|Boiling Point No. 34 - September 1994 (ITDG - ITDG, 1994, 40 p.)|
by Aletta Terblanche, Catherine M, E Nel, Louise Opperman and Helena Nyikos
For decades. coal has been and will continue to be the dominant energy source in South Africa. Approximately 60 per cent of the population relies on low-quality coal as its primary household energy source. The coal typically used for household energy in South Africa has a high ash content (43 per cent), a low volatile content (19 per cent), a sulphur content of around 0.19 per cent and a calorific value of less than 25 MJ (megajoules)/kg. When coal is burned a number of harmful pollutants, including sulphur dioxide, particulates and carbon monoxide are released into the atmosphere. In the majority of households using traditional (wood) and transitional (coal) fuels, the combustion processes are inefficient, resulting in high levels of pollutants and the unvented or poorly vented stoves cause the release of pollutants into the indoor environment. Recent studies made in South Africa, in two major coal-burning residential areas (townships), indicate that levels of particulate matter monitored at fixed outdoor monitoring stations exceed both USA standards and WHO guidelines. Mean 24 hour average concentrations of 20Oµg/m3 are recorded frequently during winter with fine particulate matter (<2.5pm in diameter) concentrations exceeding an annual average of 80µg/m3.
Data on human exposure to this type of air pollution in South Africa is limited. It is likely that indoors and outdoors exposure the townships could be worse than that recorded by the fixed outdoor monitors. Between 199 l and 1992, children living in Sebokeng, a coal burning, partially electrified township in the Vaal Triangle area situated on the Transvaal Highveld, were monitored. The primary objective was to measure total exposures to Total Suspended Particulates (TSP) over a year and, thereby, to identify the factors associated with high exposures.
The participants were selected from a group who had participated in an earlier health study, and so information on their parent's smoking, life at home and where they lived, their socio-economic status, and respiratory tract symptoms was available. The children were given portable monitors (measuring air particulates in the breathing zone of the child), which they carried while going about their normal daily activities. The children were monitored on a school day and a holiday during the winter in nonelectrified (candles and kerosene for lighting, and coal for cooking and space heating) and partially electrified (electricity mainly for lighting; coal for cooking and heating) areas. The same group of children was used throughout except on a day at the weekend when another group was used. Monitoring lasted 12 hours starting at 8.30 a.m. Fuel-burning hit its peak from 6.00 to 9.00 every morning, and from 4.00 to 8.00 in the evening. Both seasonal and day-of-the week variations in exposure levels were compared, together with summer vs winter exposures overall, days of the week (school and holiday), boys and girls, partially electrified and non-electrified areas, and non-electrified and totally electrified areas.
A total of 45 children (19 boys and 26 girls) aged between 8 and 12 (average age 10) participated in the study. Data was collected from 72 individual monitoring sessions lasting, on average, 12.2 hours. Of these, 99 per cent recorded exposures above 260µg/Jm3, the USA 24 hour-health standard for TSP. Clearly, winter exposures are significantly worse than summer exposures. It can also be observed that, for all the children, the winter non-school day resulted in lower exposures than the school day. Comparisons were drawn between exposures measured in coal only (unelectrified area), and coal and electricity (partially electrified area) during the worst pollution period (winter). Questionnaire data on household energy use was used to stratify the measurements. The results indicated no significant statistical difference between the two groups. Partial electrification of townships seems, therefore, not to be a solution in terms of reducing human exposure to TSP.
figure 1: Comparison of personal TSP exposures of children living in unelectrified and electrified areas during a summer weekend day.
Comparison of the results, from the summer weekend day, for the electrified and unelectrified areas did indicate a significant statistical difference for the total population (see figure I ). The average concentrations measured were 387µg/m3 and 620µg/m3 respectively. Although the children living in unelectrified areas did suffer higher exposures than those from electrified areas, 96 per cent of all measurements still exceeded 260µg/Jm3 and so could still be classified as high. One has to keep in mind that these measurements were taken in summer when far less coal is burned. Winter measurements will be substantially higher in the unelectrified, than in the electrified areas.The study found extremely high levels of exposure to TSP in Sebokeng; comparable to measurements taken from fixed indoor monitors in Kenya (overnight, 300-150O µg/m3), China (all day in the kitchen, 2600µg/m3), and Gambia (over 24 hours, 1000 to 2500 µg/m3). Measurements from fixed outdoor stations in the Sebokeng study area also indicate 24-hour average levels of fine particulate matter. The significantly higher exposures during winter periods are a result of both the increased use of coal for space heating and the environmental conditions on the Transvaal Highveld which are characterized by severe temperature inversions reducing the dilution and dispersion capability of the atmosphere. The lack of statistically significant differences, or weak differences between completely electrified and non-electrified areas is important, and could be attributed to their close proximity. Pollution from household coal-burning spreads for kilometres without proper dilution or dispersion, and even more so during the winter. Of great importance, however, are the higher exposures documented for boys compared to girls during the non-school (weekend) day in the summer monitoring session. This could be related to boys' specific activities or to where they spend their time. This will be investigated further.
Personal monitoring of TSP in 45 children living in non-electrified, partially electrified, and completely electrified areas of Sebokeng township in South Africa indicated that exposures are, in general, unacceptably high; particularly during the winter, because of an increase in the use of coal for space heating in homes without electricity.
The full version of this article first appeared in the Journal of Exposure Analysis and Environmental Epidemiology, Volume 3, Supplement 1, 1993.