ROUNDUP - GLYPHOSATE

environmental exposure,
toxicity and mechanisms of action
Innovation Lectures (INNOLEC)
Masaryk University, May 2012

Roundup – identity, use
•Herbicide (pesticide targetting plants)
•
•Glyphosate-based chemical
•used in home garden care,
•    sidewalks, highways, …
•Used in large scale
•    agriculture
•Used in siviculture
•Most widely used agricultural chemical globally
•Dobson, Giesy and Solomon, 2003
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• Economy – Life style
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Roundup - key issues
•RR (Roundup Ready) crops
•Exponential increase in use of Roundup in large scale agriculture
•Impact on environment
•Potential impact on health of biota and human
•Control of food production by one company
Genetically modified – GM crops

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Greater use of Glyphosate herbicides linked to GM (RR) crops

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•Roundup applied at specific time intervals
•RR genetically modified plants grow but weeds are killed
•Greater productivity of RR crops

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Roundup Ready (RR) crops have good yields


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•Glyphosate - active ingredient of Roundup
•weak organic acid, N-(phosphonomethyl)glycine
•non-selective herbicide
•herbicidal action
inhibition of synthesis of aromatic amino acids
•Roundup=glyphosate, surfactants, water, …
1. Identity and mode of action of RU
glyphosate

Herbicidal action of glyphosate
inhibition of EPSPS
(5-EnolPyruvyl Shikimic acid-3-Phosphate Synthase)

2. Degradation products of Glyphosate
AMPA
Aminomethyl-
phosphonic
 acid
N.B.
Surfactant(s)
POEA
Polyethoxylated
tallowamine
used in
commercial
glyphosate
preparations

2. Roundup - Glyphosate Exposure
Sorption, degradation, leachability of GL

• strong sorption of GL to soil particles

• contamination of ground water limited
• leaching of GL to surface waters
        during rain events
•    spraying over water, spray drift

Byer et al. 2008 Environ Sci Technol



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Exposure to GL in Lumbricus - link to oxidative stress
Toxicity of Roundup - Glyphosate
•invertebrates
Contardo-Jara et al. 2009
Environ Pollution

Toxicity of Roundup - Glyphosate
•invertebrates
Effect of RU on energetic status, lipid peroxidation,
reproductive fitness of Hyalella     Dutra et al. 2011Ecotoxicology

Mechanistic links between exposure and effects
Effects at different levels of biological organisation


Folmar et al. 1979
Toxicity
•Fish
•
Toxicity:
RU >GL
Surfactant > GL

Toxicity of Roundup - Glyphosate
Compare
•toxicity in serum-containing and serum-free medium
•toxicity of RU and GL
Benachour et al. 2007 Arch Env Contam Toxicol
•Human placental cells JEG3

Toxicity of RU >> Toxicity of GL
similar results with HepG2 cells


Role of aromatase in steroidogenesis



Walsh et al. 2000
Roundup inhibits steroidogenesis in rats
by disruption of StAR protein expression
Toxicity of Roundup - Glyphosate

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Role of StAR (Steroid Acute Regulatory Protein)
in steroidogenesis
Stocco, 2000

Toxicity of Roundup - Glyphosate
[chronic toxicity] ~   [environmental]
HQ (Hazard Quotient) analysis
•Amphibians
•very sensitive to RU-GL
•
Dinehart et al. 2010 Env Poll
studies by Relyea
controversy
•

HQ analysis = Exposure level : toxicity reference value
HQ < 1.0 no risk, acceptable risk
HQ > 1.0 need for further evaluation
HQ > 100 definite risk
Giesy, Dobson and Solomon, 2000
Ecological Risk Assessment for Roundup Herbicide
Rev Environ Contam Toxicol 167: 35-120

Toxicity of Roundup – Glyphosate
•Health concerns
Amphibians - highly sensitive
toxicity to larvae at environmental concentrations (1-2 mg/L)
Endocrine disruption
effects on aromatase
effects on StAR protein
Toxicity to non target plant species

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ROUNDUP/GLYPHOSATE - CONCERNS
•Evolution of Glyphosate-resistant weeds

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•Dependance of food production on GM seeds


Biofuel production
Food production
Risk assessment for Roundup
Greater use of RU
Economics of food
production
Contamination of
surface water
Health risks
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Waterton National Park – Alberta, Canada