Effects of ambient ozone on respiratory function in active, normal children

Seventy-five years of impactful environmental and occupational health research at the Nelson Institute of Environmental Medicine at New York University

Founded in 1947 as the Institute of Industrial Medicine, the Nelson Institute and Department of Environmental Medicine at New York University (NYU) Grossman School of Medicine (NYUGSOM) was supported by a National Institute of Environmental Health Science (NIEHS) Center Grant for over 56 years. Nelson Institute researchers generated 75 years of impactful research in environmental and occupational health, radiation effects, toxicology, and cancer. Environmental health research is continuing at NYUGSOM in its departments of medicine and population health. The objective of this historical commentary is to highlight the major achievements of the Nelson Institute and the department in the context of its history at facilities in Sterling Forest, Tuxedo, NY and Manhattan, NY. Aspects of our discussion include leadership, physical facilities, and research in many areas, including air pollution, health effects of environmental radiation exposures, inhalation toxicology methodology, carcinogenesis by chemicals, metals, and hormones, cancer chemoprevention, human microbiome, ecotoxicology, epidemiology, biostatistics, and community health concerns. The research of the institute and department benefited from unique facilities, strong leadership focused on team-based science, and outstanding investigators, students, and staff. A major lasting contribution has been the training of hundreds of graduate students and postdoctoral fellows, many of whom have been and are training the next generation of environmental and occupational health researchers at various institutions.

Assessing the impact of green nudges on ozone concentration: Evidence from China's night refueling policy

Ozone (O₃) pollution poses health risks and premature mortality, and gas stations are one of the largest sources of urban volatile organic compounds (VOCs, the main precursor to O₃). This paper investigates whether the government's call for night refueling, which can be regarded as a green nudge, can guide changes in consumer behavior and consequently improve environmental quality. Using a difference-in-differences (DID) estimation and weekly monitoring site air quality panel data, we analyze the effect of the Night Refueling Preferential Policy on O₃ concentrations. We find that the policy can reduce O₃ concentrations by 10% by encouraging consumers to refuel at night. The reduction in O₃ has brought great benefits to human health, leading to a 4-5‰ reduction in non-accidental mortality and a 6-8‰ reduction in cardiovascular mortality in Jiangsu province. The economic benefits of this policy would be approximately 62-189 billion Chinese Yuan (CNY) if it were implemented nationwide. The findings of this study suggest that the government can influence consumer behavior to promote environmental quality.

Removal of chemical hazardous compounds using CATACOAT, a nano-platinum thermal catalyst system

The performance of CATACOAT, a nano-platinum thermal catalyst system, was evaluated for the removal of chemical hazardous compounds from air. Xylene, benzene, styrene, and toluene were selected as standard volatile organic compounds (VOCs) in this study. In addition, formaldehyde was tested as a chemical hazardous compound. Each VOC, or formaldehyde, was evaporated in a 4,000 L chamber under controlled environments. At the maximum concentration point, CATACOAT was turned on and the concentrations of the chemical hazardous compounds were recorded for 5 h. The air purifier based on H-13-grade high-efficiency particulate air (HEPA) filter was tested in the same way to compare the effects of CATACOAT. Compared with the HEPA filter system, every VOC concentration was significantly decreased with the CATACOAT system only 0.025 h after turning on the air purifier (P values for xylene, benzene, styrene, and toluene are 0.00488, 0.01508, 0.00014, and 0.04690, respectively). After running the air cleaners for 5 h, every VOC and formaldehyde demonstrated significantly decreased concentrations with the CATACOAT system, compared with HEPA filter system (P values for xylene, benzene, styrene, toluene, and formaldehyde are 0.00034, 0.00009, 0.00008, 0.00001, and 0.00571, respectively). In conclusion, the CATACOAT may be a viable solution to control indoor air pollution.

Air pollution and lung function in children

In this narrative review, we summarize the literature and provide updates on recent studies of air pollution exposures and child lung function and lung function growth. We include exposures to outdoor air pollutants that are monitored and regulated through air quality standards, and air pollutants that are not routinely monitored or directly regulated, including wildfires, indoor biomass and coal burning, gas and wood stove use, and volatile organic compounds. Included is a more systematic review of the recent literature on long-term air pollution and child lung function because this is an indicator of future adult respiratory health and exposure assessment tools have improved dramatically in recent years. We present "summary observations" and "knowledge gaps." We end by discussing what is known about what can be done at the individual/household, local/regional, and national levels to overcome structural impediments, reduce air pollution exposures, and improve child lung function. We found a large literature on adverse air pollution effects on children's lung function level and growth; however, many questions remain. Important areas needing further research include whether early-life effects are fixed or reversible; and what are windows of increased susceptibility, long-term effects of repeated wildfire events, and effects of air quality interventions.

Ozone-Related Respiratory Morbidity in a Low-Pollution Region

OBJECTIVE

We evaluated the effects of ozone on respiratory-related hospital admissions in three counties in Washington State from 1990 to 2006. We further examined vulnerability to ozone by key demographic factors.

METHOD

Using linked hospital admission and ambient monitoring data, we estimated the age-, sex-, and health insurance-stratified associations between ozone (0 to 3 days' lag) and respiratory-related hospital admissions in King, Spokane, and Clark County, Washington.

RESULTS

The adjusted relative risk (RR) for a 10 ppb increase in ozone at 3 days' lag was 1.04 (95% confidence interval [CI]: 1.02, 1.07) for Clark County, 1.03 (95% CI: 1.01, 1.05) for Spokane County, and 1.02 (95% CI: 1.01, 1.03) for King County. There was consistent evidence of effect modification by age.

CONCLUSION

Ozone at levels below federal standards contributes to respiratory morbidity among high-risk groups in Washington.

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.

Weekly Personal Ozone Exposure and Respiratory Health in a Panel of Greek Schoolchildren

BACKGROUND

The association of ozone exposure with respiratory outcomes has been investigated in epidemiologic studies mainly including asthmatic children. The findings reported had methodological gaps and inconsistencies.

OBJECTIVES

We aimed to investigate effects of personal ozone exposure on various respiratory outcomes in school-age children generally representative of the population during their normal activities.

METHODS

We conducted a panel study in a representative sample of school-age children in the two major cities of Greece, Athens and Thessaloniki. We followed 188, 10- to 11-y-old, elementary school students for 5 wk spread throughout the 2013–2014 academic year, during which ozone was measured using personal samplers. At the end of each study week, spirometry was performed by trained physicians, and the fractional concentration of nitric oxide in exhaled air (F_eNO) was measured. Students kept a daily time–activity–symptom diary and measured PEF (peak expiratory flow) using peak flow meters. Mixed models accounting for repeated measurements were applied.

RESULTS

An increase of 10 μg/m³ in weekly ozone concentration was associated with a decrease in FVC (forced vital capacity) and FEV₁ (forced expiratory volume in 1 s) of 0.03 L [95% confidence interval (CI): −0.05, −0.01] and 0.01 L (95% CI: −0.03, 0.003) respectively. The same increase in exposure was associated with a 11.10% (95% CI: 4.23, 18.43) increase in F_eNO and 19% (95% CI: −0.53, 42.75) increase in days with any symptom. The effect estimates were robust to PM₁₀ adjustment. No inverse association was found between ozone exposure and PEF.

CONCLUSIONS

The study provides evidence that airway inflammation and the frequency of respiratory symptoms increase, whereas lung function decreases with increased ozone exposure in schoolchildren. https://doi.org/10.1289/EHP635.

The short-term effects of air pollution on adolescent lung function in Taiwan

A mass screening of lung function associated with air pollutants for children is limited. This study assessed the association between air pollutants exposure and the lung function of junior high school students in a mass screening program in Taipei city, Taiwan. Among 10,396 students with completed asthma screening questionnaires and anthropometric measures, 2919 students aged 12-16 received the spirometry test. Forced vital capacity (FVC) and forced expiratory flow in 1s (FEV(1)) in association with daily ambient concentrations of particulate matter with diameter of 10 μm or less (PM(10)), sulfur dioxide (SO(2)), carbon monoxide (CO), nitrogen dioxide (NO(2)), and ozone (O(3)) were assessed by regression models controlling for the age, gender, height, weight, student living districts, rainfall and temperature. FVC, had a significant negative association with short-term exposure to O(3) and PM(10) measured on the day of spirometry testing. FVC values also were reversely associated with means of SO(2), O(3), NO(2), PM(10) and CO exposed 1 d earlier. An increase of 1-ppm CO was associated with the reduction in FVC for 69.8 mL (95% CI: -115, -24.4 mL) or in FEV(1) for 73.7 mL (95% CI: -118, -29.7 mL). An increase in SO(2) for 1 ppb was associated with the reductions in FVC and FEV(1) for 12.9 mL (95% CI: -20.7, -5.09 mL) and 11.7 mL (95% CI: -19.3, -4.16 mL), respectively. In conclusion, the short-term exposure to O(3) and PM(10) was associated with reducing FVC and FEV(1). CO and SO(2) exposure had a strong 1-d lag effect on FVC and FEV(1).

Increased CCL24/eotaxin-2 with postnatal ozone exposure in allergen-sensitized infant monkeys is not associated with recruitment of eosinophils to airway mucosa

Epidemiology supports a causal link between air pollutant exposure and childhood asthma, but the mechanisms are unknown. We have previously reported that ozone exposure can alter the anatomic distribution of CD25+ lymphocytes in airways of allergen-sensitized infant rhesus monkeys. Here, we hypothesized that ozone may also affect eosinophil trafficking to allergen-sensitized infant airways. To test this hypothesis, we measured blood, lavage, and airway mucosa eosinophils in 3-month old monkeys following cyclical ozone and house dust mite (HDM) aerosol exposures. We also determined if eotaxin family members (CCL11, CCL24, CCL26) are associated with eosinophil location in response to exposures. In lavage, eosinophil numbers increased in animals exposed to ozone and/or HDM. Ozone+HDM animals showed significantly increased CCL24 and CCL26 protein in lavage, but the concentration of CCL11, CCL24, and CCL26 was independent of eosinophil number for all exposure groups. In airway mucosa, eosinophils increased with exposure to HDM alone; comparatively, ozone and ozone+HDM resulted in reduced eosinophils. CCL26 mRNA and immunofluorescence staining increased in airway mucosa of HDM alone animals and correlated with eosinophil volume. In ozone+HDM animal groups, CCL24 mRNA and immunofluorescence increased along with CCR3 mRNA, but did not correlate with airway mucosa eosinophils. Cumulatively, our data indicate that ozone exposure results in a profile of airway eosinophil migration that is distinct from HDM mediated pathways. CCL24 was found to be induced only by combined ozone and HDM exposure, however expression was not associated with the presence of eosinophils within the airway mucosa.

Relationship between ambient ozone concentrations and daily hospital admissions for childhood asthma/atopic dermatitis in two cities of Korea during 2004-2005

The objective of this study was to estimate the association between ambient ozone levels and hospitalization for asthma/atopic dermatitis among children younger than 15 years old living in Seoul and Ulsan, Korea, in the years 2004-2005. Estimated relative risks of hospital admissions associated with an interquartile range (IQR) increase in ozone concentration were calculated using a generalized additive Poisson model. For childhood asthma, the effect of an ozone increase on the relative risks in Ulsan [1.21 (95% CI, 1.10-1.34)] was higher than that in Seoul [1.05 (95% CI, 0.99-1.11)]. The relative risks for childhood atopic dermatitis were also found to be higher in Ulsan [1.38 (95% CI, 0.80-2.36)] than in Seoul [1.28 (95% CI, 1.04-1.58)]. These results support previously reported findings and also indicate that ozone concentrations at levels below the standards in the Republic of Korea can be correlated with asthma hospital admissions in children.

Public health benefits of strategies to reduce greenhouse-gas emissions: health implications of short-lived greenhouse pollutants

In this report we review the health effects of three short-lived greenhouse pollutants-black carbon, ozone, and sulphates. We undertook new meta-analyses of existing time-series studies and an analysis of a cohort of 352,000 people in 66 US cities during 18 years of follow-up. This cohort study provides estimates of mortality effects from long-term exposure to elemental carbon, an indicator of black carbon mass, and evidence that ozone exerts an independent risk of mortality. Associations among these pollutants make drawing conclusions about their individual health effects difficult at present, but sulphate seems to have the most robust effects in multiple-pollutant models. Generally, the toxicology of the pure compounds and their epidemiology diverge because atmospheric black carbon, ozone, and sulphate are associated and could interact with related toxic species. Although sulphate is a cooling agent, black carbon and ozone could together exert nearly half as much global warming as carbon dioxide. The complexity of these health and climate effects needs to be recognised in mitigation policies.

Long-term ozone exposure and mortality

BACKGROUND

Although many studies have linked elevations in tropospheric ozone to adverse health outcomes, the effect of long-term exposure to ozone on air pollution-related mortality remains uncertain. We examined the potential contribution of exposure to ozone to the risk of death from cardiopulmonary causes and specifically to death from respiratory causes.

METHODS

Data from the study cohort of the American Cancer Society Cancer Prevention Study II were correlated with air-pollution data from 96 metropolitan statistical areas in the United States. Data were analyzed from 448,850 subjects, with 118,777 deaths in an 18-year follow-up period. Data on daily maximum ozone concentrations were obtained from April 1 to September 30 for the years 1977 through 2000. Data on concentrations of fine particulate matter (particles that are < or = 2.5 microm in aerodynamic diameter [PM(2.5)]) were obtained for the years 1999 and 2000. Associations between ozone concentrations and the risk of death were evaluated with the use of standard and multilevel Cox regression models.

RESULTS

In single-pollutant models, increased concentrations of either PM(2.5) or ozone were significantly associated with an increased risk of death from cardiopulmonary causes. In two-pollutant models, PM(2.5) was associated with the risk of death from cardiovascular causes, whereas ozone was associated with the risk of death from respiratory causes. The estimated relative risk of death from respiratory causes that was associated with an increment in ozone concentration of 10 ppb was 1.040 (95% confidence interval, 1.010 to 1.067). The association of ozone with the risk of death from respiratory causes was insensitive to adjustment for confounders and to the type of statistical model used.

CONCLUSIONS

In this large study, we were not able to detect an effect of ozone on the risk of death from cardiovascular causes when the concentration of PM(2.5) was taken into account. We did, however, demonstrate a significant increase in the risk of death from respiratory causes in association with an increase in ozone concentration.

Acute respiratory health effects of air pollution on children with asthma in US inner cities

BACKGROUND

Children with asthma in inner-city communities may be particularly vulnerable to adverse effects of air pollution because of their airways disease and exposure to relatively high levels of motor vehicle emissions.

OBJECTIVE

To investigate the association between fluctuations in outdoor air pollution and asthma morbidity among inner-city children with asthma.

METHODS

We analyzed data from 861 children with persistent asthma in 7 US urban communities who performed 2-week periods of twice-daily pulmonary function testing every 6 months for 2 years. Asthma symptom data were collected every 2 months. Daily pollution measurements were obtained from the Aerometric Information Retrieval System. The relationship of lung function and symptoms to fluctuations in pollutant concentrations was examined by using mixed models.

RESULTS

Almost all pollutant concentrations measured were below the National Ambient Air Quality Standards. In single-pollutant models, higher 5-day average concentrations of NO2, sulfur dioxide, and particles smaller than 2.5 microm were associated with significantly lower pulmonary function. Higher pollutant levels were independently associated with reduced lung function in a 3-pollutant model. Higher concentrations of NO2 and particles smaller than 2.5 microm were associated with asthma-related missed school days, and higher NO2 concentrations were associated with asthma symptoms.

CONCLUSION

Among inner-city children with asthma, short-term increases in air pollutant concentrations below the National Ambient Air Quality Standards were associated with adverse respiratory health effects. The associations with NO2 suggest that motor vehicle emissions may be causing excess morbidity in this population.

Outdoor air pollution and emergency department visits for asthma among children and adults: a case-crossover study in northern Alberta, Canada

BACKGROUND

Recent studies have observed positive associations between outdoor air pollution and emergency department (ED) visits for asthma. However, few have examined the possible confounding influence of aeroallergens, or reported findings among very young children.

METHODS

A time stratified case-crossover design was used to examine 57,912 ED asthma visits among individuals two years of age and older in the census metropolitan area of Edmonton, Canada between April 1, 1992 and March 31, 2002. Daily air pollution levels for the entire region were estimated from three fixed-site monitoring stations. Similarly, daily levels of aeroallergens were estimated using rotational impaction sampling methods for the period between 1996 and 2002. Odds ratios and their corresponding 95% confidence intervals were estimated using conditional logistic regression with adjustment for temperature, relative humidity and seasonal epidemics of viral related respiratory disease.

RESULTS

Positive associations for asthma visits with outdoor air pollution levels were observed between April and September, but were absent during the remainder of the year. Effects were strongest among young children. Namely, an increase in the interquartile range of the 5-day average for NO2 and CO levels between April and September was associated with a 50% and 48% increase, respectively, in the number of ED visits among children 2 - 4 years of age (p < 0.05). Strong associations were also observed with these pollutants among those 75 years of age and older. Ozone and particulate matter were also associated with asthma visits. Air pollution risk estimates were largely unchanged after adjustment for aeroallergen levels.

CONCLUSION

Our findings, taken together, suggest that exposure to ambient levels of air pollution is an important determinant of ED visits for asthma, particularly among young children and the elderly.

Paradoxical ozone associations could be due to methyl nitrite from combustion of methyl ethers or esters in engine fuels

We review studies of the effects of low ambient ozone concentrations on morbidity that found a negative coefficient for ozone concentration. We call this a Paradoxical Ozone Association (POA). All studies were in regions with methyl ether in gasoline. All but one study carefully controlled for the effects of other criterion pollutants, so the phenomenon cannot be attributed to them. One was in southern California in mid-summer when ozone levels are highest. Because ozone is created by sunlight, the most plausible explanation for a POA would be an ambient pollutant that is rapidly destroyed by sunlight, such as methyl nitrite (MN). A previously published model of engine exhaust chemistry suggested methyl ether in the fuel will create MN in the exhaust. MN is known to be highly toxic, and closely related alkyl nitrites are known to induce respiratory sensitivity in humans. Support for the interpretation comes from many studies, including three linking asthma symptoms to methyl tertiary butyl ether (MTBE) and the observation that a POA has not been seen in regions without ether in gasoline. We also note that studies in southern California show a historical trend from more significant to less significant ozone-health associations. The timing of those changes is consistent with the known timing of the introduction of gasoline oxygenated with MTBE in that region.

Pulmonary function in long-term survivors of pediatric hematopoietic cell transplantation

BACKGROUND

The purpose of this study was to determine the prevalence of pulmonary dysfunction in pediatric hematopoietic cell transplant (HCT) survivors and to identify associated risk factors.

PROCEDURE

In a cross-sectional study, patients surviving at least 5 years after pediatric HCT were requested to undergo pulmonary function testing (PFT). Risk factors for restrictive lung disease (RLD) and obstructive lung disease (OLD) were analyzed using multivariate analysis.

RESULTS

Among 472 patients contacted, 260 (55%) participated and 215 were selected for analysis. These patients were transplanted at a median age of 8.3 (0.3-18.0) years; 175 for hematologic malignancies and 40 for non-malignant diseases. The preparative regimens for 133 patients included fractionated TBI (FTBI), 29 single-fraction TBI (SFTBI), and 53 non-TBI regimens. PFT was performed at a median of 10 (5.0-27.5) years after HCT. Forty percent of patients had either RLD or OLD (28% RLD, 9% OLD, 3% mixed RLD/OLD) and at least 15% had an isolated low-DLCO. Moderate-to-severe impairment was present in 45% of patients with RLD or OLD. In multivariate analysis, risk factors associated with RLD included transplant regimen, transplant diagnosis, scleroderma/contracture, and donor relation. Patients treated with SFTBI had the highest risk of RLD. Risk factors for OLD included chronic graft-versus-host disease, transplant regimen, and time after HCT. Patients surviving 20 or more years after HCT had the highest risk of OLD.

CONCLUSIONS

Fifty-five percent of long-term pediatric HCT survivors had pulmonary dysfunction. These findings stress the need for long-term follow-up to detect pulmonary dysfunction.

Chronic Exposure to Ambient Ozone and Lung Function in Young Adults

BACKGROUND

Tropospheric ozone (O3) is an oxidant, outdoor air pollutant. Chronic exposure has been associated with decreased lung function in children and adolescents. This study investigated the effects of long-term exposure to O3 on lung function in college freshmen.

METHODS

We recruited University of California, Berkeley students (n=255) who were lifelong residents of the Los Angeles and San Francisco Bay areas and who never smoked. Lifetime exposures to O3, small particulate matter (PM10), and nitrogen dioxide (NO2) were based on spatial interpolation of compliance monitor measurements to all residences at which students lived. Spirometry was performed between February and May, times when students would not have had recent exposure to increased levels of O3.

RESULTS

Lifetime exposure to O3 was associated with decreased levels of measures of small airways (<2 mm) function (FEF75 and FEF25-75). There was an interaction with the FEF25-75/FVC ratio, a measure of intrinsic airway size. Subjects with a large ratio were less likely to have decreases in FEF75 and FEF25-75 for a given estimated lifetime exposure to O3. This association was not altered by history of chronic respiratory disease, allergy, second-hand exposure to environmental tobacco smoke, exposure to PM10 and NO2, or measurement errors in exposure assessment.

CONCLUSIONS

A history of increased level of lifetime exposure to ambient O3 is associated with decreased function of airways in which O3 deposition in the lungs is the greatest. Adolescents with intrinsically smaller airways appear to be at greatest risk. Any environmental or genetic factors that lead to reduced airway size may lead to increased susceptibility to the adverse effects of ambient ozone.

Airborne particulates and asthma: a Maine case study

Maine currently has the second fastest growing asthma rate in the nation 9.4% of the adult population has asthma and one out of eight children is affected. The factors behind this increase are poorly understood, but previous reports suggest that biologically soluble metal ions from particulate matter (PM10) may play a role in asthma episodes. In an effort to study this issue, we first identified geographic and temporal trends in Maine asthma hospitalizations. Clinical data show a strong fall peak in asthma admissions with weaker peaks in January and May, and a summer low in asthma admissions. Asthma admissions are also higher in the cities than in the rural areas in Maine. We then analysed PM10 collected by the Maine Department of Environmental Protection in three different Maine locations in the years 2000 and 2001, at times when clinical asthma data showed peaks and during the summer low period. We also collected soil samples in the same locations. The PM10 and soils were analysed for 10 metals by acid extraction to determine total metal content and then with cell culture medium, DMEM/F12+CCS growth medium, to determine metal biosolubility. Our results showed that Mn, Cu, Pb, As, V, Ni and Al were present in the Maine PM samples. V, Ni and Pb showed seasonal variation, while the others were relatively constant throughout the year. Pb and Al did not appear to be soluble in the biological medium. There was also variation from location to location with the urban area showing the highest concentrations for most metals. Aluminium was present in the highest concentration in soil samples, followed by Mn and V. Only Cu was biologically available in soils. We determined from M/Al ratios that most of the PM10 did not originate from local crustal material.

Environmental ozone effects in different population subgroups

The study objective was to get more information on characteristics of ozone risk groups. We performed repeated (on average 16 times) lung function tests and interviews with 171 persons belonging to four different population subgroups (44 healthy children, 43 juvenile asthmatics, 43 athletes, and 41 elderly). The environmental half hour mean ozone concentrations ranged from 8 to 99 ppb. For two groups there was significant NO2 co-pollution. The asthmatics showed statistically significant ozone related increased ORs for eye irritations, the elderly for nose irritations. Significant lung function decrements (increase in ozone by 50 ppb) were found for asthmatics (FVC -4.3% afternoon one day lag, -4.9% afternoon two day lag, -3.6% morning one day lag) and children (FVC -3.2% same morning, PEF -11.9% same morning, PEF -4.6% morning one day lag). In the group of elderly, however, there were also some significant FVC and PEF increments. Ozone responders were found more often in the groups of asthmatics and children (21% resp. 18%) compared with elderly and athletes (both 5%). The results suggest that children and asthmatics have a higher risk of being ozone sensitive showing more ozone related acute lung function decrements than other population groups.

Ozone exposures during trans-continental and trans-Pacific flights

Ozone concentrations were passively monitored in passenger cabins of commercial airliners flying domestic, Pacific, and south-east Asian routes. One-hundred and six flight segments were monitored for either the full duration and/or approximately 3 h during the middle portion of the flight for a total of 145 time-integrated measurements. Over all samples the mean (+/-SD) concentration was 80 p.p.b. (30.1). Twenty percent of the measurements exceeded 100 p.p.b., the FAA-recommended level. Eleven percent of the measurements exceeded 120 p.p.b., the US EPA's short-term National Ambient Air Quality Standard for ozone. Ozone concentrations measured on Pacific flights were substantially higher during mid-flight than over the full flight (95 p.p.b. vs. 56 p.p.b). Ozone concentrations on the northern Pacific routes were higher than concentrations for other Pacific flights. Season comparison showed that ozone levels were higher during the winter and spring than for the summer and fall. Our study shows that even in aircraft with catalytic ozone converters, passengers and flight crew may be exposed to elevated ozone levels on domestic and international flights. Given the frequency of ozone excess, it is recommended that (1) ozone converters should be required equipment on all commercial passenger aircraft for mid and high latitude routes (2) improved maintenance procedures should be required for catalytic converters (e.g., more frequent servicing/replacement), and (3) ozone should be routinely monitored on all mid and high latitude flights.

PRACTICAL IMPLICATIONS

The authors have demonstrated elevated ozone concentrations in passenger cabins. They give several practical recommendations to help solve the problem.

Acute effects of winter air pollution on respiratory function in schoolchildren in southern England

AIM

To investigate the acute health effects of winter outdoor air pollution (nitrogen dioxide (NO(2)), ozone (O(3)), sulphur dioxide (SO(2)), sulphate (SO(4)(2-)),and particles (PM(10))) on schoolchildren in an area of southern England where levels of SO(2) had been reported to be high.

METHODS

A total of 179 children, aged 7-13, from three schools (two urban and one rural location), were included. Peak expiratory flow rate (PEFR) and presence or absence of upper respiratory infections were recorded on 63 school days from 1 November 1996 to 14 February 1997. Air pollution and meteorological data were taken from monitors at each school site. The analysis regressed daily PEFR on pollutant level adjusting for confounders and serial correlation and calculated a weighted pooled estimate of effect overall for each pollutant. In addition, large decrements in PEFR were analysed as a binary outcome. Same day, lag 1, lag 2, and a five day average of pollutant levels were used.

RESULTS

There were no clear effects of any pollutant on mean PEFR. In addition, we analysed large PEFR decrements (a binary outcome), observing consistent negative associations with NO(2), SO(4)(2-), and PM(10), although few lag/pollutant combinations were significant: odds ratios (95% CI) for five day average effect: NO(2) 24 h average 1.043 (1.000 to 1.089), SO(4)(2-) 1.090 (0.898 to 1.322), PM(10) 1.037 (0.992 to 1.084). The observed effects of PM(10) (only) were stronger in wheezy children (1.114 (1.057 to 1.174)). There were no consistent negative associations between large decrements and ozone or SO(2).

CONCLUSIONS

There is no strong evidence for acute effects of winter outdoor air pollution on mean PEFR overall in this area, but there is evidence for negative effects on large PEFR decrements.

Association between air pollution and lung function growth in southern California children: results from a second cohort

A cohort of 1,678 Southern California children, enrolled as fourth graders in 1996, was followed for 4 years to determine whether the growth in lung function of the children was associated with their exposure to ambient air pollutants. These subjects comprised the second cohort of fourth grade children participating in the Children's Health Study. Significant deficits in lung function growth rate were associated with exposure to acid vapor, NO(2), particles with aerodynamic diameter less than 2.5 microm (PM(2.5)), and elemental carbon. For example, the average annual growth rates of maximal midexpiratory flow and forced expiratory volume in 1 second were reduced by approximately 11% (p = 0.005) and 5% (p = 0.03), respectively, across the observed range of acid exposure. Exposure to acid vapor was also associated with reductions in the ratio of maximal midexpiratory flow to forced vital capacity (p = 0.02), whereas exposure to ozone was correlated with reduced growth in peak flow rate (p = 0.006). Larger deficits in lung function growth rate were observed in children who reported spending more time outdoors. These findings provide important replication of our previous findings of an effect of air pollution on lung function growth that were based on the first fourth-grade cohort from the Children's Health Study (Am J Respir Crit Care Med 2000;162:1383-1390).

Assessment of recent ozone short-term epidemiologic studies

The U.S. Environmental Protection Agency (EPA) revised the National Ambient Air Quality Standards (NAAQS) for ozone in 1997 based largely on short-term ozone studies published up to 1995. The U.S. EPA's conclusions must now be updated because (1) the agency did not consider many new studies published since 1995 and (2) the agency did not critically review the studies published before 1995 (i.e., it accepted the stated conclusions). In this article, we examine many recently published short-term ozone studies including 17 hospital admissions studies, 10 mortality studies, and 6 summer-camp studies. Almost all of these studies reported a significant association between ambient levels of ozone and adverse health effects. However, on close examination, it is apparent that there are mixed findings from one study to another and even within the results of a single study. Moreover, questionable statistical analyses and failure to consider confounders make a number of the reported findings doubtful and even negative.

Use of personal passive samplers for measurement of NO(2), NO, and O(3) levels in panel studies

We measured personal exposure to nitrogen dioxide (NO(2)), nitrogen monoxide (NO), and ozone (O(3)), using personal passive samplers during three 4-day periods, in a panel study of asthmatics continuing the normal activities of everyday life. Fifty-five adults, mean age 42 years, 53% men, and 39 children, mean age 11 years, 67% boys, wore two Ogawa passive samplers simultaneously: one for O(3), the other for NO(2) and NO. Mean outdoor pollution was measured at a regional monitoring network. Personal exposure levels were scattered; they were (on average) higher than stationary-site levels for NO and lower for NO(2) and O(3). In adults, 41% of the variance of personal exposure to NO(2) was explained by mean stationary-site measurement levels (P<0.0001). Twenty-one percent additional variance was explained by living near a main road, not having an extractor fan over the cooker, older age, and male sex. NO and O(3) personal exposures correlated poorly with stationary-site measurements. In panel studies of the health effects of air pollution, personal exposure to NO(2) and NO can be measured satisfactorily by passive samplers: such measurements are necessary for NO but not for NO(2). For O(3), accurate personal exposure measurement remains a challenge and further technical development is required.

Lung function growth and ambient ozone: a three-year population study in school children

We followed a cohort of 1,150 children for 3 yr to investigate long-term effects of ambient ozone. Nine study sites were selected on the basis of air-quality data to represent a broad range of ozone exposure. In 1994, 1995, and 1996 lung function was recorded biannually, always before and after summertime. The effect of ozone was analyzed with regression analyses and study-site, a child's sex, atopy, passive smoking, baseline lung function, and increase in height were considered as confounding variables. A negative effect of summertime ozone on the pre- to post-summer-time change in FEV(1) (ml/d) was present in 1994 (beta = -0.019 ml/d/ppb; p < 0.01) and in 1995 (beta = -0.017 ml/d/ ppb; p < 0.05), but not in 1996 (beta = 0. 004 ml/d/ppb; p = 0.6); corresponding estimates for FVC were in 1994: beta = -0.022 ml/d/ppb, p < 0.005; 1995: beta = -0.018 ml/d/ppb, p < 0.05; and 1996: beta = 0.006 ml/d/ppb, p = 0.46. When all three study years were considered simultaneously, i.e., the changes in lung function between each of two subsequent surveys being the dependent variable, summertime ozone was associated with a lesser increase in FEV(1) (beta = -0.029 ml/d/ppb; p < 0.001), FVC (beta = -0.018 ml/d/ppb; p < 0.001), and MEF(50) (beta = -0.076 ml/s/d; p = 0.001). No consistent associations were observed for lung function and NO(2), SO(2) and PM(10). Long-term ambient ozone exposure might negatively influence lung function growth.

Detection of ozone-induced DNA single strand breaks in murine bronchoalveolar lavage cells acutely exposed in vivo

Single-strand breaks (SSBs) in DNA have been used a biomarker of oxidative damage. The comet assay, also known as single-cell gel electrophoresis, was used to investigate the ability of ozone (O(3)) to induce DNA SSBs in murine bronchoalveolar lavage (BAL) cells. The comet assay is more sensitive than other techniques currently utilized for detecting SSBs and requires fewer cells. In the present study, 3 mice were exposed for 3 h to 0.25 ppm of O(3), and 3 to 0.5 ppm of O(3) for 3 h. Two air-exposed mice served as negative controls. All mice were euthanized 3 h after exposure, at which time BAL cells were recovered from the lungs and stained with ethidium bromide. BAL cells recovered from an air-exposed mouse were exposed to various concentrations of H(2)O(2) in vitro for 1 h at 4 degrees C. Excluding cells from the H(2)O(2) group (n = 25), 50 randomly selected BAL cells were graded by comet tail length into 1 of 4 categories: no damage (0 mm), low damage (1-10 mm), medium damage (11-30 mm), and high damage (31 + mm). The nonparametric Wilcoxon rank-sum test was used for statistical analysis, and p values lower than .05 were considered significant. The H(2)O(2) and the 0.25 and 0.5 ppm O3 groups showed statistically significant increases in DNA SSBs as compared to air-exposed controls. The results of this study indicate that (1) O(3) induces DNA strand breaks in murine BAL cells at 0.25 and 0.5 ppm, as evidenced by statistically significant increases in the length of comet tails for O(3)-exposed groups, and (2) the comet assay can be used to assess O(3)-induced SSBs for in vivo exposures. Therefore, it has the potential as a biomarker for in vivo oxidant exposures.

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.

Effects of ambient ozone exposures during the spring and summer of 1994 on pulmonary function of schoolchildren

To investigate the effect of natural exposure to ambient ozone over time, a follow-up study of school-aged children was performed in two small towns in southwestern Germany (Freudenstadt and Villingen) between March and October of 1994. Ozone half-hour mean concentrations were measured continuously and pulmonary function was tested in each child on four occasions (April, June, August, and September). To obtain an average short-term ozone effect, we first analyzed the data from the four time points separately and then constructed a model that included all information. During the study period the median (5th to 95th percentile) of all half-hour values of the ozone concentration was 101 micrograms/m3 or 50.6 ppb (45-179 micrograms/m3 or 22.5-89.8 ppb) in Freudenstadt and 64 micrograms/m3 or 32.1 ppb (1 to 140 micrograms/m3 or 0.5-70.1 ppb) in Villingen. To assess the effects of an individual ozone exposure we related the highest ozone concentration in the respective 24 hours before lung function testing to the results of the subconcentration in the respective 24 hours before lung function testing to the results of the subsequent pulmonary function tests. In the lung function test following the highest ozone exposure, the results of our cross-sectional linear regression analysis showed a significant negative correlation (P = 0.0181) between ozone exposure and forced vital capacity (FVC). In the longitudinal linear regression model we observed a negative statistical correlation between ozone exposure and lung function for the subpopulation living in the town with the high ozone levels (Freudenstadt). The association was more pronounced in boys than girls. For the children in Freudenstadt the decrement of FVC was -12.31 ml/10 micrograms/m3 ozone and the decrease in the forced expiratory volume in 1 second (FEV1) was -11.29 ml/10 micrograms/m3 ozone.

Aromatic hydroxylation in nasal lavage fluid following ambient ozone exposure

Ozone at ambient concentrations affects lung function and initiates an inflammatory response of the airways. However, the underlying mechanisms are poorly understood. In vitro studies have shown that ozone reacts with water to give reactive hydroxyl radicals capable of oxidizing a wide range of biomolecules. We conducted a study to determine if in vivo hydroxyl radical attack on human airways occurs under natural exposure to ozone. The relation of orthotyrosine to para-tyrosine as a measure of hydroxyl radical attack was analyzed in nasal lavage samples of 44 primary school children in an epidemiologic study. Repeated nasal lavages were performed between May and October 1991 both following "low" (daily half-hour maximum < 140 micrograms/m3, approximately 70 ppb) and "high" (daily half-hour maximum > 180 micrograms/m3, approximately 90 ppb) ozone exposure. Concomitantly, lung function tests were performed. On average, 11.6 (6-16) nasal lavages were performed for each of 24 study days (10 days following "low" ozone exposure and 14 days following "high" ozone exposure). Average ortho-tyrosine (median; 5-95% percentile) for each child was 0.037 mumol/L (0.016-0.064 mumol/L) and average para-tyrosine was 15.7 mumol/L (9.8-24.1 mumol/L). Ortho-tyrosine (as percentage of tyrosine) was significantly higher following days with "high" ozone exposure (0.18%) vs. days following "low" ozone exposure (0.02%; p = .0001). Ortho-tyrosine showed an inverse relationship with forced vital capacity (p = .01) but was not related to inflammation of the upper airways as assessed by cell counts of polymorphonuclear neutrophils. Hydroxyl radical attack subsequent to ambient ozone occurs in the upper airways of healthy children and is related to lung function decrements.

Effects of smog on absenteeism in forestry workers

Absenteeism among 161 Dutch forestry workers was investigated in a cohort study. The rate of taking sick leave was related to the concentrations of sulfate and ozone in ambient air, the air temperature, and the relative humidity. The incidence of absenteeism was treated as a Poisson process, with the size of population at risk as the offset factor and with the environmental monitoring data as hazard factors. There appeared to be some overdispersion; therefore, in a second analysis the incidence of absenteeism was also treated as a negative binomial outcome. With the exception of a separate overdispersion parameter in the negative binomial approach, both methods yielded approximately the same results. Although no significant association was found between absence rate and the measured ambient-air-quality data, there appeared to be a time lag of 3 d between a peak in temperature and 1 d in absenteeism.

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.

Assessment of the future impact on health of a proposed freeway development

This paper estimates the effect on health of traffic injury and air and noise pollution from a proposed inner-suburban freeway in Melbourne. We estimated levels of these health problems for the year 2001 using traffic flow projections for the presence and absence of the freeway. For noise and air pollution, it was necessary to use pollutant levels as proxies for levels of associated diseases and health states. In 2001, there will be an increase in all traffic movements in the study area but a decrease of 100,000 vehicle-kilometers per day on major roads, excluding the bypass. This is associated with a projected reduction in the study area of about 100 to 110 injuries of all types. The major air pollution problems associated with motor vehicle emissions are ozone and respirable particulates; sulphur dioxide, nitrogen dioxide and carbon monoxide are unlikely to pose a health hazard. Levels of respirable particulates, lead and polycylic aromatic hydrocarbons are generally low. There should be no detectable increase in average or maximum noise levels adjacent to the freeway if attenuation measures are employed. A reduction in average and maximum noise levels should occur on some main roads in the affected area. The effects of the freeway on the area should be favourable to health, with reduction in traffic injury and noise-related health problems outweighing any risk of a small deterioration in respiratory health associated with atmospheric pollution.

Medium and long-term behavioral effects in mice of extended gestational exposure to ozone

CD-1 mice were continuously exposed to ozone (O3) from 6 days before the formation of breeding pairs to Day 17 of pregnancy. The concentrations used were 0, 0.2, 0.4, and 0.6 ppm; the lowest-observed-effect levels for eye irritation and respiratory function are in the range of 0.08-0.2 ppm for both humans and animals (47). Ozone failed to produce significant effects on either reproductive performance, postnatal somatic and neurobehavioral development (as assessed by a Fox test battery) or adult motor activity (including within-session habituation). In social interaction tests performed in the pre-juvenile period (23-25 days) and the juvenile period (43-45 days), social response endpoints were not modified in O3 mice, but exploration and self-grooming showed concentration dependent effects (decrease and increase, respectively). Performance at 84-98 days in an eight-arm radial maze with water reinforcement was initially impaired in O3 mice, but the results were not entirely consistent; e.g., the data failed to show a concentration dependence of the effects. Overall, the data confirm previous results of an experiment with more limited exposure [pregnancy Days 7-17 (6)] by showing that prenatal O3 exposure, even when extended to include a period before the start of pregnancy and the preimplantation phase, does not produce major or widespread somatic and neurobehavioral effects. Some of the results, however, point to subtle or borderline behavioral deficits which deserve to be considered both in further animal experiments and in the assessment of risk to developing humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between summertime ambient ozone levels and emergency department visits for asthma in central New Jersey

The 5-year retrospective study of the association between temperature and emergency department (ED) visits for asthma with mean ambient ozone levels between 10:00 and 15:00 was conducted in central New Jersey during the summer months. An association was identified in each of the years (1986-1990). Between 8 and 34% of the total variance in ED visits for asthma was explained by the two environmental variables in the step-wise multiple regression analysis. ED visits occurred 28% more frequently when the mean ozone levels were > 0.06 ppm than when they were < 0.06 ppm. This result was statistically significant in a covariance analysis. An evaluation of the effects of ozone on asthmatics reported in the literature was completed to determine if, as proposed by Bates, the results from different types of studies were coherent among the health metrics. A consistency in the magnitude of reported effects and the time lag between exposure and response for four different health indices (symptom reports, decrements in expiratory flow, ED visits, and hospital admissions) was identified and indicates a coherence between ozone and respiratory response to ozone exposure. This supports a proposition that ozone adversely affects asthmatics at levels below the current U.S. standard.

Acute respiratory effects of summer smog in primary school children

In 535 primary school children we studied the effects of exposure to summer smog on respiratory health. Baseline measurements were performed during low air pollution levels (max. 24-h concentrations of SO2, O3 and NO2 were 55, 49 and 58 micrograms/m3, respectively) consisting of lung function measurements using spirometry and the forced oscillation technique (FOT) and the prevalence of respiratory symptoms, determined by a written questionnaire. During a summer smog episode, 212 randomly chosen children were re-examined, characterised by 8-h ozone levels > 120 micrograms/m3 (max. 163 micrograms/m3) and 1-h ozone levels > 160 micrograms/m3 (max. 215 micrograms/m3). Overall, small decrements were observed in the forced expiratory volume in 1 s (FEV1), (P < 0.05) and the forced expiratory volume between 25 and 75% of the vital capacity (FEF25-75%) (P < 0.01). On the contrary, there was a statistically significant decrease in resistance parameters. No increases were observed in the prevalence of acute respiratory symptoms. In conclusion, in this study we found small inconsistent changes in lung function and no increase of respiratory symptoms after short-time exposure to moderately high ozone levels.

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.

Ozone- and endotoxin-induced mucous cell metaplasias in rat airway epithelium: novel animal models to study toxicant-induced epithelial transformation in airways

Mucous (goblet) cell proliferation and hypersecretion of airway mucus are important characteristics of human respiratory disorders, especially chronic bronchitis and cystic fibrosis. These changes in secretory patterns also occur in animals experimentally exposed to chemical irritants such as ozone (O3), sulfur dioxide (SO2), and cigarette smoke. The cellular and molecular mechanisms involved in irritant-induced mucous cell metaplasia (MCM; transformation of airway epithelium, normally devoid of mucous cells, to a secretory epithelium containing numerous mucous cells) are still unclear. We used two experimental models of toxicant-induced MCM in rat airways to study the cellular and molecular changes that occur during the development of this respiratory tract lesion. MCM can be induced in the nasal transitional epithelium of rats by repeated exposure to ambient levels of ozone. In addition, MCM can be induced in the tracheobronchial airways of rats repeatedly exposed to endotoxin, a lipopolysaccharide-protein molecule found in the outer walls of Gram-negative bacteria. The pathogenesis of ozone- or endotoxin-induced MCM has been partially characterized using a variety of morphometric and histochemical techniques. Toxicant-induced changes in the numbers and types of airway epithelial cells have been estimated using morphometric methods designed for estimating the abundance of cell populations. Nasal pulmonary airway tissues are also processed for light microscopy and stained with Alcian Blue (pH 2.5)/Periodic Acid Schiff (AB/PAS) for detection of acidic and neutral mucosubstances (the specific glycoprotein product of mucous cells), respectively, within the tissue. Computerized image analysis is used to quantitate the amount of the stained mucous product within the airway epithelium. To better characterize the molecular and cellular events in the pathogenesis of ozone- or endotoxin-induced MCM in the rat airway epithelium, we are conducting studies to determine when, and in which epithelial cells, the mucin gene is expressed after exposure to the toxicant. In these studies, rats undergo single or repeated exposures to ozone or endotoxin and are then sacrificed immediately or a few days after the end of the exposures. Airway tissues are microdissected from specific regions of the exposed respiratory tract, and changes in mucin core polypeptide mRNA are evaluated by Northern analysis using human and rat mucin cDNA. In future studies using in situ hybridization, we will establish when, and in which epithelial cells, the expression of high molecular weight airway mucin is initiated in response to ozone or endotoxin.(ABSTRACT TRUNCATED AT 400 WORDS)

Predictors of individual differences in acute response to ozone exposure

The purpose of this study was to identify personal characteristics that predict individual differences in acute FEV1 response to ozone exposure. Response and predictor data were collected on 290 white male volunteers 18 to 32 yr of age who were each exposed to one of six concentrations of ozone between 0.0 and 0.40 part per million. The sample was divided into an exploratory sample of 96 and a confirmatory sample of 194 subjects. Exploratory analysis indicated that ozone, age, and several other variables explained a significant proportion of the variance in response. In the confirmatory sample, only age and ozone concentration predicted FEV1 decrement. For the combined sample ozone explained 31% of the variance, with age accounting for an additional 4%. The model predicted a decreasing response with increasing age for all nonzero ozone concentrations. For exposure to 0.40 ppm, the model predicts decrements in FEV1 of 1.07 and 0.47 L for 18- and 30-yr-old subjects, respectively. We concluded that for white male subjects age was a significant predictor of response, with older subjects being less responsive to ozone. Furthermore, we demonstrated that exploratory analysis without control of type I statistical error rates may result in apparent findings that cannot be replicated.

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)

Effects of air pollution on the respiratory tract of children

The effects of air pollution on pulmonary function and respiratory status was evaluated in 1,626 school aged children from a European Alpine region. Based on measurements of SO2, NO2, and O3 as well as infrared imaging and lichen mapping, three zones of exposure were defined. Results of standardized respiratory questionnaires, medical examinations, and lung function tests were compared among the children in the three different exposure zones. After controlling for age, sex, height, socioeconomic status, and exposure to environmental tobacco smoking, areas of increased SO2 and NO2 as well as areas of increased ozone (max. half hourly mean value, 146 ppb) were significantly associated with decrements of forced expiratory volume in 1 s (FEV1) and flow rates at 50 and 75% of vital capacity (FEF50, FEF75). In addition, areas with increased ozone had a higher prevalence of asthma In all regions, maternal smoking was associated with reduced expiratory flow rates and increased prevalence of asthma. The results provide evidence that outdoor pollution and exposure to passive smoking are risk factors for childhood respiratory health.

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.