1. The soil is poisoned because farmers use too many pesticides and herbicides.
→ If farmers use too many pesticides and herbicides, the soil will be poisoned
2. I can’t help you unless you tell me what’s wrong.
→ If you don't tell me what's wrong, I can't help you
3. Many people have stomachache due to the contaminated food.
→ If the  food is contaminated, many people will have stomachache
4. Stop swimming in that lake, or you will have skin rashes.
→ If you don't stop swimming on that lake, you will have skin rashes
5. John lives in the area affected by air pollution, so he has breathing problems.
→ If John lives in the area affected by air pollution, he will have breathing problems.