Ozone destroys crops by producing chemicals which attack plants’ membranes. The dangerous gas is produced when nitrogen oxides produced by cars reacts with hydrocarbons in sunlight. Because this reaction takes time to occur, ozone is found in higher levels in agricultural areas, away from the site of the pollution.

Karen's research is focused on the massive levels of pollution in urban areas of the Indian sub-continent. Vehicle pollution is particularly harmful in India because of the large population, the growing number of cars, and the fact that, as Karen points out, "these cars are often poorly looked after - they don't have catalytic converters or any control over output." The worst aspect of this pollution is that the traffic which chokes up Indian cities can damage crops in agricultural areas several hundreds of kilometres away. The reaction which produces ozone takes place in a drifting cloud of polluting materials which becomes at its most toxic as it moves towards rural areas.

Karen's research is concentrated on the chick pea plant, which is a staple of the Indian diet. Damage done to chick pea crops hits the poorest people hardest, as it is grown on a subsistence basis for food rather than for export. Yields can be badly damaged by ozone pollution, but Karen's research has isolated species which are ozone resistant. By isolating these resistant types, Karen has already pinpointed a way to alleviate the damage done to chick pea yields in India. Closer examination of these strains shows the way to unpicking the plant's defence mechanism. Plants use antioxidants to protect themselves from ozone and other pollutants, and Karen is working towards isolating the specific antioxidant responsible for protecting the plant. This antioxidant could then be incorporated into plants which are non-ozone-resistant.

This should benefit crops in Britain too, where ozone pollution causes the same sort of damage as it does in India. Once isolated, the resistant antioxidant could, according to Karen, "prevent the same sort of damage to other crops all over the world." Short of a drastic cut in worldwide vehicle usage, Karen's work could be our best hope for protecting the world's plants against ozone.