Comparative Kinetics and Distribution to Target Tissues of Organophosphates Using Physiologically-Based Pharmacokinetic Modeling
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Organophosphate Poisoning : a Review
120 Sinha and Sharma Med J Indones Organophosphate poisoning : A review Parmod K. Sinha, Ashok Sharma Abstrak Pestisida organofosfat digunakan secara luas di seluruh dunia. Keracunan oleh bahan ini merupakan masalah kesehatan masyarakat, terutama di negara berkembang. Zat neurotoksik organofosfat merupakan bahan yang dianggap mengancam dalam bidang militer dan terorisme. Mekanisme toksisitas bahan ini adalah dengan cara menghambat asetilkolinesterase yang mengakibatkan menumpuknya neurotransmitor asetilkolin dan terjadi rangsangan terus-menerus pada reseptor asetilkolin pada sistem saraf sentral maupun perifer. Selain krisis kolinergik, organofosfat dapat menimbulkan berbagai sindrom neurologis, baik akut maupun kronik. Sedangkan gejala peralihan ( intermediate) terjadi 1-4 hari setelah krisis kolinergik teratasi. Pengobatan standar terdiri dari reaktivasi asetilkolinesterase dengan antidot golongan oksim (prolidoksim, oksidoksime, HI-6 dan HLo7), dan pengendalian efek biokimia asetilkolin dengan menggunakan atropin. Golongan oksim yang baru HI-6 dan Hlo7 merupakan reaktivator asetilkolinesterase yang lebih cocok dan efektif untuk keracunan akut dan berat dibandingkan dengan prolidoksim dan obidoksim. Penderita yang mendapat pengobatan segera, biasanya dapat sembuh dari toksisitas akut, namun gejala neurologis ikutan dapat saja terjadi. (Med J Indones 2003; 12: 120-6) Abstract Organophosphate pesticides are used extensively worldwide, and poisoning by these agents, particularly in developing nations is a public health problem. Organophosphorous -
2018 Treated Water Undetected Chemical Contaminant List
2018 Treated Water Undetected Chemical Contaminant List ESTROGENS AND OTHER HORMONES Diethylstilbestrol (DES) Estrone 17alpha-Estradiol 17alpha-Ethynal estradiol 17beta-Estradiol Progesterone Estriol cis-Testosterone trans-Testosterone INORGANIC CHEMICALS Antimony Niobium Arsenic Osmium Beryllium Palladium Cadmium Platinum Cerium Praseodymium Cesium Rhenium Cobalt Rhodium Cyanide Ruthenium Dysprosium Samarium Erbium Selenium Europium Silver Gadolinium Tantalum Gallium Tellurium Germanium Thallium Gold Thorium Hafnium Thulium Holmium Tin Iridium Titanium Lanthanum Tungsten Lead Uranium Lutetium Vanadium Mercury Ytterbium Molybdenum Zinc Neodymium Zirconium Nickel NITROSAMINES N-Nitropyrrolidine (NPYR) N-Nitrosomorpholine (NMOR) N-Nitrosodi-N-butylamine (NDBA) N-Nitrosodiphenylamine (NDPhA) N-Nitrosodiethylamine (NDEA) N-Nitrosodi-N-propylamine (NDPA) N-Nitrosodimethylamine (NDMA) N-Nitrosomethylethylamine (NMEA) N-Nitrosopiperidine (NPIP) 1 ORGANIC CHEMICALS Acenaphthene Butylbenzylphthalate Acenaphthylene Butyraldehyde (Butanal) Acetaldehyde Carbaryl Acetochlor Carbofuran Acetone Carbon disulfide Acrylamide Carbophenothion Acrylonitrile Carbon tetrachloride Alachlor Carboxin Aldicarb (Temik) Chlordane Aldicarb sulfone Chlordane, alpha Aldicarb sulfoxide Chlordane, gamma Aldrin Chlorfenvinphos Allyl chloride Chloroacetonitrile Tert-Amyl Methyl ether Chlorobenzene Ametryn Chlorobenzilate Anilizine 2-Chlorobiphenyl Anthracene 1-Chlorobutane Aspon Chloroethane Atraton Chloromethane Atrazine Chloroneb Azinphos-ethyl Chloroprene Azinphos-methyl -
2002 NRP Section 6, Tables 6.1 Through
Table 6.1 Scoring Table for Pesticides 2002 FSIS NRP, Domestic Monitoring Plan } +1 0.05] COMPOUND/COMPOUND CLASS * ) (EPA) (EPA) (EPA) (EPA) (EPA) (FSIS) (FSIS) PSI (P) TOX.(T) L-1 HIST. VIOL. BIOCON. (B) {[( (2*R+P+B)/4]*T} REG. CON. (R) * ENDO. DISRUP. LACK INFO. (L) LACK INFO. {[ Benzimidazole Pesticides in FSIS Benzimidazole MRM (5- 131434312.1 hydroxythiabendazole, benomyl (as carbendazim), thiabendazole) Carbamates in FSIS Carbamate MRM (aldicarb, aldicarb sulfoxide, NA44234416.1 aldicarb sulfone, carbaryl, carbofuran, carbofuran 3-hydroxy) Carbamates NOT in FSIS Carbamate MRM (carbaryl 5,6-dihydroxy, chlorpropham, propham, thiobencarb, 4-chlorobenzylmethylsulfone,4- NT 4 1 3 NV 4 4 13.8 chlorobenzylmethylsulfone sulfoxide) CHC's and COP's in FSIS CHC/COP MRM (HCB, alpha-BHC, lindane, heptachlor, dieldrin, aldrin, endrin, ronnel, linuron, oxychlordane, chlorpyrifos, nonachlor, heptachlor epoxide A, heptachlor epoxide B, endosulfan I, endosulfan I sulfate, endosulfan II, trans- chlordane, cis-chlordane, chlorfenvinphos, p,p'-DDE, p, p'-TDE, o,p'- 3444NV4116.0 DDT, p,p'-DDT, carbophenothion, captan, tetrachlorvinphos [stirofos], kepone, mirex, methoxychlor, phosalone, coumaphos-O, coumaphos-S, toxaphene, famphur, PCB 1242, PCB 1248, PCB 1254, PCB 1260, dicofol*, PBBs*, polybrominated diphenyl ethers*, deltamethrin*) (*identification only) COP's and OP's NOT in FSIS CHC/COP MRM (azinphos-methyl, azinphos-methyl oxon, chlorpyrifos, coumaphos, coumaphos oxon, diazinon, diazinon oxon, diazinon met G-27550, dichlorvos, dimethoate, dimethoate -
Chemical Name Federal P Code CAS Registry Number Acutely
Acutely / Extremely Hazardous Waste List Federal P CAS Registry Acutely / Extremely Chemical Name Code Number Hazardous 4,7-Methano-1H-indene, 1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro- P059 76-44-8 Acutely Hazardous 6,9-Methano-2,4,3-benzodioxathiepin, 6,7,8,9,10,10- hexachloro-1,5,5a,6,9,9a-hexahydro-, 3-oxide P050 115-29-7 Acutely Hazardous Methanimidamide, N,N-dimethyl-N'-[2-methyl-4-[[(methylamino)carbonyl]oxy]phenyl]- P197 17702-57-7 Acutely Hazardous 1-(o-Chlorophenyl)thiourea P026 5344-82-1 Acutely Hazardous 1-(o-Chlorophenyl)thiourea 5344-82-1 Extremely Hazardous 1,1,1-Trichloro-2, -bis(p-methoxyphenyl)ethane Extremely Hazardous 1,1a,2,2,3,3a,4,5,5,5a,5b,6-Dodecachlorooctahydro-1,3,4-metheno-1H-cyclobuta (cd) pentalene, Dechlorane Extremely Hazardous 1,1a,3,3a,4,5,5,5a,5b,6-Decachloro--octahydro-1,2,4-metheno-2H-cyclobuta (cd) pentalen-2- one, chlorecone Extremely Hazardous 1,1-Dimethylhydrazine 57-14-7 Extremely Hazardous 1,2,3,4,10,10-Hexachloro-6,7-epoxy-1,4,4,4a,5,6,7,8,8a-octahydro-1,4-endo-endo-5,8- dimethanonaph-thalene Extremely Hazardous 1,2,3-Propanetriol, trinitrate P081 55-63-0 Acutely Hazardous 1,2,3-Propanetriol, trinitrate 55-63-0 Extremely Hazardous 1,2,4,5,6,7,8,8-Octachloro-4,7-methano-3a,4,7,7a-tetra- hydro- indane Extremely Hazardous 1,2-Benzenediol, 4-[1-hydroxy-2-(methylamino)ethyl]- 51-43-4 Extremely Hazardous 1,2-Benzenediol, 4-[1-hydroxy-2-(methylamino)ethyl]-, P042 51-43-4 Acutely Hazardous 1,2-Dibromo-3-chloropropane 96-12-8 Extremely Hazardous 1,2-Propylenimine P067 75-55-8 Acutely Hazardous 1,2-Propylenimine 75-55-8 Extremely Hazardous 1,3,4,5,6,7,8,8-Octachloro-1,3,3a,4,7,7a-hexahydro-4,7-methanoisobenzofuran Extremely Hazardous 1,3-Dithiolane-2-carboxaldehyde, 2,4-dimethyl-, O- [(methylamino)-carbonyl]oxime 26419-73-8 Extremely Hazardous 1,3-Dithiolane-2-carboxaldehyde, 2,4-dimethyl-, O- [(methylamino)-carbonyl]oxime. -
Lifetime Organophosphorous Insecticide Use Among Private Pesticide Applicators in the Agricultural Health Study
Journal of Exposure Science and Environmental Epidemiology (2012) 22, 584 -- 592 & 2012 Nature America, Inc. All rights reserved 1559-0631/12 www.nature.com/jes ORIGINAL ARTICLE Lifetime organophosphorous insecticide use among private pesticide applicators in the Agricultural Health Study Jane A. Hoppin1, Stuart Long2, David M. Umbach3, Jay H. Lubin4, Sarah E. Starks5, Fred Gerr5, Kent Thomas6, Cynthia J. Hines7, Scott Weichenthal8, Freya Kamel1, Stella Koutros9, Michael Alavanja9, Laura E. Beane Freeman9 and Dale P. Sandler1 Organophosphorous insecticides (OPs) are the most commonly used insecticides in US agriculture, but little information is available regarding specific OP use by individual farmers. We describe OP use for licensed private pesticide applicators from Iowa and North Carolina in the Agricultural Health Study (AHS) using lifetime pesticide use data from 701 randomly selected male participants collected at three time periods. Of 27 OPs studied, 20 were used by 41%. Overall, 95% had ever applied at least one OP. The median number of different OPs used was 4 (maximum ¼ 13). Malathion was the most commonly used OP (74%) followed by chlorpyrifos (54%). OP use declined over time. At the first interview (1993--1997), 68% of participants had applied OPs in the past year; by the last interview (2005--2007), only 42% had. Similarly, median annual application days of OPs declined from 13.5 to 6 days. Although OP use was common, the specific OPs used varied by state, time period, and individual. Much of the variability in OP use was associated with the choice of OP, rather than the frequency or duration of application. -
The List of Extremely Hazardous Substances)
APPENDIX A (THE LIST OF EXTREMELY HAZARDOUS SUBSTANCES) THRESHOLD REPORTABLE INVENTORY RELEASE QUANTITY QUANTITY CAS NUMBER CHEMICAL NAME (POUNDS) (POUNDS) 75-86-5 ACETONE CYANOHYDRIN 500 10 1752-30-3 ACETONE THIOSEMICARBAZIDE 500/500 1,000 107-02-8 ACROLEIN 500 1 79-06-1 ACRYLAMIDE 500/500 5,000 107-13-1 ACRYLONITRILE 500 100 814-68-6 ACRYLYL CHLORIDE 100 100 111-69-3 ADIPONITRILE 500 1,000 116-06-3 ALDICARB 100/500 1 309-00-2 ALDRIN 500/500 1 107-18-6 ALLYL ALCOHOL 500 100 107-11-9 ALLYLAMINE 500 500 20859-73-8 ALUMINUM PHOSPHIDE 500 100 54-62-6 AMINOPTERIN 500/500 500 78-53-5 AMITON 500 500 3734-97-2 AMITON OXALATE 100/500 100 7664-41-7 AMMONIA 500 100 300-62-9 AMPHETAMINE 500 1,000 62-53-3 ANILINE 500 5,000 88-05-1 ANILINE,2,4,6-TRIMETHYL- 500 500 7783-70-2 ANTIMONY PENTAFLUORIDE 500 500 1397-94-0 ANTIMYCIN A 500/500 1,000 86-88-4 ANTU 500/500 100 1303-28-2 ARSENIC PENTOXIDE 100/500 1 THRESHOLD REPORTABLE INVENTORY RELEASE QUANTITY QUANTITY CAS NUMBER CHEMICAL NAME (POUNDS) (POUNDS) 1327-53-3 ARSENOUS OXIDE 100/500 1 7784-34-1 ARSENOUS TRICHLORIDE 500 1 7784-42-1 ARSINE 100 100 2642-71-9 AZINPHOS-ETHYL 100/500 100 86-50-0 AZINPHOS-METHYL 10/500 1 98-87-3 BENZAL CHLORIDE 500 5,000 98-16-8 BENZENAMINE, 3-(TRIFLUOROMETHYL)- 500 500 100-14-1 BENZENE, 1-(CHLOROMETHYL)-4-NITRO- 500/500 500 98-05-5 BENZENEARSONIC ACID 10/500 10 3615-21-2 BENZIMIDAZOLE, 4,5-DICHLORO-2-(TRI- 500/500 500 FLUOROMETHYL)- 98-07-7 BENZOTRICHLORIDE 100 10 100-44-7 BENZYL CHLORIDE 500 100 140-29-4 BENZYL CYANIDE 500 500 15271-41-7 BICYCLO[2.2.1]HEPTANE-2-CARBONITRILE,5- -
Quantum Chemical Study of the Thermochemical Properties of Organophosphorous Compounds A
QUANTUM CHEMICAL STUDY OF THE THERMOCHEMICAL PROPERTIES OF ORGANOPHOSPHOROUS COMPOUNDS A. Khalfa, M. Ferrari, R. Fournet, B. Sirjean, L. Verdier, Pierre-Alexandre Glaude To cite this version: A. Khalfa, M. Ferrari, R. Fournet, B. Sirjean, L. Verdier, et al.. QUANTUM CHEMICAL STUDY OF THE THERMOCHEMICAL PROPERTIES OF ORGANOPHOSPHOROUS COMPOUNDS. Journal of Physical Chemistry A, American Chemical Society, 2015, 119 (42), pp.10527-10539. 10.1021/acs.jpca.5b07071. hal-01241498 HAL Id: hal-01241498 https://hal.archives-ouvertes.fr/hal-01241498 Submitted on 10 Dec 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. QUANTUM CHEMICAL STUDY OF THE THERMOCHEMICAL PROPERTIES OF ORGANOPHOSPHOROUS COMPOUNDS A. Khalfa, M. Ferrari1, R. Fournet1, B. Sirjean1, L. Verdier2, P.A. Glaude1 1Laboratoire Réactions et Génie des Procédés, Université de Lorraine, CNRS, 1 rue Grandville, BP 20451, 54001 NANCY Cedex, France, 2DGA Maîtrise NRBC, Site du Bouchet, 5 rue Lavoisier, BP n°3, 91710 Vert le Petit, France Abstract Organophosphorous compounds are involved in many toxic compounds such as fungicides, pesticides, or chemical warfare nerve agents. The understanding of the decomposition chemistry of these compounds in the environment is largely limited by the scarcity of thermochemical data. -
US EPA Risks of Phosmet Use to the Federally Threatened And
Risks of Phosmet Use to the Federally Threatened and Endangered California Tiger Salamander (Ambystoma californiense) N-(Mercaptomethyl) phthalimide-S-(O,O-dimethyl phosphorodithioate) CAS Registry Number: 732-11-6 PC Code: 059201 Pesticide Effects Determinations Environmental Fate and Effects Division Office of Pesticide Programs Washington, D.C. 20460 29 March 2010 Primary Authors: Chuck Peck, Environmental Engineer Catherine Aubee, Biologist Secondary Review: Marietta Echeverria, Environmental Scientist/RAPL Melissa Panger, Biologist Branch Chief, Environmental Risk Assessment Branch 4: Elizabeth Behl 2 Acknowledgement We would like to acknowledge the contribution of the Litigation Steering Committee in compiling detailed information on the species and Geographic Information System analysis used to define the potential overlap between habitat and occurrence with the areas of potential effects. Additionally, the Steering Committee has provided invaluable guidance toward achieving greater consistency in format and content between chemicals being assessed. 3 Table of Contents 1. EXECUTIVE SUMMARY ............................................................................. 14 1.1. PURPOSE OF ASSESSMENT....................................................................................14 1.2. SCOPE OF ASSESSMENT........................................................................................14 1.2.1. Uses Assessed............................................................................................14 1.2.2. Environmental Fate -
Insecticide Choice for Alfalfa May Protect Water Quality I I- I- Rachael Freeman Long Mary Nett Daniel H
Insecticide choice for alfalfa may protect water quality i I- I- Rachael Freeman Long Mary Nett Daniel H. Putnam Guomin Shan w Jerry Schmierer Barbara Reed n Some insecticides used for control- ling Egyptian alfalfa weevil have been detected in California’s surface waters and are of concern, I due to their impact on water quality and toxicity to some aquatic life. To assess the impact of insec- ticide choice on water quality, we collected tail-water samples from on-farm alfalfa sites in the northern Sacramento Valley over a 3-year period. Samples were To investigate the potential movement of organophosphate and pyrethroid insecticides collected during irrigation after from alfalfa fields, the authors sampled inflows and outflows on alfalfa farms in the organophosphate and pyrethroid northern Sacramento Valley. UC Davis graduate student Corin Pease collects irrigation source water. sprays were applied. We found significant differences between insecticide classes in the mortality lfalfa is grown on over 1 million (Malathion) and dimethoate (Cygon); of Ceriodaphnia dubia (water flea), A acres in California. With an an- the pyrethroids permethrin (Ambush), a test organism used to detect nual value of $873 million in 2001, it lambda-cyhalothrin (Warrior) and pesticides in water. Nearly all sites ranks as one of the state’s top field cyfluthrin (Baythroid);and the car- where organophosphate insec- crops in gross revenue. Alfalfa is pri- bamate carbofuran (Furadan) (Sum- ticides were used resulted in 100% marily used as high-quality feed for mers and Godfrey 2001). An average water flea mortality in a 24-hour dairies, the state’s number one agricul- of 708,600 pounds of these insecticides test of tail-water samples: tural enterprise at about $4.6 billion in was applied to about 1 million acres of ppthroid-treated sections of the 2001. -
SECRETARY HICKEL BANS USE of 16 PESTICIDES on ANY INTERIOR LANDS OR PROGRAMS -- June 18, 1970
i DEPARTMENT of the INTERIOR news release OFFICE OF THE SECRETARY For Release Thursday, June 18, 1970 SECRETARYHICKEL BANS USE OF 16 PESTICIDES ON ANY INTERIOR LANDS OR PROGRAMS Secretary of the Interior Walter J. Hickel today announced a new policy flatly banning the use of 16 types of pesticides on any lands managed by the Department's bureaus and agencies, or in any program run by them. The Department administers approximately 70 percent of all federally owned lands. Included in this list of prohibited pesticides are such widely-known substances as DDT, Aldrin, 2, 4, 5,-T, Dieldrin, Endrin, Heptachlor, Lindane and Toxaphene. Also on the list of unconditionally banned items are Amitrol, arsenical compounds (inorganic), Azodrin, Bidrin, DDD (TDE), mercurial compounds, Strobane, and Thallium Sulfate. The Secretary pointed out that nearly all use of these pesticides has been banned on Interior Lands during recent years. The purpose of the new statement, he said, is to establish a policy for guidance of all Interior personnel. Another group of chemical pesticides, titled the Restricted List, are to be used only when non-chemical techniques have been considered and found inadequate, and when use can be limited to small-scale applications. Secretary Hickel emphasized that the use of any chemical pesticide by his agencies must be aimed at a specific pest problem, and involve minimum strength and minimum frequency of application. "We in the Interior Department-- the Nation's chief conservation agency have a special obligation to protect the environment for all the people,“’ Secretary Hickel said. "We are charged by law with responsibility for protecting interstate and coastal water quality, our fish and wildlife resources, the integrity of our national parks, public lands, and recreation areas," the Secretary continued. -
Acutely / Extremely Hazardous Waste List
Acutely / Extremely Hazardous Waste List Federal P CAS Registry Acutely / Extremely Chemical Name Code Number Hazardous 4,7-Methano-1H-indene, 1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro- P059 76-44-8 Acutely Hazardous 6,9-Methano-2,4,3-benzodioxathiepin, 6,7,8,9,10,10- hexachloro-1,5,5a,6,9,9a-hexahydro-, 3-oxide P050 115-29-7 Acutely Hazardous Methanimidamide, N,N-dimethyl-N'-[2-methyl-4-[[(methylamino)carbonyl]oxy]phenyl]- P197 17702-57-7 Acutely Hazardous 1-(o-Chlorophenyl)thiourea P026 5344-82-1 Acutely Hazardous 1-(o-Chlorophenyl)thiourea 5344-82-1 Extemely Hazardous 1,1,1-Trichloro-2, -bis(p-methoxyphenyl)ethane Extemely Hazardous 1,1a,2,2,3,3a,4,5,5,5a,5b,6-Dodecachlorooctahydro-1,3,4-metheno-1H-cyclobuta (cd) pentalene, Dechlorane Extemely Hazardous 1,1a,3,3a,4,5,5,5a,5b,6-Decachloro--octahydro-1,2,4-metheno-2H-cyclobuta (cd) pentalen-2- one, chlorecone Extemely Hazardous 1,1-Dimethylhydrazine 57-14-7 Extemely Hazardous 1,2,3,4,10,10-Hexachloro-6,7-epoxy-1,4,4,4a,5,6,7,8,8a-octahydro-1,4-endo-endo-5,8- dimethanonaph-thalene Extemely Hazardous 1,2,3-Propanetriol, trinitrate P081 55-63-0 Acutely Hazardous 1,2,3-Propanetriol, trinitrate 55-63-0 Extemely Hazardous 1,2,4,5,6,7,8,8-Octachloro-4,7-methano-3a,4,7,7a-tetra- hydro- indane Extemely Hazardous 1,2-Benzenediol, 4-[1-hydroxy-2-(methylamino)ethyl]- 51-43-4 Extemely Hazardous 1,2-Benzenediol, 4-[1-hydroxy-2-(methylamino)ethyl]-, P042 51-43-4 Acutely Hazardous 1,2-Dibromo-3-chloropropane 96-12-8 Extemely Hazardous 1,2-Propylenimine P067 75-55-8 Acutely Hazardous 1,2-Propylenimine 75-55-8 Extemely Hazardous 1,3,4,5,6,7,8,8-Octachloro-1,3,3a,4,7,7a-hexahydro-4,7-methanoisobenzofuran Extemely Hazardous 1,3-Dithiolane-2-carboxaldehyde, 2,4-dimethyl-, O- [(methylamino)-carbonyl]oxime 26419-73-8 Extemely Hazardous 1,3-Dithiolane-2-carboxaldehyde, 2,4-dimethyl-, O- [(methylamino)-carbonyl]oxime. -
Qsar Analysis of the Chemical Hydrolysis of Organophosphorus Pesticides in Natural Waters
QSAR ANALYSIS OF THE CHEMICAL HYDROLYSIS OF ORGANOPHOSPHORUS PESTICIDES IN NATURAL WATERS. by Kenneth K. Tanji Principal Investigator and Jonathan 1. Sullivan Graduate Research Assistant Department of Land, Air and Water Resources University of California, Davis Technical Completion Report Project Number W-843 August, 1995 University of California Water Resource Center The research leading to this report was supported by the University of California Water Resource Center as part of Water Resource Center Project W-843. Table of Contents Page Abstract 2 Problem and Research Objectives 3 Introduction 5 Theoretical Background 6 QSAR Methodology 7 Molecular Connectivity Theory 8 Organophosphorus Pesticides 12 Experimental Determination of Rates 15 Results and Discussion 17 Principal Findings and Significance 19 References 34 List of Tables Page Table 1. Statistical relationship between OP pesticides and first-order MC/'s. 30 Table 2. Inherent conditions of waters used in experimental work. 16 Table 3. Estimated half-lives for organophosphorus esters derived from model. 31 Table 4. Half-lives and first-order MCI' sfor model calibration data set. 31 Table 5. Experimental kinetic data for validation set compounds, Sacramento. 33 List of Figures Page Figure 1. Essential Features OfQSAR Modeling Methodology. 21 Figure 2. Regression plot for In hydrolysis rate vs. 1st order MCl' s. 22 Figure 3. a 3-D molecular model, a line-segment model and a graphical model. 23 Figure 4. Molecular connectivity index suborders. 24 Figure 5. Chlorpyrifos and its fourteen fourth order path/cluster fragments. 25 Figure 6. Abridged MClndex output. 26 Figure 7. Parent acids of most common organophosphorus pesticides. 12 Figure 8.