Dr. Bajnóczy Gábor Tonkó Csilla
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Transcript of Dr. Bajnóczy Gábor Tonkó Csilla
Dr. Bajnóczy GáborTonkó 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 monthsSlowly 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 advantageousDegradation types: biological, photochemical, water hydrolyses
TOXIC EFFECT TO LIVING ORGANISMS
Most commonly used: LD50 (lethal dose)
• amount of material [mg / bodymass kg] causes 50% death in the population examined during the test period (e.g. 24 hours).
LD50 value depend on the way of poison acces: oral or dermal.
Poison category acute, oral LD50
[mg/body mass kg]
Strong poison < 50Poison 50 – 500Weak poison 500 – 5000Non-toxic > 5000
measured in rats
toxic effect of pesticide to small mammals (rat)
oral LD50 dermal LD50 *[mg / bm kg] *[mg / bm kg]
Chlorinated hydrocarbon DDT 200 – 400Organophosphates malathion 100 – 200 2000 – 3000 dichlorophosphate 10 – 80 100 – 200Carbamates carbaryl 300 – 2000pyrethroids 250 - 1500
Pyrethroids: mammals –> good resistancefishes –> LD50 in 1,8 μg/ water dm3 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.
http://www.whale.to/vaccines/ddt_spraying.html http://www.life.com/animals-pictures/50531439/mobile-ddt-spraying-machine-in-action
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: 70 000 !!
sea waterfresh water
water plants plankton
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 otherImportant hormones e.g. estradiol (responsible of the calcium intake intothe 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 existingindividuals 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 molecule non toxic, polar moleculeurine
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 butchronic effect of
chlorinated hydrocarbons
http://www.eoearth.org/article/Chemical_use_in_Africa:_opportunities_and_risks
ORGANOPHOSPHATESDeveloped instead of chlorinated hydrocarbons
faster degradation → difficult to develop resistance and accumulation
R
R’P
Y
X Z
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.
ORGANOPHOSPHATESEster bond degrades rapidly under environmental conditions
Disadvantage: frequent use is necessary
Hydrolysis and conversion of parathion
(RO) 2
(RO)2P
S
O NO2
(RO)2
(RO)2P
S
O NO2
(RO)2
(RO)2P
O
O NO2
H HO
wateroxygen (air)
non-toxic non-toxic
toxic
over time, transformed into another toxic substance
hydrolysis → non-toxic compounds
HOP
O
O HHO
NH2HO
biological decaybacterial 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 lightAdvantage: natural, household utilisation, non-toxic effect to mammals.
Synthetic pyrethroids: pyrethrin base compounds:permethrin, cypermethrin, deltamethrin etc. effect: long-term, slightly toxic to mammals, toxic to bees and fishes
Permethrin
( 2.0 μg/dm3, 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