Which topic is too broad for a cause-and-effect essay?

eductions in local garbage production due to recycling programs

the effect of after-school jobs on dropout rates

what causes famine in underdeveloped countries

how high cholesterol contributes to heart disease

I believe the first one is too broad.

"eductions in local garbage production due to recycling programs" would be my guess. This is because "recycling programs" are very vague, and finding out the exact values of how much garbage is thrown out in response to these programs is almost impossible. It's most likely not recorded and it's also most likely very trivial in nature.