Visualizing Environmental Science

84 CHAPTER 4 Risk Analysis and Environmental Health Hazards

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KAREN KASMAUSKI/NG Image Collection

This net was treated with DDT to kill malaria-transmitting

mosquitoes. Photographed in Nigeria.

These symptoms may, for example, decrease fishes’
competitiveness or increase their chances of being
eaten by predators.
Mobility of persistent toxicants is also a risk for
h umans. In 1994 the Environmental Working Group, a
private organization, analyzed five common herbicides
(weed-killing chemicals) found in drinking water. It con-
cluded that 3.5 million people in the Midwest face a
slightly elevated cancer risk because of exposure to the
herbicides. The EPA has since mandated a reduction in
use of the five herbicides.

The Global Ban of Persistent
Organic Pollutants

The Stockholm Convention on

Persistent Organic Pollutants,

which was adopted in 2001, is an

important U.N. treaty that seeks

to protect human health and the

environment from the 12 most

toxic persistent organic pollutants

(POPs) on Earth ( Table 4.2). Some

POPs disrupt the endocrine system (discussed later in this

chapter), cause cancer, or adversely affect the developmen-

tal processes of organisms.

The Stockholm Convention requires countries to de-

velop plans to eliminate the production and use of in-

tentionally produced POPs. A notable exception to this

requirement is that DDT is still produced and used to

control malaria- carrying mosquitoes in countries where

no affordable alternatives exist (ˆ}ÕÀiÊ{°£ä).

1. What is a persistent toxicant?


2. How does DDT become magnified through
   a food chain?


3. What is the Stockholm Convention on
   Persistent Organic Pollutants?

persistent organic

pollutants (POPs)

Persistent toxicants

that bioaccumulate in

organisms and travel

through air and water

to contaminate sites

far from their source.

Persistent organic pollutants: The “dirty dozen”

sTable 4.2

Persistent organic pollutant Use

Aldrin Insecticide

Chlordane Insecticide

DDT (dichlorodiphenyl- Insecticide

trichloroethane)

Dieldrin Insecticide

Endrin Rodenticide and

insecticide

Heptachlor Fungicide

Hexachlorobenzene Insecticide; fire

retardant

Mirex™ Insecticide

Toxaphene™ Insecticide

PCBs (polychlorinated Industrial chemicals

biphenyls)

Dioxins By-products of certain

manufacturing processes

Furans (dibenzofurans) By-products of certain

manufacturing processes