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Characterisation Method Information
Characterisation Method Name:
Cd air emissions impact on morbidity
Version:
1999
Date Completed:
1999
Principal Method Name:
EPS: direct inhalation and oral pathways
Method Description:
Model 1, direct inhalation pathway

The characterisation factor is determined by the empirical method.

Category indicator value in system considered
The health effects of Cd on kidney functions are described in WHO air quality guidelines
for Europe (1987). At about 200 mg/kg wet weight in renal cortex there is a dysfunction
in the kidney. This corresponds approximately to an average air concentration of 2.9 m g/m 3 and a liver concentration of 30 mg/kg. Assuming log normal distributions of the sensitivity to Cd and the exposure to Cd respectively, it will be possible to calculate the number of morbidity cases from Cd. In order to find the constants for the log normal distributions results from two studies are used. First a study quoted by WHO in which Cd
concentration in liver is correlated to abnormal metabolic changes.

An exposure to 2.9 mg/m 3 would thus give a liver concentration of 30 ppm and kidney
dysfunction in 5% of the population. The sensitivity to Cd is approximately log-normal
distributed among the persons examined. Assuming this distribution may be extrapolated to lower concentrations and being representative for the entire Swedish population of 8 million inhabitants about 1 person would be sensitive to 0.6, 10 persons to 0.7, 100 persons to 0.8 and 1000 persons to 0.9 mg/m 3 . At an average exposure of 0.2 ng/m 3 and approximately 10% of the population being exposed to a doubled concentration (derived from what is normal to average NOx-distribution ) there will be no persons exposed to levels like 1 ng/m 3 . The conclusion is that health effects merely from direct exposure in air are negligible. However as other routes of Cd intake exists (smoking, occupational exposure, food) the average concentration in renal cortex is about 20 mg/kg today (corresponding to about 1.5 mg/kg in the liver) indicating that a sensitive part of the population could be influenced. If we transform the data to a dose-response curve and investigate the slope we see that each mg of an extra dose above 20 mg/kg will give and extra 0.5% of the population at the threshold level affected.

The question is just: how many are on the threshold level?

According to WHO the threshold level for non-occupational exposure is 10 mg/kg in the
liver. If we use the experience of air pollutant concentrations to be log-normal distributed and use the ratio of median to 90%ile values for NOx (about 2), which like Cd to a large extent is generated from combustion sources, the 99.99 percentile would be around 10 mg/kg. Therefore, the part of the population at the threshold level would be 8.6E+06*E-04 = 860 persons
If the average population exposure is 0.2 ng/m3 this corresponds to 30*0.2/2900 =
0.00207 mg/kg or ppm by weight. This would cause 0.00207*0.005*8.6E+06 * E-04 =
0.0089 person-years of morbidity.

Contribution to category
indicators value from a flow unit

The same contribution as in Cd air emissions impact on YOLL may be valid, i.e. 1/6250 per kg Cd.

Calculation of characterisation factor

The characterisation factor would therefore be 0.0089/6250 = 0.0142E-04 person-years/
kg Cd.

Model 2, oral pathway

The characterisation factor is determined by the empirical method.

Category indicator value in system considered

According to Sivertsen (1986), the danish population’s total exposure to Cd was
approximately to 35% originating from air emissions which had been accumulated in soil or on crop surfaces. Less than 1% was inhaled directly. This means that there would be in the order of 35*0.0089 = 0.3115 person years of morbidity

Contribution to category
indicators value from a flow unit

The same contribution as in "Cd air emissions impact on YOLL" may be valid, i.e. 1/6250 per kg Cd.

Calculation of pathway specific characterisation factor

The characterisation factor is thus 0.3115/6250 = 0.498E-04 person-years/kg Cd.

Calculation of characterisation factor
The characterisation factor of Cd for the added impacts are 0.0142 E-04 + 0.498E-04 =
0.512E-04 person-years/kg Cd.
Literature Reference:
1. WHO, Air Quality Guidelines for Europe, WHO Regional Publications, European Series, No 23, 1987. 2. Sivertsen, B. (ed), “Relative Contribution of Air Pollutants from Various Sources to Man and Environment”, Report 1986:4 from the Nordic Council of Ministers.
Methodological Range:
In terms of contribution to population exposure urban populations are receiving the highest doses. The main contribution comes from sources in the urban area, but in Southern Sweden the regional background is also important. This means that the trans-boundary pollution can not be neglected (Sievertsen 1986) and that both to Swedish and external sources must be allocated to the category indicator value. Considering an incubation time of the order of 20 years, and that most of the data available are from 1985 the system is defined as Sweden at the state of 1985 during 20 years.
Notes:

Existing Characterisation Factors of Cd air emissions impact on morbidity
Characterisation Parameter Category Indicator Impact Indication Principle Aspect Substance Quantity Unit Notes
CFactor Morbidity EPS/2000
Type = Emission
Direction = Output
Media = Air
Geography = *
Cd 0.512E-04 p yr/kg 2 pathways