what is The problem of the drunkard in a valley?

What is a solution to the winter pollution problem in Cache Valley, Utah?

• The combination of cattle and car exhaust results in particulate matter 2.5 at unhealthy levels. There is no emissions testing in the valley. Obviously emissions testing could be implemented, but is it that simple of a fix, or are there other factors?

• Answer:

  Cache Valley has an annual atmospheric inversion, which prevents air pollution from escaping the valley into the wider atmosphere. Prevailing winds pass over the mountains, blowing rising air back down into the valley and creating a kind of bubble or cycle that holds the same air in the valley all winter. (Mexico City's pollution problem is aggravated by a similar circumstance.) Reductions of emissions would make that bubble fill up with pollutants more slowly, but it doesn't aid the escape of the pollutants out of the valley. With Cache Valley's population (of people, and of cars) increasing every year, even a hard limit to the emissions per vehicle won't limit the total emissions of the whole valley. Whether these facts lead one to conclude a) that emissions testing is fundamentally ineffective and therefore not worthwhile or b) that emissions testing is essential but insufficient is largely a matter of subjective ideology rather than objective fact.