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

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 advantageous

Degradation 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 – 400

Organophosphates malathion 100 – 200 2000 –

3000

dichlorophosphate 10 – 80 100 – 200

Carbamates carbaryl 300 – 2000

pyrethroids 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.htmlhttp://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 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 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 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 butchronic effect of

chlorinated hydrocarbons

http://www.eoearth.org/article/Chemical_use_in_Africa:_opportunities_and_risks

ORGANOPHOSPHATES

Developed 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.

ORGANOPHOSPHATES

Ester bond degrades rapidly under environmental conditions Disadvantage: frequent use is necessary

Hydrolysis and conversion of parathion

(RO)2

(RO)2

P

S

O NO2

(RO)2

(RO)2

P

S

O NO2

(RO)2

(RO)2

P

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

NH2

HO

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 light

Advantage: 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