What are the three harmful substances in tobacco smoke?

1. Tar: Tar is a sticky, brown substance that forms when tobacco is burned. It contains many chemicals that can cause cancer, including arsenic, benzene, and formaldehyde.

2. Carbon Monoxide: Carbon monoxide is a poisonous gas that is produced when tobacco is burned. It can cause headaches, dizziness, and nausea. In high doses, it can be fatal.

3. Nicotine: Nicotine is the addictive drug in tobacco. It can cause increased heart rate, blood pressure, and breathing. It can also damage the brain and lungs.