Movement and Fate of Toxicants 81many governments and individuals. The virus often origi-
nates in areas that have dense populations of domestic
animals, especially chickens and pigs, raised in small
cages or close to human households (Figure 4.7). In the
past decade, large numbers of domestic pigs, cows, and
poultry have been killed and burned to prevent or stop
disease outbreaks.
Researchers believe that many diseases could be-
come more prevalent as the climate changes, both
because temperature increases will extend the range of
cold-intolerant diseases and because increased humid-
ity and rainfall will benefit other diseases. For example,
mosquito-borne diseases such as malaria and West Nile
virus are expected to expand north and south both be-
cause winter temperatures will remain above those that
kill mosquitoes and because there may be more standing
water to harbor mosquito larvae.- What is the difference between toxicology and
epidemiology? - Why is the fecal coliform test performed on
public drinking water supplies? - How is the incidence of swine flu related to
human activities that alter the environment?
Bay Ismoyo/AFP/Getty Images, Inc.People and livestock in close
«ÀÝÌÞÊUÊ}ÕÀiÊ{°ÇÊÊ
These children in rural Jiangxi, China, live and play near where
pigs are raised. Humans and livestock, including chickens and
pigs, share enough genetic similaries that some diseases can
be transferred from species to species. This includes the swine
flu epidemic of 2009, which started in rural Mexico and spread
around the world in a matter of months.
Understanding and controlling an influenza pan-
demic requires study of the environment that allows the
virus to survive and travel, as well as cooperation among
pesticides, radioactive isotopes, heavy metals such as
mercury, flame retardants such as PBDEs (polybromi-
nated diphenyl ethers), and industrial chemicals such
as PCBs (polychlorinated biphenyls).
Mercury is the only metal that is liquid at room tem-
perature. As such, it moves readily through air, water,
and land. Mercury can cause brain and nerve damage,
loss of hair, and even death.
The effects of the pesticide DDT (dichlorodiphen-
yltrichloroethane) on many bird species demonstrate
the problem. Falcons, pelicans, bald eagles, and many
other birds are sensitive to traces of DDT in their tissues.Movement and Fate of Toxicants
LEARNING OBJECTIVES
- Distinguish among persistence, bioaccu mulation,
and biological magnification of toxicants. - Discuss the mobility of persistent toxicants in
the environment. - Describe the purpose of the Stockholm
Convention on Persistent Organic Pollutants.
S
ome chemically stable toxicants are par-
ticularly dangerous because they resist
degradation and readily move around in
the environment. These include certain