Pesticides: Organochlorines Dr. Bergfelt Flashcards
What role does the EPA have concerning the registration of pesticides?
Determines whether a “safe” level of pesiticide residue, called a “tolerance” can be established before registration
What are organochlorines (OC)
aka chlorinated hydrocrbons
natural sourced
Oceans are main source followed by soil
or can be synthetically produced
Chemical properties of OC
persistent in environment
Chlorination of organic compounds reduces reactivity
Stability is manifested as environmental persistence,
which increases with increasing chlorination
Lipophilic
Types of OC as pesticides
1st generation: e.g. arsenic & hydrogen cyanide
Discontinued - ineffective & highly toxic
2nd generation: e.g. Synthetic organochlorine compounds
What are the 2 main groups of OC
DDT-type compounds
Chlorinated alicyclics (e.g. lindane)
neurotoxiants with different mechanisms of action
most major types are banned in US (e.g. DDT)
DDT
dichlorodiphenyltrichloroethane
EPA banned production 1972
DDT in soil bioaccumulated in earthworms & biomagnified in robins
Bioaccumulation of DDT/DDE
DDT/DDE have relatively long half-lives up to 15 years! This gives small organisms a lot of time to take up and accumulate
DDT/DDE in fatty tissue, which can lead to toxics levels and death
Biomagnification
Takes place when organisms higher in the food chain eat the smaller organisms lower in the food chain such that the environmental chemical is biomagnified
What was an environmental impact of DDT
eggshell thining as a result of biomagnification
What is an OC used today as an insecticide & ectoparasiticide on pets & livestock
Lindane
What are some long term effects of OC use as pesticides
EPA deregistered most organochlorines for use in the U.S.
Lindane and Endosulfan are still used
Methoxychlor remains on the market as long as supplies last
Organochlorines may be imported illegally and are still in use internationally (developing countries!)
Persist in the environment
Potential for exposure and toxicity still remains today
Absorption of OC
Dermal most common - damaged skin facilitates
LIndane & Endosulfan well absorbed dermally
GI absorption enhance by fat or solvents
Aerosols may be deposited in airways, inhaled or swallowed
Distribution of OC
stored in body fat (lipophilic)
biologically inactive while partitioned & stored in adipose
Disease, ging, fasting, lactation can redistribute & mobilize → levels that can be toxic
Metabolism/excretion of OC
liver metabolism
Biliary excretion is major route of decontamination
watch for enterohepatic recycling
excreted in milk, feces, & urine
MoA of DDT type OC
Hyper excitability of nerve
