3. Air pollution. Do one of three

What this is made of

• 3(a). Particulate matter, and an experiment to detect it
• 3(b). Transport and air pollution, compared
• 3(c). The Clean Air Act

Where this step comes from

1. Environmental Science Merit Badge Requirements (Merit Badge Hub, last modified 2026-05-12), Requirement 3 · One of the three, which is what the air pollution question resolves.