CE 3231 - Introduction to Environmental Engineering and Science

CE 3231 - Introduction to Environmental Engineering and Science

Readings for This Class:

Ohio Northern University

Introduction Chemistry, Microbiology & Material Balance Water & Air Pollution Env Risk Management

Partition Coefficients and ModelingReal data characterizing risk is difficult and expensive to come across. As thousands of chemicals enter the market place each year, models help estimate the risk based upon compound structure and physical-chemical properties. Here, we examine how partition coefficients are used to make decisions.

Exposure Assessment

pathways of exposure calculating CDI

Lecture 32Partition Coefficents and Modeling Risk

(Risk III)

Risk & Risk Assessment

Topics Covered Include: New Chemicals Review Risk Models Partitioning Coefficients

Octanol water Vapor pressure

New Chemicals Review Program

New Chemicals Review Program – Premanufacture Notice

US Environmental Protection AgencyOffice of Pollution Prevention and ToxicsToxic Substance Control Act – Section 5

Program Goal

Serve as a “gatekeeper to help manage the potential risk from chemicals new to the

marketplace.”


Risk Evaluations

Risk Based - potential health risks - toxicological investigations

Exposure Based - potential exposure risks - chemical property investigations - fate modeling: ranks outcomes I to IV


Physical/Chemical Properties

Estimate Concentration

in Water

Estimate Absorption

through skin, lungs and GI

Estimate Bioconcentration

Estimate Risk to Human Health and the Environment

Estimate Migration

through Soil to Groundwater

Estimate Toxicity

Boiling Point

Vapor Pressure

Estimate Concentration

in Air

Estimate Inhalation Exposure

Estimate Henry’s Law Constant

Estimate Volatilization from water

Water Solubility (estimate)

Octanol/Water Partition

Coefficient (Kow, P)

Melting Point

Estimate Removal in Wastewater Treatment

Soil/Sorption Coefficent (Koc)

(estimate)

CAS Number : 000105-55-5Chem Name : n-boulangerMol Formula: StRuCtUrEMol Weight : 186Melting Pt : -10 deg CBoiling Pt : 128 deg CWater Solubility: Value : 0.01 mg/L Temp : 37 deg C Type : EXPLog Kow (logP): Value : 3.57 Type : EXPVapor Pressure: Value : 210 mm Hg Temp : 25 deg C Type : EXPHenry's Law Constant: Value : 6.85E-004 atm-m3/mole Temp : 25 deg C Type : EST

N-boulanger is used to formulate air fresheners.

Illustrating Example


Octanol/Water Partitioning

• Reported as log Kow or log P• Used to estimate water solubility, soil sediment adsorption, biological absorption (dermal, oral, GI, inhalation), bioaccumulation, and toxicity• model for partitioning within body



80% of PMN process is determined through use of log Kow

- fuels QSARs (Quantitative Structural Activity Relationships) or EPA’s ECOSAR (Ecological Structural Activity Relationship) used during the evaluation

Experimental Determination

1. Shake Flask Method

2. Slow Stir

3. Generator Column via HPLC



Non-experimental Estimation Methods

1. Fragment/segment summation

2. Correlations with molecular descriptors (shape, volume,…) with known chemistries

3. Correlations with Reversed Phase HPLC Retention Times of known chemistries

4. 3 dimensional structure


The Agency prefers

experimentally derived Kow values.

Whenever non-experimental methods will be estimated, the

most conservative value will be used!

Log Kow drives partitioning between the substance and biological tissues


Vapor Pressure

• rate of vapor condensation = vaporization rate of liquid• determined experimentally through automated instruments, an isoteniscope, or gas saturation procedure• strongly hints at air fraction• can be correlated for most compounds


Vapor Pressure drives partitioning of compound between atmosphere.

CAS Number : 000105-55-5Chem Name : n-boulangerMol Formula: StRuCtUrEMol Weight : 186Melting Pt : -10 deg CBoiling Pt : 128 deg CWater Solubility: Value : 0.01 mg/L Temp : 37 deg C Type : EXPLog Kow: Value : 3.57 Type : EXPVapor Pressure: Value : 210 mm Hg Temp : 25 deg C Type : EXPHenry's Law Constant: Value : 6.85E-004 atm-m3/mole Temp : 25 deg C Type : EST

N-boulanger is used to formulate air fresheners.

Putting Values into Context

Aqueous Solubility Ranges

High > 500 mMmoderate 100 - 500 mMlow < 100 mM

Putting Numbers into Context

Vapor Pressure Ranges (mmHg) @ 20-30 deg F

Very highly volatile > 10-3

highly volatile 10-4 to 10-3

moderately volatile 10-5 to 10-4

low volatility 10-5 to 10-6

non volatile < 10-7

logP considered a problem when logKow > 5 (will bioaccumulate)

logP from 2 to 5 considered likely to bioaccumulate

logP from 0 to 2 potential to bioaccumulate

Henry's Constant Ranges (atm m3/mol)

non volatile < 3x10-7

low volatility 3x10-7 to 1x10-5

moderate volatility 1x10-5 to 1x10-3

high volatility > 1x10-3







logKow considered a problem when logKow > 5 (will bioaccumulate)

logKow from 2 to 5 considered likely to bioaccumulate

logKow from 0 to 2 potential to bioaccumulate








non volatile < 10-7








CAS Number : 000105-55-5Chem Name : n-boulangerMol Formula: StRuCtUrEMol Weight : 186Melting Pt : -60 deg C LIQUIDBoiling Pt : 128 deg CWater Solubility: Value : 0.01 mg/L LOW SOLUBILITY Temp : 37 deg C Type : EXPLog Kow: Value : 3.57 LIKELY TO BIOACCUMULATE Type : EXPVapor Pressure: Value : 210 mm Hg VERY HIGHLY VOLATILE Temp : 25 deg C Type : EXPHenry's Law Constant: Value : 6.85E-004 atm-m3/mole Temp : 25 deg C MODERATELY VOLATILE Type : EST


Fate considers reactions too!

1. Biologically mediated degradation

2. Hydrolysis

3. Photolysis (direct or indirect)


All the models EPA uses to determine reactions are based upon the physical/chemical parameters reported in the PMN



Putting Numbers into Context






non volatile < 10-7

logP considered a problem when logKow > 5 (will bioaccumulate)

logP from 2 to 5 considered likely to bioaccumulate

logP from 0 to 2 potential to bioaccumulate






New Chemicals Process

1. Gatekeeper for new chemicals

2. Dependent upon partitioning

3. Physical/chemical properties key

4. Modeling approach


“…we’re busy alright. I can send you home with about 500 submissions right now. Do you have a U-Haul?...”

Documents

CE 3231 - Introduction to Environmental Engineering and Science