Environmental Engineering Reference
In-Depth Information
Cl
O
Cl
O
FIGURE 7.18
Basic structure of permethrin.
O
virus and was used in the 1980s in southern California to combat the Mediterranean Fruit
Fly (ATSDR 2003c). Exposure to high amounts of malathion can cause difficulty breathing,
chest tightness, vomiting, cramps, diarrhea, blurred vision, sweating, headaches, dizzi-
ness, loss of consciousness, and possibly death (ASTDR 2003c). If appropriate treatment is
provided rapidly, there may be no long-term harmful effects.
Permethrin
is a widely used synthetic insecticide and insect repellent used on cotton,
wheat, maize, and alfalfa crops. It is also used to kill parasites on chickens and other
poultry, and flea treatments for dogs. Permethrin is considered a neurotoxin and is highly
toxic to both freshwater and estuarine aquatic organisms (ATSDR 2005e; USEPA 2006b).
Figure 7.18 shows the basic molecular structure of permethrin.
Toxaphene
is an insecticide composed of a mixture of over 670 chemicals (ATSDR 1997c).
Toxaphene was one of the most widely used insecticides in the United States until 1982
when use dropped significantly and then was banned in 1990. It was primarily used in the
southern states where it was applied to cotton to control pests, and also used elsewhere
to control pests on livestock and to kill unwanted fish in lakes (ATSDR 1997c). Exposure
to toxaphene may cause damage to the lungs, nervous system, and kidneys and can even
cause death if exposure is extreme (ATSDR 1997c).
Glyphosate
and
2,4D
are widely used herbicides in the United States. A common name or
trade name for glyphosate is
Roundup
. USEPA (2009b) does not currently classify glypho-
sate and 2,4D as carcinogenic. However, these two compounds may affect the immune
system, kidneys, and the liver (USEPA 2009b).
PCP
was discussed in Section 7.6.2.
A review of the chemical formulas of the compounds listed in Table 7.14 indicates
many of these pesticides and herbicides are
organochlorines
—an organic compound con-
taining at least one covalently bonded chlorine atom. Chlorine released into the environ-
ment presents special challenges because (1) it is highly toxic, (2) tends to be persistent
due to the strength of the chlorine-carbon bonds, and (3) has an affinity for fatty tissues
in vertebrates (fish and mammals), thus enabling bioaccumulation, a process where con-
centrations of a toxin increase at higher trophic levels in a food chain. Numerous stud-
ies have noted the presence of trace amounts of organochlorines in human breast milk
(Calle et al. 2002).
7.8.2 Dioxins
Compounds generally referred to as
dioxins
represent a diverse set of halogenated sub-
stances and include other substances called furans. There are 75 dioxin isomers and 135
furan isomers. Dioxins are not intentionally produced and have no known use (ATSDR
2006c); they form unintentionally as a by-product of many industrial
processes involving chlorine such as waste incineration and combus-
tion. Dioxin compounds may also form as a by-product during the man-
ufacture of chlorinated compounds and paper bleaching (ATSDR 2006c).
A dioxin compound consists of two benzene molecules joined with two
oxygen bridges. Figure 7.19 shows the basic structure of dioxin (National
Research Council 2006).
O
O
FIGURE 7.19
Basic structure of a
dioxin molecule.
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