Experts estimate that 50% of children under the age of five are exposed to environmental tobacco smoke (ETS) after birth. Another name for ETS is second hand smoke. Exposure to ETS is linked to increased occurrences of asthma, middle ear infections, respiratory tract infections, and decreased lung function (the ability to exchange gasses between air and blood).

How does tobacco smoke contribute to these lung problems? We don't know yet, but studies of other toxic compounds show that toxins can cause changes in lung growth and development. Therefore, one might guess that ETS has a similar effect.

Hypothesis

A hypothesis is a scientist's best guess about what might happen in an experiment. For this activity our hypothesis is that exposure to cigarette smoke while pregnant and after birth will result in changes in lung growth and development. To test this hypothesis, you will determine if mice exposed to ETS have changes in the amount of septal tissue in their lung.