Environmental Indexes

by Amit Joshi

Purpose

Assess the potential risks posed by releases from industrial sources

Conduct preliminary impact assessment

Tool for screening analysis

Classification

Abiotic IndexesHealth-Related IndexesEcotoxicity Indexes

Abiotic Indexes

Global WarmingStratospheric Ozone DepletionAcid DepositionSmog Formation

Health-Related Indexes

Inhalation ToxicityIngestion ToxicityInhalation Carcinogen Toxicity Ingestion Carcinogen Toxicity

Ecotoxicity Indexes

Fish Aquatic Toxicity

Global Warming Index

Ratio of cumulative infrared energy capture from the release of 1 kg of a green-house gas relative to that from 1 kg of carbon dioxide (IPCC,1991)

n

0

dtCa

n

0

dtCa

GWPi

22 coco

ii

ai is the predicted radiative forcing of the gas i (Wm-2)

Ci is its predicted concentration in the atmosphere (ppm)

n is the number of years over which the integration is performed

Global Warming Index (contd..)

The product of GWP and the mass emission rate of the greenhouse chemical gives the emission in terms of CO2 (the benchmark compound)

IGW= (GWPi * mi) For the, organic compounds, with atmospheric reaction

residence time less than ½ a year, an indirect GWP is defined (Shonnard and Hiew, 2000)

i

2

MW

MW Nc ect)GWPi(indir

CO

Nc is the number of carbon atoms in the chemical

MWi is the molecular wt.

Global Warming Index (contd..)

Factors affecting GWP

1) Chemical’s tropospheric residence time

2) The strength of its infrared radiation absorbance

Ozone Depletion Index

Ratio of the predicted time- and height- integrated change

[O3] in stratospheric ozone caused by the release of a specific quantity of the chemical relative to that caused by the same quantity of a benchmark compound, tricholorofluoromethane (CFC-11,CCL3F) (Fisher et al., 1990)

113

3

][

][

CFC

i

O

O

Ozone Depletion Index (contd..)

The product of ODP and the mass emission rate of the greenhouse chemical gives the emission in terms of CFC-11, the benchmark compound.

IOD= (ODPi * mi)

Acid Rain Index

The number of H+ created per number of moles of the compound emitted as shown in the following equation

X + ------------- H+ + ----------- where, X is the emitted chemicals substance initiating

acidification and is a molar stoichiometric coefficient.H+ created per mass of substance emitted (i,H+moles/ kg i)

i= i__

MWi

MWi is the molecular weight of the emitted substance (moles i /kg i )

Acid Rain Index (contd..)

ARPi = __i__

SO2

expressed in terms of benchmark compound SO2

The product of ARP and the mass emission rate of the chemical gives the emission in terms of SO2 (the benchmark compound)

IAR= (ARPi * mi)

Smog Formation Index

Incremental reactivity (IR) for evaluation of SWP

Definition: The Change in moles of ozone formed as a result of emission into an air shed of one mole of the VOC (Carter and Atkinson,1989)

VOC IR is proportional to NOx level relative to reactive organic gases (ROG)

Smog Formation Index (contd..)

Maximum Incremental Reactivity (MIR)- Most relavent scale for comparing VOCs. MIR occurs under high NOx conditions when the highest ozone formation occurs (Carter,1994)

SFPi= __MIRi__

MIRROG

MIRROG is the average value for background organic gases, the benchmark compound for this index

Smog Formation Index (contd..)

The product of SFP and the mass emission rate of the chemical gives the emission in terms of background ROG, the benchmark compound

ISF= (SFPi * mi)

Toxicity Potentials

Toxicity : Complex function of dose and responseDose: Depends on complex series of steps involving

1) manner of release

2) environmental fate and transport of chemicals

3) uptake mechanismsResponse: Response by the target organ in the body is a complex

function of

1) chemical structure

2) modes of action

Toxicity Potentials (contd..)

Types of Toxicity

1) Carcinogenic Toxicity: defined in terms of Benzene

2) Non-Carcinogenic Toxicity : defined in terms of Toluene

Dominant exposure routes for human contact with toxic chemicals in the environment

1) Inhalation

2) Ingestion

Toxicity Potentials (contd..)

Non-Carcinogenic Toxicity controlled by threshold exposure i.e., doses below the

threshold value do not manifest a toxic response whereas the doses above this will do.

Key parameters for chemicals Ingestion : reference does (RfD(mg/kg/day))

: lethal dose (LD50) Inhalation: reference concentration (RfC(mg/m3))

: lethal concentration(LC50)

RfCs and RfDs are not available for all chemicals so LD50 and LC50 are used

Toxicity Potentials (contd..)

Non-Carcinogenic Ingestion Toxicity Potential

Ingestion Toxicity Potential

Inhalation Toxicity Potential

I*ING

CW ,i LD50, Toluene

CW ,Toluene LD50,i

I*INH

CA, i LC50,Toluene

CA, Toluene LC50,i

C w,i and C w,Toluene are the steady-state concentrations of the chemical and the benchmark compound in the water compartment

C a,i and C a,Toluene are the steady-state concentrations of the chemical and the benchmark compound in the air compartment

Toxicity Potentials (contd..)

Non-Carcinogenic Ingestion Toxicity Potential (contd..)

The product of I*INGi and the mass emission rate of the chemical

gives the emission in terms of Toluene, the benchmark compound

IING= (I*INGi * mi)

The product of I*INHYi and the mass emission rate of the chemical

gives the emission in terms of Toluene, the benchmark compound.

IINH= (I*INHi * mi)

Toxicity Potentials (contd..)

Carcinogenic Toxicity

Ingestion Toxicity Potential

Inhalation Toxicity Potential

I*CING

CW ,i HVi

CW ,Benzene HVBenzene

I*CINH

CA, i HVi

CA ,Benzene HVBenzene

HV is the hazard value for carcinogenic health effects

Toxicity Potentials (contd..)

Carcinogenic Toxicity(contd..)

The product of I*CINGi and the mass emission rate of the chemical

gives the emission in terms of Toluene (the benchmark compound)

ICINGi= (I*CINGi * mi)

The product of I*INHYi and the mass emission rate of the chemical

gives the emission in terms of Toluene (the benchmark compound)

ICINHi= (I*CINHi * mi)

Toxicity Potentials (contd..)

In non-carcinogenic toxicity indexes, RfDs and RfCs can also be used if available instead of LD50 and LC50 .

In carcinogenic toxicity indexes, Slope Factor (SF) can be used instead of hazard values for chemicals.

Slope Factor : Known as a cancer slope potency factor. It is obtained using the excess cancer versus administered dose data

Ecotoxicity Index

Fish Toxicity Index

LC50 - the 4-day rodent or fish lethal dose (mg/l) which causes 50%

mortality in a test population.

Benchmark compound: PCP - pentachlorophenol

I*FT

CW,i LC50 f ,PCP

CW,PCP LC50 f ,i

Summary

R ela tiv e R isk In d e x E q u a tio n

IG W , i* GWP i

G lo b a l W a r m in g

IG W , i* N C

MW C O2

MW i

O zo n e D ep le t io nIO D, i

* ODP i

S m o g F o rm a tio nI S F, i

* MIR i

MIR R O G

A cid R a inIA R, i

* ARP i

ARP S O2

GW P = g lo b a l w a rm in g p o ten tia l, N C = n u m b er o f c a rb o n s a to m s, O DP = o zo n ed e p le tio n p o te n ta l, M IR = m a x im u m in c re m e n ta l rea c tiv ity , A R P = a c id ra in p o ten tia l .

Summary (contd..)

Relative Risk Index Equation

Human Toxicity Ingestion Route I*

ING CW ,i LD50, Toluene

CW ,Toluene LD50,i

Human Toxicity Inhalation Route I*

INH CA, i LC50,Toluene

CA, Toluene LC50,i

Human Carcinogenicity Ingestion Route

I*CING

CW ,i HVi

CW ,Benzene HVBenzene

Human Carcinogenicity Inhalation Route

I*CINH

CA, i HVi

CA ,Benzene HVBenzene

Fish Toxicity

I*FT

CW,i LC50 f ,PCP

CW,PCP LC50 f ,i

LD50 = lethal dose 50% mortality, LC50 = lethal concentration 50% mortality, and HV = hazard value for carcinogenic health effects.