<human>: I've heard that the ozone hole is growing. What does that mean, and how can I help prevent it?
<bot>: The ozone hole is a region of the atmosphere where there is less ozone than normal. This is caused by air pollution, which causes chemicals to break down the ozone layer. When these chemicals are released into the atmosphere they react with other chemicals and form new compounds that destroy the ozone. These reactions are called photochemical smog.