Ozone is associated with health impacts including respiratory outcomes; however, results differ across studies. Meta-analysis is an increasingly important approach to synthesizing evidence across studies. We conducted meta-analysis of short-term ozone exposure and respiratory hospitalizations to evaluate variation across studies and explore some of the challenges in meta-analysis. We identified 136 estimates from 96 studies and investigated how estimates differed by age, ozone metric, season, lag, region, disease category, and hospitalization type. Overall results indicate associations between ozone and various types of respiratory hospitalizations; however, study characteristics affected risk estimates. Estimates were similar, but higher, for the elderly compared to all ages and for previous day exposure compared to same day exposure. Comparison across studies was hindered by variation in definitions of disease categories, as some (e.g., asthma) were identified through ≥3 different sets of ICD codes. Although not all analyses exhibited evidence of publication bias, adjustment for publication bias generally lowered overall estimates. Emergency hospitalizations for total respiratory disease increased 4.47% (95% interval 2.48, 6.50%) per 10ppb 24-hr ozone among the elderly without adjustment for publication bias and 2.97% (1.05, 4.94%) with adjustment. Comparison of multi-city study results and meta-analysis based on single-city studies further suggested publication bias.

The convective injection and subsequent fate of the peroxides H₂O₂ and CH₃OOH in the upper troposphere is investigated using aircraft observations from the NASA Pacific Exploratory Mission‐Tropics A (PEM‐Tropics A) over the South Pacific up to 12 km altitude. Fresh convective outflow is identified by high CH₃I concentrations; CH₃I is an excellent tracer of marine convection because of its relatively uniform marine boundary layer concentration, relatively well‐defined atmospheric lifetime against photolysis, and high sensitivity of measurement. We find that mixing ratios of CH₃OOH in convective outflow at 8–12 km altitude are enhanced on average by a factor of 6 relative to background, while mixing ratios of H₂O₂ are enhanced by less than a factor of 2. The scavenging efficiency of H₂O₂ in the precipitation associated with deep convection is estimated to be 55–70%. Scavenging of CH₃OOH is negligible. Photolysis of convected peroxides is a major source of the HO_x radical family (OH + peroxy radicals) in convective outflow. The timescale for decay of the convective enhancement of peroxides in the upper troposphere is determined using CH₃I as a chemical clock and is interpreted using photochemical model calculations. Decline of CH₃OOH takes place on a timescale of a 1–2 days, but the resulting HO_x converts to H₂O₂, so H₂O₂ mixing ratios show no decline for ∼5 days following a convective event. The perturbation to HO_x at 8–12 km altitude from deep convective injection of peroxides decays on a timescale of 2–3 days for the PEM‐Tropics A conditions.