There are a number of ways this can happen. By reducing people's wealth, their access to life-saving products and services is reduced. Also, over-regulating one area can lead to an increase of another threat. For instance, prohibiting the draining of swamps can easily result in more malaria.
Some examples are given in this article:
Precaution (Of A Sort) Without Principle
One of them is where the Peruvian government discontinued the use of chlorination in water in response to pressure from envrionmentalists. This resulted in 11,000 deaths from cholera.
I grant that 20 a year is a problem, but it it worth the destruction of 260 million lives when you destroy the economy?
How many REAL LIVES are going to be ruined and REAL HEALTH hazards increased (or worsened/shortened) by the depression that results when the US economy is cut by 20% to meet your artificial atmospheric limts?