How could government make a choice between two health effects? For instance, eliminating mosquitoes may end a nuisance and help prevent some diseases. To eliminate mosquitoes may require spraying a city with a toxic chemical, or using a chemical in lakes and streams that could have a biological effect.
Is there such a thing as a good monopoly?
The answer to your first question is that the government could do a cost-benefit analysis. The analysis should include both indirect and direct social benefits/costs - that is, the financial costs/benefits, opportunity costs, and valuation of utility. For example, suppose that:
* People would be willing to pay $10 Million (in total) to live in a bug-free world. That means the value of their utility is $10 Million
* Lost wages ...
This post explains a cost-benefit analysis. The expert determines how the government could make a choice of two health effects.