Environmental Encyclopedia

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Environmental Encyclopedia 3

Chesapeake Bay

surrounding Chesapeake Bay was rapidly colonized by Euro-

peans. In many ways, the United States grew up around

Chesapeake Bay. The colonists harvested the Bay’s resources

and used its waterways for

transportation

. Today 10 million

people live in the Chesapeake Bay’s drainage basin, and

many of their activities affect the environmental quality of

the Bay as did the activities of their ancestors.

The rivers emptying into the Bay were also used by

the colonists to dispose of raw sewage. By the middle 1800s

some of the rivers feeding the Bay were polluted: the Poto-

mac was recorded as emitting a lingering stench. The first

sewer was constructed in Washington, DC, and it pumped

untreated waste into the Bay. It was recognized in 1893 that

the diseases suffered by humans consuming shellfish from

the Bay were directly related to the

discharge

of raw sewage

into the Bay. Despite this recognition, efforts in 1897 by

the mayor of Baltimore to oppose the construction of a

sewage system that discharged sewage into the Bay in favor of

a “land

filtration

technique” failed. Ultimately, a secondary

treatment system discharging into the Bay was constructed.

In the mid-1970s, a $27 million government-funded study

of the Bay’s condition concluded that the deteriorating qual-

ity of the Chesapeake Bay was a consequence of human

impacts. But it was not until the early 1980s that an

Environ-

mental Protection Agency

(EPA) report on the Chesa-

peake focused interest on saving the Bay, and $500 million

was spent on cleanup and construction of

sewage treat-

ment

plants.

While the Chesapeake Bay is used primarily as a trans-

portation corridor, its natural resources rank a close second

in importance to humans. The most commercially important

fisheries in the Bay are the native American oyster (Crassos-

trea virginica), blue crab (Callinectes sapidus), American shad

(Alosa sapidissima), and striped bass (Marone saxatilis). Fish-

erman first began to notice a decline in fish populations in

the 1940s and 1950s, and since then abundances have de-

clined even further. Since the turn of the century, the oyster

catch has declined 70%, shad 85%, and striped bass 90%.

In the late 1970s, the EPA began to study the declining

oyster and striped bass populations and concluded that their

decline was due to a combination of over-harvesting and

pollution

Work by the EPA and other federal and state agencies

has identified six areas of environmental concern for the

Bay: (1) excess

nutrient

input from both sewage treatment

plants discharging into the Bay and

runoff

from agricultural

land; (2) low oxygen levels as a result of increased

biochemi-

cal oxygen demand

, which increases dramatically with

of organic material; (3) loss of

submerged aquatic

vegetation

due to an increase in turbidity; (4) presence

of chemical

toxins

; (5) loss to development of

wetlands

surrounding the Bay that serve as nurseries for juvenile fish

237

and shellfish and as buffers for runoff of nutrients and toxic

chemicals

; and (6) increasing acidity of water (measured by

) in streams that feed the Bay. These streams are also

nursery areas for larval fish that may be adversely affected

by decreasing pH.

The increasing growth of phytoplankton—free-float-

ing single- celled plants—in the Bay is generally considered

to be a significant contributor to the decline in environmental

quality of the Chesapeake Bay. The number of algal blooms

has increased dramatically since the 1950s and is attributed

to the high levels of the plant nutrients

nitrogen

and

phos-

phorus

that are discharged into the Bay. In the 1980s and

1990s, it was estimated that discharge from sewage treatment

plants and agricultural runoff accounted for 65% of the nitro-

gen and 22% of the phosphorus found in the Bay.

Acid rain

formed from discharges from industrial plants in Canada and

the northeast United States, contributed 25% of the nitrogen

found in the Bay. Excess nutrients encourage

phytoplank-

ton

growth, and as the large number of phytoplankton die

and settle to the bottom, their

decomposition

robs the

water of oxygen needed by fish and other aquatic organisms.

When oxygen levels fall too low, these organisms die or flee

from the regions of low oxygen. Decomposition of dead

organic matter further reduces the concentration of oxygen.

During the late twentieth and early twenty-first centuries,

Finfish and shellfish kills became increasingly common in

the Bay.

Phytoplankton blooms and the increase in suspended

sediments resulting from shoreline development and poor

agricultural practices have increased turbidity and led to

a decline in submerged aquatic vegetation (SAV) such as

eelgrass

. SAV is extremely important in the prevention of

erosion

of bottom

sediment

and as

critical habitat

for

nursery grounds of commercially important fish and

shellfish.

Chemicals introduced into the Bay from several sites

may have contributed to the decline in the Bay’s fish and

bird populations. For example, in 1975, the

pesticide Kep-

one

was leaked or dumped into the James River,

poisoning

fish and shellfish. Harvests of some

species

are still restricted

in the area of this spill.

Chlorine

biocides used in

waste-

water

treatment plants and

power plants

, which discharge

into the Bay, are known human carcinogens and can be toxic

to aquatic organisms.

Polycyclic aromatic hydrocarbons

(PAH) have caused dermal lesions in fish populations in the

Elizabeth River. PAHs also affect shellfish populations. In

the 1990s, public concern focused on

tributyl tin

(TBT)

that was used in anti-fouling paint on recreational and com-

mercial boats. TBTs belong to a family of chemicals known

as organotins, which are toxic to shellfish and crustaceans.

The diversity of chemical pollutants found in the Bay is

exemplified by the results of research that identified 100

Environmental Encyclopedia 3

Child survival revolution

inorganic and organic contaminants in striped bass caught

in the Bay. As of 2002, research efforts were underway to

determine the extent of the damage from toxins to natural

resources.

Work by private and governmental agencies has started

to reverse the declining environmental quality of the Chesa-

peake Bay. In 1983 Maryland, Virginia, Pennsylvania, the

District of Columbia, the Chesapeake Bay Commission, and

the EPA signed the Chesapeake Bay Agreement, which

outlined procedures to correct many of the Bay’s ecological

problems, particularly those caused by nutrient enrichment.

In 1987 the agreement was significantly expanded and re-

quired that the signatories adopt a strategy that would result

in at least a 40% reduction in nitrogen and phosphorus

entering the Bay by the year 2000. Since 1985, increasing

compliance with discharge permits, prohibition of the sale

of phosphate-based

detergents

, and the upgrading of

wastewater plants has resulted in a 2% reduction in the

discharge of nitrogen and a 39% reduction of phosphorous

from point sources of pollution. Controls on agriculture

and urban development have resulted in approximately 7%

reductions in the amount of both nitrogen and phosphorus

entering the Bay from nonpoint sources. The amount of

toxins entering the Bay have also been reduced. Tributyl tin

has been banned for use in anti-fouling paints on non-

military vessels, pesticide runoff has been reduced by using

alternate strategies for

pest

control, and since 1987, toxic

emissions from industrial sources have declined more than

40%. At the same time, some of the Bay’s critical habitats

are recovering: 22,000 more acres of SAVs are now growing

than in 1984, although the total amount of 60,000 acres is

still a fraction of the estimated 600,000 acres the historical

SAV distribution, man-made oyster reefs are being created

to expand suitable

habitat

for oysters, and rivers are being

cleared of obstacles such as

dams

and spillways to provide

access to spawning areas by migratory fish.

Conflict between commercial and environmental in-

terests have encumbered some of the restoration efforts.

Research on the life-history of crabs and oysters shows that

limiting the size of crabs that can be sold and the numbers

of oysters that can be harvested will help these fisheries

rebound, but regulations to limit crab and oyster catches

have met with strong

resistance

from watermen who are

struggling to survive economically in a declining fishery.

The planned introduction of a non-native Asian oyster

(Crassostrea ariakensis) by the Virginia Seafood Council,

raised hopes that a new oyster fishery could be built around

the harvest of this disease-resistant, fast-growing species. In

May 2002, the United States

Fish and Wildlife Service

called for a moratorium on the introduction of the Asian

oyster, until researchers could determine whether its intro-

duction would endanger native species, or bring new and

238

deadly disease organisms into Chesapeake Bay. A study by

the

National Academy of Sciences

was commenced in

2001 with the goal of making information on these concerns

available in summer of 2003.

As of 2002, portions of Chesapeake Bay and its tribu-

taries were still listed as impaired waters under Section

303(d) of the

Clean Water Act

, but progress on arresting

the decline of environmental quality of Chesapeake Bay and

restoring some of its natural resources continued. In the

Chesapeake 2000 Bay Agreement (C2K), Maryland, Penn-

sylvania, Virginia, and the District of Columbia, together

with the Chesapeake Bay Commission and the Federal Gov-

ernment committed to “correct the nutrient- and sediment-

related problems in the Chesapeake Bay and its tidal tributar-

ies sufficiently to remove the Bay and the tidal portions of

its tributaries from the list of impaired waters under the

Clean Water Act.” This consortium of stakeholders, jurisdic-

tions, and federal agencies is evidence that citizens, govern-

ment, and industry can work cooperatively. The Chesapeake

Bay program is a national model for efforts to restore other

degraded ecosystems.

[William G Ambrose Jr. and Paul E Renaud and Marie H.

Bundy]

ESOURCES

OOKS

Brown, L. R. “Maintaining World Fisheries.” In State of the World, edited

by L. Starke. New York: Norton, 1985.

Majumdar, S., et al. Contaminant Problems and Management of Living

Chesapeake Bay Resources. Easton, NJ: Typehouse of Easton, 1987.

ERIODICALS

D’Elia, C. “Nutrient Enrichment of the Chesapeake Bay.” Environment

29 (1987): 6-11.

RGANIZATIONS

Chesapeake Bay Foundation, Philip Merrill Environmental Center, 6

Herndon Avenue, Annapolis, MD 21403 410/268-8816, Email: http://

www.cbf.org/about_cbf/contact_us.htm

Child survival revolution

Every year in the developing countries of the world, some

14 million children under the age of five die of common

infectious diseases. Most of these children could be saved

by simple, inexpensive, preventative medicine. Many public

health officials argue that it is as immoral and unethical to

allow children to die of easily preventable diseases as it would

be to allow them to starve to death or to be murdered. In

1986, the United Nations announced a worldwide campaign

to prevent unnecessary child deaths. Called the “child sur-

vival revolution,” this campaign is based on four principles,

designated by the acronym GOBI.

Environmental Encyclopedia 3

Chimpanzees

“G” stands for growth monitoring. A healthy child is

considered a growing child. Underweight children are much

more susceptible to infectious diseases, retardation, and other

medical problems than children who are better nourished.

Regular growth monitoring is the first step in health mainte-

nance.

“O” stands for oral rehydration therapy (ORT). About

one-third of all deaths under five years of age are caused by

diarrheal diseases. A simple solution of salts, glucose, or rice

powder and boiled water given orally is almost miraculously

effective in preventing death from dehydration shock in these

diseases. The cost of treatment is only a few cents per child.

The British medical journal Lancet, called ORT “the most

important medical advance of the century.”

“B” stands for breast-feeding. Babies who are breast-

fed receive natural immunity to diseases from antibodies in

their mothers’ milk, but infant formula companies have been

persuading mothers in many developing countries that bot-

tle-feeding is more modern and healthful than breast-feed-

ing. Unfortunately, these mothers usually do not have access

to clean water to combine with the formula and they cannot

afford enough expensive synthetic formula to nourish their

babies adequately. Consequently, the

mortality

among bot-

tle-fed babies is much higher than among breast-fed babies

in developing countries.

“I” is for universal immunization against the six largest,

preventable,

communicable diseases

of the world: measles,

tetanus, tuberculosis, polio, diphtheria, and whooping

cough. In 1975, less than 10% of the developing world’s

children had been immunized. By 1990, this number had

risen to over 50%. Although the goal of full immunization

for all children has not yet been reached, many lives are being

saved every year. In some countries, yellow fever, typhoid,

meningitis,

cholera

, and other diseases also urgently need

attention.

Burkina Faso provides an excellent example of how a

successful immunization campaign can be carried out. Al-

though this West African nation is one of the poorest in

the world (annual gross national product per capita of only

$140), and its roads, health care clinics, communication,

and educational facilities are either nonexistent or woefully

inadequate, a highly successful “vaccination commando” op-

eration was undertaken in 1985. In a single three-week

period, one million children were immunized against three

major diseases (measles, yellow fever, and meningitis) with

only a single injection. This represents 60% of all children

under age 14 in the country. The cost was less than $1

per child.

In addition to being an issue of humanity and compas-

sion, reducing child mortality may be one of the best ways

to stabilize world

population growth

. There has never been

a reduction in birth rates that was not preceded by a reduction

239

in infant mortality. When parents are confident that their

children will survive, they tend to have only the number of

children they actually want, rather than “compensating” for

likely deaths by extra births. In Bangladesh, where ORT

was discovered, a children’s health campaign in the slums

of Dacca has reduced infant mortality rates 21% since 1983.

In that same period, the use of birth control increased 45%

and birth rates decreased 21%.

Sri Lanka, China, Costa Rica, Thailand, and the Re-

public of Korea have reduced child deaths to a level compara-

ble to those in many highly developed countries. This child

survival revolution has been followed by low birth rates and

stabilizing populations. The United Nations Children’s

Fund estimates that if all developing countries had been able

to achieve similar birth and death rates, there would have

been nine million fewer child deaths in 1987, and nearly 22

million fewer births. See also Demographic transition

[William P. Cunningham Ph.D.]

ESOURCES

OOKS

UNICEF. The State of the World’s Children. New York: Oxford University

Press, 1987.

Chimpanzees

Common chimpanzees (Pan troglodytes) are widespread in

the forested parts of West, Central, and East Africa. Pygmy

chimpanzees, or bonobos (P. paniscus), are restricted to the

swampy lowland forests of the Zaire basin. Despite their

names, common chimpanzees are no longer common, and

pygmy chimpanzees are no smaller than the other

species

Chimpanzees are partly arboreal and partly ground-

dwelling. They feed in fruit trees by day, nest in other trees

at night, and can move rapidly through treetops. On the

ground chimpanzees usually walk on all fours (knuckle walk-

ing), since their arms are longer than their legs. Their hands

have fully opposable thumbs and, although lacking a

preci-

sion

grip, can manipulate objects dexterously. Chimpanzees

make and use a variety of tools: they shape and strip “fishing

sticks” from twigs to poke into termite mounds, and they

chew the ends of shoots to fashion fly whisks. They also

throw sticks and stones as offensive weapons and hunt and

kill young monkeys.

These apes live in small nomadic groups of three to six

animals (common chimpanzee) or six to 15 animals (pygmy

chimpanzee) which make up a larger community (30–80

individuals) that occupies a territory. Adult males cooperate

in defending their territory against predators. Chimpanzee

Environmental Encyclopedia 3

Chipko Andolan movement

A chimpanzee (

Pan troglodytes

). (Photograph by

Nigel J. Dennis. Photo Researchers Inc. Reproduced by

permission.)(Photograph by Nigel J. Dennis. Photo Re-

searchers Inc. Reproduced by permission.)

society consists of fairly promiscuous mixed-sex groups. Fe-

male common chimpanzees are sexually receptive for only

a brief period in mid-month (estrous), while female pygmy

chimpanzees are sexually receptive for most of the month.

240

Ovulating females capable of fertilization have swollen pink

hind quarters and copulate with most of the males in the

group. Female chimpanzees give birth to a single infant after

a gestation period of about eight months.

Jane Goodall

has studied common chimpanzees for

almost 30 years in the Gombe Stream

National Park

Tanzania. She found that chimpanzee personalities are as

variable as those of humans, that chimpanzees form alliances,

have friendships, have personal dislikes, and run feuds.

Chimpanzees also have a cultural tradition, that is, they pass

learned behavior and skills from generation to generation.

Chimpanzees have been taught complex sign language (the

chimpanzee larynx won’t allow speech) through which ab-

stract ideas have been conveyed. These studies show that

chimpanzees can develop a large vocabulary and that they

can manipulate this vocabulary to frame new thoughts.

Humans share 98.4% of their genes with chimpanzees,

so only 1.6% of human DNA is responsible for all the

differences between the two species. The DNA of gorillas

differs 2.3% from chimpanzees, which means that the closest

relatives of chimpanzees are humans, not gorillas. Further

studies of these close relatives would undoubtedly help to

better understand the origins of human social behavior and

human

evolution

. Despite this special status, both species

of chimpanzees are threatened by the destruction of their

forest

habitat

hunting

and by capture for research.

[Neil Cumberlidge Ph.D.]

ESOURCES

OOKS

Diamond, J. M. The Third Chimpanzee: The Evolution and Future of the

Human Animal. New York: Harper Collins, 1992.

Goodall, Jane. Through a Window: My Thirty Years With the Chimpanzees

of Gombe. Boston: Houghton Mifflin, 1990.

Peterson, Dale, and Jane Goodall. Visions of Caliban: On Chimpanzees and

People. Boston: Houghton Mifflin, 1993.

ERIODICALS

“Chimp, Human Genes much alike, except for Brain.” USA Today (February

12, 2002).

Chipko Andolan movement

India has a long history of non-violent, passive

resistance

in social movements rooted in its Hindu concept of ahimsa,

or “no harm.” During the British occupation of India in the

early twentieth century, Indian leader Mohandas K. Gandhi

began to employ a method of resistance against the British

that he called satyagraha (meaning “force of truth"). Synthe-

sized from his knowledge of

Henry David Thoreau

, Leo

Tolstoy, Christianity and Hinduism, Gandhi’s concept of

satyagraha involves the absolute refusal to cooperate with a

Environmental Encyclopedia 3

Chlorinated hydrocarbons

perceived wrong and the use of nonviolent tactics in combi-

nation with complete honesty to confront, and ultimately

convert, evil.

During the occupation, the rights of peasants to gather

products, including forest materials, was severely curtailed.

New land ownership systems imposed by the British trans-

formed what had been communal village resources into the

private property of newly created landlords. Furthermore,

policies that encouraged commercial exploitation of forests

were put into place. Trees were felled on a large scale to

build ships for the British Royal Navy or to provide ties for

the expanding railway network in India, severely depleting

forest resources on which traditional cultures had long de-

pended.

In response to British rule with its forest destruction

and impoverishment of native people, a series of non-violent

movements utilizing satyagraha spread throughout India.

The British and local aristocracy suppressed these protests

brutally, massacring unarmed villagers by the thousands, and

jailing Gandhi a number of times, but Gandhi and his allies

remained steadfast in their resistance. The British, forced

to comprehend the horror of their actions and unable to

scapegoat the nonviolent Indians, at last withdrew from

India.

After India gained independence, two of Gandhi’s

disciples, Mira Behn and Sarala Behn, moved to the foothills

of the Himalayas to establish ashramas (spiritual retreats)

dedicated to raising women’s status and rights. Their project

was dedicated to four major goals: 1) organizing local

women, 2) campaigning against alcohol consumption, 3)

fighting for forest protection, and 4) setting up small, local,

forest-based industries.

During the 1970s, commercial loggers began large-

scale tree felling in the Garhwal region in the state of Uttar

Pradesh in northern India. Landslides and floods resulted

from stripping the forest cover from the hills. The firewood

on which local people depended was destroyed, threatening

the way of life of the traditional forest culture.

In April, 1973, village women from the Gopeshwar

region who had been educated and empowered by the princi-

ples of non-violence devised by the Behns began to confront

loggers directly, wrapping their arms around trees to protect

them. The outpouring of support sparked by their actions

was dubbed the Chipko Andolan movement (literally, “move-

ment to hug trees"). This crusade to save the forests eventu-

ally prevented

logging

on 4,633 mi

(12,000 km

) of sensi-

tive watersheds in the Alakanada basin. Today, the Chipko

Andolan movement has grown to more than four thousand

groups working to save India’s forests. Their slogan is: “What

do the forests bear?

Soil

, water, and pure air.”

The successes of this movement, both in empowering

local women and in saving the forests on which they depend,

241

are inspiring models for grassroots green movements around

the world.

[William P. Cunningham Ph.D. and Jeffrey Muhr]

URTHER

EADING

Bandyopadhyay, J., and V. Shiva. “Chipko: Rekindling India’s Forest Cul-

ture.” Ecologist 17 (1987): 26-34.

———. “Development, Poverty and the Growth of the Green Movement

in India.” Ecologist 19 (1989): 111-17.

Durning, A. B. “Environmentalism South.” Amicus Journal 12 (Summer

1990): 12-18.

Chisel plow

see

Conservation tillage

Chisso Chemical Company

see

Minamata disease

Chlordane

Chlordane and a closely related compound, heptachlor, be-

long to a group of chlorine-based pesticides known as cyclo-

dienes. They were among the first major

chemicals

to attract

national attention and controversy, mainly because of their

devastating effects on

wildlife

and domestic animals. By the

1970s, they had become two of the most popular pesticides

for home and agricultural uses (especially for termite con-

trol), despite links between these chemicals and the

poison-

ing

of birds and other wildlife, pets and farm animals, as

well as links to

leukemia

and other cancers in humans.

In 1975, environmentalists finally persuaded

Environ-

mental Protection Agency

(EPA) to issue an immediate

temporary ban on most uses of chlordane and heptachlor

based on an “imminent hazard of

cancer

in man.” In 1978,

when the EPA agreed to phase out most remaining uses of

chlordane and heptachlor, the agency stated that “virtually

every person in the United States has residues...in his body

tissues.” Chlordane has now been banned, at least temporar-

ily, for sale or use in the U.S. But potentially dangerous

levels of the chemical are still found occasionally in food-

stuffs, homes, and the

environment

Chlorinated hydrocarbons

Chlorinated

hydrocarbons

are compounds made of

car-

bon

hydrogen

, and

chlorine

atoms. These compounds

can be aliphatic, meaning they do not contain

benzene

,or

aromatic, meaning they do. The chlorine functional group

gives these compounds a certain character; for instance, the

Environmental Encyclopedia 3

Chlorination

aromatic organochlorine compounds are resistant to micro-

bial degradation; the aliphatic chlorinated solvents have cer-

tain anesthetic properties (e.g., chloroform); some are known

for their antiseptic properties (e.g., hexachloraphene). The

presence of chlorine imparts toxicity to many organochlorine

compounds (e.g., chlorinated pesticides).

Chlorinated hydrocarbons have many uses, including

chlorinated solvents, organochlorine pesticides, and indus-

trial compounds. Common chlorinated solvents are dichlo-

romethane (methylene chloride), chloroform, carbon tetra-

chloride, trichloroethane, trichloroethylene,

tetrachloroethane,

tetrachloroethylene

. These compounds

are used in drycleaning solvents, degreasing agents for ma-

chinery and vehicles, paint thinners and removers, laboratory

solvents, and in manufacturing processes, such as coffee

decaffeination. These solvents are hazardous to human

health and exposures are regulated in the workplace. Some

are being phased out for their toxicity to humans and the

environment

, as molecules have the potential to react with

and destroy stratospheric

ozone

The organochlorine pesticides include several sub-

groups, including the cyclodiene insecticides (e.g.,

chlor-

dane

, heptachlor, dieldrin), the DDT family of compounds

and its analogs, and the hexachlorocyclohexanes (often in-

correctly referred to as BHCs, or benzene hexachlorides).

These insecticides were developed and marketed extensively

after World War II, but due to their toxicity, persistence,

widespread environmental contamination, and adverse eco-

logical impacts, most were banned or restricted for use in

the United States in the 1970s and 80s. These insecticides

generally have low water solubilities, a high affinity for or-

ganic matter, readily bioaccumulate in plants and animals,

particularly aquatic organisms, and have long environmental

half-lives compared to the currently-used insecticides.

There are many chlorinated industrial products and

reagent materials. Examples include

vinyl chloride

, which

is used to make PVC (

polyvinyl chloride

)

plastics

; chlori-

nated benzenes, including hexachlorobenzene; PCB (poly-

chlorinated biphenyl), used extensively in electrical trans-

formers and capacitors; chlorinated phenols, including

pentachlorophenol

(PCP); chlorinated naphthalenes; and

chlorinated diphenylethers. They represent a diversity of

applications, and are valued for their low reactivity and high

insulating properties.

There are also chlorinated byproducts of environmen-

tal concern, particularly the polychlorinated dibenzo-p-diox-

ins (PCDDs) and the polychlorinated dibenzofurans

(PCDFs). These families of compounds are products of

incomplete

combustion

of organochlorine-containing ma-

terials, and are primarily found in the

fly ash

municipal

solid waste

incinerators. The most toxic component of

PCDDs, 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-

242

TCDD), was a trace contaminant in the production of the

herbicide 2,4,5-T

and is found in trace amounts in 2,4,5-

trichlorophenol and technical grade pentachlorophenol.

PCDDs and PCDFs can also be formed in the chlorine

bleaching process of

pulp and paper mills

, and have been

found in their

effluent

and in trace amounts in some paper

products.

[Deborah L. Swackhammer]

URTHER

EADING

Brooks, G. T. Chlorinated Insecticides. Cleveland, OH: CRC Press, 1974.

Chau, A. S. Y., and B. K. Afghan. Analysis of Pesticides in Water, Vol. II.

Boca Raton, FL: CRC Press, 1982.

Fleming, W. J., D. R. Clark, Jr. and C. J. Henny. Organochlorine Pesticides

and PCBs: A Continuing Problem for the 1980s. Washington, DC: U. S.

Fish and Wildlife Service, 1985.

Manahan, S. E. Environmental Chemistry, 5th ed. Ann Arbor, MI: Lewis

Publishers, 1991.

Chlorination

Chlorination refers to the application of

chlorine

for the

purposes of oxidation. The forms of chlorine used for chlori-

nation include: chlorine gas, hypochlorous

acid

(HOCl),

hypochlorite

ion

(OCl), and chloramines or combined chlo-

rine (Mono-, di-, and tri-chloramines). The first three forms

of chlorine are known as free chlorine.

Chlorine (Cl) has three valences under normal envi-

ronmental conditions, -1, 0 and +1. Environmental scientists

often refer only to the chlorine forms having 0 and +1

valences as chlorine; they refer to the -1 form as chloride.

Chlorine with a valence of 0 (Cl

) and chlorine with a valence

of +1 (HOCl) both have the ability to oxidize materials,

whereas chlorine at a -1 valence, chloride, is already at its

lowest oxidation state and has no oxidizing power.

The functions of chlorination are to disinfect water or

wastewater

, decolorize waters or fabrics, sanitize and clean

surfaces, remove iron and manganese, and reduce odors. The

fundamental principle of each application is that due to its

oxidizing potential, chlorine is able to effect many types of

chemical reactions. Chlorine can cause alterations in DNA,

cell-membrane porosity,

enzyme

configurations, and other

biochemicals; the oxidative process can also lead to the death

of a cell or

virus

. Chemical bonds, such as those in certain

dyes, can be oxidized, causing a change in the color of

a substance. Textile companies sometimes use chlorine to

decolorize fabrics or process waters. In some cases, odors

can be reduced or eliminated through oxidation. However,

the odor of certain compounds, such as some phenolics, is

aggravated through a reaction with chlorine. Certain soluble

metals can be made insoluble through oxidation by chlorine

Environmental Encyclopedia 3

Chlorination

(soluble Fe

is oxidized to insoluble Fe

), making the metal

easier to remove through

sedimentation

filtration

Chlorine is commercially available in three forms; it

can also be generated on-site. For treating small quantities

of water, calcium hypochlorite (Ca(OCl)

), commonly re-

ferred to as high test hypochlorite (HTH) because one mole

of HTH provides two OCl

ions, is sometimes used. For

large applications, chlorine gas (Cl

) is the most wide used

source of chlorine. It reacts readily with water to form various

chlorine

species

and is generally the least expensive source.

There are, however, risks associated with the handling and

transport of chlorine gas, and these have convinced some to

use sodium hypochlorite (NaOCl) instead. Sodium hypo-

chlorite is more expensive than chlorine gas, but less expen-

sive than calcium hypochlorite. Some utilities and industries

have generated chlorine on-site for many years, using elec-

trolysis to oxidize chloride ions to chlorine. The process is

practical in remote areas where brine, a source of chloride

ions, is readily available.

Chlorine has been used in the United States since the

early 1900s for disinfection. It is still commonly used to

disinfect wastewater and drinking water, but the rules guid-

ing its use are gradually changing. Until recently, chlorine

was added to wastewater effluents from treatment plants

without great concern over its effects on the

environment

The environmental impact was thought to be insignificant

since chlorine was being used in such low concentrations.

However, evidence has accumulated showing serious envi-

ronmental consequences from the

discharge

of even low

levels of various forms of chlorine and chlorine compounds,

and many plants now dechlorinate their wastewater after

allowing the chlorine to react with the wastewater for 30–

60 minutes.

The use of chlorine to disinfect drinking water is un-

dergoing a similar review. Since the 1970s, it has been sus-

pected that chlorine and some by-products of chlorination

are carcinogenic. Papers published in 1974 indicated that

halogenated methanes are formed during chlorination. Dur-

ing the mid-1970s the

Environmental Protection Agency

(EPA) conducted two surveys of the

drinking-water sup-

ply

in the United States, the National Organics Reconnais-

sance Survey and the National Organics Monitoring Survey,

to determine the extent to which

trihalomethanes

(THMs)

(chloroform, bromodichloromethane, dibromochlorometh-

ane, bromoform) and other halogenated organic compounds

were present. The studies indicated that drinking water is

the primary route by which humans are exposed to THMs

and that THMs are the most commonly detected synthetic

organic

chemicals

in United States’ drinking water.

Chloroform was the THM found in the highest con-

centrations during the surveys. The risks associated with

drinking water containing high levels of chloroform are not

243

clear. It is known that 0.2 qt (200 ml) of chloroform is

usually fatal to humans, but the highest concentrations in

the drinking water surveyed fell far below (311 ug/l) this

lethal dose. The potential carcinogenic effects of chloroform

are more difficult to evaluate. It does not cause Salmonella

typhimurium in the

Ames test

to mutate, but it does cause

mutations in yeast and has been found to cause tumors in

rats and mice. However, the ability of chloroform to cause

cancer

in humans is still questionable, and the EPA has

classified it and other THMs as probable human carcino-

gens. Based on these data, the maximum contaminant level

for THMs in drinking water is now 100 ug/l. This is an

enforceable standard and requires the monitoring and re-

porting of THM concentrations in drinking water.

There are several ways to test for chlorine, but among

the more common methods are iodometric, DPD (N,N-

Diethyl-p-phenylenediamine) and amperometric. DPD and

amperometric methods are generally used in the water and

wastewater treatment industry. DPD is a dye which is oxi-

dized by the presence of chlorine, creating a reddish color.

The intensity of the color can then be measured and related

to chlorine level; the DPD solution can be titrated with a

reducing agent (ferrous ammonium sulfate) until the reddish

color dissipates. In the amperometric titration method, an

oxidant sets up a current in a solution which is measured

by the amperometric titrator. A reducing agent (phenylarsine

oxide) is then added slowly until no current can be measured

by the titrator. The amount of titrant added is commonly

related to the amount of chlorine present.

To minimize the problem of chlorinated by-products,

many cities in the United States, including Denver, Portland,

St. Louis, Boston, Indianapolis, Minneapolis, and Dallas,

use chloramination rather than simple chlorination. Chlo-

rine is still required for chloramination, but ammonia is

added before or at the same time to form chloramines.

Chloramines do not react with organic precursors to form

halogenated by-products including THMs. The problem in

using chloramines is that they are not as effective as the free

chlorine forms at killing pathogens.

Questions still remain about whether the levels of

chlorine currently used are dangerous to human health. The

level of chlorine in most water supplies is approximately 1

mg/l, and some scientists believe that the chlorinated by-

products formed are not hazardous to humans at these levels.

There are some risks, nevertheless, and perhaps the most

important question is whether these outweigh the benefits

of using chlorine. The final issue concerns the short-term

and long-term effects of discharging chlorine into the envi-

ronment. Dechlorination would be yet another treatment

step, requiring the commitment of additional resources. At

the present time, the general consensus is that chlorine is

more beneficial than harmful. However, it is important to

Environmental Encyclopedia 3

Chlorine

note that a great deal of research is now underway to explore

the benefits of using alternative disinfectants such as

ozone

chlorine dioxide, and ultraviolet light. Each alternative poses

some problems of its own, so despite the current availability

of a great deal of research data, the selection of an alternative

is difficult.

[Gregory D. Boardman]

ESOURCES

OOKS

Tchobanoglous, G., and E. D. Schroeder. Water Quality. Reading, MA:

Addison-Wesley, 1985.

Chlorine

Chlorine is an element of atomic number 17 and atomic

mass of 35.45 atomic mass units. It belongs to Group 17

of the periodic table and is thus a halogen. Halogens are a

highly reactive group of elements that, in addition to chlo-

rine, include fluorine, iodine,

bromine

and another element

that does not occur in

nature

, astatine, but is produced

by bombarding bismuth with alpha particles. Halogens are

extremely reactive because they have an unpaired electron

in their outermost electron shell. Thus so highly reactive,

chlorine is usually not found in a pure form in nature, but

is rather typically bound to other elements such as sodium,

calcium, or potassium. In its pure form, chlorine exists as a

diatomic molecule, meaning a molecule containing two of

the same atoms. This form of chlorine is a yellow-green gas

at room temperature. Chlorine gas is more dense than air,

condenses to form a liquid at -29°F(-34°C), and freezes into

a solid at -153°F(-103°C). Because of its reactivity, desirable

properties, and abundance, chlorine is an exceptionally useful

element. Since it readily combines with other elements and

molecules, chlorine is a main component and vital reactant in

the manufacture of thousands of useful products. In addition,

almost all municipal

water treatment

systems in the United

States depend on chlorine

chemicals

to provide clean and

safe drinking water. It is estimated that chlorine is used in

the production of 85% of all pharmaceuticals, and in 96%

of all crop protection chemicals (pesticides and herbicides).

Also, chlorine chemicals are powerful bleaching agents used

in paper processing and inexpensive but highly effective dis-

infectants.

Chlorine also has an important impact on the econ-

omy. The chlorine industry provides almost 2 million jobs

having a combined yearly payroll of over $52 billion. In the

United States, 212 industries are direct users of chlorine or

related products. The Chlorine Chemistry Council reports

that nearly 40% of U.S. jobs and income are directly or

indirectly dependent on chlorine. The chlorine-dependent

244

industries are mostly found in Texas, Michigan, and New

Jersey. The

automobile

industry relies heavily on chlorine

because cars contain many components that use chlorine in

their manufacture. Three chlorine products, PVC, pickled

steel, and paint create more than 345,000 jobs in the United

States. Polyvinylchloride (or PVC) is a chlorinated hydrocar-

bon polymer that is used to make dashboards, air bags, wire

covers, and sidings. Chlorine is also used in the manufacture

of car exterior paints. Automobile coatings typically use tita-

nium dioxide which requires chlorine for synthesis. In addi-

tion, chlorine is used in the production of pickled steel for

automobile frames and undercarriages. The pickling process

provides an impurity-free steel surface for rust

resistance

treatment and painting. Hydrochloric

acid

, a chlorine chem-

ical, is a main component in pickling steel. Roughly 25% of

the hydrochloric acid produced in the United States is used

in steel pickling for the auto industry. Overall, the auto

industry consumes 3.1% of all chlorine produced in the form

of hydrochloric acid, 30% of all chlorine produced in the

form of PVC, and 4.1% of all chlorine produced involved

in the manufacture of titanium dioxide for paints.

Industrially, chlorine is also used in massive quantities

for

sanitation

purposes. An important advancement in pub-

lic health has been the widespread

chlorination

of drinking

water. Chlorine-based water purifying chemicals were first

introduced in 1908. Chlorine water purification has practi-

cally eradicated diseases that were once devastating, such as

cholera

and dysentery. In 1992, the Public Health Advisory

Board was created to guide the chlorine industry in issues

pertaining to drinking water safety. Because it is so highly

reactive, chlorine is one of the most effective germicides

available. Chlorine chemicals kill bacteria, algae,

fungi

, and

protozoans and inactivate viruses. Simple household bleach,

sodium hypochlorite, can even inactivate and sterilize equip-

ment from such deadly viruses as the

Ebola virus

. Chlorine

is also used to sanitize pools and spas. Chlorine disinfectants

are used to prevent institutional disease transmission in food

preparation, day care centers, nursing homes, and hospitals.

Chlorine is a vital chemical in the pharmaceutical and

medical industries. Approximately 85% of all drugs either

contain chlorine or are manufactured using chlorine. The

chemical addition of chlorine to a drug molecule can enhance

its

absorption

and delay its elimination from the body,

increasing the duration of its action. Also, chlorine can be

used to create soluble forms of drugs that dissolve easily into

solutions. When hydrochloric acid is reacted with poorly

soluble drugs that are weak bases, the result is a chloride

salt that is more soluble in water. Greater solubility enhances

absorption and allows some drugs to be incorporated into

syrups or elixirs. This is very useful since many people prefer

oral liquid drug intake. Soluble drugs also have the advantage

that they can be inhjected. Finally, about 25% of all medical

Environmental Encyclopedia 3

Chlorine

equipment is made from

chlorinated hydrocarbons

, vinyl

or PVC.

Chlorinated

hydrocarbons

are specific hydrocarbon

molecules that also have atoms of the element chlorine chem-

ically bonded to them. The number of

carbon

atoms and

how they are arranged in three-dimensions determines the

chemical and physical properties of these compounds. Be-

cause there is a wide variety of possible chlorinated hydrocar-

bons, this class of useful chemicals has a wide range of

applications that are of great economic and practical impor-

tance. Chlorinated hydrocarbons include products such as

the synthetic rubbers used in car tires and tennis shoes. They

are also used in packaging

plastics

, and a variety of products

such as fluid pipes, furniture, home siding, credit cards,

fences, and toys. Chlorinated hydrocarbons also can be used

as precursors in the production of non-stick coatings such

as Teflon. Chlorine is also used in the manufacture of sol-

vents such as carbon tetrachloride and trichloroethylene used

dry cleaning

In addition to their use in the manufacture of polymers,

rubbers, plastics, solvents, and cleaners, chlorinated hydro-

carbons also are powerful pesticides. They rank among the

most potent and environmentally persistent insecticides, and

when combined with fluorine, they yield the refrigerants

called

chlorofluorocarbons

, or CFCs. Because of their

wide array of uses, chlorinated hydrocarbons are among the

most important industrial organic compounds. Perhaps the

best known chlorinated hydrocarbon insecticide is Dichloro-

DiphenylTrichloroethane, or DDT. DDT was first used as an

insecticide in 1939. After its effectiveness and relative safety

to humans was established, the use of DDT burgeoned

around the world in the war against disease-carrying and

agricultural insect pests. However, the very success of DDT

in the fight against insect-transmitted diseases (especially

malaria

) subsequently led to its massive overuse. Wide-

spread excessive use led to the emergence of DDT-resistant

insects. Additionally, evidence started to show that toxic

levels of DDT could accumulate in the fatty tissues of mam-

mals, including humans. Because of such harmful effects,

the use of DDT has now been banned in many countries

despite its effectiveness. Another important issue with chlo-

rinated hydrocarbons is their environmental persistence.

Many, such as DDT, refrigerants, and solvents are not easily

broken-down in the environent. Also, because other, less

persistent, insecticide alternatives have been developed, the

use of chlorinated insecticides has been drastically reduced.

Other toxic chemicals resistant to degradation also

contain chlorine such as chlorinated and

polychlorinated

biphenyls

(PCBs) and polyaromatic hydrocarbons (PAHs).

These substances are known environmental pollutants, with

PAHs found for example in diesel exhaust emissions and

PCBs in industrial effluents, contaminating rivers as well as

245

the Oceans. They have been shown to accumulate in

whales

and a variety of other marine mammals.

Another environmentally important chlorine com-

pound class are the chemicals known as ChloroFluoroCarbons,

or CFCs. Chlorofluorocarbons are single carbon atoms

chemically bound to both chlorine and fluorine. The com-

pounds trichlorofluoromethane (Freon-11) and dichlorodi-

fluoromethane (Freon-12) are widely used CFCs. They are

odorless, nonflammable, very stable compounds that are used

as refrigerants in commercial refrigerators and air condition-

ers. CFCs are also used as

aerosol propellants

. Because

CFCs are detrimental to the

ozone

layer, the portion of

the

atmosphere

that blocks out the harmful wavelengths

of ultraviolet light associated with skin

cancer

, they are

being phased out as propellants and refrigerants. An ozone

hole detected above

Antarctica

has been attributed by scien-

tists to the release of CFCs into the atmosphere.

The

Environmental Protection Agency

(EPA) is

concerned with toxic and persistent chlorine chemicals that

are the byproducts of industrial activity. Two such byprod-

ucts are dioxins and

furans

, produced when organic (carbon-

containing) compounds are heated to high temperatures in

the presence of chlorine. Together, dioxins and furans repre-

sent a group of over two hundred chemicals. Some dioxins

are extremely toxic and are a significant cause for concern

to environmental agencies.

Dioxin

compounds are highly

persistent in the

environment

. The most toxic dioxin is

2,3,7,8-tetrachlorodibenzo-p-dioxin or TCDD. Dioxins are

also by-products of industrial processes involving chlorine

such as waste

incineration

, chemical and

pesticide

manu-

facturing and pulp and paper bleaching. Dioxin is a known

carcinogen

and was the principal toxic component of

Agent

Orange

. The EPA reports that incinerators are the largest

source of dioxins and furans released into the environment

in the United States. Other industrial sources of these toxic

compounds include smelters, cement kilns, and fossil fuel

burning

power plants

. Because of new standards for incin-

eration, the levels of dioxins and furans have been steadily

declining.

[Terry Watkins]

ESOURCES

OOKS

Khanna, N. “Chlorine Dioxide in Food Applications.” In: Proceedings of

the Fourth International Symposium, Chlorine dioxide: The state of science,

regulatory, environmental issues, and case histories. Denver: American Water

Works Association, 2002.

Stringer, Ruth, and Paul Johnston. Chlorine and the Environment: An Over-

view of the Chlorine Industry. New York: Kluwer Academic Publishers, 2001.

Watts, Susan. Chlorine (Elements). Tarrytown: Benchmark Books, 2001.

White, G.C. “Chlorination of Potable Water.” In: The Handbook of Chlori-

nation, 2nd Ed. New York: Nostrand Reinhold, 1986.

Environmental Encyclopedia 3

Chlorine monoxide

ERIODICALS

Bal’a, M.F.A. et al. “Moderate heat or chlorine destroys Aeromonas hy-

drophila biofilms on stainless steel.” Dairy, Food, and Environmental Sanita-

tion 19, (1999): 29-34.

McFarland, M. “Investigations of the environmental acceptability of fluoro-

carbon alternatives to chlorofluorocarbons.” Proc. Natl. Acad. Sci. U.S.A 89,

no. 3 (February, 1992): 807-811.

THER

Winter, Mark. Chlorine. WebElements Periodic Table. <http://www.webe-

lements.com/webelements/scholar/index.html>

RGANIZATIONS

Chlorine Chemistry Council (CCC), 1300 Wilson Boulevard, Arlington,

VA USA 22209 703) 741-5000, , http://c3.org/index.html

Euro Chlor: Chlorine Online Information Ressource, Avenue E Van

Nieuwenhuyse 4, box 2, Brussels, Belgium B-1160 + 32 2 676 7211, Fax:

+ 32 2 676 7241, Email: eurochlor@cefic.be , <http://www.eurochlor.org>

Chlorine monoxide

One of two oxides of

chlorine

, either Cl

O or ClO. When

used in

environmental science

, it usually refers to the latter.

Chlorine monoxide (ClO) is formed in the

atmosphere

when free chlorine atoms react with

ozone

. In the reaction,

ozone is converted to normal, diatomic oxygen (O

). This

process appears to be a major factor in the destruction of

ozone in the

stratosphere

observed by scientists in recent

years. The most important sources of chlorine by which this

reaction is initiated appear to be

chlorofluorocarbons

and

other synthetic chlorine compounds released by human ac-

tivities.

Chlorofluorocarbons

The chlorofluorocarbons (CFCs) are a family of organic

compounds containing

carbon

hydrogen

(usually), and

either

chlorine

or fluorine, or both. The members of this

family can be produced by replacing one or more hydrogen

atoms in

hydrocarbons

with a chlorine or fluorine atom.

In the simplest possible case, treating

methane

(CH

) with

chlorine yields chloromethane, CH

Cl. Treating this prod-

uct with fluorine causes the replacement of a second hydro-

gen atom with a fluorine atom, producing chlorofluorometh-

ane, CH

ClF.

This process can be continued until all hydrogen atoms

have been replaced by chlorine and/or fluorine atoms. By

using larger hydrocarbons, an even greater variety of CFCs

can be produced. The compound known as CFC-113, for

example, is made from ethane (C

) and has the formula

Over the last three decades, the CFCs have become

widely popular for a number of commercial applications.

These applications fall into four general categories: refriger-

246

ants, cleaning fluids,

propellants

, and blowing agents. As

refrigerants, CFCs have largely replaced more harmful gases

such as ammonia and

sulfur dioxide

in refrigerators, freez-

ers, and air conditioning systems. Their primary application

as cleaning fluids has been in the computer manufacturing

business where they are used to clean circuit boards. CFCs

are used as propellants in hair sprays, deodorants, spray

paints, and other types of sprays. As blowing agents, CFCs

are used in the manufacture of fast-food take-out boxes and

similar containers. By the early 1990s, CFCs had become

so popular that their production was a multi-billion dollar

business worldwide.

For many years, little concern was expressed about the

environmental hazards of CFCs. The very qualities that

made them desirable for commercial applications—their

sta-

bility

, for example—appeared to make them environmen-

tally benign.

However, by the mid-1970s, the error in that view

became apparent. Scientists began to find that CFCs in the

stratosphere

decomposed by sunlight. One product of that

decomposition

, atomic chlorine, reacts with

ozone

)to

form ordinary oxygen (O

). The apparently harmless CFCs

turned out, instead, to be a major factor in the loss of ozone

from the stratosphere.

By the time this discovery was made, levels of CFCs

in the stratosphere were escalating rapidly. The concentra-

tion of these compounds climbed from 0.8 part per billion

in 1950 and 1.0 part per billion in 1970 to 3.5

parts per

billion

in 1987.

A turning point in the CFC story came in the mid-

1980s when scientists found that a large hole in the ozone

layer was opening up over the Antarctic each year. This

discovery spurred world leaders to act on the problem of

CFC production. In 1987, about 40 nations met in Montreal

to draft a treaty that will reduce the production of CFCs

worldwide.

This action is encouraging, but it hardly solves the

CFC problem. These compounds remain in the

atmo-

sphere

for long periods of time (about 77 years for CFC-

11 and 139 years for CFC-12), so they will continue to pose

a threat to the ozone layer for many decades to come.

[David E. Newton]

ESOURCES

OOKS

Selinger, B. Chemistry in the Marketplace. 4th ed. Sydney: Harcourt Brace

Jovanovich Publishers, 1989.

ERIODICALS

O’Sullivan, D. A. “International Gathering Plans Way to Safeguard Atmo-

spheric Ozone.” Chemical & Engineering News (26 June 1989): 33-36.