The U.S. Environmental Protection Agency recently proposed reducing the limit for tropospheric ozone from 75 ppb to 65-70 ppb. They’re also mulling a drop to 60 ppb. Is this change a good idea?
The following background facts are not in dispute AFAIK. Tropospheric ozone is formed when various precursors (nitrogen oxides, carbon monoxide, volatile organic compounds) react with other chemicals in the atmosphere. These precursors are typically emitted during the combustion of hydrocarbon fuels. Ozone is a powerful oxidant that can react with us, plants, and useful materials (like the tires on your car). It can react with other molecules in the atmosphere to produce other harmful products. It damages plants. It irritates our lungs. Tropospheric ozone kills people.
Also not disputed, AFAIK, is that ozone mitigation costs money. These costs arise from scrubbing or treating exhaust, adopting cleaner methods of generating electricity, moving emission sources outside of areas with air quality issues, etc.
I asked, “Is this change a good idea?” I don’t know if it is. A cost benefit analysis with people’s lives makes me uncomfortable, but that’s essentially what we need to do here in order to answer the question.
EPA claims that “the U.S. will annually avoid as many as 4,300 premature deaths, 2,300 cases of acute bronchitis in children, 4,300 asthma-related emergency room visits, 960,000 asthma attacks in children, 180,000 missed days of work and up to a million missed days of school.” They value these gains at “$6.4 to $13 billion annually in 2025 for a standard of 70 ppb, and $19 to $38 billion annually in 2025 for a standard of 70 ppb,” excluding California. They say it will cost $4 billion or $15 billion per year, depending on the standard.
Our friends at the WSJ don’t like the EPA proposal. They point out that about a third of the country is out of compliance with the current 75 ppb standard. Some 95% percent of the lower 48 would be out of compliance at a 60 ppb standard. I don’t know how maps for the intermediate standards would look. As for the cost, “EPA estimates are always wrong by at least an order of magnitude.” No cite, of course.
C&EN (probably paywalled, sorry) has some information on costs, mostly via the American Chemistry Council, and only for a 60 ppb standard. A NOx offset can cost $175,000/ton. There are some $125 billion in planned chemical industry investments that are at risk under the proposed limits. “A study NAM [National Association of Manufacturers] released in July says a stronger standard could carry a compliance price tag of as much as $2.2 trillion from 2017 to 2040,” which is ~$95B/year. However, Clean air Watch says “History has shown time and time again that industry’s ‘the sky is falling’ predictions about the cost of clean air controls have been wrong.'”
So we have divergent cost estimates. I haven’t seen much criticism of the estimated benefits. I’m at a loss as to how to proceed with the analysis, and was hoping that dopers who are knowledgeable in this area could weigh in.