Pulmonary function and symptom responses after 6.6-hour exposure to 0.12 ppm ozone with moderate exercise

The rationale behind updates to ambient ozone guidelines and standards

Although air quality has gradually improved in recent years, as shown by the decrease in PM2.5 concentration, the problem of rising ambient ozone has become increasingly serious. To reduce hazards to human health and environmental welfare exposure to ozone, scientists and government regulators have developed ozone guidelines and standards. These answer the questions of which levels of exposure are hazardous to human health and the environment, and how can ambient ozone exposure be guaranteed, respectively. So what are the basis for the ozone guidelines and standards? This paper reviews in detail the process of revising ozone guidelines and standards by the World Health Organization (WHO) and the United States Environmental Protection Agency (EPA). The present study attempts to explore and analyze the scientific basis and empirical methods for updating guidelines and standards, in a view to guide the future revision process and provide directions for further scientific research. We found many epidemiological and toxicological studies and exposure-response relationships provided strong support for developing and revising the ozone guidelines. When setting standards, ozone exposure has been effectively considered, and the economic costs, health, and indirect economic benefits of standard compliance were reasonably estimated. Accordingly, epidemiological and toxicological studies and the establishment of exposure-response relationships, as well as exposure and risk assessment and benefit-cost estimates of standards compliance should be strengthened for the further update of guidelines and standards. In addition, with the increasing prominence of combined air pollution led by ozone and PM2.5, more joint exposure scientific research related to ozone guidelines and standards should be undertaken.

Atmospheric Pollutants Affect Physical Performance: A Natural Experiment in Horse Racing Studied by Principal Component Analysis

Simple Summary

Thoroughbred horse racing is a natural experiment to study the effect of air pollutants on animal performance. In this activity, the animals are exposed to multiple mixtures of pollutants in the air and varying conditions of humidity and ambient temperature. Thus, in this work, in a homogeneous group of races, we used principal component analysis, which allowed us to gather information from all the environmental parameters measured, forming new variables called principal components. We found that the principal component is mainly determined as nitrogen oxides and carbon monoxide, while secondarily as particulate matter and sulfur oxides. Furthermore, this component is negatively related to the speed of the analyzed races. Thus, it is shown that air pollutants affect animal performance.

Abstract

The impact of some atmospheric pollutants (PM₁₀, PM_2.5, O₃, NO₂, NO, SO₂, CO), humidity and temperature were studied on the performance of thoroughbred racehorses. The study included 162 official handicap races held in 2012 in Santiago de Chile, at distances of 1000, 1100 and 1200 m, on a track in good condition, with a layout that included a bend, during the summer and winter months. The environmental variables were measured at the time of the race and were obtained from a monitoring station located 470 m from the equestrian center. The environmental variables showed an autocorrelation of variables, so they were reduced using principal component analysis. Subsequently, the principal components were correlated with running speed using Pearson’s method. Totals of 60.17 and 23.29% of the total variability of the data was explained by principal components 1 and 2 (PC1 and PC2), respectively. PC1 was mainly determined by NO, NO₂, and CO (loadings~0.90) and secondarily by PM₁₀, PM_2.5, and SO₂ (loadings~0.6), with which the data showed inverse associations, while with temperature and O₃ it showed direct associations (loadings~0.7). In addition, this component correlated negatively with running speed (r = −0.50), while PC2 was not associated with this variable. In conclusion, using the principal component analysis strategy, it was determined that running speed is affected by air pollutants.

Pulmonary Effects Due to Physical Exercise in Polluted Air: Evidence from Studies Conducted on Healthy Humans

Physical inactivity has caused serious effects on the health of the population, having an impact on the quality of life and the cost of healthcare for many countries. This has motivated government and private institutions to promote regular physical activity, which, paradoxically, can involve health risks when it is carried out in areas with poor air quality. This review collects information from studies conducted on healthy humans related to the pulmonary effects caused by the practice of physical activity when there is poor air quality. In addition, several challenges related to the technological and educational areas, as well as to applied and basic research, have been identified to facilitate the rational practice of exercise in poor air quality conditions.

Does Nitrogen Dioxide Exposure Increase Airways Responsiveness?

A number of reports have suggested that exposure to nitrogen dioxide (NO2) may cause increased airways responsiveness (AR). Twenty studies of asthmatics and five studies of healthy subjects exposed to NO2 were used to test this hypothesis using a simple method of meta-analysis. Individual data were obtained for the above studies and the direction of change in AR was determined for each subject. Only studies with available individual data were used. Subjects from these studies whose directional change in AR could not be determined were excluded. The fraction of positive responses (i.e. increased AR) was determined for all subjects within a group and tested for significance using a sign test. Data were also grouped according to NO2 concentration and by whether the exposure included exercise. There was an overall trend among asthmatics for AR to increase (60%) but this was primarily due to increased AR seen in resting exposures (70%). Among healthy subjects AR also increased with NO2 exposure but only at concentrations above 1.0 ppm. This analysis suggests that NO2 exposure causes increased airway responsiveness in healthy and asthmatic subjects but that exercise during exposure may modify this response in asthmatics.

Tropospheric ozone assessment report: Global ozone metrics for climate change, human health, and crop/ecosystem research

Assessment of spatial and temporal variation in the impacts of ozone on human health, vegetation, and climate requires appropriate metrics. A key component of the Tropospheric Ozone Assessment Report (TOAR) is the consistent calculation of these metrics at thousands of monitoring sites globally. Investigating temporal trends in these metrics required that the same statistical methods be applied across these ozone monitoring sites. The nonparametric Mann-Kendall test (for significant trends) and the Theil-Sen estimator (for estimating the magnitude of trend) were selected to provide robust methods across all sites. This paper provides the scientific underpinnings necessary to better understand the implications of and rationale for selecting a specific TOAR metric for assessing spatial and temporal variation in ozone for a particular impact. The rationale and underlying research evidence that influence the derivation of specific metrics are given. The form of 25 metrics (4 for model-measurement comparison, 5 for characterization of ozone in the free troposphere, 11 for human health impacts, and 5 for vegetation impacts) are described. Finally, this study categorizes health and vegetation exposure metrics based on the extent to which they are determined only by the highest hourly ozone levels, or by a wider range of values. The magnitude of the metrics is influenced by both the distribution of hourly average ozone concentrations at a site location, and the extent to which a particular metric is determined by relatively low, moderate, and high hourly ozone levels. Hence, for the same ozone time series, changes in the distribution of ozone concentrations can result in different changes in the magnitude and direction of trends for different metrics. Thus, dissimilar conclusions about the effect of changes in the drivers of ozone variability (e.g., precursor emissions) on health and vegetation exposure can result from the selection of different metrics.

Are the elements of the proposed ozone National Ambient Air Quality Standards informed by the best available science?

The United States Environmental Protection Agency (US EPA) issues National Ambient Air Quality Standards (NAAQS) for six criteria pollutants, including ozone. Each standard has four elements: an indicator, level, averaging time, and form. Ozone levels (i.e., air concentrations) alone in scientific studies are not directly comparable to the "level" element of the NAAQS because the standard considers the level in the context of its relation to the remaining elements. Failure to appreciate this has led to misunderstandings regarding NAAQS that would be health-protective. This can be seen with controlled human ozone exposure studies, which often involved small numbers of people exercising quasi-continuously for a long duration at an intensity not common in the general population (and unlikely achievable by most sensitive individuals), under worst-case exposure profiles. In addition, epidemiology studies have used different averaging times and have had methodological limitations that may have biased results. Such considerations can make it difficult to compare ozone levels and results across studies and to appropriately apply them in a NAAQS evaluation. Relating patterns and circumstances of exposure, and exposure measurements, to all elements of the NAAQS can be challenging, but if US EPA fully undertook this, it would be evident that available evidence does not indicate that proposed lower ozone standards would be more health protective than the current one.

Interaction effects of temperature and ozone on lung function and markers of systemic inflammation, coagulation, and fibrinolysis: a crossover study of healthy young volunteers

BACKGROUND

Trends in climate suggest that extreme weather events such as heat waves will become more common. High levels of the gaseous pollutant ozone are associated with elevated temperatures. Ozone has been associated with respiratory diseases as well as cardiovascular morbidity and mortality and can reduce lung function and alter systemic markers of fibrinolysis. The interaction between ozone and temperature is unclear.

METHODS

Sixteen healthy volunteers were exposed in a randomized crossover study to 0.3 ppm ozone and clean air for 2 hr at moderate (22°C) temperature and again at an elevated temperature (32.5°C). In each case lung function was performed and blood taken before and immediately after exposure and the next morning.

RESULTS

Ozone exposure at 22°C resulted in a decrease in markers of fibrinolysis the next day. There was a 51.8% net decrease in PAI-1 (plasminogen activator inhibitor-1), a 12.1% net decrease in plasminogen, and a 17.8% net increase in D-dimer. These significantly differed from the response at 32.5°C, where there was a 44.9% (p = 0.002) and a 27.9% (p = 0.001) increase in PAI-1 and plasminogen, respectively, and a 12.5% (p = 0.042) decrease in D-dimer. In contrast, decrements in lung function following ozone exposure were comparable at both moderate and elevated temperatures (forced expiratory volume in 1 sec, -12.4% vs. -7.5%, p > 0.05). No changes in systemic markers of inflammation were observed for either temperature.

CONCLUSION

Ozone-induced systemic but not respiratory effects varied according to temperature. Our study suggests that at moderate temperature ozone may activate the fibrinolytic pathway, while at elevated temperature ozone may impair it. These findings provide a biological basis for the interaction between temperature and ozone on mortality observed in some epidemiologic studies.

The health effects of exercising in air pollution

The health benefits of exercise are well known. Many of the most accessible forms of exercise, such as walking, cycling, and running often occur outdoors. This means that exercising outdoors may increase exposure to urban air pollution. Regular exercise plays a key role in improving some of the physiologic mechanisms and health outcomes that air pollution exposure may exacerbate. This problem presents an interesting challenge of balancing the beneficial effects of exercise along with the detrimental effects of air pollution upon health. This article summarizes the pulmonary, cardiovascular, cognitive, and systemic health effects of exposure to particulate matter, ozone, and carbon monoxide during exercise. It also summarizes how air pollution exposure affects maximal oxygen consumption and exercise performance. This article highlights ways in which exercisers could mitigate the adverse health effects of air pollution exposure during exercise and draws attention to the potential importance of land use planning in selecting exercise facilities.

Evaluation of adverse human lung function effects in controlled ozone exposure studies

The US EPA is evaluating controlled human ozone exposure studies to determine the adequacy of the current ozone National Ambient Air Quality Standard of 75 ppb. These studies have shown that ozone exposures of 80 ppb and greater are associated with lung function decrements. Here, we critically review studies with exposures below 80 ppb to determine the lowest ozone concentration at which decrements are causally associated with ozone exposure and could be considered adverse using the Adverse Effects/Causation Framework. Regarding causation, the framework includes consideration of whether exposure-related effects are primary or secondary, statistically significant, isolated or independent, or due to study limitations. Regarding adversity, the framework indicates one should consider whether effects are adaptive, compensatory, precursors to an apical effect, severe, transient and/or reversible. We found that, at exposures below 72 ppb ozone, lung function effects are primary effects, but are isolated, independent and not statistically different compared to effects observed during filtered air exposure, indicating a lack of causation. Up to 72 ppb, lung function effects may be precursors to an apical effect, but are not likely adverse because they are transient, reversible, of low severity, do not interfere with normal activity and do not result in permanent respiratory injury or progressive respiratory dysfunction. Overall, these studies do not demonstrate a causal association between ozone concentrations in the range of the current National Ambient Air Quality Standard and adverse effects on lung function.

Small things make a big difference: particulate matter and exercise

The increased risk of morbidity and mortality among adults and children with pre-existing cardiovascular or respiratory illness from emission-derived particulate matter (PM) is well documented. However, the detrimental effects of PM inhalation on the exercising, healthy population is still in question. This review will focus on the acute and chronic responses to PM inhalation during exercise and how PM exposure influences exercise performance. The smaller ultrafine PM (<0.01 μm aerodynamic diameter) appears to have the most severe health consequences compared with the larger coarse PM (2.5 < PM <10 μm aerodynamic diameter). While the response to PM inhalation may affect those with a pre-existing condition, the healthy population is not immune to the effects of PM inhalation, especially during exercise. This population, including the competitive athlete, is susceptible to pulmonary inflammation, decreased lung function (both acute and chronic in nature), the increased risk of asthma, vascular endothelial dysfunction, mild elevations in pulmonary artery pressure and diminished exercise performance. PM exposure is usually associated with vehicular traffic, but other sources of PM, including small engines from lawn and garden equipment, cigarette smoke, wood smoke and cooking, may also impair health and performance. The physiological effects of PM are dependent on the source of PM, various environmental factors, physical attributes and nature of exercise. There are a number of measures an athlete can take to reduce exposure to PM, as well as the deleterious effects that result from the inevitable exposure to PM. Considering the acute and chronic physiological responses to PM inhalation, individuals living and exercising in urban areas in close proximity to major roadways should consider ambient air pollution levels (in particular, PM and ozone) prior to engaging in vigorous exercise, and those exposed to PM through other sources may need to make lifestyle alterations to avoid the deleterious effects of PM inhalation. Although it is clear that PM exposure is detrimental to healthy individuals engaging in exercise, further research is necessary to better understand the role of PM on athlete health and performance, as well as measures that can attenuate the harmful effects of PM.

Lung function and inflammatory responses in healthy young adults exposed to 0.06 ppm ozone for 6.6 hours

RATIONALE

Exposure to ozone causes a decrease in spirometric lung function and an increase in airway inflammation in healthy young adults at concentrations as low as 0.08 ppm, close to the National Ambient Air Quality Standard for ground level ozone.

OBJECTIVES

To test whether airway effects occur below the current ozone standard and if they are more pronounced in potentially susceptible individuals, such as those deficient in the antioxidant gene glutathione S-transferase mu 1 (GSTM1).

METHODS

Pulmonary function and subjective symptoms were measured in 59 healthy young adults (19-35 yr) immediately before and after exposure to 0.0 (clean air, CA) and 0.06 ppm ozone for 6.6 hours in a chamber while undergoing intermittent moderate exercise. The polymorphonuclear neutrophil (PMN) influx was measured in 24 subjects 16 to 18 hours postexposure.

MEASUREMENTS AND MAIN RESULTS

Subjects experienced a significantly greater (P = 0.008) change in FEV(1) (± SE) immediately after exposure to 0.06 ppm ozone compared with CA (-1.71 ± 0.50% vs. -0.002 ± 0.46%). The decrement in FVC was also greater (P = 0.02) after ozone versus CA (-2.32 ± 0.41% vs. -1.13 ± 0.34%). Similarly, changes in %PMN were greater after ozone (54.0 ± 4.6%) than CA (38.3 ± 3.7%) exposure (P < 0.001). Symptom scores were not different between ozone versus CA. There were no significant differences in changes in FEV(1), FVC, and %PMN between subjects with GSTM1-positive and GSTM1-null genotypes.

CONCLUSIONS

Exposure of healthy young adults to 0.06 ppm ozone for 6.6 hours causes a significant decrement of FEV(1) and an increase in neutrophilic inflammation in the airways. GSTM1 genotype alone appears to have no significant role in modifying the effects.

6.6-hour inhalation of ozone concentrations from 60 to 87 parts per billion in healthy humans

RATIONALE

Identification of the minimal ozone (O(3)) concentration and/or dose that induces measurable lung function decrements in humans is considered in the risk assessment leading to establishing an appropriate National Ambient Air Quality Standard for O(3) that protects public health.

OBJECTIVES

To identify and/or predict the minimal mean O(3) concentration that produces a decrement in FEV(1) and symptoms in healthy individuals completing 6.6-hour exposure protocols.

METHODS

Pulmonary function and subjective symptoms were measured in 31 healthy adults (18-25 yr, male and female, nonsmokers) who completed five 6.6-hour chamber exposures: filtered air and four variable hourly patterns with mean O(3) concentrations of 60, 70, 80, and 87 parts per billion (ppb).

MEASUREMENTS AND MAIN RESULTS

Compared with filtered air, statistically significant decrements in FEV(1) and increases in total subjective symptoms scores (P < 0.05) were measured after exposure to mean concentrations of 70, 80, and 87 ppb O(3). The mean percent change in FEV(1) (+/-standard error) at the end of each protocol was 0.80 +/- 0.90, -2.72 +/- 1.48, -5.34 +/- 1.42, -7.02 +/- 1.60, and -11.42 +/- 2.20% for exposure to filtered air and 60, 70, 80, and 87 ppb O(3), respectively.

CONCLUSIONS

Inhalation of 70 ppb O(3) for 6.6 hours, a concentration below the current 8-hour National Ambient Air Quality Standard of 75 ppb, is sufficient to induce statistically significant decrements in FEV(1) in healthy young adults.

Effects of exposure to 0.06 ppm ozone on FEV1 in humans: a secondary analysis of existing data

BACKGROUND

Ozone is a potent photochemical oxidant that produces transient, reversible decrements in the lung function of acutely exposed individuals. A recent study provided previously unavailable clinical data for 30 healthy young adults exposed to O(3) at 0.06 ppm. That study showed significant effects of 0.08 ppm on lung function, confirming the findings of others. However, exposure to 0.06 ppm O(3) was not reported to significantly affect lung function.

OBJECTIVES

We conducted this analysis to reevaluate the existing lung function data of the volunteers previously exposed to 0.06 ppm O(3).

METHODS

We obtained pre- and postexposure data on forced expiratory volume in 1 sec (FEV(1)) for all subjects who were previously exposed for 6.6 hr to filtered air or to 0.06 ppm or 0.08 ppm O(3). We used standard statistical methods appropriate for paired comparisons to reanalyze FEV(1) responses after exposure to 0.06 ppm O(3) relative to filtered air.

RESULTS

Controlling for filtered air responses, 24 of the 30 subjects experienced an O(3)-induced decrement in FEV(1). On average, 0.06 ppm O(3) exposure caused a 2.85% reduction in FEV(1) (p < 0.002), which was consistent with the predicted FEV(1) response from existing models. Although the average response was small, two subjects had > 10% FEV(1) decrements.

CONCLUSIONS

Exposure to 0.06 ppm O(3) causes a biologically small but highly statistically significant decrease in mean FEV(1) responses of young healthy adults.

Time course of ozone-induced changes in breathing pattern in healthy exercising humans

We examined the time course of O3-induced changes in breathing pattern in 97 healthy human subjects (70 men and 27 women). One- to five-minute averages of breathing frequency (fB) and minute ventilation (V̇e) were used to generate plots of cumulative breaths and cumulative exposure volume vs. time and cumulative exposure volume vs. cumulative breaths. Analysis revealed a three-phase response; delay, no response detected; onset, fB began to increase; response, fB stabilized. Regression analysis was used to identify four parameters: time to onset, number of breaths at onset, cumulative inhaled dose of ozone at onset of O3-induced tachypnea, and the percent change in fB. The effect of altering O3 concentration, V̇e, atropine treatment, and indomethacin treatment were examined. We found that the lower the O3 concentration, the greater the number of breaths at onset of tachypnea at a fixed ventilation, whereas number of breaths at onset of tachypnea remains unchanged when V̇e is altered and O3 concentration is fixed. The cumulative inhaled dose of O3 at onset of tachypnea remained constant and showed no relationship with the magnitude of percent change in fB. Atropine did not affect any of the derived parameters, whereas indomethacin did not affect time to onset, number of breaths at onset, or cumulative inhaled dose of O3 at onset of tachypnea but did attenuate percent change in fB. The results are discussed in the context of dose response and intrinsic mechanisms of action.

The effect of exercise on nasal uptake of ozone in healthy human adults

The nose may help protect the lower respiratory tract from the effects of ambient ozone by scrubbing ozone from inspired air. Reductions in both nasal resistance and nitric oxide production with exercise may influence the efficiency of ozone uptake in the nose. Nasal ozone uptake was measured in 10 healthy volunteers before and after 15 min of moderate bicycle exercise. Ozone (0.2 parts/million) was pulled through both nostrils and out of the mouth at a constant flow while the subjects closed their epiglottises. Nasal uptake of ozone was determined by comparing the ozone concentration entering the nostrils to that exiting the mouth. Average preexercise uptake of ozone was 56 +/- 7.8 and 37 +/- 4.9% at 10 and 20 l/min, respectively. These averages did not significantly differ from those immediately postexercise (55 and 37%). Nasal ozone uptake increased significantly (P < 0.001) with decreasing flow rate, but intersubject variability in uptake could not be predicted by nasal volume or cross-sectional areas (as measured by acoustic rhinometry) or endogenous nitric oxide production. However, the percent change in ozone uptake after exercise, within an individual, was correlated with both 1) percent change in nasal volume (r = 0.70 at 10 l/min) and 2) percent change in the rate of volumetric expansion between the nasal valve and turbinates (r = 0.82 at 10 l/min). These results may be useful for assessing human risk associated with ozone exposure during exercise.

Acute Effects of Ozone on Mortality from the “Air Pollution and Health

In the Air Pollution and Health: A European Approach (APHEA2) project, the effects of ambient ozone concentrations on mortality were investigated. Data were collected on daily ozone concentrations, the daily number of deaths, confounders, and potential effect modifiers from 23 cities/areas for at least 3 years since 1990. Effect estimates were obtained for each city with city-specific models and were combined using second-stage regression models. No significant effects were observed during the cold half of the year. For the warm season, an increase in the 1-hour ozone concentration by 10 mug/m3 was associated with a 0.33% (95% confidence interval [CI], 0.17-0.52) increase in the total daily number of deaths, 0.45% (95% CI, 0.22-0.69) in the number of cardiovascular deaths, and 1.13% (95% CI, 0.62-1.48) in the number of respiratory deaths. The corresponding figures for the 8-hour ozone were similar. The associations with total mortality were independent of SO2 and particulate matter with aerodynamic diameter less than 10 mum (PM10) but were somewhat confounded by NO2 and CO. Individual city estimates were heterogeneous for total (a higher standardized mortality rate was associated with larger effects) and cardiovascular mortality (larger effects were observed in southern cities). The dose-response curve of ozone effects on total mortality during the summer did not deviate significantly from linearity.

Modeling the interactions of ozone with pulmonary epithelial lining fluid antioxidants

Water soluble antioxidant--ascorbate (AA), urate (UA), and reduced glutathione (GSH)--consumption by ozone (O3) was investigated in a range of pulmonary epithelial lining fluid (ELF) models. Antioxidants were exposed individually and as a composite mixture, with and without human albumin to a range of ambient O3 concentrations: 0-1500 ppb using a continually mixed, interfacial exposure setup. We observed the following: (1) UA constituted the most o3-reactive substrate in each of the models examined. Reactivity hierarchies in each were as follows: UA > AA >> GSH (individual antioxidant), UA > AA > GSH (composite antioxidant), and UA >> AA approximately equal to GSH (composite antioxidant + albumin). Consumption of GSH as a pure antioxidant solution was associated with a 2:1 stoichiometric conversion of GSH to GSSG. This simplistic relationship was lost in the more complex models. (3) Consumption of antioxidants by O3 occurred without alteration of sample pH. (4) Protein carbonyl formation was observed when albumin alone was exposed to O3. However, in the presence of the composite antioxidant solution no evidence of this oxidative modification was apparent. These data indicate that GSH does not represent an important substrate for O3. In contrast, UA displays high reactivity consistent with its acting as a sacrificial substrate in the ELF. As UA concentrations are highest in the ELF of the proximal airways, its localization, allied to its reactivity, suggesting that it plays important roles, both in conferring protection locally and also by "scrubbing" O3, from inhaled air, limiting its penetration to the more sensitive distal lung.

Sensitivity to ozone: could it be related to an individual's complement of antioxidants in lung epithelium lining fluid?

Ozone, though not a free radical species, mediates its toxic effects through free radical reactions as a consequence of its high redox potential. Upon inspiration the first physical interface encountered by ozone is a thin layer of aqueous material, the epithelium lining fluid (ELF) which overlays, and is partially derived from, the underlying pulmonary epithelium. ELF is the first physical interface encountered by ozone and the majority of its primary actions are confined to this compartment. ELF contains a range of antioxidants, including the small molecular weight antioxidants: uric acid (UA), ascorbic acid (AH2) and reduced glutathione (GSH). These compounds are present in large quantities and display high intrinsic reactivities toward ozone, consistent with their role as sacrificial substrates in this setting. In this paper we examine the concept that antioxidants, in ELF, represent the first tier of defence against the oxidizing effects of ozone. Since the concentration of these antioxidants appears to differ between individuals, we propose that these protective substances may dictate, in part, an individual's sensitivity to oxidizing air pollutants such as ozone.

Individual variability in human lung function responses to ozone exposure

Ozone is a common photochemical air pollutant which is present in the ambient air of many urban areas at concentrations sufficient to produce acute respiratory effects in humans. Because individuals vary considerably in the magnitude of their responses to ozone exposure, it is difficult to estimate the number of individuals in a given population who are experiencing adverse effects. Consequently risk and benefits analysis for various regulatory scenarios cannot be carried out with precision. As an aid to risk assessment this paper presents a method of predicting the proportion of individuals in the population who experience a particular health effect. Risk equations predicting the proportion of individuals experiencing lung function decrements as a function of ozone concentration, duration of exposure, and age are presented.

Effects of chronic ozone (O3) exposure on vocal-fold mucosa in bonnet monkeys

Effects of ambient ozone (O3) on the respiratory tract have been frequently reported. However, little is known regarding possible effects of chronic exposure to O3 on the larynx or on vocal-fold mucosa. In this study, six bonnet monkeys were exposed to 1 ppm O3 8 h per day, 5 days per week, for 3 months. Three of the monkeys' larynges were examined 4 h after exposure, and three were examined 9 months after exposure. Tissues were subjected to histological staining and morphometric quantification. Results revealed increased thickness of epithelial and connective tissue components of vocal-fold mucosa in the 4-h group and connective tissue changes that persisted in mucosa examined 9 months after exposure. Additional changes indicative of hyperplasia and disorganization of epithelial and connective tissue, as well as disruption of glands and vessels, were also noted in tissues examined at both postexposure intervals. Implications of the data for the larynx and voice quality in humans exposed to similar environmental toxins are discussed.

Tropospheric ozone: respiratory effects and Australian air quality goals

OBJECTIVE

To review the health effects of tropospheric ozone and discuss the implications for public health policy.

DESIGN

Literature review and consultation with scientists in Australia and overseas. Papers in English or with English language abstracts were identified by Medline search from the international peer reviewed published reports. Those from the period 1980-93 were read systematically but selected earlier papers were also considered. Reports on ozone exposures were obtained from environmental agencies in the region.

RESULTS

Exposure to ozone at concentrations below the current Australian air quality goal (0.12 ppm averaged over one hour) may cause impaired respiratory function. Inflammatory changes in the small airways and respiratory symptoms result from moderate to heavy exercise in the presence of ozone at levels of 0.08-0.12 ppm. The changes in respiratory function due to ozone are short lived, vary with the duration of exposure, may be modified by levels of other pollutants (such as sulphur dioxide and particulates), and differ appreciably between individuals. Bronchial lavage studies indicate that inflammation and other pathological changes may occur in the airways before reductions in air flow are detectable, and persist after respiratory function has returned to normal. It is not known whether exposures to ozone at low levels (0.08-0.12 ppm) cause lasting damage to the lung or, if such damage does occur, whether it is functionally significant. At present, it is not possible to identify confidently population subgroups with heightened susceptibility to ozone. People with asthma may be more susceptible to the effects of ozone than the general population but the evidence is not consistent. Recent reports suggest that ozone increases airway reactivity on subsequent challenge with allergens and other irritants. Animal studies are consistent with the findings in human populations.

CONCLUSION

A new one hour air quality ozone goal of 0.08 ppm for Australia, and the introduction of a four hour goal of 0.06 ppm are recommended on health grounds.

Bronchoalveolar lavage neutrophilia in asthmatic and healthy volunteers after controlled exposure to ozone and filtered purified air

STUDY OBJECTIVE

To characterize the pulmonary response of asthmatic and healthy nonsmoking adult men to 0.20 ppm ozone by controlled chamber exposure.

DESIGN

A prospective, crossover study of five atopic asthmatic and five normal subjects randomly exposed to ozone and filtered purified air (FPA) for 6 h, consisting of 30-min alternating periods of rest and moderate exercise. The two exposures were separated by at least 30 days.

SETTING

A controlled exposure in a stainless steel chamber.

PATIENTS

Five atopic asthmatic and five normal subjects between 18 and 45 years of age. Treatment with medications was withheld from asthmatics prior to the exposures. All subjects were nonsmokers.

INTERVENTIONS

Symptoms were assessed throughout the exposures. Pulmonary function was measured at baseline, hourly throughout an exposure, and after an exposure. Bronchoalveolar lavage (BAL) was performed 18 h after the completion of an exposure. The BAL fluid (BALF) was analyzed for cell count and differential; the cell-free supernatant was analyzed for albumin, tumor necrosis factor (TNF), interleukin 1 (IL-1), interleukin 6 (IL-6), and interleukin 8 (IL-8).

RESULTS

There were statistically significant increases in IL-8 levels, as well as percent polymorphonuclear neutrophils (PMNs) and PMNs per milliliter of lavage in asthmatics exposed to ozone as compared with the same asthmatics exposed to FPA and the same normal subjects exposed to ozone and FPA. Interleukin 6 was also significantly increased in asthmatics exposed to ozone. The BALF albumin, TNF, and IL-1 levels were not significantly different among the four groups. There were no differences between asthmatics and healthy controls exposed to ozone or FPA in baseline to postexposure FEV1, FVC, FEV1/FVC, and sRaw.

CONCLUSIONS

We conclude that asthmatics exposed to ozone develop a significant BALF neutrophilia and increased levels of the cytokines, IL-8 and IL-6. These BALF findings occur even though the level of ozone exposure was not significant enough to reduce pulmonary function.

Acute effects of ambient ozone on respiratory function of Swiss schoolchildren after a 10-minute heavy exercise

This study was conducted in Switzerland between May and October 1989 to assess possible decrements in lung function occurring as a result of 10 minute exposure to ambient air containing different ozone concentrations. Once a month, 128 children in two different areas of Southern Switzerland (Chiasso and Aurigeno) had a pulmonary function test before and after a standardized 10 minute exercise (pulse rate, 170/min) on a cycle ergometer, outdoors. Ozone concentrations were similar in both areas, ranging from 40 to 157 micrograms/m3 (1/2h means) during the exercise tests. The two communities differed with respect to long-term average pollution levels. The mean NO2 concentration over the six months study period was 70 micrograms/m3 in Chiasso and 18 micrograms/m3 in rural Aurigeno. Of the eligible children 85% participated and attended 4-6 tests. Parents completed a standardized questionnaire on family background, home characteristics and the child's early and present illness history. A total of 500 acceptable pairs of spirograms and corresponding ozone concentrations (average 3.8 per child) were available for analysis. Regressions of each individual's pre-post differences of FVC, FEV1 and peak flow on ozone concentrations measured during the outdoor exercise indicated that elevated ozone levels significantly reduced peak flow values. Adjustments for temperature and relative humidity increased the magnitude of the peak flow slopes. The average adjusted regression coefficient for delta-peak flow on ozone was -2.28 mL/s/micrograms/m3 (95% CI, -0.57 -3.99). It is noteworthy that the observed relationships occurred at ozone concentrations below 160 micrograms/m3 and after an exercise duration of only 10 minutes.

Ambient ozone causes upper airways inflammation in children

Ozone constitutes a major air pollutant in Western Europe. During the summer national air quality standards are frequently exceeded, which justifies concern about the health effects of ozone at ambient concentrations. We studied upper airways inflammation after ozone exposure in 44 children by repeated nasal lavages from May to October 1991. During this time period five to eight lavages were performed for each child. On 14 days following high ozone exposure (daily maximum > or = 180 micrograms/m3) 148 nasal lavages were performed, and on 10 days following low ozone exposure (daily maximum < or = 140 micrograms/m3) 106 nasal lavages were performed. A significant increase of intra-individual mean polymorphonuclear leukocytes (PMN) counts from low ozone days (median, 20.27 x 10(3)) to high ozone days (median, 27.38 x 10(3); p < 0.01) was observed. Concomitant with a decrease of ozone concentrations in the fall mean PMN counts showed a downward trend. Linear regression analysis of log-PMN counts yielded a significant effect for ozone (p = 0.017). In a subsample humoral markers of inflammation were measured for each child's highest and lowest exposure. A significant increase was observed for eosinophilic cationic protein (median, 77.39 micrograms/L on low ozone days versus 138.6 micrograms/L on high ozone days; p < 0.05). Thus we conclude that ozone at ambient concentrations initiates a reversible inflammatory response of the upper airways in normal children.

The role of air pollution in asthma

Laboratory studies have clearly shown that inhalation of SO2 by asthmatics can cause a significant degree of wheezing at concentrations considerably lower than those which affect non-asthmatics. Concentrations as low as 0.2 p.p.m. have a significant effect, especially in subjects who are mouth breathing or undergoing heavy exercise. The effects of SO2 appear to be short-lived and not increased by more prolonged exposure (10 min versus 1 hr). WHO air quality guidelines on levels of SO2 have been based to a large extent on these studies and are set at or just below the reported threshold for effects on at risk groups. Thus the 1 hr recommended maximum is 0.16 p.p.m. (350 micrograms/m3). These guidelines have been exceeded in the U.K. on many occasions in the recent past [2] suggesting that asthmatics are at risk in high pollution areas from SO2 induced exacerbations of their asthma. This is particularly true considering that virtually all the laboratory studies have been performed on mild asthmatics. The effects on moderate and severe asthmatics, or those with marked lability of their asthma, could conceivably be seen at much lower concentrations of SO2. Similarly O3 can cause impairment in lung function at concentrations frequently detected in ambient air in the U.K. in both asthmatics and non-asthmatics with no evidence of an increased effect on asthmatics. This appears to be a restrictive rather than an obstructive defect. Ozone can also cause an increase in airways responsiveness to both non-specific bronchoconstrictors such as histamine and specific allergen. Both these effects are likely to be due to the pro-inflammatory effects of ozone and as such could be implicated both in exacerbating asthma through increased airway responsiveness and causing asthma through triggering an inflammatory reaction in the airways. No study has addressed the important question as to whether the incidence of bronchial hyperresponsiveness is increased in areas of high ozone pollution. The results with NO2 in the laboratory are equivocal. On balance the evidence suggests that any effect on asthmatics is likely to be small. Similarly while inhalation studies with acid aerosols have demonstrated some impairment in lung function in asthmatics the changes have been small and of brief duration. Laboratory studies while raising the level of suspicion and allowing dose response curves to be calculated cannot accurately mimic the effects of real air pollution with its combination of interacting circumstances and effects of prolonged exposure.(ABSTRACT TRUNCATED AT 400 WORDS)

The impact of pollution on the voice

Pollution is responsible for the presence of toxic substances and conditions throughout our environment. Inhalation of toxic pollutants may affect the voice adversely by direct laryngeal injury, by causing pulmonary dysfunction that results in voice maladies, or through impairments elsewhere in the vocal tract. Ingested substances--especially those that have neurolaryngologic effects--may also adversely affect the voice. Non-chemical environmental pollutants such as noise may also be responsible for voice abnormalities. Most of the information about the effects of pollution on the voice is anecdotal. Equipment and techniques that permit valid, reliable voice research have recently become available; and studies on the impact of pollution on communication, and specifically on voice, should be encouraged.

Pulmonary performance of elderly normal subjects and subjects with chronic obstructive pulmonary disease exposed to 0.3 ppm nitrogen dioxide

Symptoms and changes in pulmonary function of subjects with chronic obstructive pulmonary disease (COPD) and elderly normal subjects, induced by a 4-h exposure to 0.3 ppm NO2, were investigated using a double-blind, crossover design with purified air. The 5-day experimental protocol required approximately 2 wk with at least a 5-day separation between randomized 4-h exposures to either NO2 or air which included several periods of exercise. Over a 2-yr period, COPD subjects, all with a history of smoking, consisting of 13 men and 7 women (mean age of 60.0 yr) and 20 elderly normal subjects of comparable age and sex were evaluated. During intermittent light exercise, COPD subjects demonstrated progressive decrements in FVC and FEV1 compared with baseline with 0.3 ppm NO2, but not with air. Differences in percent changes from baseline data (air-NO2) showed an equivocal reduction in FVC by repeated measures of analysis of variance and cross-over t tests (p less than 0.10). Subgroup analyses suggested that responsiveness to NO2 decreased with severity of COPD; in elderly normal subjects, NO2-induced reduction in FEV1 was greater among smokers than never-smokers. A comparison of COPD and elderly normal subjects also revealed distinctions in NO2-induced responsiveness.

Respiratory response of humans exposed to low levels of ozone for 6.6 hours

Recent evidence suggests that prolonged exposures of exercising men to 0.08 ppm ozone (O3) result in significant decrements in lung function, induction of respiratory symptoms, and increases in nonspecific airway reactivity. The purpose of this study was to confirm or refute these findings by exposing 38 healthy young men to 0.08 ppm O3 for 6.6 h. During exposure, subjects performed exercise for a total of 5 h, which required a minute ventilation of 40 l/min. Significant O3-induced decrements were observed for forced vital capacity (FVC, -0.25 l), forced expiratory volume in 1 s (FEV1.0, -0.35 l), and mean expiratory flow rate between 25% and 75% of FVC (FEF25-75, -0.57 l/s), and significant increases were observed in airway reactivity (35%), specific airway resistance (0.77 cm H2O/s), and respiratory symptoms. These results essentially confirm previous findings. A large range in individual responses was noted (e.g., percentage change in FEV1.0; 4% increase to 38% decrease). Responses also appeared to be nonlinear in time under these experimental conditions.

Exposure of humans to ambient levels of ozone for 6.6 hours causes cellular and biochemical changes in the lung

An acute (2 h) exposure of humans to 0.4 ppm ozone initiates biochemical changes in the lung that result in the production of components mediating inflammation and acute lung damage as well as components having the potential to lead to long-term effects such as fibrosis. However, many people are exposed to lower levels of ozone than this, but for periods of several hours. Therefore, it is important to determine if a prolonged exposure to low levels of ozone is also capable of causing cellular and biochemical changes in the lung. Nonsmoking males were randomly exposed to filtered air and either 0.10 ppm ozone or 0.08 ppm ozone for 6.6 h with moderate exercise (40 liters/min). Bronchoalveolar lavage (BAL) was performed 18 h after each exposure, and cells and fluid were analyzed. The BAL fluid of volunteers exposed to 0.10 ppm ozone had significant increases in neutrophils (PMNs), protein, prostaglandin E2 (PGE2), fibronectin, interleukin-6 (IL-6), and lactate dehydrogenase (LDH) compared with BAL fluid from the same volunteers exposed to filtered air. In addition, there was a decrease in the ability of alveolar macrophages to phagocytize yeast via the complement receptor. Exposure to 0.08 ppm ozone resulted in significant increases in PMNs, PGE2, LDH, IL-6, alpha 1-antitrypsin, and decreased phagocytosis via the complement receptor. However, BAL fluid protein and fibronectin were no longer significantly elevated. We conclude that exposure of humans to as low a level as 0.08 ppm for 6.6 h is sufficient to initiate an inflammatory reaction in the lung.

Tropospheric ozone: the dynamics of human exposure

The conditions in the ambient atmosphere conducive to ozone exposure are examined, and placed into a context of the time and locations where individuals would be expected to be affected by high ozone. This is done for both 1 h and 8 h averaging times. Concentrations of ozone in the ambient atmosphere can violate the National Ambient Air Quality Standard (NAAQS) and also the Time Weighted Average-Threshold Limit Value (TWA-TLV) for workers. Exposures that occurred in a 1982 episode associated with a health effects study are described in detail. The effective dose received by a camper at a children's summer camp appeared to be similar to that delivered to volunteers during a controlled human exposure study in which effects on pulmonary function were observed.