Comments on your slides.
1. Like everybody said, trim your text contents if you are giving a on-stage presentation of that. You don't read from the slides. The slides should include only the keypoints with no more than 5/6 lines per slide.
2. Change your background image. The text at the lower part is hard to read because of the background graphics turned on(that brownish part). Use a smoother gradient or just plain color instead.
3. Try to avoid using any WordArt.
4. Support your slides with good quality images. You can get many images for your topic in google. See for example
Air Pollution
5. Always leave a space after the bullets/numbering.
6. Be consistent with your slide transitions. Don't use too much of effects. A simple fade-in and slide effects will do. Check your transition timings.
Check the starting slide I have made.
and the remaining slide template.

I prepared this background gradient from the original background pic in 1st slide. You can also use simple 2-color gradient that goes with the colors in the 1st slide background pic.
Good luck.