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

The Acute Effects of Exercising in Air Pollution: A Systematic Review of Randomized Controlled Trials

BACKGROUND

The acute effects of air pollution (AP) exposure during physical activity have been studied. However, comprehensive systematic reviews are lacking, particularly regarding moderate-to-vigorous physical activity (MVPA).

OBJECTIVE

Our objective was to determine the acute health- and exercise-related effects of AP exposure during a bout of MVPA in healthy individuals.

METHODS

We searched for randomized controlled trials in MEDLINE, Embase, Cochrane CENTRAL, SPORTDiscus, Agricultural and Environmental Science Database, ClinicalTrials.gov, International Standard Randomised Controlled Trial Number Registry, and the World Health Organization (WHO) International Clinical Trials Registry Platform up to July 2020 without language or date restrictions. Studies including healthy subjects engaging in a bout of MVPA while exposed to one or more of the following air pollutants were eligible: particulate matter, black carbon, carbon monoxide, nitrogen dioxide, ozone, diesel exhaust, and traffic-related air pollution (TRAP). Main outcome measures were markers of pulmonary function, symptoms, cardiovascular function, cognitive function, systemic inflammation, and exercise response. The evidence was synthesized by vote counting based on direction of effect.

RESULTS

In total, 53 studies were included in the systematic review. Studies employed a heterogeneous mix of exercise protocols, AP interventions, and measured outcomes. Pooled results suggest ozone exposure during MVPA has an adverse effect on pulmonary function (100% [95% confidence interval (CI) 88-100], p < 0.001; high-certainty evidence) and reported symptoms (88% [95% CI 69-96], p < 0.001; low-certainty evidence). The effect of exposure to carbon monoxide, nitrogen dioxide, small engine exhaust, or diesel exhaust during MVPA on health- and exercise-related outcomes is uncertain because of insufficient evidence and the low to very low certainty of available evidence.

DISCUSSION

The evidence is strongest for ozone, exposure to which generally induced a reduction in pulmonary function and increased symptoms during MVPA. The research related to other outcome domains remains inconclusive. Although long-term exposure to AP is proven to be hazardous, the evidence for healthy individuals to forgo MVPA during periods of high (non-ozone) pollution remains weak.

TRIAL REGISTRATION

Retrospectively registered in PROSPERO (CRD42020188280) on 10 July 2020.

Sex Modifies Acute Ozone-Mediated Airway Physiologic Responses

Sex differences clearly exist in incidence, susceptibility, and severity of airway disease and in pulmonary responses to air pollutants such as ozone (O3). Prior rodent O3 exposure studies demonstrate sex-related differences in the expression of lung inflammatory mediators and signaling. However, whether or not sex modifies O3-induced airway physiologic responses remains less explored. To address this, we exposed 8- to 10-week-old male and female C57BL/6 mice to either 1 or 2 ppm O3 or filtered air (FA) for 3 h. At 12, 24, 48, and 72 h following exposure, we assessed airway hyperresponsiveness to methacholine (MCh), bronchoalveolar lavage fluid cellularity, cytokines and total protein/albumin, serum progesterone, and whole lung immune cells by flow cytometry. Male mice generated consistent airway hyperresponsiveness to MCh at all time points following exposure. Alternatively, females had less consistent airway physiologic responses to MCh, which were more variable between individual experiments and did not correlate with serum progesterone levels. Bronchoalveolar lavage fluid total cells peaked at 12 h and were persistently elevated through 72 h. At 48 h, bronchoalveolar lavage cells were greater in females versus males. Bronchoalveolar lavage fluid cytokines and total protein/albumin increased following O3 exposure without sex differences. Flow cytometry of whole lung tissue identified dynamic O3-induced immune cell changes also independent of sex. Our results indicate sex differences in acute O3-induced airway physiology responses and airspace influx without significant difference in other injury and inflammation measures. This study highlights the importance of considering sex as a biological variable in acute O3-induced airway physiology responses.

Ozone exposure and pulmonary effects in panel and human clinical studies: Considerations for design and interpretation

A wealth of literature exists regarding the pulmonary effects of ozone, a photochemical pollutant produced by the reaction of nitrogen oxide and volatile organic precursors in the presence of sunlight. This paper focuses on epidemiological panel studies and human clinical studies of ozone exposure, and discusses issues specific to this pollutant that may influence study design and interpretation as well as other, broader considerations relevant to ozone-health research. The issues are discussed using examples drawn from the wider literature. The recent panel and clinical literature is also reviewed. Health outcomes considered include lung function, symptoms, and pulmonary inflammation. Issues discussed include adversity, reversibility, adaptation, variability in ozone exposure metric used and health outcomes evaluated, co-pollutants in panel studies, influence of temperature in panel studies, and multiple comparisons. Improvements in and standardization of panel study approaches are recommended to facilitate comparisons between studies as well as meta-analyses. Additional clinical studies at or near the current National Ambient Air Quality Standard (NAAQS) of 70 ppb are recommended, as are clinical studies in sensitive subpopulations such as asthmatics.

IMPLICATIONS

The pulmonary health impacts of ozone exposure have been well documented using both epidemiological and chamber study designs. However, there are a number of specific methodological and related issues that should be considered when interpreting the results of these studies and planning additional research, including the standardization of exposure and health metrics to facilitate comparisons among studies.

Differential expression of pro-inflammatory and oxidative stress mediators induced by nitrogen dioxide and ozone in primary human bronchial epithelial cells

CONTEXT

NO2 and O3 are ubiquitous air toxicants capable of inducing lung damage to the respiratory epithelium. Due to their oxidizing capabilities, these pollutants have been proposed to target specific biological pathways, but few publications have compared the pathways activated.

OBJECTIVE

This work will test the premise that NO2 and O3 induce toxicity by activating similar cellular pathways.

METHODS

Primary human bronchial epithelial cells (HBECs, n = 3 donors) were exposed for 2 h at an air-liquid interface to 3 ppm NO2, 0.75 ppm O3, or filtered air and harvested 1 h post-exposure. To give an overview of pathways that may be influenced by each exposure, gene expression was measured using PCR arrays for toxicity and oxidative stress. Based on the results, genes were selected to quantify whether expression changes were changed in a dose- and time-response manner using NO2 (1, 2, 3, or 5 ppm), O3 (0.25, 0.50, 0.75, or 1.00 ppm), or filtered air and harvesting 0, 1, 4 and 24 h post-exposure.

RESULTS

Using the arrays, genes related to oxidative stress were highly induced with NO2 while expression of pro-inflammatory and vascular function genes was found subsequent to O3. NO2 elicited the greatest HMOX1 response, whereas O3 more greatly induced IL-6, IL-8 and PTGS2 expression. Additionally, O3 elicited a greater response 1 h post-exposure and NO2 produced a maximal response after 4 h.

CONCLUSION

We have demonstrated that these two oxidant gases stimulate differing mechanistic responses in vitro and these responses occur at dissimilar times.

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.

Peripheral blood neutrophilia as a biomarker of ozone-induced pulmonary inflammation

BACKGROUND

Ozone concentrations are predicted to increase over the next 50 years due to global warming and the increased release of precursor chemicals. It is therefore urgent that good, reliable biomarkers are available to quantify the toxicity of this pollutant gas at the population level. Such a biomarker would need to be easily performed, reproducible, economically viable, and reflective of ongoing pathological processes occurring within the lung.

METHODOLOGY

We examined whether blood neutrophilia occurred following a controlled ozone challenge and addressed whether this could serve as a biomarker for ozone-induced airway inflammation. Three separate groups of healthy subjects were exposed to ozone (0.2 ppm, 2h) and filtered air (FA) on two separate occasions. Peripheral blood samples were collected and bronchoscopy with biopsy sampling and lavages was performed at 1.5h post exposures in group 1 (n=13), at 6h in group 2 (n=15) and at 18h in group 3 (n=15). Total and differential cell counts were assessed in blood, bronchial tissue and airway lavages.

RESULTS

In peripheral blood, we observed fewer neutrophils 1.5h after ozone compared with the parallel air exposure (-1.1±1.0x10(9) cells/L, p<0.01), at 6h neutrophil numbers were increased compared to FA (+1.2±1.3x10(9) cells/L, p<0.01), and at 18h this response had fully attenuated. Ozone induced a peak in neutrophil numbers at 6h post exposure in all compartments examined, with a positive correlation between the response in blood and bronchial biopsies.

CONCLUSIONS

These data demonstrate a systemic neutrophilia in healthy subjects following an acute ozone exposure, which mirrors the inflammatory response in the lung mucosa and lumen. This relationship suggests that blood neutrophilia could be used as a relatively simple functional biomarker for the effect of ozone on the lung.

Seasonal variation in the acute effects of ozone on premature mortality among elderly Japanese

We conducted a multicity time-series study using monitoring data to assess seasonal patterns of short-term ozone-mortality association among elderly aged 65 years and over in Japan. Daily exposure to ambient ozone was computed using hourly measurements of photochemical oxidants available at multiple monitoring stations in each city. Effects of ozone on daily all-cause non-accidental, cardiovascular, and respiratory mortality were estimated using distributed lag linear models, controlling for confounding by temporal, day of the week, temperature, and flu epidemics. City-level effect estimates were combined using inverse variance meta-analysis. In spring and autumn, a 10-ppbv increase of daily maximum 8-h average ozone concentration in the previous 3 days was associated with 0.69 % (95 % confidence interval (CI): 0.27-1.10), 1.07 % (0.34-1.82), and 1.77 % (0.78-2.77) increases in daily all-cause, cardiovascular, and respiratory mortality, respectively. Forward displacement of respiratory mortality was large during the cold season despite lower ozone concentration. Results were generally independent of fine particulate matter and nitrogen dioxide. Findings suggest significant mortality effects of short-term ozone exposure among the elderly during the moderate season. Those with underlying respiratory diseases were susceptible, even during winter.

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.

Prediction of lung function response for populations exposed to a wide range of ozone conditions

CONTEXT

A human exposure-response (E-R) model previously demonstrated to accurately predict population mean FEV₁ response to ozone exposure has been proposed as the foundation for future risk assessments for ambient ozone.

OBJECTIVE

Fit the original and related models to a larger data set with a wider range of exposure conditions and assess agreement between observed and population mean predicted values.

MATERIALS AND METHODS

Existing individual E-R data for 23 human controlled ozone exposure studies with a wide range of concentrations, activity levels, and exposure patterns have been obtained. The data were fit to the original model and to a version of the model that contains a threshold below which no response occurs using a statistical program for fitting nonlinear mixed models.

RESULTS

Mean predicted FEV₁ responses and the predicted proportions of individuals experiencing FEV₁ responses greater than 10, 15, and 20% were found to be in agreement with observed responses across a wide range of exposure conditions for both models. The threshold model, however, provided a better fit to the data than the original, particularly at the lowest levels of exposure.

CONCLUSION

The models identified in this manuscript predict population FEV₁ response characteristics for 18-35-year-old individuals exposed to ozone over a wide range of conditions and represent a substantial improvement over earlier E-R models. Because of its better fit to the data, particularly at low levels of exposure, the threshold model is likely to provide more accurate estimates of risk in future risk assessments of ozone-induced FEV₁ effects.

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.

An alternative form and level of the human health ozone standard

Controlled human laboratory studies have shown that there is a disproportionately greater pulmonary function response from higher hourly average ozone (O3) concentrations than from lower hourly average values and thus, a nonlinear relationship exists between O3 dose and pulmonary function (FEV1) response. The nonlinear dose-response relationship affects the efficacy of the current 8-h O3 standard to describe adequately the observed spirometric response to typical diurnal O3 exposure patterns. We have reanalyzed data from five controlled human response to O3 health laboratory experiments as reported by Hazucha et al. (1992), Adams (2003, 2006a, 2006b), and Schelegle et al. (2009). These investigators exposed subjects to multi-hour variable/stepwise O3 concentration profiles that mimicked typical diurnal patterns of ambient O3 concentrations. Our findings indicate a common response pattern across most of the studies that provides valuable information for the development of a lung function (FEV1)-based alternate form for the O3 standard. Based on our reanalysis of the realistic exposure profiles used in these experiments, we suggest that an alternative form of the human health standard, similar to the proposed secondary (i.e., vegetation) standard form, be considered. The suggested form is an adjusted 5-h cumulative concentration weighted O3 exposure index, which addresses both the delay associated with the onset of response (FEV1 decrement) and the nonlinearity of response (i.e., the greater effect of higher concentrations over the mid- and low-range values) on an hourly basis.

Air pollution toxicology--a brief review of the role of the science in shaping the current understanding of air pollution health risks

Human and animal toxicology has had a profound impact on our historical and current understanding of air pollution health effects. Early animal toxicological studies of air pollution had distinctively military or workplace themes. With the discovery that ambient air pollution episodes led to excess illness and death, there became an emergence of toxicological studies that focused on industrial air pollution encountered by the general public. Not only did the pollutants investigated evolve from ambient mixtures to individual pollutants but also the endpoints and outcomes evaluated became more sophisticated, resulting in our present state of the science. Currently, a large toxicological database exists for the effects of particulate matter and ozone, and we provide a focused review of some of the major contributions to the biological understanding for these two "criteria" air pollutants. A limited discussion of the toxicological advancements in the scientific knowledge of two hazardous air pollutants, formaldehyde and phosgene, is also included. Moving forward, the future challenge of air pollution toxicology lies in the health assessment of complex mixtures and their interactions, given the projected impacts of climate change and altered emissions on ambient conditions. In the coming years, the toxicologist will need to be flexible and forward thinking in order to dissect the complexity of the biological system itself, as well as that of air pollution in all its varied forms.

Investigating performance and lung function in a hot, humid and ozone-polluted environment

Large urbanized areas, where sports events take place, have a polluted environment and can also reach high temperatures and humidity levels. The aim of this study was to investigate the impact of a hot, humid and ozone-polluted (O(3)) environment on (1) performance of an 8 km time trial run, (2) pulmonary function, and (3) subjective respiratory symptoms in endurance-trained runners. Using crossover randomized design, 10 male participants (mean V(O)₂(max)= 64.4 mlO(2) kg(-1) min(-1), SD = 4.4) took part in a time trial run under four different conditions: 20 degrees C + 50% relative humidity (rh) (Control), 20 degrees C + 50% rh + 0.10 ppm O(3) (Control + O(3)), 31 degrees C + 70% rh (Heat), 31 degrees C + 70% rh + 0.10 ppm O(3) (Heat + O(3)). Heart rate, ratings of perceived exertion and minute ventilation were collected during the run. Lung function was measured pre and post-exercise. The runners completed a respiratory symptoms questionnaire after each trial. The completion time of both the Heat (32 min 35 s) and Heat + O(3) (33 min 09 s) trials were significantly higher (P < 0.0001) when compared to the Control + O(3) (30 min 27 s) and Control (30 min 15 s) trials. There were no significant changes between pre/post lung function measures or between trials. The effective dose of ozone simulated in the present study did not affect the performance and therefore, ozone-pollution, at an environmentally relevant concentration, did not compound the impairment in performance beyond that induced by a hot, humid environment.

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.

The temporal dynamics of ozone-induced FEV1 changes in humans: an exposure-response model

Although ozone is known to induce reversible decrements in forced expiratory volume in 1 s (FEV1), no exposure-response model has been identified that accurately describes the dynamics of response to the changing concentrations and activity patterns of normal ambient human exposure. The purpose of the current analysis was to identify and evaluate a dynamic model of FEV1 response using a large existing data set (541 volunteers, 864 exposures, 3485 FEV1 measures) with a wide range of exposure conditions (ozone = 0.0 to 0.4 ppm, activity level = rest to heavy exercise, duration = 1 to 7.6 h), including recovery in clean air. A previously described model containing a differential equation and a logistic function was modified to include a new between-subjects variance structure and was fitted to the data. The model described well the mean observed response data across the range of exposure conditions, including the periods of recovery in clean air. Predicted values of individual responses were distributed lognormally and appeared to accurately describe the distribution of observed responses. We observed that responsiveness to ozone decreased with age, that response was weakly related to body size, and that response was marginally more sensitive to changes in ozone concentration than to changes in minute ventilation. In summary, we have identified a dynamic ozone exposure-response model that accurately describes the temporal pattern of FEV1 response to a wide range of changing exposure conditions and that may have utility for predicting population responses to ambient exposures.

Comparison of chamber 6.6-h exposures to 0.04-0.08 PPM ozone via square-wave and triangular profiles on pulmonary responses

It has become increasingly well realized that laboratory simulations of air pollution risk assessment need to employ O(3) concentration profiles that more accurately mimic those encountered during summer daylight ambient air pollution episodes. The present study was designed to compare the pulmonary function and symptoms of breathing discomfort responses to a 6.6-h square-wave 0.08-ppm O(3) chamber exposure to those observed in a triangular O(3) exposure profile (mean of 0.08 ppm), as well as to both a 0.06-ppm square-wave and triangular mean 0.06-ppm exposure, and to those observed during a triangular mean 0.04-ppm exposure and to a filtered air (FA) square-wave exposure. Thirty young adults (15 of each gender) served as subjects, each completing all exposures. While the 6.6-h postexposure responses to the acute triangular exposure to a mean O(3) concentration of 0.08 ppm did not differ significantly from those observed in the square-wave exposure, forced expiratory volume in 1 s (FEV)(1.0) and total symptoms severity (TSS) were significantly different from preexposure at 4.6 h (when O(3) concentration was 0.15 ppm) in the triangular exposure, but not until 6.6 h in the square-wave exposure. Thus, significant pulmonary function and symptoms responses were observed over a longer period in the triangular exposure protocol at a mean O(3) concentration of 0.08 ppm. These results support previous evidence that O(3) concentration has a greater singular effect in the total inhaled O(3) dose than do V(E) and exposure duration. Subtracting pulmonary function effects consequent to O(3) exposure to existent 8-h average background levels (e.g., approximately 0.04 ppm, rather than those observed in FA exposures) from those observed at higher concentrations (e.g., approximately 0.08 ppm) represents a means of focusing the regulatory effort on effects that can be controlled. The greatest pulmonary function and symptoms responses observed for a 0.04-ppm triangular exposure were nearly the same as those for the FA square-wave exposure. Thus, results of the present study show that calculating the net pulmonary function effect of exposure to 0.08 ppm with "correction" for FA response, or for that incurred for 0.04 ppm O(3), does not result in any statistically significant difference.

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.

Human pulmonary responses with 30-minute time intervals of exercise and rest when exposed for 8 hours to 0.12 ppm ozone via square-wave and acute triangular profiles

Hazucha et al. (1992) compared pulmonary function responses during 8-h square-wave exposures to FA and to 0.12 ppm O3, as well as to an acute triangular exposure to a mean O3 concentration of 0.12 ppm. With 30 min of moderate exercise each hour during 8 h of continuous exposure, significantly greater pulmonary function responses were observed between 5 h and 7 h when O3 was varied in an acute triangular configuration from 0.00 ppm to 0.24 ppm over the first 4 h and back to 0.00 ppm during the last 4 h than when O3 concentration was maintained constant at 0.12 ppm throughout. These investigators employed equal periods of 30 min of exercise, in which mean VE was approximately 40 L/min, and 30 min of rest, with pulmonary function measurements taken at the end of each hour. This procedure (i.e., taking measurements at the end of each hour) could attenuate the full effect that would be observed very soon after exercise cessation, and permit some recovery to occur. Accordingly, in the present study, the primary objective was to determine what effect observations of pulmonary responses assessed immediately following repeated 30 min exercise bouts, as well as those at the end of each hour (following approximately 30 min rest) during 8-h square-wave exposures to FA and to 0.12 ppm O3, as well as to an acute triangular exposure to a mean O3 concentration of 0.12 ppm. During the last 4 h of the 8-h, 0.12-ppm square-wave exposure, the 30-min mean increases in FEV1.0 responses were consistently greater at the end of the first half hour immediately following exercise (-1.22%) than at the end of the second half-hour following 30 min of rest (+0.01%). Further, even though O3 concentration was steadily decreasing from 0.24 ppm to 0 ppm during the last 4 h of the triangular exposure, similar increases in FEV1.0 decrement (-1.38%) immediately after each 30 min exercise bout, and small recovery at the end of each 30 min rest (+0.56%) were observed. Symptom scores in both exposures during the last 4 h also showed this effect.

Vitamin supplementation does not protect against symptoms in ozone-responsive subjects

Vitamin supplements have been reported to reduce the magnitude of symptoms in subjects exposed to oxidant air pollution. To confirm whether supplementation with vitamins C and E could reduce lung function decrements, airway inflammation, and epithelial injury in subjects sensitive to ozone, a double-blinded, crossover control study was performed. Fourteen ozone-responsive subjects were randomly exposed to both air and ozone (0.2 ppm for 2 h) after 7 days of either placebo treatment or supplementation with vitamin C (500 mg/day) and E (100 mg/day). Lung function was assessed pre- and immediately postexposure and blood samples were taken at set intervals. Inflammatory, tissue injury, and antioxidant responses were examined in lavage fluid obtained by bronchoscopy 6 h postexposure. Exposure to ozone resulted in significant (P < 0.01) decrements in FEV1 with no protection observed following vitamin supplementation (-8.5%) versus placebo (-7.3%) treatment. Similarly, ozone-induced neutrophilia were of a similar magnitude after both treatments (P < 0.05). This lack of protection was observed despite elevated plasma vitamin C (+60.1%) and vitamin E (+51.4%) concentrations following supplementation, and increased vitamin C concentrations in the airways after supplementation following ozone exposure. These data do not therefore support the contention that acute ozone-induced symptoms can be attenuated through the use of dietary antioxidants in well-nourished individuals.

Ozone exposure decreases the effect of a deep inhalation on forced expiratory flow in normal subjects

Sixteen healthy nonsmoking subjects (7 women), 21-49 yr old, were exposed in a climate chamber to either clean air or 300 parts/billion ozone on 4 days for 5 h each day. Before each exposure, the subjects had been pretreated with either oxidants (fish oil) or antioxidants (multivitamins). The study design was double-blind crossover with randomized allocation to the exposure regime. Full and partial flow-volume curves were recorded in the morning and before and during a histamine provocation at the end of the day. Nasal cavity volume and inflammatory markers in nasal lavage fluid were also measured. Compared with air, ozone exposure decreased peak expiratory flow, forced expiratory volume in 1 s, and forced vital capacity (FVC), with no significant effect from the pretreatment regimens. Ozone decreased the ratio of maximal to partial flow at 40% FVC by 0.08 ± 0.03 (mean ± SE, analysis of variance: P = 0.018) and at 30% FVC by 0.10 ± 0.05 ( P = 0.070). Ozone exposure did not significantly increase bronchial responsiveness, but, after treatment with fish oil, partial flows decreased more than after vitamins during the histamine test, without changing the maximal-to-partial flow ratio. The decreased effect of a deep inhalation after ozone exposure can be explained by changes in airway hysteresis relative to parenchymal hysteresis, due either to ozone-induced airway inflammation or to less deep inspiration after ozone, not significantly influenced by multivitamins or fish oil.

Effects of ozone on lung function and lung diseases

Ozone (O3) is an air pollutant produced by sunlight-driven reactions involving the oxides of nitrogen and volatile organic compounds. The population of many large metropolitan areas in the US is exposed to high levels of O3, particularly in the summer months. Individuals exposed to O3 levels in human experiments at higher than common ambient levels develop reversible reductions in lung function often associated with symptoms, such as airway hyperreactivity and lung inflammation. Animal models have helped characterize potential mechanisms of lung injury from O3 exposure. Defining the adverse effects of chronic exposure to ambient levels of O3 on lung function and disease have been challenging, in part due to the presence of co-pollutants, such as particulate matter. The US Environmental Protection Agency's 1997 revised standard for O3 (0.08 ppm averaged over 8 hours) is designed to provide better protection to susceptible individuals. The revised standard is being implemented following the failure of court challenges.

Effect of acute ozone exposure on pregnant rat uterus contractile responses

Pulmonary effects of ozone (O(3)) inhalation have been comprehensively studied, but little is known about its extrapulmonary consequences, particularly in the reproductive tract. Thus, the effects of an acute O(3) exposure on the contractile response of the pregnant rat uterus were evaluated. Nonpregnant and pregnant (5, 10, and 18 days of gestation) rats were exposed to air or O(3) (3 ppm) for1 h, and uterine strips isolated from these animals were studied 16-18 h later. Contractile responses to acetylcholine (ACh) and oxytocin (OT) were evaluated with respect to three parameters (area under the curve, amplitude, and frequency). O(3) did not modify the sensitivity (-logEC(50)) to either agonist at any pregnancy stage, but induced a statistically significant increase in all maximum responses to OT at gestational day 5, and increased the maximum response (area under the curve) to ACh at pregnancy days 5 and 10. Our results suggest that O(3) inhalation can produce abnormal contractility in the pregnant uterus, and identify the need for further investigation of this issue.

Effect of antioxidant supplementation on ozone-induced lung injury in human subjects

To determine whether antioxidants can influence human susceptibility to ozone (O(3))-induced changes in lung function and airway inflammation, we placed 31 healthy nonsmoking adults (18 to 35 yr old) on a diet low in ascorbate for 3 wk. At 1 wk, subjects were exposed to filtered air for 2 h while exercising (20 L/min/m(2)), and then underwent bronchoalveolar lavage (BAL) and were randomly assigned to receive either a placebo or 250 mg of vitamin C, 50 IU of alpha-tocopherol, and 12 oz of vegetable cocktail daily for 2 wk. Subjects were then exposed to 0.4 ppm O(3) for 2 h and underwent a second BAL. On the day of the O(3) exposure, supplemented subjects were found to have significantly increased levels of plasma ascorbate, tocopherols, and carotenoids as compared with those of the placebo group. Pulmonary function testing showed that O(3)-induced reductions in FEV(1) and FVC were 30% and 24% smaller, respectively, in the supplemented cohort. In contrast, the inflammatory response to O(3) inhalation, as represented by the percent neutrophils and the concentration of interleukin-6 recovered in the BAL fluid at 1 h after O(3) exposure was not different for the two groups. These data suggest that dietary antioxidants protect against O(3)-induced pulmonary function decrements in humans.

Short-term effects of air pollution on mortality in the cities of Rouen and Le Havre, France, 1990-1995

In this study, the authors examined the short-term effects of ambient air pollution on mortality across 2 French cities: Rouen and Le Havre. In Poisson regression models, which controlled for day-of-week effects, the authors used nonparametric smoothing to control for temporal trend, weather, and influenza epidemics. In Rouen, an interquartile range increase of 60.5-94.1 microg/m3 of ozone was associated with an increase of 4.1% (95% confidence interval = 0.6, 7.8) of total mortality. Daily variations in sulfur dioxide (interquartile range increase = 17.6-36.4 microg/m3) were also associated with an 8.2% increase (95% confidence interval = 0.4, 16.6) in respiratory mortality. An increase of 6.1% (95% confidence interval = 1.5, 10.9) of cardiovascular mortality was also observed with an interquartile range increase of nitrogen dioxide (i.e., 25.3-42.2 microg/m3). With respect to Le Havre, an interquartile range increase in daily levels of sulfur dioxide (11.3-35.6 microg/m3) was associated with an increase of approximately 3% (95% confidence interval = 0.8, 5) of cardiovascular mortality. For particulate matter less than or equal to 13 microm in diameter (interquartile increase = 21.5, 45.4 microg/m3), an increase of 6.2% (95% confidence interval = 0.1, 12.8) was observed. The estimates of pollutant effects and their standard deviations were slightly affected by the degree of smoothing temporal variations in this study. When low collinearity was present, the 2-pollutant models provided acceptable estimates of pollutant effects. They suggested that the ozone effect was independent of the Black Smoke effect, and that the effects of sulfur dioxide and nitrogen dioxide were unlikely to be confounded by ozone concentrations. However, high collinearity leads to large estimates of the pollutant coefficient variances and, therefore, leads to inaccurate estimates of pollutant effects. The analysis of the contributory effects of different pollutant mixtures requires further investigation in those instances in which high collinearity between pollutants is present.

The effect of repeated ozone exposures on inflammatory markers in bronchoalveolar lavage fluid and mucosal biopsies

The aim of this study was to investigate the cellular and biochemical events associated with repeated exposures to ozone. Twenty-three healthy subjects underwent single exposures to 200 ppb ozone and to filtered air (FA), as well as repeated exposures to 200 ppb ozone on 4 consecutive days, each for 4 h of intermittent exercise. Bronchoalveolar lavage was performed and mucosal biopsies were taken 20 h after the single or the last of the repeated exposures. As compared with FA, the single exposure to ozone caused a decrease in FEV(1), an increase in the percentages of neutrophils and lymphocytes, the concentrations of total protein, IL-6, IL-8, reduced glutathione, urate, and ortho-tyrosine in BAL fluid (BALF), but no changes in the cellular composition of biopsy. After the repeated exposure, the effect on lung function was abolished and differential cell counts in BALF were not significantly different from those after FA. However, the concentrations of total protein, IL-6, IL-8, reduced glutathione, and ortho-tyrosine were still increased. IL-10 could only be detected in BALF after repeated ozone exposures. Furthermore, macroscopic scores for bronchitis, erythema, and hypervulnerability of airway mucosa were increased, as well as numbers of neutrophils in bronchial mucosal biopsies. Our data demonstrate that airway inflammation persists after repeated ozone exposure, despite attenuation of some inflammatory markers in BALF and adaptation of lung function.

Acute airway effects of formaldehyde and ozone in BALB/c mice

1. Concentration and time-effect relationships of formaldehyde and ozone on the airways were investigated in BALB/c mice. The effects were obtained by continuous monitoring of the respiratory rate, tidal volume, expiratory flow rate, time of inspiration, time of expiration, and respiratory patterns. 2. With concentrations up to 4 p.p.m., formaldehyde showed mainly sensory irritation effects of the upper airways that decrease the respiratory rate from a trigeminal reflex. The no-effect level (NOEL) was about 0.3 p.p.m. This value is close to the human NOEL, which is about 0.08 p.p.m. 3. Ozone caused rapid, shallow breathing in BALB/c mice. Later on, the respiratory rate decreased due to another vagal response that indicated an incipient lung oedema. The NOEL in mice was about 1 p.p.m. during 30 min of ozone exposure. No major effect occurs in resting humans at about 0.4 p.p.m. 4. Thus, the upper airway irritant, formaldehyde, and the deep lung irritant, ozone, showed the same types of respiratory effects in humans and in BALB/c mice. Also, the sensitivity was nearly identical. Continuous monitoring of respiratory effects in BALB/c mice, therefore, may be a valuable method for the study of effects of other environmental pollutants, which, however, should be confirmed in further studies.

Ozone at high-pollution urban levels causes airway hyperresponsiveness to substance P but not to other agonists

Ozone (O(3)) causes airway hyperresponsiveness, but few studies have evaluated this effect at urban concentrations. In this work dose-response curves to intravenous acetylcholine, histamine or substance P were performed in guinea pigs with or without previous exposure to O(3) (0.15, 0.3, 0.6 or 1.2 ppm for 4 h, 16-18 h before the studies). We found airway hyperresponsiveness to histamine, but not to acetylcholine, only after 1.2 ppm O(3). By contrast, airway hyperresponsiveness to substance P was developed at O(3) levels encountered in highly-polluted cities (0.3 ppm). These results suggest that excitatory non-adrenergic non-cholinergic responses could be affected by air pollution, and that substance P is a useful pharmacological tool for evaluating the airway hyperresponsiveness induced by low O(3) concentrations.

Mechanisms of pollution-induced airway disease: in vivo studies

Several studies have investigated the effects of ozone, sulphur dioxide (SO2), and nitrogen dioxide (NO2) on lung function in normal and asthmatic subjects. Decreased lung function has been observed with ozone levels as low as 0.15 ppm-this effect is concentration dependent and is exacerbated by exercise. A number of lines of evidence suggest that the effect on lung function is mediated, at least in part, by neural mechanisms. In both normals and asthmatics, ozone has been shown to induce neutrophilic inflammation, with increased levels of several inflammatory mediators, including prostaglandin E2. However, in normal subjects, none of the markers of inflammation correlate with changes in lung function. The lung function changes in asthmatics may be associated with inflammatory effects; alternatively, ozone may prime the airways for an increased response to subsequently inhaled allergen. Indeed, an influx of both polymorphonucleocytes and eosinophils has been observed in asthmatic patients after ozone exposure. It has been suggested that the effect of ozone on classic allergen-induced bronchoconstriction may be more significant than any direct effect of this pollutant in asthmatics. SO2 does not appear to affect lung function in normal subjects, but may induce bronchoconstriction in asthmatics. Nasal breathing, which is often impaired in asthmatics, reduces the pulmonary effects of SO2, since this water-soluble gas is absorbed by the nasal mucosa. NO2 may also influence lung function in asthmatics, but further research is warranted. SO2 and NO2 alone do not seem to have a priming effect in asthmatics, but a combination of these two gases has resulted in a heightened sensitivity to subsequently inhaled allergen.

Acute effects of summer air pollution on respiratory function in primary school children in southern England

BACKGROUND

There is growing concern about health effects of air pollution in the UK. Studies in the USA have reported adverse effects on lung function among children but no comparable studies have been published in the UK. This study investigates the relationship between daily changes in ambient air pollution and short term variations in lung function in a panel of school children.

METHODS

One hundred and fifty four children aged 7-11 attending a primary school adjacent to a major motorway in Surrey, south-east England, were studied. Bellows spirometry was performed daily on 31 schooldays between 6 June and 21 July 1994. Levels of ozone, nitrogen dioxide, and particulates of less than 10 microns in diameter (PM10) were measured continuously at the school and the pollen count was measured six miles away. Relationships between daily changes in forced expiratory volume in 0.75 seconds (FEV0.75), forced vital capacity (FVC), the FEV0.75/FVC ratio and pollutants were analysed using separate autoregressive models for each child. A weighted average of the resulting slopes was then calculated.

RESULTS

There was a significant inverse relationship between daily mean PM10 levels lagged one day and FVC, with a reduction in lung function of 1% (95% CI 0.3% to 2%) across the whole range of PM10 levels (20-150 micrograms/m3). The effect on FEV0.75 was similar (-0.5%) but was not significant when weighted by 1/SE2 (95% CI -1.2% to 0.2%). There was no effect of PM10 levels on the FEV0.75/FVC ratio. No significant association was seen between FEV0.75, FVC, or the FEV0.75/FVC ratio and either ozone or nitrogen dioxide levels. There was no evidence that wheezy children were more affected than healthy children. Pollen levels on the previous day had no effect on lung function and did not change the air pollution results.

CONCLUSIONS

There is a very small, but statistically significant, adverse effect of airborne respirable particulate matter, measured as PM10, on lung function in this study group. There is no evidence for an inverse association of lung function with levels of ozone or NO2 measured on the previous day.

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.

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.

Transient changes in the pulmonary function of welders: a cross sectional study of Monday peak expiratory flow

OBJECTIVES

The aim was to compare the peak expiratory flow (PEF) of welders and non-welders over a 12 hour period from the start of work on Monday.

METHODS

The two study groups consisted of 20 welders and 20 non-welders, all men who had essentially never smoked, with no significant difference in age, height, ethnicity, or baseline spirometry between the groups. The PEF was measured for each welder before the start of work and 15 minutes, 30 minutes, and 1, 2, 4, 7, and 12 hours after the start of welding. The same method was applied to the non-welders, for whom a proxy time for the start of welding was used.

RESULTS

The percentage change in baseline PEF was calculated for each subject at each of the recording times. The welder and non-welder group means for these results were significantly different at 15 minutes (p = 0.028). Also, the group mean for maximum fall in PEF (at any of the recording times during the 12 hour period) was significantly greater for the welders (p = 0.011). 50% of the welders (10/20), but only 5% of the non-welders (1/20), experienced a fall in PEF in excess of 5% (p = 0.0046). 25% of the welders (5/20) experienced drops of greater than 5% within the first 15 minutes.

CONCLUSION

The results are suggestive of an immediate type reaction in welders, similar to that seen in some cases of occupational asthma, although not so severe. Studies to determine if these reactions reflect non-specific bronchial hyper-responsiveness would be useful. It is recommended that future studies also undertake breathing zone measurements to relate the response to particular constituents of the welding plume, especially the gases ozone and nitrogen dioxide.

Ozonation of DNA forms adducts: a 32P-DNA labeling and thin-layer chromatography technique to measure DNA environmental biomarkers

Little direct documented evidence of ozone's genotoxicity exists. Deoxyribonucleic acid (DNA) adducts are produced by environmental toxic agents, including ozone. We have described a modified thin-layer chromatography (TLC) technique that can assess adduct formation as a biomarker of ozone injury. This requires 32P-labeling DNA, digestion of deoxynucleotides (dNMPs), and separation in two-dimensional PEI-cellulose TLC. We have applied this technique to control DNAs, to control DNA in solution exposed to acute ambient ozone, and to control DNA exposed to acute bubbled-through ozone (2 ppm for 24 h). We detected stable DNA adducts, including hydroxymethyluracil (HMU), thymine glycol (TG), 8-hydroxyguanine (8-OHG), and demonstrated, as yet, unidentified adducts that may serve as a "fingerprint" pattern of DNA adduction. This technique quantifies low-molecular-mass DNA adducts, both in vivo and in vitro, with potential applications to environmental toxicology.

Effect of ambient ozone on peak expiratory flow of exercising children in The Netherlands

The potential effects of elevated ozone concentrations in The Netherlands were evaluated by the measurement of peak expiratory flow (PEF) of exercising children. Peak expiratory flow was measured with mini-Wright peak flow meters, both before and after out-door sports training. The relationship between PEF and ozone was investigated with individual regression analysis. The difference of PEF after and before training (delta PEF) and the PEF after training were used as dependent variables. The ozone concentration during the training and the 1-h maximum ozone concentration of the same and the previous day were used as independent variables. The highest observed 1-h maximum ozone concentration was 236 micrograms/m3. delta PEF was unrelated to the ambient ozone concentration during training. Peak flow measured after the training was positively correlated with ambient temperature. The high correlation between ozone and temperature prevented the evaluation of effects of the maximum ozone concentration of the same day on PEF after training. A small negative association of borderline statistical significance between PEF after training and previous-day maximum ozone was observed.

Acute effects of ambient ozone on pulmonary function of children in The Netherlands

In the spring and summer of 1989 an epidemiologic study was conducted to evaluate the acute effects of photochemical air pollution episodes on pulmonary function of children living in three nonindustrial towns in the Netherlands. Spirometry was performed repeatedly in the schools of the children, mostly during the morning hours. Data from 533 children having more than four valid pulmonary function tests were included in the analyses. The association between previous-day ambient ozone concentration and pulmonary function was evaluated, using individual linear regression analysis and subsequent evaluation of the distribution of individual regression coefficients. One hour maximum ambient ozone concentrations frequently exceeded 160 micrograms/m3 but were all lower than the Dutch Air Quality Guideline of 240 micrograms/m3 for all three populations. Significant negative associations of previous-day ambient ozone with FVC, FEV1, peak expiratory flow (PEF), and maximal midexpiratory flow (MMEF) were observed. There were indications of systematic differences in responses among the children. Children with chronic respiratory symptoms did not have a stronger response than children without these symptoms.