited
• Only symptomatic treatment usually
required
• Antibiotics (sulfa drugs, quinolones)
may slightly reduce duration of illness
Dysentery
• Enteroinvasive disease
caused by any of
several organisms
– Salmonella, Shigella,
Campylobacter
Salmonella infantis
• Bloody mucoid diarrhea
with fever, fecal
leukocytes
• Antibiotic treatment
recommended
Protozoan Infections
Protozoal Infections
• Common cause of
endemic diarrheal
illness
• Typically spread
through fecal-oral
transmission
• Common types include
– Cryptosporidium
– Giardia
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
• 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
• 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
• Multiple viral pathogens
– Rotaviruses
– Hepatitis A
– Enteroviruses
• Most common epidemic
(not endemic) diarrheal
illnesses
• No specific treatment
Norwalk Virus
• Common cause of
epidemic diarrheal
illness
• Responsible for
recent outbreaks on
cruise ships
Prevention
• Hygiene
– Reduce fecal-oral
transmission
– Hand-washing
– Sanitization of
surfaces
• Vaccination
– Effective for hepatitis
A prevention
Reported Cases of Hepatitis A, United States
45
40
1995: Vaccine Licensed
1996: ACIP recommendations
Rate per 100,000
35
30
1999 ACIP
recommendations
25
20
15
10
5
0
52
Source: NNDSS, CDC
56
60
64
68
72
76
Year
80
84
88
92
96 2002
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
0-1
2-3
4-5
6-7
8-10
Hepatitis A Incidence, United States
1987-97 average incidence
2002 incidence
NYC
DC
NYC
DC
rate per 100,000
0-4
>=20
5-9
10-19
Rate per 100,000
> = 20
10 - 19
5-9
0-4
rate per 100,000
0-4
>=20
5-9
10-19
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
• 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
• 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
• 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
• 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)
Observations
• 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
Investigation
• 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
• 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 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
• 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
References
• http://www.atsdr.cdc.gov/hac/pha/hebbr
onville/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
References
• American Academy of Pediatrics. 1970.
Policy statement. Infant
methemoglobinemia: the role of dietary
nitrate. Pediatrics 46(3):475-8
References
• 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