1) What in the air can cause health problems?
2) Where pollutants can cause health problems?
3) What pollutants can cause in the air?
4) What problems can pollutants cause in the air?
5) What pollutants can do in the air?
1) What in the air can cause health problems?
2) Where pollutants can cause health problems?
3) What pollutants can cause in the air?
4) What problems can pollutants cause in the air?
5) What pollutants can do in the air?