a diet of other fish. Methylmercury levels in the
flesh of these kinds of fish are higher than in other
kinds of fish. The advisory recommends that preg-
nant women and women who are BREASTFEEDING
avoid eating these kinds of fish. Salmon, cod, alba-
core tuna, pollock, haddock, ocean perch, tilapia,
and fresh-water trout have the lowest levels of
mercury.
Thimerosal, a common preservative in vaccines
and some other biologic agents, contains mercury.
Though pharmaceutical manufacturers are mov-
ing away from its use, thimerosal remains a con-
cern especially with childhood vaccinations.
Individuals should ask for thimerosal-free vaccines
and other biologic agents for themselves and for
their children. US health agencies have called for
the complete eradication of thimerosal as a medic-
inal preservative.
Copper Though copper occurs in nature, the
most common source of human exposure to cop-
per is through water supplies that travel through
copper pipes. Water that is highly acidic corrodes
the pipes, drawing copper into the water. Exces-
sive copper accumulations in the body can cause
irreversible LIVERand KIDNEYdamage. Copper also
can accumulate in the brain, causing cognitive
dysfunction. People who have WILSON’S DISEASE, a
hereditary disorder in which the body cannot
metabolize copper, are especially vulnerable to
copper in the food supply and the environment
because copper accumulates in their bodies. The
body needs only a very small amount of copper,
which it uses to make certain enzymes and to
facilitate iron METABOLISMfor HEMOGLOBINproduc-
tion.
Iron The body needs iron to produce hemoglo-
bin, the protein in the blood that binds with oxy-
gen. Iron deficiency is fairly common, and many
people take iron supplements. These supplements
are the most frequent source for iron poisoning,
especially among young children. Excessive
amounts of iron in the body slow the HEART RATE
and force of contractions, reducing the flow of
blood. Other chemical changes that take place at
the molecular level affect the ability of cells
throughout the body to function. People who
have the hereditary condition HEMOCHROMATOSIS
cannot properly metabolize iron, resulting in toxic
accumulations over years to decades. Iron is also
highly toxic to the liver, resulting in hepatonecro-
sis (death of hepatocytes, the primary functional
cells in the liver).
See also DRINKING WATER STANDARDS; POISON PRE-
VENTION.hepatitis prevention Although acute (sudden
and limited) HEPATITISinfections are on the decline
in the United States, chronic hepatitis infections
(long-term) have reached epidemic proportions.
Nearly a third of the US population has had hepa-
titis A INFECTION, an acute form of the disease that
is sudden and limited. While the numbers of new
cases are dropping each year because of vaccina-
tion and education efforts, hepatitis A remains a
significant health threat because it can so easily be
transmitted from one person to another. Hepatitis
A spreads via oral–fecal contamination as a conse-
quence of failing to wash the hands after using the
bathroom. This spreads the VIRUS to items the
infected person touches. A significant source of
infection is contaminated uncooked foods such as
salads. Hepatitis A outbreaks can sweep through
schools, day care centers, cruise ships, prisons, and
other environments in which large groups of peo-
ple are in close contact.
Another 7 percent of Americans have chronic
forms of hepatitis, either hepatitis B or hepatitis C.
The rate of infection for chronic hepatitis is high-
est among injectable DRUGusers and homosexual
men (because of bodily fluid contact). Health-care
and public safety workers are also at high risk for
infection as a result of occupational exposures.
However, hepatitis is so pervasive that anyone can
become infected without being aware they have
been exposed. Some people can carry hepatitis
without themselves being sick and usually do not
know they are carriers. Yet they can spread the
hepatitis virus to others.
Of the five most common hepatitis viruses,
fecal–oral contact is the primary infectious route
for two: hepatitis A and hepatitis E. These forms of
hepatitis are generally acute (sudden and limited).
Blood and body fluid contact, such as via sexual
intercourse and shared needles among injectable
drug users, spread hepatitis B and hepatitis C.
Hepatitis D is a risk only for people infected with
hepatitis B, as it can replicate only by “hijacking”
the hepatitis B virus’s genetic material.hepatitis prevention 31