Agriculture Reference
In-Depth Information
Table 5.5 Organochlorine products
endrin (Hexadrin)
chlordecone (Kepone)
aldrin (Aldrite, Drinox)
terpene polychlorinates (Strobane)
endosulfan (Thiodan)
chlordane (Chlordan)
dieldrin (Dieldrite)
dicofol (Kelthane)
toxaphene (Toxakil, Strobane-T)
mirex (Dechlorane)
lindane (gamma BHC or HCH, Isotox)
methoxychlor (Marlate)
hexachlorocyclohexane (BHC)
dienochlor (Pentac)
DDT (chlorophen othane)
TDE (000, Rhothane)
heptachlor (Heptagran)
ethylan (Perthane)
The United States Environmental Protection Agency has sharply curtailed
the availability of many organochlorines, particularly DDT, dieldrin, hepta-
chlor, mirex, chlordecone, and chlordane. Others, however, are still the active
ingredients of various home and garden products and some agricultural, struc-
tural, and environmental pest control products. Hexachlorobenzene is used as
a seed protectant fungicide. Technical hexachlorocyclohexane (misnamed ben-
zene hexachloride, BHC) includes multiple stereoisomers; only the gamma
isomer (lindane) is insecticidal. Lindane is the active ingredient of some pest
control products used in the home and garden, on the farm, and in forestry and
animal husbandry. It is also the active agent in the medicinal Kwell, used for
human ectoparasitic disease.
Toxicology and Mode of Action
In varying degrees, organochlorines are absorbed orally, by inhalation, and
by dermal absorption. The efficiency of dermal absorption is variable. Hexa-
chlorocyclohexane, including lindane, the cyclodienes (aldrin, dieldrin, endrin,
chlordane, heptachlor) and endosulfan are efficiently absorbed across skin,
while dermal absorption efficiencies of DDT, perthane, dicofol, methoxychlor,
toxaphene, mirex, and kepone are substantially less. Gastrointestinal, and
probably dermal, absorption of organochlorines is enhanced by fat and fat sol-
vents. While most of the solid organochlorines are not highly volatile, pesti-
cide-laden aerosol or dust particles trapped in respiratory mucous and subse-
quently swallowed may be vehicles leading to significant gastrointestinal ab-
sorption.
Following exposure to some organochlorines (notably DDT), a signifi-
cant part of the absorbed dose is stored in fat tissue as the unchanged parent
compound. Most organochlorines are in some degree dechlorinated, oxidized,
then conjugated. The chief route of excretion is biliary, although nearly all
organochlorines yield measurable urinary metabolites. Unfortunately, many
of the unmetabolized pesticides are efficiently reabsorbed by the intestine (en-
terohepatic circulation) substantially retarding fecal excretion. Metabolic dis-
positions of DDT and DDE (a DDT degradation product), the beta isomer of
hexachlorocyclohexane, dieldrin, heptachlor epoxide, mirex, and kepone tend
