a recent set of experiments has proved that exposure to excessive airborne ozone, one of the more noxious constituents of smog, can cause asthma.

The experiments were carried out on young rhesus monkeys. One group of monkeys had ozone added to their air supply, while a second group breathed air containing the dust mite allergen, part of the household dust that is a common trigger of asthma. A third group was made to breathe air containing both the allergen and ozone. The last group breathed clean air. The amount of ozone added was the equivalent to that found in the ambient air.

The monkeys breathed ozone-replete air for five days, followed by nine