PESTICIDES A restricted use pesticide , defined as generally causing undesirable effects on the environment, applicator, or workers can only be purchased and applied by an individual who is licensed to do that Based on toxicity potency pesticides are classified Adjust categories LD50 Category I: highly hazardous (and restricted use) with an oral LD50 less than or equal to 1.0 mg/kg of body weight Category II: moderately toxic and have an oral LD50 less than or equal to 500 mg/kg Category III: generally nontoxic and have an oral LD50 less than or equal to 15,000 mg/kg 31
Organochlorine Insecticides chlorinated hydrocarbon: e.g. DDT (was banned in 1977) and dieldrin There use was ceased since decades because they were found to be neurotoxicants and cause acute effects by interfering with the transmission of nerve impulses 32
Organophosphorus Insecticides (OPs) phosphoric acid esters or thiophosphoric acid esters E.g. parathion and malathion (the least toxic one) inhibit acetylcholinesterase resulting in accumulation of acetylcholine especially in peripheral neurons Generally are nonpersistent in the environment (only few hours to several months) 33
Organophosphorus Insecticides (OPs) some OP compounds have been associated with delayed neurotoxicity, known as organophosphorus- induced delayed neuropathy bilateral paralysis of the distal muscles, predominantly of the lower extremities, occurring some 7 to 10 days following ingestion 34
Carbamate Insecticides esters of N-methyl carbamic acid (H2NCOOH) Acetylcholinesterase inhibition Inhibition more rapidly reversed than with OPs compounds Generally are nonpersistent in the environment (only few hours to several months) 35
New Insecticide Classes applied at low dosages and are extremely effective but are relatively nontoxic to humans E.g. fiproles and fipronil 36
Rodenticides E.g. warfarin warfarin inhibits the synthesis of vitamin K-dependent clotting factors, which include Factors II, VII, IX, and X, and the anticoagulant proteins C and S potent toxicant with an oral LD50 of 3.0 mg/kg As the rats navigate through narrow passages, they bruise themselves, developing small hemorrhages Warfarin prevents the blood from clotting, and the animals bleed to death in about a week Toxicity in humans is treated with vitamin K, and if the poisoning is severe, blood transfusions as a treatment 37
TOXINS A toxicant is any chemical, of natural or synthetic origin, capable of causing a deleterious effect on a living organism A toxin is a toxicant that is produced by a living organism and is not used as a synonym for toxicant—all toxins are toxicants, but not all toxicants are toxins Toxins may be of animals, plants, insects, or microbes origin Toxins are generally metabolic products that have evolved as defense mechanisms for the purpose of repelling or killing predators or pathogens 38
Microbial Toxins high molecular weight and have antigenic properties E.g. tetanus toxin, botulinus toxin, and diphtheria toxin
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