Air pollution as a biological danger

Inaugural lecture--Department of Botany, Rand Afrikaans University, 15 October 1969Air pollution is a world wide problem. It has been known for centuries and had its origin towards the end of the 13th century when coal became popular as a fuel. The problem of air pollution was largely ignored until air pollution disasters occurred in Belgium (1930), in the U.S.A. (1948), and in England (1952 and 1956). These disasters were caused by high concentrations of sulphur dioxide, and were accompanied by a large number of human fatalities. A new kind of air pollution, exhaust gas, developed with the increase in the number of motor vehicles. This was first noticed in Los Angeles, U.S.A. Exhaust gas usually consists of a mixture of carbon monoxide, nitrogen oxides, hydrocarbons and lead. In the presence of sunlight the nitrogen oxides and hydrocarbons react with the atmospheric oxygen to form secondary compounds like ozone and peroxyacetyl nitrate. These secondary compounds cause considerable damage to plants and led to extensive crop losses in Southern California. In South Africa the problem of air pollution has not reached the critical stage yet, but with the increased industrialisation rate in this country, more and stricter control measures will be required. A serious air pollution problem could, however, develop with the increase in the number of motor vehicles in South Africa. With the projected number of four million vehicles by 1990, an annual petrol consumption of about 3 870 million litre can be expected. The use of this volume of petrol will cause a daily production of 9 000 metric ton of carbon monoxide, 1 800 metric ton of hydrocarbons, 480 metric ton of nitrogen oxides and 45 metric ton of lead as air pollutants. Fifteen per cent of this will be produced in the city of Johannesburg