Dr. Bajnóczy Gábor Tonkó Csilla PESTICIDES BUDAPEST UNIVERSITY OF TECHNOLOGY AND ECONOMICS DEPARTMENT OF CHEMICAL AND ENVIRONMENTAL PROCESS ENGINEERING FACULTY OF CHEMICAL AND BIOCHEMICAL ENGINEERING

PESTICIDES Why they are necessary? Insects, rodents, weeds, fungi are competitors in human feeding. Used chemical matters against them : pesticides Success is not exclusive ↔ significant environmental damage Groups of pesticides (by effects): -Insecticides -Fungicides -Herbicides -Rodenticides -Molluscicides -Akaricides -Nematocides

TYPES OF PESTICIDES (BY CHEMICAL ASPECT) Chlorinated hydrocarbons (insecticides) Limited utilization Chlorophenoxy acides (weed killers) Significant amount Organophosphates (insecticides) Aim: substitution of chlorinated hydrocarbons Carbamates (insecticides) Aim: substitution of organophosphates Pyrethroids (insecticides) Aim: production of natural pesticides Other heterocycle compounds

MOST IMPORTANT PROPERTIES OF PESTICIDES (ENVIRONMENTAL ASPECTS) Lifetime of pesticides: The lifetime of a pesticide is the time after which 95 % efficiency reduction occurs at ambient conditions Fast degradable agents: degradation 1 – 12 weeks Moderately fast degradable agents: degradation 1 – 18 months Slowly degradable agents: degradation more than 2 years Disadvantage of slow degradation: a./ accumulation in food chain b./ development of resistance New type of pesticides: fast degradation is advantageous Degradation types: biological, photochemical, water hydrolyses

TOXIC EFFECT TO LIVING ORGANISMS Most commonly used: LD 50 (lethal dose) amount of material [mg / bodymass kg] causes 50% death in the population examined during the test period (e.g. 24 hours). LD 50 value depend on the way of poison acces: oral or dermal. Poison category acute, oral LD 50 [mg/body mass kg] Strong poison < 50 Poison 50 – 500 Weak poison 500 – 5000 Non-toxic > 5000 measured in rats

toxic effect of pesticide to small mammals (rat) oral LD 50 dermal LD 50 *[mg / bm kg] *[mg / bm kg] Chlorinated hydrocarbon DDT 200 – 400 Organophosphates malathion 100 – – 3000 dichlorophosphate 10 – – 200 Carbamates carbaryl 300 – 2000 pyrethroids Pyrethroids: mammals –> good resistance fishes –> LD 50 in 1,8 μg/ water dm 3 96 hours TOXIC EFFECT TO LIVING ORGANISMS *[mg / bm kg] = [mg / bodymass kg]

CHLORINATED HYDROCARBONS The best know: DDT Non-polar – solubility is negligible in water (this was thought) Large amount of DDT has been sprayed. Catch in membrane pore of nerve tissue → inhibition of nerve transfer. Non-chemical effect. Stereo chemically similar compounds: DDT effect is observed

DDT ACCUMULATION IN FOOD CHAIN DDT conc. of sea water = 1 ppb → DDT conc. of oyster: DDT ~ 70 ppm Degree of enrichment: !! sea water fresh water water plantsplankton sea fish invertebrates freshwater fish birds

EFFECT OF DDT ACCUMULATION ? low calcium content of egg shell: eggs break under penguin fast degradable agent: biological accumulation has less opportunity Increased DDT level increases the amount of cytochrome P-450 enzyme. The non selective oxidizing enzyme oxidizes not only the DDT, but other Important hormones e.g. estradiol (responsible of the calcium intake into the egg shell.

FORMATION OF RESISTANCE I. If the organism contested gets less than the lethal dose it has opportunity to learn how organization protect themselves against the effects of the pesticide. This ability developed is heritable. Due to the apolar skin only apolar pesticides are able to penetrate the skin. In case of rapidly degrade pesticides the time is short to create the defense! non-polar pesticide polar molecule enzyme excreted by urine fast, easy

FORMATION OF RESISTANCE II. In case of a significant number of individuals (millions) due to the biological diversification there are existing individuals which already have a deactivating enzyme that can disarm the pesticide applied. The capability of existing defence is heritable. In this case, the pesticide lifetime life is irrelevant.

FORMATION OF RESISTANCE III. disarming options of non-polar DDT molecule in wildlife fruit fly stable fly mosquito mammals toxic, non-polar moleculenon toxic, polar molecule urine

CHLORINATED HYDROCARBONS TODAY Forbidden or significantly limited: on the northern hemisphere of the Earth In some developing countries, due to the large number of diseases (malaria, yellow fever) and the food production threatened by pests now the ban could not be done. The crop contaminated by chlorinated hydrocarbons, once it enters the EU moves freely in the member states. opportunities in Africa premature death (famine or disease) longer life but chronic effect of chlorinated hydrocarbons

ORGANOPHOSPHATES Developed instead of chlorinated hydrocarbons faster degradation → difficult to develop resistance and accumulation R R’ P Y XZ X and Y : sulfur or oxygen R, R’ : hydrocarbon, oxygen content is possible Z : complex organic group The acetylcholine plays a significant role in the nerve transfer among the nerve cells. After the job is finished, the enzyme acetylcholin is decayed by acetylcholine esterase. Organophosphates block the acetylcholine esterase. Acute toxicity to humans and animals as well ! The toxic potency can be influenced by the quality of the chemical groups! Freely available or official authorization is necessary for purchase.

ORGANOPHOSPHATES Ester bond degrades rapidly under environmental conditions Disadvantage: frequent use is necessary Hydrolysis and conversion of parathion (RO) 2 2 P S O NO 2 (RO) 2 2 P S ONO 2 (RO) 2 2 P O O NO 2 HHO water oxygen (air) non-toxic toxic over time, transformed into another toxic substance hydrolysis → non-toxic compounds HO P O OH NH 2 HO biological decay bacterial transformation conjugation to humic acids

CARBAMATES Developed to substitute organophophates Insecticide effect, less toxic to mammals, fast degradable agent bacterial decay light water

CARBAMATES degradation of carbamates → hydroxy naphthalenes STRUCTURE OF HUMIC ACID incorporation into the humic acid content of the soil

PYRETHROIDS Any of several synthetic compounds similar to pyrethrin, used as an insecticide. Pyrethrin: multicomponent insecticid effect agent from powdered flower of Dalma flowers (Chrysanthemum cinerariaefolium) Disadvantage: easy deagradation in visible light Advantage: natural, household utilisation, non-toxic effect to mammals. Synthetic pyrethroids: pyrethrin base compounds: permethrinpermethrin, cypermethrin, deltamethrin etc.cypermethrindeltamethrin effect: long-term, slightly toxic to mammals, toxic to bees and fishes Permethrin ( 2.0 μg/dm 3, lethal effect on carp after 96 hours)

THIRD GENERATION INSECTICIDES First generation insecticides: agents before World War II. - toxic inorganic compounds (lead-arsenate, mercury and lead-containing compounds) - toxic organic compounds, e.g. nicotine, pyrethrin Second generation insecticides: - synthetic insecticides (chlorinated hydrocarbons, organophosphates, carbamates, pyrethroids) Third generation insecticides: - attractive materials (detection of swarming period → spraying in right time → decreasing the unnecessary amount of pesticide) - pheromones (sex pheromones – can disturb reproduction) - viruses (specifically killing organisms) - hormones (effect on insects evolution, effective only in a particular stage of life) - sterilization (inhibition of reproduction e.g. with irradiation)

Herbicides Chlorophenoxy acids (amine salts and esters) Pesticides used in the largest quantity in the world. Hormonal effect agent against dicotyledonous weeds Degradation is a few weeks in soil. Low toxic effect to invertebrates, vertebrates, but the chronic effect is not clearly demonstrated. 2,4 - dichlorophenoxi acetic acid (2,4-D) 2,4,5 - trichlorophenoxi acetic acid (2,4,5-T) Forced fast growing → not enough nutrient → decay of plant

DEGRADATION OF CHLOROPHENOXY ACIDS IN THE ENVIRONMENT Microbiological degradation Dispersion of large amount of chlorophenoxy acids (Vietnam War, Agent Orange) terratogen effect to population Cause: by-product: dioxine (in ppm) range