|Characterisation Method Name:|
|NH3 impact on severe morbidity|
|Principal Method Name:|
|EPS: secondary aerosol pathway|
|Model for secondary aerosol pathway|
The characterisation factor is determined by an equivalency method using PM10 as a reference. The reason for using PM10 and not SO2 as a reference as in "NH3 impact on YOLL" is that the main contribution to severe morbidity is from global warming while the main contribution to YOLL was direct exposure for PM10. For global warming effects the local exposure patterns is of less importance, and the easiest model was chosen.
An equivalency factor with PM10 could be determined through the formula:
MNH4/MNH3 * htrans * CPM10/CPM2.5 , where
MNH4 and MNH3 are the molecular weights of NH4 + and NH3, respectively,
htrans is the transformation efficiency of NH3 to NH4 + , i.e. which part of the NH3 entering the atmosphere that become particles (in the form of ammonium salts) and
C2.5 and CPM10 is the concentration of PM2.5 particles compared to that of PM10.
Many authors consider PM2.5 particles to be responsible for the impact found to correlate
with PM10 (Wilsson, 1996). As most of the NH4 + -salt particle mass consists of particles less than 2.5 mm the ratio CPM10/CPM2.5 is used as an approximation for the enhanced potency of NH4 + -salt particles.
CPM10/CPM2.5 has been determined in several studies. (Brook et al. 1997), (Haller et al.,
1999). Brook et al. studied the PM10/PM2.5 ratio at 19 sites in Canada between 1984 and
1993, Their average value, 1.89 will be used here. (For arid areas, the ratio increase, e.g. to 2.5) On the regional scale the transmission efficiency is very close to 1.
Thus the equivalency factor is 18/17*1*1.89 = 2.00
Calculation of pathway specific characterisation factor
According to "PM10 impact on severe morbidity" there is - 2.33E-06 person-years/kg PM10. We thus obtain -2.33E-06
*2.00 = -4.66E-06 person-years of severe morbidity per kg of NH3.
|1. Wilson, R. and Spengler, J., “particles in Our Air: Concentration and health effects”, Harvard University Press, 1996, Harvard School of Public Health. 2. Haller, L., Claiborn, C., Larson, T., Koenig, J., Norris, G. and Edgar, R., (1999) “Airborne Particular Matter Size Distributions in an Arid Urban Area”, J. Air & Waste Manage. Assoc., Vol. 49, p. 161-168.|
|The system is global and the time period is 1990.|
|Characterisation Parameter||Category Indicator||Impact Indication Principle||Aspect||Substance||Quantity||Unit||Notes|
|NH3||-4.66E-06||p yr/kg||secondary aerosol pathway|