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Environmental concerns of pesticides

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2Outline

Effect on human Pesticides resistance & resurgencePesticide on target organism Pesticide on non-target organisms Pesticide on soil environmentPesticide on water and air ecosystemPesticide biomagnification

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3Introduction

The use of chemicals in modern agriculture has significantly increased productivity.

Their has been an increase in the concentration of pesticides in food and in our environment, with associated negative effects on human health and the environment.

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4Pesticides and human health

Annually there are dozens of million cases of pesticide poisonings worldwide (Richter, 2002).

Pesticide effects to human can be categorized as acute i.e those with quick felt effects e.g. nausea or chronic i.e those with long term felt effects such as the case of leukemia.

Health effect on people with direct exposure Health effect on people with indirect exposure Health effect on consumers

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5Health effect on people with direct exposure

Person who are most affected are the persons who are involved in actual application or who work in areas application of pesticides takes place e.g. Farm sprayers Farm workers

These are the most common health effects. Cancers Depressions/neurological deficits Diabetes Respiratory diseases Women specific disorders General health/multiples diseases

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6Health effect on people with direct exposure

Cancers Studies have shown exposure to pesticides increases risk of

cancer which is high among persons or workers exposed to pesticides compared to general population e.g. Prostate cancers among men has been studied to occur most among

men exposed to Organochlorine pesticides. Exposure of farm workers to pesticides such as Chlorpyrifos has

shown some evidence that suggest that these workers suffer a higher incidence of lung cancer compared to control.

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7Health effect on people with direct exposure

Depressions/neurological deficits Studies suggests that high‐intensity and cumulative pesticide

exposure contributes to depression among pesticide applicators. E.g.

Studies have also shown that pesticides heavily affect the neurology of person with direct exposure. E.g. OPPs are inhibitory to esterase which leads to accumulation of

acetylcholine at the nerve endings causing cholinergic crises by initial stimulation and eventually exhaustion of cholinergic synapses.

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8Health effect on people with direct exposure

Diabetes Studies have in the recent years linked pesticides to diabetes

cases. E.g. Exposure to organochlorine/handling of organophospates

compounds is associated with increased prevalence of diabetes.

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9Health effect on people with direct exposure

Respiratory disorders/ diseases Pesticides have been linked to respiratory related

diseases/disorders. E.g. Asthma in children has been associated with

exposure to pesticides such as parathion and coumaphos in 12 studies done specifically for maternal organochlorines, organophosphates, b and fungicides exposure.

Others include bronchitis, rhinitis disease etc.

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10Health effect on people with direct exposure

Women specific disorders Women are most vulnerable when exposed to pesticides and

have effects such as: Miscarriages – Exposure to pesticides such as abamectin,

imidacloprid, methiocarb, deltamethrin and pirimicarb causes miscarriage among women.

Organochlorines pesticides that disturb the normal estrogen –progesterone balance which is particularly important in the maintenance of pregnancy.

Other cases include menopause and hormonal disorders among women.

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11Health effect on people with direct exposure

General health/ multiple diseases Once the immunity of the a person is

compromised the whole health of a person is compromised.

This allows pathogen to gain entry into the body and cause diseases.

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12Health effect on people with indirect exposure

Person can also be affected health wise by pesticides indirectly through: Exposure to dust/ soil contaminated with pesticides. Clothing contaminated with pesticides Toys for kids contaminated with pesticides Etc.

These effect are felt in farm workers homes or among people living within areas where pesticides are used frequently.

All health complication mentioned above in health effect on people with direct exposure apply also in this case.

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13Health effect on consumers

Pesticides need a given time to breakdown once inside the target point e.g. in tomato.

When the PHI i.e (pre harvest interval) is not strictly adhered to then there are some pesticides residue left in the product which has potential to cause harm to consumer.

Such health complications include : Cancers General health/ multiple diseases

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14Health effect on consumers

Cancers Presence of pesticide residue in products such

as fish, milk, vegetables have contributed to cancer cases.

Pesticides such as DDT, DDD (dichlorodiphenyldichloroethane),PCB (polychlorinated biphenyls) present a higher cancer risk to consumers.

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15Health effect on consumers

General health/multiples diseases Persons health is compromised once he/she

consumes products with pesticide residues. E.g. Parathion has a high case of pesticide

residue in vegetables in areas which experience winters because its highly used during that time.

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16Pesticide residue in foods

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17Effect of pesticide on the environment

Once a pesticides is released into the environment it has effects on two broad areas i.e

Effect on target organism e.g. insect pest, weeds etc.

Effect on non-target organisms e.g. earthworms, pollinators, humans etc.

On the target organism also their can be cases such:Resistance to pesticideResurgence of pest

Pesticides and soil environment Pesticide in water and air ecosystem Pesticide & bio-magnification

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18Effect on target organism

In the recent past their has been an increase in pesticide application targeting a broad spectrum of pests.

This has lead to the pest adapting or moving to new environments.

This is attributed to gene mutation, increase in no.of generations, change in pop growth rate.

This in turn has lead to pest resurgence & resistance to pesticides.

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19Resurgence

Resurgence is defined as the rapid reappearance of a pest population in injurious numbers following pesticide application.

Persistence & broad spectrum pesticides which kill even beneficial & natural enemies account for resurgence of pest.

Other factor leading to resurgence include: Increase in feeding and reproductive rates of insect pests. Application of sub-lethal doses of pesticides. Elimination of a primary pest.

Some of the pests which have resurged include cotton bollworm Helicoverpa armigera

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20Resistance

Resistance may be defined as a heritable change in the sensitivity of a pest population that is reflected in the repeated failure of a product to achieve the expected level of control when used according to the label recommendation for that pest species.

Resistant pop continue to multiply till they become dominant proportion of pop.

As majority of pest is resistant pesticide appear to be ineffective when used.

The no of resistant species among organisms is on the increase ag in insects and mites it stood at 600 in 1990 and rose to 700 in 2001.

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21Pesticides and resistance development

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22Resistance to fungicides

Resistance is a genetic adjustment by a fungus that results in reduced sensitivity to a fungicide.

Reduced sensitivity is thought to be a result of genetic mutations which occur at low frequencies (one in a million or less) or of naturally occurring sub-populations of resistant individuals.

The resistance trait may result from single gene or multiple gene mutations. The build-up of resistant strains is caused by repeated use of the fungicide which exerts

selection pressure on the population. This shift toward resistance occurs at different rates, depending on the number of genes

conferring resistance. When single gene mutations confer resistance, a rapid shift toward resistance may occur,

leading to a population that is predominantly resistant and where control is abruptly lost . When multiple genes are involved, the shift toward resistance progresses slowly, leading

to a reduced sensitivity of the entire population .

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23Effect of pesticides on non-targets

Pesticide effect on non-target has become a worldwide point of discussion.

E.g. The reduction of natural enemies and pollinator numbers by some of the insecticides in the recent years.

Their destruction has led to a surge in pest levels in the environment & use of more pesticides to control the pest wrecking havoc.

Pesticides affect both invertebrates e.g. earthworms and vertebrates e.g. humans.

Below are some of cases discussed including- earthworms, pollinators, predators and humans.

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24Effect of pesticides on earthworms

Earthworms rep +80% of the terrestrial invertebrates and are responsible of soil fertility by decomposing soil organic matter in humus.

Studies have shown pesticide application lead to their decline. For example Carbamate insecticides are very toxic to earthworms and

some organophosphates have been shown to reduce earthworm populations.

Pesticides affects: Earthworm growth Reproduction(cocoon production, hatchling per cocoon, incubation period) Neurotoxicity Physiological damage i.e cellular dysfunction & protein catabolism Earthworm general mortality to pesticide exposure

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25Effect of pesticides on earthworms

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26Effect of pesticides on pollinators

Pollinators are biotic agents that play a very important role in pollination process.

They include bees (honey, bumble), fruit flies, beetles, birds (hummingbirds, sunbirds).

Pesticides application affect various activities of pollinators such as: Foraging behavior Colony mortality Pollen collecting efficiency

Application of neonicotinoid insecticides such as imidacloprids leads to the above effects on pollinators.

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27Effect of pesticides on bees

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28Effect on predators

Predators are organisms that live by preying on other organisms and they play a very crucial role in keeping pest populations under control.

These include coccinellids, braconid wasps and predatory spiders.

E.g. cypermethrin and imidacloprids cause high mortality rate of the above mentioned predators than when bio-pesticides are used such neem.

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29Effect of pesticide on natural enemies

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30Effect on human Pesticides effect on human is a result of increase in

pesticide persistence in environment and ability to enter into food chain.

Pesticides can gain entry into humans through direct contact, contaminated food/water/air.

Pesticides effects can be either acute or chronic. Acute effects include -headaches, body aches, skin

rashes, poor concentration, nausea, dizziness, impaired vision, cramps etc.

Chronic effects include- cancers, birth defects, diabetes etc

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31Pesticides and soil environment Use of pesticides in agriculture/other purpose lead to accumulation of

such pesticides in the soil. Indiscriminate use of pesticides further worsen the already stressed

soils. The pesticides fate is determined by soil properties such as

degradation, transport, adsorption/desorption. Effects of pesticides in soil include:

1. Alter soil microbial diversity/biomass.2. Affect soil vital biochemical reactions.3. Affect mineralization of soil organic matter. 4. Disturb local metabolism/alter soil enzymatic activity.

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32Pesticides and soil environment1. Alter soil microbial diversity/biomass Pesticides that reach soil affect microflora/fauna in the

following ways. Affect the growth, microbial diversity or microbial

biomass of the soil microflora. E.g sulfonylurea herbicides- metsulfuron methyl, chlorsulfuron and thifensulfuron methyl reduce the growth of the fluorescent bacteria Pseudomonas strains.

Inhibit or kill certain group of microorganisms and outnumber other groups by releasing them from the competition E.g Endosulfan increase bacteria biomass by 76% and reduce fungal biomass by 47%.

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33Cont..

Source of energy leading to increase in growth and disturbance in soil ecosystem of some microbial groups. E.g. Bacterial are known to use chlorpyriphos as a source of carbon for their own growth.

Reduce the functional structure and functional diversity of microorganisms, but increase the microbial biomass E.g. methamidophos and urea decreased the microbial biomass and increased the functional diversity of soil as determined by microbial biomass and community level physiological profiles.

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34Pesticides and soil environment2. Affect soil vital biochemical reactionsPesticides affect reactions such as nitrogen fixation , nitrification and ammonification by activating/deactivating specific soil microorganisms and enzymes. The synergistic and additive interactions between

pesticides, micro-organisms and soil properties ultimately govern increase or decrease in rate of soil biochemical reactions.

E.g. Population of Azospirillum spp bacteria + rate of ammonification increased at a particular pesticide concentration (I.e 2.5 to 5.0 kg/ha) in both laterite & vertisol soils planted with groundnuts.

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35Pesticides and soil environment

3.Affect mineralization of soil organic matterPesticides have been reported to influence mineralization of soil organic matter a key soil property influencing soil quality and productivity. E.g. Significant reduction in soil organic matter

was found after the application of four herbicides (atrazine, primeextra, paraquat, and glyphosate).

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36Pesticides and soil environment

4. Disturb local metabolism/alter soil enzymatic activity Soil in general contains an enzymatic pool which comprises of free

enzymes, immobilized extracellular enzymes and enzymes excreted by (or within) microorganisms that are indicator of biological equilibrium including soil fertility and quality.

E.g. phosphate (hydrolyze organic P compound into inorganic P) when exposed to pesticides such as 2,4-D nitrapyrin, mancozeb, carbendazim and the enzymatic activity increases but high concentration increase incubation period leading to inhibitory effect.

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37Pesticides in water and air ecosystem Pesticide residues in water and air are a major concern as they pose a

serious threat to biological communities. Pesticides get into water through:

Accidental spillage, industrial effluent, surface run off and transport from pesticide treated soils, washing of spray equipment's after spray operation, drift into water points, aerial spray to control water-inhibiting pests etc.

Pesticides get into air through: Spray drift, volatilization from the treated surfaces, and aerial application of

pesticides. Once in these environments pesticides affect several organisms such

as: Birds, fish, amphibians etc.

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38Pesticides in water and air ecosystem

Fishes Fishes are an important part of marine ecosystem

as they interact closely with physical, biological and chemical environment.

Fishes provide food source for other animals such as sea birds and marine mammals and thus fishes form an integral part of the marine food web.

Pesticides have been directly linked to causing fish mortality worldwide.

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39Effect of pesticides on fish

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40Pesticides in water and air ecosystem

Birds Birds are a diverse group, and apart from their distinct songs and

calls, showy displays and bright colors adding enjoyment to lives of humans, they play a very critical role in food chains and webs in our ecosystems.

Pesticides exposure by different means such as direct ingestion of pesticide granules and treated seeds, treated crops, direct exposure to sprays, contaminated water, or feeding on contaminated prey, and baits cause birds mortality.

Carbamates, organochlorines, and organophosphates can cause a decline in the populations of raptorial birds by altering their feeding behavior and reproduction.

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41Effects of pesticides on birds

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42Pesticides in water and air ecosystem

Amphibians The global decline in the amphibian population has

become an environmental concern worldwide. Many amphibian species are on the brink of extinction

with 7.4% listed as critically endangered, and at least 43.2% experiencing some sort of population decrease.

Glyphosate has far reaching effects on non-target amphibians juvenile frog.

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43Effect of pesticide on amphibians

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44Pesticides and biomagnification Biomagnification is the increase of some of the pesticides

due to its persistent and non-biodegradable nature in the tissue of organ at each successive level of food chain.

Organisms at the higher levels of food chain experience greater harm as compared to those at lower levels.

For example, out of 36 species collected from three lakes of northeastern Louisiana (USA) that were found to contain residues of 13 organochlorines.

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