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Characterisation Method Information
Characterisation Method Name:
Benzene impact on severe morbidity
Version:
1999
Date Completed:
1999
Principal Method Name:
EPS: cancer pathway, global warming and oxidant pathways
Method Description:
Model 1, cancer pathway

The characterisation factor is determined by the empirical method.

Category indicator value in system considered
The portion of cancer incidences not causing death (36%) is classified as severe
morbidity. The average length of the morbidity is not known at present, but is assumed to be 5 years. This means that the total indicator value in the environmental system is (5/24)*(0.36/0.64)*6.24E+04 = 7.31E+03 person-years of severe morbidity, where 6.24E+04 is the indicator value determined in "Benzene impact on YOLL".

Contribution to category indicators value from a flow unit

The same contribution as in "Benzene impact on YOLL" is valid, i.e. 3.12E-10 per kg benzene.

Calculation of characterisation factor

This would mean that the characterisation factor would be (5/24)*(0.36/0.64)* 5.91E+04
*3.12E-10 = 2.28E-06 person-years/kg benzene.

Model 2, global warming pathway

The characterisation factor is determined by an equivalency method using CO2 as a reference.

Equivalency factor

The GWP100 was estimated by IPCC (Intergovernmental Panel on Climate Change ) to 11 in one of the early reports. (1990). Later this statement was withdrawn by IPCC, with the motivation that the uncertainty was too large. In the EPS context however, omitting it would create a larger error than including it, so the equivalency factor 11 will still be used.

Calculation of pathway specific characterisation factor

As the characterisation factor of CO2 for severe morbidity is 3.53E07 person-years/kg
CO2 (CO2 impact on severe morbidity) we obtain the pathway specific characterisation factor of benzene to severe morbidity to 11*3.53E07 = 3.88E06

Model 3, oxidant pathway

The characterisation factor is determined by an equivalency method using ethene as a
reference.

Equivalency factor

Benzene has a photochemical peak oxidant formation potential (POCP-1) of 0.317
(Lindfors et.al 1994) relative to ethylene.

Calculation of pathway specific characterisation factor

The oxidant pathway specific characterisation factor of ethylene for severe morbidity is determined to 6.76E-07 person-years/kg ethylene. This gives an oxidant pathway specific characterisation factor of benzene for severe morbidity of 0.317*6.76E-07 =2.14E-07 person-years/kg.

Calculation of characterisation factor

The characterisation factor for the added impacts from all pathways is 2.28E-06 +
3.88E06 + 2.14E-07 = 6.16E06 person-years/ kg benzene


Literature Reference:
Houghton, J.T Jenkins, G.J. and Ephraums, J.J., (Ed.) (1990) Climate change The IPCC scientific assessment. Cambridge University Press
Methodological Range:
The residence time of benzene is in the order of days to weeks. As the regional background concentration of benzene in a rural area is low compared to the one measured in an urban area, the main contribution to the population dose occurs in urban areas close to the sources and within hours of release. The main source of benzene is cars and the gasoline fuel system. Gasoline contains several percent of benzene. This means that emissions occur worldwide and mostly at ground level. The environmental system is therefore global with a focus on urban areas. The temporal system border is the year 1990 for oxidant effects and for the cancer pathway and 100 years for the global warming pathway. The cancer pathway has a longer time scale, maybe in the order of 20 years, but the model is assuming linearity, why it does not make any difference for the model if an instant dose-response is assumed.
Notes:

Existing Characterisation Factors of Benzene impact on severe morbidity
Characterisation Parameter Category Indicator Impact Indication Principle Aspect Substance Quantity Unit Notes
CFactor Severe morbidity EPS/2000
Type = Emission
Direction = Output
Media = Air
Geography = *
Benzene 6.16E-06 p yr/kg 3 pathways