Which of the following is not an effect from losing ozone in the stratosphere?

increase in harmful UV light rays can reach Earth's surface
increased incidence of skin cancers in humans
increase in number of pesticide runoff events
increase in immune issues for humans

increase in number of pesticide runoff events

The effect on immune issues for humans is not directly caused by losing ozone in the stratosphere. The other options mentioned – an increase in harmful UV light rays reaching Earth's surface, an increased incidence of skin cancers in humans, and an increase in the number of pesticide runoff events – are associated with the depletion of ozone in the stratosphere.