Asked by: Dougie Lindsay, Galashiels
It won’t. Humans are not like yeast, which continues to metabolise uncontrolledly, until it is poisoned by its own waste products. As human pollution levels rise, the political imperative for us to do something about it increases as well. The Great Smog of London in 1952, which killed 4,000 people, was followed four years later by the Clean Air Act.
Similar legislation in the USA has seen the overall emissions of air pollutants fall by about 60 per cent in the last 35 years. The US 1990 Oil Pollution Act required oil tankers to have double hulls to reduce the risk of spills. The 1987 Montreal Protocol eliminated almost all CFCs from industrial and consumer products worldwide. Leaded petrol and the pesticide DDT are also banned in most of the world.
Air and water pollution are still a major problem in newly industrialised countries, particularly China, India and in South America. But even there, pollution is rising more slowly than it did when the west went through its industrial revolution, because of better awareness and technology, and pressure from the rest of the world.
Global population is expected to peak around 10 or 11 billion and with care, it’s possible that we may be able to sustain a habitable planet for that many humans more or less indefinitely. We may still become extinct through climate change, disease, nuclear war or meteorite impact but humanity probably has enough foresight and resources to avoid poisoning itself to death.