SMOC gaf eerder op haar website aan: waar zijn de alarmbellen? Die vraag was gerechtvaardigd, want de waarden voor zwaveldioxide (SO2) waren afgelopen weekend boven de 700 µg/m3 (spreek uit als microgram per kubieke meter) en dat voor tijdsperioden van fors meer dan 10 minuten. In dezen moet worden opgemerkt dat volgens de WHO (World Health Organization) een gemiddeld persoon niet langer dan 10 minuten mag worden blootgesteld aan waarden van 500 µg/m3. Hier zit het probleem? Op Dushi Korsou bevonden de mensen onder de rook zich uren in een alarmerende situatie en dat bij concentraties van boven de 700 µg/m3! Met name voor mensen die lijden aan astma was dit een groot probleem. Lees hieronder de tekst van de WHO:
Sulfur dioxide (SO2)
Guideline values
SO2
20 μg/m3 24-hour mean
500 μg/m3 10-minute mean
A SO2 concentration of 500 µg/m3 should not be exceeded over average periods of 10 minutes duration. Studies indicate that a proportion of people with asthma experience changes in pulmonary function and respiratory symptoms after periods of exposure to SO2 as short as 10 minutes.
The revision of the 24-hour guideline for SO2 from 125 to 20 μg/m3 is based on the following considerations:
- Health effects are now known to be associated with much lower levels of SO2 than previously believed.
- A greater degree of protection is needed.
- Although the causality of the effects of low concentrations of SO2 is still uncertain, reducing SO2 concentrations is likely to decrease exposure to co-pollutants.
Definition and principal sources
SO2 is a colourless gas with a sharp odour. It is produced from the burning of fossil fuels (coal and oil) and the smelting of mineral ores that contain sulfur. The main anthropogenic source of SO2 is the burning of sulfur-containing fossil fuels for domestic heating, power generation and motor vehicles.
Health effects
SO2 can affect the respiratory system and the functions of the lungs, and causes irritation of the eyes. Inflammation of the respiratory tract causes coughing, mucus secretion, aggravation of asthma and chronic bronchitis and makes people more prone to infections of the respiratory tract. Hospital admissions for cardiac disease and mortality increase on days with higher SO2 levels. When SO2 combines with water, it forms sulfuric acid; this is the main component of acid rain which is a cause of deforestation.