New air pollution monitoring results suggest that the Engen petrol refinery was responsible for the majority of sulphur dioxide pollution at the Settlers Primary School in Merebank, Durban, last year.
Last month, a study conducted by a group of American and South African medical researchers indicated that the rate of asthma at the school in Lakhimpur Road was among the highest in the world, and that asthma complaints were linked strongly to sulphur dioxide pollution levels.
The interim results of the health study, led by Professor Tom Robins of the University of Michigan, indicate that the prevalence of asthma among Settlers primary children is "strikingly high" in comparison with findings of medical studies in other parts of the world, including inner-city pollution levels in Detroit, Michigan.
The study notes that, even though air pollution levels at the Settlers school were lower in 2001 when compared with 2000, the current South African air pollution guidelines may not be adequate to protect the health of some people in the area, particularly asthmatics.
According to air pollution measurements by the private-sector Ecoserv pollution monitoring company, there was a significant overall drop in sulphur dioxide pollution in Merebank in comparison with the past several years.
Nevertheless, two recent Ecoserv reports state that sulphur dioxide pollution in Merebank exceeded World Health Organisation guidelines on 124 occasions between November 1, 2000 and October 31, 2001.
The authors of the Ecoserv report make the point that it is very difficult to pinpoint the exact origin of air pollution in a residential area which is surrounded by two petrol refineries, a paper mill, an airport and several other pollution sources, particularly at times when there are swirling winds which do not disperse pollution in a straight-line.
However, after gathering information on wind speed, wind direction and the proximity of pollution sources, the Ecoserv reports prepared for Durban city health officials and refinery managers suggest that between 77 percent and 90 percent of the highest sulphur dioxide readings at the Settlers school last year appeared to emanate from Engen, which is located 700m away from the school.
A smaller proportion of the instantaneous sulphur dioxide pollution readings were linked to Sapref (about 4 percent), to Sapref, Mondi or Sasol Fibres (about 6 percent), or to a combination of Mondi and other industries in Mobeni (about 4 percent).
Responding to the findings of the monitoring reports, Engen spokesman Ian Khathi said the refinery was committed to a progressive reduction of its pollution levels.
Last year, he said, Engen was closed down for almost three months, during which time the refinery was adapted to run on methane rich gas, a cleaner source of heating fuel.
Mr Khathi said he was confident that emission levels had dropped markedly since the refinery converted to methane-rich gas and that most of the exceedances linked to Engen would have occurred prior to July 2001.
"We believe that, when they become available, the latest monitoring reports for the last period of 2001 and early 2002 will demonstrate our impact on the school has been reduced significantly."
But, according to the Ecoserv monitoring reports, the highest monthly average levels of sulphur dioxide last year were recorded in August, one month after the switch-over to methane gas at Engen.
The report said the high levels in August, when WHO guidelines were exceeded 19 times on two consecutive days, was "most likely related to Engen emissions", although winds were blowing from the direction of Sapref for some of this time.