- Boston, Mass. -- Increased precipitation
caused by global warming may increase flooding in some areas, which could
lead to drinking water contamination, so a team of Penn State economists
is investigating the economic costs associated with a possible increase
of waterborne diseases due to climate change.
- "Cryptosporidiosis is one of many
waterborne diseases whose prevalence could increase with increased precipitation
and flooding triggered by climate change," says Dr. Patricia L. Kocagil,
postdoctoral associate in agricultural economics.
- According to the Centers for Disease
Control in Atlanta, Cryptosporidium parvum, a protozoan parasite, was first
recognized in 1976 as producing illness in humans. Causing a diarrheal
disease that lasts for one to two weeks in healthy individuals, Cryptosporidium
can be fatal among immunocompromised persons.
- The researchers, who include Kocagil;
Dr. Ann Fisher, senior scientist; and Dr. James Shortle, professor of agricultural
economics, are looking at Lancaster County, Pa., to evaluate and assess
the problems and costs associated with Cryptosporidiosis outbreaks and
the increased risks with global warming.
- "So far, there is no medication
to cure Crypto, tests for the organism are not routinely done on water
supplies, and current detection technology is not always reliable,"
- Evaluating what is known about this disease,
the researchers told attendees at the spring meeting of the American Geophysical
Union Meeting today (May 26) that the cost to society of a current outbreak
is about $211 per person. This includes the actual costs of medical care,
such as the costs of medication, hospitalization and physicians' services,
as well as the cost of time lost from work and leisure activities. Added
to that is the cost of trying to avert an outbreak with "boil water"
edicts and purchasing or hauling water.
- "But this is for an outbreak today,
under current circumstances," says Kocagil. "Things could change
as climate changes."
- Even today, an outbreak can be costly
in both dollars and human suffering. In 1993, during an outbreak in Milwaukee,
Wisconsin, 400,000 people became ill.
- One problem assessing the impact of this
disease in an altered climate regime is the prevalence of very tiny Cryptosporidium
oocysts -- the protozoan equivalent of a fertilized chicken egg. Reservoirs
for Cryptosporidium exist in livestock, such as cattle and dairy cows and
wildlife such as deer. Runoff from agricultural areas can release the Cryptosporidium
oocysts into the drinking water supply.
- Another problem is that the standard
purification approach for drinking water in the United States, chlorination,
has little effect on the organism. Filtration can remove the oocysts, but
because of their small size, filters must be properly monitored and managed.
The U.S. Environmental Protection Agency is currently proposing expanding
water treatment requirements to safeguard water supplies from Cryptosporidium.
- "We are looking at a situation where
there is no known medical cure, where water treatment must be closely monitored
because standard purification methods do not work, where testing of water
is not routinely carried out and where routine screening for the disease
only takes place in previously immunocompromised individuals," says
Kocagil. "What happens now if global warming increases the frequency
of a 100-year flood to every 50 years?"
- The researchers have estimated that doubling
of the frequency of 100 year floods could add up to $70 to the per person
cost under certain conditions.
- "Part of the problem is that we
do not know how prevalent this disease is now," says Kocagil. "Many
people do not go to the doctor with diarrheal diseases that clear up on
- It was only in 1982, when the number
of cases among HIV-infected people began to rise that outbreaks among immunocompetent
people were reported.
- What level of oocyst in the water is
acceptable? Should all drinking water sources be tested? Should tests for
Cryptosporidium become routine in diarrheal outbreaks? When should a "boil
water" directive be issued and when should one be rescinded?
- "There are gaps in scientific understanding
and available data for assessing the magnitude of drinking water health
threats today," says Kocagil. "This makes it very difficult to
assess the drinking water problems under a global warming scenario."