A recent study by researchers at several major universities claims that current models used to determine concentrations of ground-level ozone might be underestimating the pollutant in areas where nitrogen dioxide concentrations are the highest. Andrew Mollner, et al., “Rate of Gas Phase Association of Hydroxyl Radical and Nitrogen Oxide,” Volume 330, Science, October 29, 2010. Researchers focused on the formation rate of nitric acid compounds from nitrogen dioxide and hydroxyl radicals. Uncertainty about the rates of formation and ratios of the nitric acid types has contributed to uncertainty in ozone modeling.

By using revised rates of nitric acid formation, the researchers calculated ambient concentrations of ozone in the 2010 ozone season for the Los Angeles basin. The revised calculations found actual ozone concentrations were 5 parts per billion (ppb) to 10 ppb greater than predictions indicated by currently-used models. According to the study, a 10-ppb increase in ozone concentrations increases the risk of death from respiratory disease by 4 percent.