Rise In Ozone Research Articles

Update of Air Quality Health Index (AQHI) and harmonization of health protection and climate mitigation

Hong Kong has used a risk-based Air Quality Health Index (AQHI) system for nearly a decade, which aggregates hospitalization risks associated with short-term exposure to pollutants. Serving as an air pollution risk communication tool, it keeps the public informed about the current air quality, anchoring around the World Health Organization's (WHO) 2005 Air Quality Guidelines (AQGs). Given the WHO's recent update to the AQGs in 2021, it is pertinent to examine how Hong Kong's air quality risk communication might be enhanced using these updated guidelines.The AQHI currently focuses only on short-term health risks, potentially leading to an underestimation of cumulative impacts. To address this, we propose enhancing the AQHI to include both long-term and short-term health risks. Short-term risks are estimated based on excess hospitalization risks from various pollutants using local data, while long-term risks are estimated using beta coefficients from the WHO due to limited local data. We further suggest using the WHO's Interim Targets (ITs) as thresholds for health risk categories, eliminating arbitrary cut-points.Promoting both public health protection and climate mitigation is important but challenging, particularly with the surge in ozone levels due to enhanced NOx controls in VOC-limited regions like Hong Kong and Guangdong. Nevertheless, despite the rise in ozone, combined health risks in these areas have decreased due to reductions in NO2 and PM concentrations. Shifting to an AQHI-like total health risk assessment emphasizes the harmonization of health protection and climate mitigation goals. This health-focused framework posits that rigorous NOx controls can effectively serve both policy objectives in tandem.

Reducing aerosol pollution could lead to an unexpected rise in ozone

Reducing aerosol pollution could lead to an unexpected rise in ozone

Frequent new particle formation over the high Arctic pack ice by enhanced iodine emissions

In the central Arctic Ocean the formation of clouds and their properties are sensitive to the availability of cloud condensation nuclei (CCN). The vapors responsible for new particle formation (NPF), potentially leading to CCN, have remained unidentified since the first aerosol measurements in 1991. Here, we report that all the observed NPF events from the Arctic Ocean 2018 expedition are driven by iodic acid with little contribution from sulfuric acid. Iodic acid largely explains the growth of ultrafine particles (UFP) in most events. The iodic acid concentration increases significantly from summer towards autumn, possibly linked to the ocean freeze-up and a seasonal rise in ozone. This leads to a one order of magnitude higher UFP concentration in autumn. Measurements of cloud residuals suggest that particles smaller than 30 nm in diameter can activate as CCN. Therefore, iodine NPF has the potential to influence cloud properties over the Arctic Ocean.

Observing and Understanding Tropospheric Ozone Changes: Tropospheric Ozone Changes Workshop; Boulder, Colorado, 14–16 October 2009

Prompted by the lack of consensus on, and the need to assess current understanding of, long‐term changes in tropospheric ozone, a workshop was held in Colorado to (1) evaluate the consistency of data records; (2) assess robust long‐term changes; (3) determine how to combine observations and model studies; and (4) define research and observation needs for the future.At the workshop, long‐term ozone records from regionally representative surface and mountain sites, ozonesondes, and aircraft were reviewed by region. In western Europe there are several time series of ∼15–40 years from all platforms. Overall, they show a rise in ozone into the middle to late 1990s and a leveling off, or in some cases declines, in the 2000s, in general agreement with precursor emission changes. However, significant differences in detail in the time series from nearby locations provide less confidence in changes before the late 1990s.

An assessment of the impact of climate change on air quality at two UK sites

Possible effects of climate change on air quality are studied for two urban sites in the UK, London and Glasgow. Hourly meteorological data were obtained from climate simulations for two periods representing the current climate and a plausible late 21st century climate. Of the meteorological quantities relevant to air quality, significant changes were found in temperature, specific humidity, wind speed, wind direction, cloud cover, solar radiation, surface sensible heat flux and precipitation. Using these data, dispersion estimates were made for a variety of single sources and some significant changes in environmental impact were found in the future climate. In addition, estimates for future background concentrations of NO x, NO 2, ozone and PM 10 upwind of London and Glasgow were made using the meteorological data in a statistical model. These showed falls in NO x and increases in ozone for London, while a fall in NO 2 was the largest percentage change for Glasgow. Other changes were small. With these background estimates, annual-average concentrations of NO x, NO 2, ozone and PM 10 were estimated within the two urban areas. For London, results averaged over a number of sites showed a fall in NO x and a rise in ozone, but only small changes in NO 2 and PM 10. For Glasgow, the changes in all four chemical species were small. Large-scale background ozone values from a global chemical transport model are also presented. These show a decrease in background ozone due to climate change. To assess the net impact of both large scale and local processes will require models which treat all relevant scales.

Impacts of formaldehyde photolysis rates on tropospheric chemistry

AbstractA global chemistry transport model is employed to investigate the impact of recent laboratory determinations of photolysis parameters for formaldehyde on concentrations of tropospheric trace gases. Using the new laboratory data, the photolysis of formaldehyde is a more significant removal pathway. HOx levels are increased with the greatest changes towards the top of the troposphere and the poles, making formaldehyde a more significant source of upper tropospheric HOx than previously thought. Global totals of ozone and secondary organic aerosol increase with the rise in ozone being more significant at higher solar zenith angles. Copyright © 2010 Royal Meteorological Society

Effect of ambient air pollution on pulmonary exacerbations and lung function in cystic fibrosis.

Information concerning the impact of environmental factors on cystic fibrosis (CF) is limited. We conducted a cohort study to assess the impact of air pollutants in CF. The study included patients over the age of 6 years enrolled in the Cystic Fibrosis Foundation National Patient Registry in 1999 and 2000. Exposure was assessed by linking air pollution values from the Aerometric Information Retrieval System with the patients' home zip code. After adjusting for confounders, a 10 microg/m(3) rise in particulate matter (both with a median aerodynamic diameter of 10 microm (PM(10)) or less and with an aerodynamic diameter of 2.5 microm or less (PM(2.5)) was associated with an 8% (95% confidence interval [CI], 2-15%) and 21% (95% CI, 7-33%) increase in the odds of two or more exacerbations, respectively; a 10-ppb rise in ozone was associated with a 10% (95% CI, 3-17%) increase in odds of two or more exacerbations. For every increase in PM(2.5) of 10 microg/m(3), there was an associated fall in FEV(1) of 24 ml (7-40) (95% CI) after adjusting for confounders. PM(2.5)'s association with mortality did not achieve statistical significance (adjusted RR = 1.32 per 10 microg/m(3) 0.91-1.93; 95% CI). Annual average exposures to particulate air pollution was associated with an increased risk of pulmonary exacerbations and a decline in lung function, suggesting a role of environmental exposures on prognosis in CF.

Vertical variations in O3 concentrations before and after a gust front passage

Two consecutive increases in surface ozone, occurring after the cessation of photochemical ozone production, are investigated. A unique suite of instruments, including an ozone profiling lidar, a Doppler lidar, surface chemistry sensors, surface meteorological sensors, and a radar wind profiler, was deployed during the Southern Oxidants Study of 1999 in Nashville, Tennesee. Time series of ozone at 10, 405, and 1035 m above ground level (AGL) on 22 June 1999 showed variations in the vertical gradient of ozone over the course of the afternoon and evening. Analysis of time series of vertical velocity at 8 m AGL and its standard deviation, the variance in Doppler lidar calculated horizontal wind speed from near the surface to 500 m AGL, wind profiles, and meteorological surface station data, revealed mechanisms responsible for these changes in ozone. An early evening rise in surface ozone occurred with the passage of a thunderstorm gust front. Analysis showed that downward mixing of ozone‐rich air from a residual layer (RL) of ozone above 400 m caused a sharp rise in ozone at the surface and a decrease of ozone in the RL. Doppler lidar measurements showed details of the postgust front wind flow, such as the depth of the air mass behind the front, the turbulent wake region, and inferred vertical velocities throughout a layer several hundred meters deep. The second rise in surface ozone was caused by turbulent mixing due to elevated directional wind shear, which mixed ozone‐rich air down to the surface.

Exposure to Low Levels of Ozone Results in Enhanced Pulmonary Retention of Inhaled Asbestos Fibers

Health effects associated with exposure to ozone at environmentally relevant concentrations are subject to considerable controversy. Currently, no compelling evidence exists that exposure to low levels of ozone leads to lasting impairment of pulmonary structure or function. One adverse health effect of ozone may be to change lung uptake or clearance functions for other inhaled air pollutants. As a test of this hypothesis, Fischer 344 rats were continuously exposed to 0.06 ppm ozone 7 days a week with a slow rise in ozone to a peak of 0.25 ppm and subsequent decrease to 0.06 ppm over a 9-h period five times each week for 6 wk. Three days after the end of ozone exposure, animals-were exposed to aerosolized asbestos fibers for 5 h and examined immediately after or 30 days after exposure to asbestos. Filtered air control animals were simultaneously exposed to asbestos. Immediately after the end of fiber exposure, lung asbestos fiber burden was similar in both groups. However, 1 month after exposure, fiber mass and fiber number were significantly greater (p less than 0.05) in the lungs of animals exposed to ozone than in the lungs of those exposed to air. These findings suggest that ambient levels of ozone can impair clearance of fibrogenic and carcinogenic materials such as asbestos from the lungs and represent an important adverse effect of prolonged exposure to low levels of this oxidant gas.

A model investigation of the impact of increases in anthropogenic NO x emissions between 1967 and 1980 on tropospheric ozone

Recent observations suggest that the abundance of ozone between 2 and 8 km in the Northern Hemisphere mid-latitudes has increased by about 12% during the period from 1970 to 1981. Earlier estimates were somewhat more conservative suggesting increases at the rate of ∼7% per decade since the start of regular observations in 1967. Previous photochemical model studies have indicated that tropospheric ozone concentrations would increase with increases in emissions of CO, CH4 and NO x . This paper presents an analysis of tropospheric ozone which suggests that a significant portion of its increase may be attributed to the increase in global anthropogenic NO x emissions during this period while the contribution of CH4 to the increase is quite small. Two statistical models are presented for estimating annual global anthropogenic emissions of NO x and are used to derive the trend in the emissions for the years 1966–1980. These show steady increase in the emissions during this interval except for brief periods of leveling off after 1973 and 1978. The impact of this increase in emissions on ozone is estimated by calculations with a onedimensional (latitudinal) model which includes coupled tropospheric photochemistry and diffusive meridional transport. Steady-state photochemical calculations with prescribed NO x emissions appropriate for 1966 and 1980 indicate an ozone increase of 8–11% in the Northern Hemisphere, a result which is compatible with the rise in ozone suggested by the observations.