Ground-level ozone affects human health by impairing respiratory and cardiovascular function, which leads to more hospital admissions, school and work absences, medication use, and even premature mortality.

The Water Gum produces low level volatile organic compounds (VOCs) that can contribute to ozone, the Plane Tree is a much higher-level emitter of isoprene, which has a more significant role in ground-level ozone formation, particularly during hot weather and when mixed with vehicle emissions. So it unsafe to be near a Plane Tree when the temperature is above 30C.