Bio 430: Chemicals in the environmentoregonstate.edu/instruct/bi430-fs430/Documents-2004/4B...Oregon State University Pesticide Properties used to evaluate fate in the Environment

Bio 430: Chemicals in the environment

Jeffrey JenkinsDepartment of Environmental and

Molecular ToxicologyOregon State University

Oregon State University

Chemical fate: transformation and transport within and between

Soil-Air-Water-Biota

Source: U.S. Geological Survey


leach toward groundwater

plant uptake microbial or chemical

degradation

photodegradation

runoff

sorption to soil particles

volatilization

Chemical fate processes

wind erosion

washoff

interception


sediments

water

atmosphere direct + indirect

photolysis

air/water exchange

wet + drydeposition

groundwaterinfiltration/exfiltration

sediment/waterexchange

chemical + biologicaltransformation

photodegradation

sorption to sediment and particleschemical + biological

transformation

runoff outflow



Chemical fate in the environment

Molecular interactions(physical-chemical properties, reactivities)

Environmental factors(Temperature, pH, light intensity, ion composition and strength,

microbial activity, natural organic matter, etc.)

Environmental processes(e.g. air/water exchange, sorption/desorption, chemical,

photochemical and biological transformation)


Chemical fate in the environment

Transport and mixing processes

Dynamic behavior in a natural system(mathematical models and field investigations)


Chemicals in the Environment

Initial distribution to environment (manufacture and use):emission in: air-soil-water-biota compartments

Transformation: degradation/metabolism

Redistribution- transport in and between compartments:

diffusion/advection-dispersion/mass transport


Chemicals in the Environment

Understanding chemical fate, what scale?

Local scale: site-specific inputs, potential for off-site transport.

Watershed scale: integration of site-specific inputs and transport, particular emphasis on water quality.

Regional scale: integration of watershed-airshed chemical inputs and redistribution, long range transport of persistent compounds.


Range of ESA Listed Salmon


Pesticides in the EnvironmentInitial distribution in the environment:method of applicationtiming of applicationfrequency of applicationamount of active ingredientformulation (other ingredients)


Environmental Behavior of Pesticides in Soils

Initial distribution

Persistenceand

Mobility

Environmental Fate

temperature

soil pH

soil texture

sunlight

organic matter

moisture


Pesticide Fate and Transport

Physical-chemical properties:

• Water solubility• Vapor Pressure• Kd (soil/water partition coefficient)• Henrys Law Constant• Soil half-life• Foliar half-life


Sorption

binding to soil or sediment particles


Soil sorption

soil particlesoil water

K

K describes the relationship between pesticide sorbed to soil particles and pesticide dissolved in soil water.

concentration of pesticide sorbed to soil

concentration of pesticide in solution

d

d


Soil sorption

To account for different soil types and organic matter content the Kd is normalized for % organic carbon.

doc *

KK% organic carbon

=

* decimal equivalent


Soil Properties that Influence Leaching and Runoff

• Permeability • Water table conditions• Organic matter content• Clay content



Course textured soils and other soil conditions thatresult in preferential flow paths must also be considered.


Pesticides in Ground and Surface Water


Pesticides in surface water

Mass transfer primarily in the dissolved phase, will vary with pesticide’s solubility in water and soil sorption.

soil particlewater

concentration of pesticide sorbed to soil

concentration of pesticide in solution


Partitioning between soil compartments(soil, water air)

soil particle

soil water

K

K describes the relationship between pesticide concentration in soil water and pesticide concentration in air.

K

air

chemicalin air

Chemical in water

h

h

d


Volatilization

volatile loss from plant, water, or soil surfaces


Atmospheric Transport Zones




Volatile loss as Percent Applied

Pesticide Application Rate(kg a.i./Ha)

Vapor Pressure(mPa @ 25 oC)

24 hr Volatile lossas % Applied

Chlorpyrifos 1.9 2.50 16.5

Ethofumesate 2.5 0.650 6.3

Triclopyr (acid) 1.1 0.170 4.5

Triadimefon 3.1 0.060 2.1

Propiconazole 2.2 0.056 1.1

Cyfluthrin 0.2 0.004 ND


Pesticide Fate

• Field dissipation: sum of chemical and biological processes including:

– Chemical degradation1

– Biological degradation (microbial + plant)1

– Photodegradation2

– Volatilization

1Approximated with a 1st order rate constant2Approximated with a psuedo 1st order rate

constant


Pesticide degradation half-life

Half-life = the amount of time it takes the parent compound to decay to half its original amount

Half-life in an environmental compartment: (soil-air-water-biota) sum of all degradation and transport pathways


Pesticide degradation half-life

No of ½ lives

% amount remaining

3.3 106.6 110 0.1


Sunlight photolysis of an aqueous suspension of nitrofen

OCl

Cl

NO2

OHCl

Cl

OHCl

OH

OCl

Cl

NH2 OH NH2 OH NH2

OH

OCl

Cl

O

Cl

ClN N

OH OH

OH OH

OH

POLYMER

nitrofen


Chemical and microbial degradation of chloroanilines

NH2

Cl

NH2

Cl

OH

Cl

OH

OHCl

CHOCOOH

OHCl

COOHCOOH

Cl

CO2

OH2

COOH

COOH

Cl

OO COOH

O

HOOC

COOH

O2

O2

A. faecalis

Ps. diminuta


NOAEL

LD50: lethal dosefor ½ the test animals


Aldicarb degradation pathways and LD50 values (rat acute oral)

NO

O NSCH3

CH3

CH3CH3

NO

O NSCH3

CH3

CH3CH3

O

NO

O NSCH3

CH3

CH3CH3

O

O

NS

CH3

CH3

CH3OH N

SCH3

CH3

CH3

NS

CH3

CH3

CH3

O

OH NS

CH3

CH3

CH3

O

NS

CH3

CH3

CH3

O

OOH

NS

CH3

CH3

CH3

O

O

Aldicarb0.9 mg/kg

sulfone24 mg/kg

sufoxide oxime8060 mg/kg

sulfone oxime1590 mg/kg

oxime2380 mg/kg

nitrile570 mg/kg

sulfoxide0.9 mg/kg sulfone nitrile

4000 mg/kg

sulfone nitrile350 mg/kg

H20

H20

H20

O2 , fast

O2


Pesticide Properties used to evaluate fate in the Environment

water solppm

Kocml/g

Vaporpressure

mm Hg

soil 1/2 life

days

foliar 1/2 life

days

Atrazine 33 100 2.90E-07 60 5

Diuron 42 480 6.90E-08 90 30

MCPA ester 5 1000 1.50E-06 25 8

pendimethalin 28 5000 9.40E-06 90 30

triclopyr ester 23 780 1.26E-06 46 15

carbaryl 120 300 1.20E-06 10 7

chlorpyrifos 0.4 6070 1.70E-05 30 3

malathion 130 1800 8.00E-06 1 3

esfenvalerate 0.002 5300 1.10E-08 35 8


Chemical fate determines exposure to humans and aquatic life

leach toward groundwater

plant uptake microbial or chemical

degradation

photodegradation

runoff

sorption to soil particles

volatilization


wind erosion


13.4 million lbs of pesticides used annually in OregonWhat are the risks and who decides?

Federal Insecticide, Fungicide, and Rodenticide Act regulates pesticide manufacture, use, storage, and disposal (benefit-risk balancing statute.)

Under Authority of the Clean Water Act, ODEQ has the authority to set pesticide water quality standards for waters of the state (TMDLs).

Under the Endangered Species Act NMFS and USFWS have the authority to set rules deemed necessary to prevent more species declines under a provision called “Four D.”

EPA, NMFS, and USFWS have “overlapping” jurisdiction with regards to pesticide use and the Endangered Species Act.


EPA Risk Assessment

Risk = f (exposure, toxicity)

Source: Purdue University Pesticides Program


Pesticide Risk Assessment

RFD: The Reference Dose is the amount of a pesticide residue a person could consume daily for 70 years with no harmful non-cancereffects.


Pesticide Risk Assessment

The RFD is determined by dividing the NOAEL by a safety factor, usually between 100 and 1000,

to account for uncertainty in extrapolating from animal studies and to protect sensitive individuals, including infants and children.


Quantitative Assessment of Health Risks of Pesticides in Drinking Water

MCL - The Maximum Contaminant Level permissible in water which is delivered to any user of a public water system (Safe Drinking Water Act; ~50 pesticides have MCLs)

HA - Health Advisory: EPA guidance for drinking water contaminants based on lifetime exposure and non-carcinogenic endpoints. HA is derived from the DWEL.

DWEL - Drinking Water Equivalent Level, based on the Reference Dose (RfD) and assuming 70 Kg person drinks 2 liters per day over a lifetime. The DWEL has been adjusted assuming that drinking water comprises 20% of the allowable daily intake.


Pesticide Risk Assessment: Wildlife

What is the toxicity of the pesticide and it’s degradates to wildlife?

Acute toxicity (high dose-short exposure)

Chronic toxicity (low dose-long exposure)

Most sensitive adverse effect

Sensitive sentinel species


EPA Pesticide Aquatic Risk: Wildlife Toxicity Assessment

• Laboratory tests are used to determine the NOAEL in representative species.

• The hazard quotient is the ratio of the NOAEL to the expected environmental concentration.

• If the hazard quotient is greater than 1.0, the potential exists for adverse ecological effects.


Use of models for evaluating hazards associated with chemicals in the

environment

Models use a systems approach to understanding complex phenomenon.

Computer based environmental models present a conceptual framework and a mathematical formulation of fate and transport between compartments (soil, air, water, biota) based upon scientific principles.


Environmental fate models

PRZM and EXAMS (EPA)CalTOX (California EPA)Fugacity Model Levels I, II, III (Mackay)Gaussian plume models (EPA, NOAA)

http://www.lanl.gov/orgs/d/d4/movies.shtml

http://www.lanl.gov/orgs/d/d4/movies.shtml


Fugacity Model for Biphenyl


Fugacity Model for Biphenyl


How Do We Assess Risk?Follow the National Academy of Sciences (NAS)

four-step risk assessment paradigm*:

HazardIdentification

Risk Characterization

ExposureDose-

Response Assessment

* From the National Research Council’s Risk Assessment in the Federal Government: Managing the Process, 1983.