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Tool 10 - Estimating the Health Effects of Sulfur Dioxide (SO2)
This tool allows you to estimate the health effects of SO2 by demonstrating the effect of SO2 concentrations on the urban population. It is based on a WHO methodology for estimating air pollution health effects and can be applied by individual cities for such estimations.
The results can assist Working Groups in deciding whether or not SO2 is a priority pollutant in their own cities, using different scenarios of dose-response coefficients.
Dose response is the change in effect on an organism caused by differing levels of exposure to a substance. This may apply to individuals (for example, a small amount has no observable effect, a large amount is fatal), or to populations (for example, how many people are affected at different levels of exposure). Studying dose response, and developing dose response models, is central to determining "safe" and "hazardous" levels and dosages for drugs, potential pollutants, and other substances that humans are exposed to. These conclusions are often the basis for public policy (wikipedia).
Note that models such as this are a cost-effective alternative to data collection and processing. Unfortunately, many cities in developing countries do not have a comprehensive set of monitors. Therefore, as an alternative, dispersion models such as this can be developed and used. One should keep in mind that dispersion models are always less precise than actual monitoring. For guidance on how to prepare a complete emissions inventory, refer to Tool 19: 'Preparing An Emissions Inventory'.
How to Use the Spreadsheet
The link below will allow you to open an easy to use spreadsheet. The spreadsheet is organized in three worksheets:
- The first worksheet (SO2 Entry Sheet) allows you to enter data which are specific to your local authority. It will immediately provide you with results, which are based on central dose-response coefficients.
- The second worksheet (SO2 Your City) contains the detailed calculation formulas. Here you can read the values for low and high scenarios as well.
- The third (SO2 Example) worksheet is similar to the second sheet and contains sample data from a fictive city.
Certain blocks with red squares at the corners contain comments. By placing your cursor over these boxes you will be able to read these comments and view the formulas used in calculations.
Please note: the worksheets are protected in order to avoid accidental deletion or changing of formulas. Only the entry fields are accessible. In case that you want to modify formulas, please unprotect the sheet (in Microsoft EXCEL: Tools - Protection - Unprotect Sheet; in OpenOffice: Tools - Protect Document - Sheet).
For conversions (ppm, ppb and ug/m3) see Tool 28.
STEP 1: Insert data and view results:
Insert your city specific information into the white field in the first
worksheet.
The results focus on children and adults. You need to insert the respective population ratio and the average mortality rate.
Information on health statistics and air pollution may be obtained from: Ministry of Health, hospitals, public health officials, statistics departments, motor vehicle registration.
Then, please fill in the total SO2 concentration four your city.
This first worksheet automatically calculates the expected health effects based on the central scenario of dose-response coefficients. In the result box, the number of affected citizens is displayed.
STEP 2: View detailed results:
Open the second worksheet (SO2 Your City).
The relevant percentage of the population within your targeted age bracket in your city is displayed in column C. Column C is the part of the urban population for which the health effect is being estimated. For example, if we want to know the children that experience respiratory illness, we would place the percentage of the population below 18 years. Column D shows the results for the three scenarios.
Table 10.1 The Example of City X
Manual Application
Working Groups can also use the table for manual calculations. The number
of citizens affected is a product of the population, concentration of
SO2, dose-response coefficient, and the part of the population to be counted.
Formula:
number of citizens effected = population * concentration of lead * dose-response
coefficient * percentage of the population to be counted
Table 10.2 to Aid Manual Calculations
Data for the health effects coefficients used in this tool were compiled from: Estimating the Health Effects of Air Pollutants: A Method with an Application to Jakarta, # 1301 in Policy Working Paper Series, The World Bank.