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

Ear, nose and throat disorders and international travel

BACKGROUND

Disorders of the ear, nose and throat may be the most commonly occurring pre-existing health condition in international travellers. Despite their high incidence, there is limited guidance for travellers and their clinicians on their prevention and management. This narrative review addresses this deficit by compiling and discussing available evidence on this neglected subject.

METHODS

A comprehensive review of the literature was undertaken using Medine and Scopus databases and multiple combinations of relevant MeSH search terms. Further references were obtained from focused searches on specific issues and manual review of the reference lists of articles obtained from the primary search.

RESULTS

Nasal congestion or discharge are among the most common complaints amongst travellers and various causes are reviewed. Changes in elevation result in a pressure differential between the atmospheric pressure and the middle ear and paranasal sinuses. The effects of air travel, recreational high-altitude exposure and diving are considered. Various causes of epistaxis in travellers such as cold air exposure and recreational cocaine use are discussed. The aetiology of a discharging ear in travellers includes otitis externa. The most frequently described travel-specific aetiology of dizziness is motion sickness while mal de debarquement is a specific subtype which affects travellers and is most commonly associated with sea travel. Surgical tourism for treatment of ear, nose and throat pathology is well established and various precautions are presented for post-operative travel. Obstructive sleep apnoea is discussed from the perspective of international travel. The challenges facing travellers with hearing impairment are explored.

CONCLUSIONS

This review critically discusses the prevention, diagnosis, and management of acute and chronic ENT conditions in the travelling population. Several areas of inquiry are highlighted that require further investigation. Close communication between ENT specialists and travel medicine practitioners is recommended in the preparation of selected patients for international travel.

Estimating the exposure-response function between long-term ozone exposure and under-5 mortality in 55 low-income and middle-income countries: a retrospective, multicentre, epidemiological study

BACKGROUND

In 2021, WHO suggested new target concentration limits for long-term exposure to ambient ozone. However, the harmful effects of ozone on vulnerable children have not been sufficiently studied. We aimed to evaluate the association between long-term ozone exposure and mortality in children younger than 5 years (hereafter denoted under-5 mortality) in low-income and middle-income countries (LMICs) and to estimate this mortality burden for 97 LMICs.

METHODS

By combining information from 128 Demographic and Health Surveys, we evaluated the association between the survival status of more than 1·2 million children younger than 5 years from 2457 sampling strata in 55 LMICs and the average peak-season ozone concentration during the life course, using a fixed-effects Cox model. A non-linear exposure-response function was developed by integrating the marginal effects of within-strata variation in exposure. We extrapolated the function obtained from the 55 LMICs to estimate the under-5 mortality burden attributable to ozone exposure in 97 LMICs, in which more than 95% of global deaths in this age group occur.

FINDINGS

The fixed-effects model showed a robust association between ozone and under-5 mortality. According to the fully adjusted linear model, an increment of 10 ppb in the life-course average peak-season ozone concentration was associated with a 6·4% (95% CI 2·4-10·7) increase in the risk of under-5 mortality. The non-linear exposure-response function showed a sublinear curvature with a threshold, suggesting that the effect of ozone exposure was non-significant at concentrations lower than the first-stage interim target (100 μg/m3) recommended by WHO. Using this function, we estimate that, in 2010, long-term ozone exposure contributed to 153 361 (95% CI 17 077-276 768; 2·3% [0·3-4·1]) deaths of children younger than 5 years in 97 LMICs, which is equivalent to 56·8% of all ozone-related deaths in adults (269 785) in these countries. From 2003 to 2017, the ozone-related under-5 mortality burden decreased in most of the 97 LMICs.

INTERPRETATION

Long-term exposure to ozone concentrations higher than the WHO first-stage interim target is a risk factor for under-5 mortality, and ozone exposure contributes substantially to mortality in this age group in LMICs. Increased efforts should be made to control ambient ozone pollution as this will lead to positive health benefits.

FUNDING

Ministry of Science and Technology of the People's Republic of China and China National Natural Science Foundation.

Ambient air pollution, lung function and COPD: cross-sectional analysis from the WHO Study of AGEing and adult health wave 1

BACKGROUND

Long-term exposure to ambient air pollution leads to respiratory morbidity and mortality; however, the evidence of the effect on lung function and chronic obstructive pulmonary disease (COPD) in older adult populations is inconsistent.

OBJECTIVE

To address this knowledge gap, we investigated the associations between particulate matter (PM), nitrogen dioxide (NO2) exposure and lung function, as well as COPD prevalence, in older Chinese adults.

METHODS

We used data from the WHO Study on global AGEing and adult health (SAGE) China Wave 1, which includes 111 693 participants from 64 townships in China. A cross-sectional analysis explored the association between satellite-based air pollution exposure estimates (PM with an aerodynamic diameter of ≤10 µm [PM10], ≤2.5 µm [PM2.5] and NO2) and forced expiratory volume in one second (FEV1), forced vital capacity (FVC), the FEV1/FVC ratio and COPD (defined as post-bronchodilator FEV1/FVC <70%). Data on lung function changes were further stratified by COPD status.

RESULTS

Higher exposure to each pollutant was associated with lower lung function. An IQR (26.1 µg/m3) increase in PM2.5 was associated with lower FEV1 (-71.88 mL, 95% CI -92.13 to -51.64) and FEV1/FVC (-2.81 mL, 95% CI -3.37 to -2.25). For NO2, an IQR increment of 26.8 µg/m3 was associated with decreases in FEV1 (-60.12 mL, 95% CI -84.00 to -36.23) and FVC (-32.33 mL, 95% CI -56.35 to -8.32). A 31.2 µg/m3 IQR increase in PM10 was linked to reduced FEV1 (-8.86 mL, 95% CI -5.40 to 23.11) and FEV1/FVC (-1.85 mL, 95% CI -2.24 to -1.46). These associations were stronger for participants with COPD. Also, COPD prevalence was linked to higher levels of PM2.5 (POR 1.35, 95% CI 1.26 to 1.43), PM10 (POR 1.24, 95% CI 1.18 to 1.29) and NO2 (POR 1.04, 95% CI 0.98 to 1.11).

CONCLUSION

Ambient air pollution was associated with lower lung function, especially in individuals with COPD, and increased COPD prevalence in older Chinese adults.

Assessing schoolchildren's exposure to air pollution during the daily commute - A systematic review

Air pollution is mostly caused by emissions from human activities, and exposure to air pollution is linked with numerous adverse human health outcomes. Recent studies have identified that although people only spend a small proportion of time on their daily commutes, the commuter microenvironment is a significant contributor to their total daily air pollution exposure. Schoolchildren are a particularly vulnerable cohort of the population, and their exposure to air pollution at home or school has been documented in a number of case studies. A few studies have identified that schoolchildren's exposure during commutes is linked with adverse cognitive outcomes and severe wheeze in asthmatic children. However, the determinants of total exposure, such as route choice and commute mode, and their subsequent health impacts on schoolchildren are still not well-understood. The aim of this paper is to review and synthesize recent studies on assessing schoolchildren's exposure to various air pollutants during the daily commute. Through reviewing 31 relevant studies published between 2004 and 2020, we tried to identify consistent patterns, trends, and underlying causal factors in the results. These studies were carried out across 10 commute modes and 12 different air pollutants. Air pollution in cities is highly heterogeneous in time and space, and commuting schoolchildren move through the urban area in complex ways. Measurements from fixed monitoring stations (FMSs), personal monitoring, and air quality modeling are the three most common approaches to determining exposure to ambient air pollutant concentrations. The time-activity diary (TAD), GPS tracker, online route collection app, and GIS-based route simulation are four widely used methods to determine schoolchildren's daily commuting routes. We found that route choices exerted a determining impact on schoolchildren's exposure. It is challenging to rank commute modes in order of exposure, as each scenario has numerous uncontrollable determinants, and there are notable research gaps. We suggest that future studies should concentrate on examining exposure patterns of schoolchildren in developing countries, exposure in the subway and trains, investigating the reliability of current simulation methods, exploring the environmental justice issue, and identifying the health impacts during commuting. It is recommended that three promising tools of smartphones, data fusion, and GIS should be widely used to overcome the challenges encountered in scaling up commuter exposure studies to population scales.

The Impact of Economic Growth and Air Pollution on Public Health in 31 Chinese Cities

The rapid economic growth of China in the last twenty years has caused a commensurate rise in atmospheric pollution which has had an impact on both the environment and public health. Since 2013, SO₂, CO₂ and nitrogen oxide levels have reached a level that may cause climate change and have adverse effects on the health of the local residents. Past environmental efficiency analyses have rarely examined economic development, air pollution and health as interacting systems; therefore, this study used a new two-stage DEA model, the Modified Undesirable EBM Two Stage DEA (Epsilon-Based Measure) to explore the environmental, economic and health efficiencies in thirty-one major cities in China. The results were as follows: while all cities needed to improve their GDP, the environmental efficiencies were continuing to rise in most cities. The health efficiency index indicated that disease efficiency had increased in most cities but declined in one third; therefore, it is necessary to strengthen treatment. The respiratory disease treatment efficiency in most cities was rising, and the room for improvement had significantly reduced. There were improvements in the mortality rate in 15 cities; however, the mortality rate treatment efficiency declined in 11 cities.

Consumption of fruit and vegetables might mitigate the adverse effects of ambient PM2.5 on lung function among adults

BACKGROUND

Evidence on the effects of ambient PM_2.5 on lung function is limited among adults and the effect modification by dietary fruit and vegetables remains largely unknown.

METHODS

We interviewed 29,032 participants aged 50 years and older from the WHO Study on global AGEing and adult health. Annual average PM_2.5 levels were estimated for each community using satellite data. We applied multi-level linear regressions to examine the association between ambient PM_2.5 and lung function (forced vital capacity (FVC), forced expiratory volume in 1-sec (FEV₁), FEV₁/FVC ratio, peak expiratory flow (PEF), and forced expiratory flow between 25th and 75th percentiles of FVC (FEF_25-75)).

RESULTS

We found that ambient PM_2.5 was associated with lower lung functions. Each 10μg/m³ increase in PM_2.5 corresponded to reductions of 123.58ml in FVC (95% CI: -185.21, -61.95), 126.64ml in FEV₁ (95% CI: -186.04, -67.23) and 178.93ml/s FEV_25-75 (95% CI: -249.20, -108.66). Lower effect estimates were observed among those with higher consumption of fruit and vegetables.

CONCLUSION

Our study suggests that exposure to ambient PM_2.5 might be one risk factor of reduced lung function in adults and that higher consumption of fruit and vegetables may mitigate this effect.

Respiratory health outcomes and air pollution in the Eastern Mediterranean Region: a systematic review

Exposure to air pollution can cause detrimental health and be an economic burden. With newly developed equipment, monitoring of different air pollutants, identifying the sources, types of air pollutants and their corresponding concentrations, and applying mitigation intervention techniques became a crucial step in public health protection. Countries in the Eastern Mediterranean Region (EMR) are highly exposed to dust storms, have high levels of particulate matter (PM) concentrations, and have a unique climatic as well as topographic and socio-economic structure. This is the first study conducted to systemically and qualitatively assess the health impacts of air pollution in the EMR, identify susceptible populations, and ascertain research and knowledge gaps in the literature to better inform decisions by policy makers. We screened relevant papers and reports published between 2000 and 2014 in research databases. A total of 36 published studies met the inclusion criteria. A variety of indoor and outdoor exposures associated with various acute and chronic respiratory health outcomes were included. Respiratory health outcomes ranged in severity, from allergies and general respiratory complaints to lung cancer and mortality. Several adverse health outcomes were positively associated with various indoor/outdoor air pollutants throughout the EMR. However, epidemiological literature concerning the EMR is limited to a few studies in a few countries. More research is needed to elucidate the health outcomes of air pollution. Standardized reliable assessments on the national level for various air pollutants in different regions should be implemented and made publically available for researchers to utilize in their research. Moreover, advancing and utilizing more sound epidemiological designs and studies on the effect of air pollution on the respiratory health outcomes is needed to portray the actual situation in the region.

Particulate air pollution and impaired lung function

Air pollution is a leading cause of morbidity and mortality throughout the world, particularly in individuals with existing lung disease. Of the most common air pollutants, particulate matter (PM) is associated with an increased risk of exacerbations and respiratory symptoms in individuals with existing lung disease, and to a lesser extent, in those without known respiratory issues. The majority of published research has focused on the effects of PM exposures on symptoms and health care utilization. Fewer studies focus on the impact of PM on objective measurements of pulmonary function. This review will focus on the effects of PM exposure on objective measurements of lung function in both healthy individuals and those with existing lung disease.

Respiratory effects of air pollution on children

A substantial proportion of the global burden of disease is directly or indirectly attributable to exposure to air pollution. Exposures occurring during the periods of organogenesis and rapid lung growth during fetal development and early post-natal life are especially damaging. In this State of the Art review, we discuss air toxicants impacting on children's respiratory health, routes of exposure with an emphasis on unique pathways relevant to young children, methods of exposure assessment and their limitations and the adverse health consequences of exposures. Finally, we point out gaps in knowledge and research needs in this area. A greater understanding of the adverse health consequences of exposure to air pollution in early life is required to encourage policy makers to reduce such exposures and improve human health.

[Effects of outdoor pollutants on the respiratory health of children]

The exposure against common air pollutants such as NO2, PM10 and SO2 has decreased in the last decades due to efforts of the EC to reduce emissions of industrial or traffic related origins. However, ozone exposure demonstrates an upward trend. New epidemiologic studies use geographical information systems for a more precise special and temporal categorisation of exposure. They show adverse effects of ultrafine particles as well as elemental carbon on the respiratory system of children. Children growing up next to busy traffic routes are most affected. Adverse effects include respiratory symptoms as well as a delay in lung growth. Intrauterine exposure against PM10 seems to effect lung function in newborns. There is a lack of data about other organic substances widely used in synthetic materials in the outdoor air such as phthalates or bisphenols, some studies show detrimental effects.

Estimation of future PM2.5- and ozone-related mortality over the continental United States in a changing climate: An application of high-resolution dynamical downscaling technique

This paper evaluates the PM2.5- and ozone-related mortality at present (2000s) and in the future (2050s) over the continental United States by using the Environmental Benefits Mapping and Analysis Program (BenMAP-CE). Atmospheric chemical fields are simulated by WRF/CMAQ (horizontal resolution: 12×12 km), applying the dynamical downscaling technique from global climate-chemistry model under the Representative Concentration Pathways scenario (RCP 8.5). Future air quality results predict that the annual mean PM2.5 concentration in continental U.S. decreases nationwide, especially in the Eastern U.S. and west coast. However, the ozone concentration is projected to decrease in the Eastern U.S. but increase in the Western U.S. Future mortality is evaluated under two scenarios (1) holding future population and baseline incidence rate at the present level and (2) using the projected baseline incidence rate and population in 2050. For PM2.5, the entire continental U.S. presents a decreasing trend of PM2.5-related mortality by the 2050s in Scenario (1), primarily resulting from the emissions reduction. While in Scenario (2), almost half of the continental states show a rising tendency of PM2.5-related mortality, due to the dominant influence of population growth. In particular, the highest PM2.5-related deaths and the biggest discrepancy between present and future PM2.5-related deaths both occur in California in 2050s. For the ozone-related premature mortality, the simulation shows nation-wide rising tendency in 2050s under both scenarios, mainly due to the increase of ozone concentration and population in the future. Furthermore, the uncertainty analysis shows that the confidence interval of all causes mortality is much larger than that for specific causes, probably due to the accumulated uncertainty of generating datasets and sample size. The confidence interval of ozone-related all cause premature mortality is narrower than the PM2.5-related all cause mortality, due to its smaller standard deviation of the concentration-mortality response factor.

IMPLICATIONS

The health impact of PM2.5 is more linearly proportional to the emission reductions than ozone. The reduction of anthropogenic PM2.5 precursor emissions is likely to lead to the decrease of PM2.5 concentrations and PM2.5 related mortality. However, the future ozone concentrations could increase due to increase of the greenhouse gas emissions of methane. Thus, to reduce the impact of ozone related mortality, anthropogenic emissions including criteria pollutant and greenhouse gas (i.e. methane) need to be controlled.

Long term effects of prenatal and postnatal airborne PAH exposures on ventilatory lung function of non-asthmatic preadolescent children. Prospective birth cohort study in Krakow

The main goal of the study was to test the hypothesis that prenatal and postnatal exposures to polycyclic aromatic hydrocarbons (PAH) are associated with depressed lung function in non-asthmatic children. The study sample comprises 195 non-asthmatic children of non-smoking mothers, among whom the prenatal PAH exposure was assessed by personal air monitoring in pregnancy. At the age of 3, residential air monitoring was carried out to evaluate the residential PAH exposure indoors and outdoors. At the age of 5 to 8, children were given allergic skin tests for indoor allergens; and between 5 and 9 years lung function testing (FVC, FEV05, FEV1 and FEF25-75) was performed. The effects of prenatal PAH exposure on lung function tests repeated over the follow-up were adjusted in the General Estimated Equation (GEE) model for the relevant covariates. No association between FVC with prenatal PAH exposure was found; however for the FEV1 deficit associated with higher prenatal PAH exposure (above 37 ng/m(3)) amounted to 53 mL (p=0.050) and the deficit of FEF25-75 reached 164 mL (p=0.013). The corresponding deficits related to postnatal residential indoor PAH level (above 42 ng/m(3)) were 59 mL of FEV1 (p=0.028) and 140 mL of FEF25-75 (p=0.031). At the higher residential outdoor PAH level (above 90 ng/m(3)) slightly greater deficit of FEV1 (71 mL, p=0.009) was observed. The results of the study suggest that transplacental exposure to PAH compromises the normal developmental process of respiratory airways and that this effect is compounded by postnatal PAH exposure.

Ozone-induced airway epithelial cell death, the neurokinin-1 receptor pathway, and the postnatal developing lung

Children are uniquely susceptible to ozone because airway and lung growth continue for an extensive period after birth. Early-life exposure of the rhesus monkey to repeated ozone cycles results in region-specific disrupted airway/lung growth, but the mediators and mechanisms are poorly understood. Substance P (SP), neurokinin-1 receptor (NK-1R); and nuclear receptor Nur77 (NR4A1) are signaling pathway components involved in ozone-induced cell death. We hypothesize that acute ozone (AO) exposure during postnatal airway development disrupts SP/NK-1R/Nur77 pathway expression and that these changes correlate with increased ozone-induced cell death. Our objectives were to 1) spatially define the normal development of the SP/NK-1R/Nur77 pathway in conducting airways; 2) compare how postnatal age modulates responses to AO exposure; and 3) determine how concomitant, episodic ozone exposure modifies age-specific acute responses. Male infant rhesus monkeys were assigned at age 1 mo to two age groups, 2 or 6 mo, and then to one of three exposure subgroups: filtered air (FA), FA+AO (AO: 8 h/day × 2 days), or episodic biweekly ozone exposure cycles (EAO: 8 h/day × 5 days/14-day cycle+AO). O3 = 0.5 ppm. We found that 1) ozone increases SP/NK-1R/Nur77 pathway expression in conducting airways, 2) an ozone exposure cycle (5 days/cycle) delivered early at age 2 mo resulted in an airway that was hypersensitive to AO exposure at the end of 2 mo, and 3) continued episodic exposure (11 cycles) resulted in an airway that was hyposensitive to AO exposure at 6 mo. These observations collectively associate with greater overall inflammation and epithelial cell death, particularly in early postnatal (2 mo), distal airways.

Transcriptome profiling of the newborn mouse lung response to acute ozone exposure

Ozone pollution is associated with adverse effects on respiratory health in adults and children but its effects on the neonatal lung remain unknown. This study was carried out to define the effect of acute ozone exposure on the neonatal lung and to profile the transcriptome response. Newborn mice were exposed to ozone or filtered air for 3h. Total RNA was isolated from lung tissues at 6 and 24h after exposure and was subjected to microarray gene expression analysis. Compared to filtered air-exposed littermates, ozone-exposed newborn mice developed a small but significant neutrophilic airway response associated with increased CXCL1 and CXCL5 expression in the lung. Transcriptome analysis indicated that 455 genes were down-regulated and 166 genes were up-regulated by at least 1.5-fold at 6h post-ozone exposure (t-test, p < .05). At 24h, 543 genes were down-regulated and 323 genes were up-regulated in the lungs of ozone-exposed, compared to filtered air-exposed, newborn mice (t-test, p < .05). After controlling for false discovery rate, 50 genes were identified as significantly down-regulated and only a few (RORC, GRP, VREB3, and CYP2B6) were up-regulated at 24h post-ozone exposure (q < .05). Gene ontology enrichment analysis revealed that cell cycle-associated functions including cell division/proliferation were the most impacted pathways, which were negatively regulated by ozone exposure, an adverse effect that was associated with reduced bromo-deoxyuridine incorporation. These results demonstrate that acute ozone exposure alters cell proliferation in the developing neonatal lung through a global suppression of cell cycle function.

Developmental exposure to concentrated ambient particles and preference for immediate reward in mice

BACKGROUND

Recent epidemiological studies indicate negative associations between a diverse group of air pollutants and cognitive functioning in children and adults, and aspects of attention deficit in children. Neuroinflammation and oxidative stress are two putative biological mechanisms by which air pollutants may adversely affect the brain.

OBJECTIVES

We sought to determine whether exposure to concentrated ambient particulate matter (CAPS) during the first 2 weeks of life, alone or again in adulthood, could alter responding for delayed reward, a critical component of human decision making. Greater preference for immediate reward has been implicated as a component of several psychiatric disorders, addiction, obesity, and attention deficit.

METHODS

C57BL/6J mice were exposed to ultrafine particles (< 100 nm in aerodynamic diameter; CAPS) using the Harvard University Concentrated Ambient Particle System (HUCAPS) or filtered air in the postnatal period (days 4-7 and 10-13) with and without adult exposure over days 56-60. In adulthood, delay behavior was assessed using a fixed-ratio waiting-for-reward (FR wait) paradigm in which 25 responses (FR25) were required to initiate the waiting-for-reward component during which mice obtained "free" sucrose pellets with the stipulation that these "free" pellets were delivered at increasing delay intervals.

RESULTS

Coupled with increased FR response rates, mice exposed to postnatal CAPS displayed increased FR resets that reinstated short delays, indicating a preference for shorter delays, despite the added response cost of the FR25. No associated changes in locomotor activity were observed.

CONCLUSIONS

Postnatal CAPS exposure produces an enhanced bias towards immediate rewards, a risk factor for several central nervous system (CNS) disorders. This enhancement does not appear to be the result of hyperactivity. The findings underscore the need for further evaluation of air pollution effects on the CNS and its potential contribution to CNS diseases and disorders.

Variations in peak expiratory flow measurements associated to air pollution and allergic sensitization in children in Sao Paulo, Brazil

BACKGROUND

In the last 20 years, there has been an increase in the incidence of allergic respiratory diseases worldwide and exposure to air pollution has been discussed as one of the factors associated with this increase. The objective of this study was to investigate the effects of air pollution on peak expiratory flow (PEF) and FEV1 in children with and without allergic sensitization.

METHODS

Ninety-six children were followed from April to July, 2004 with spirometry measurements. They were tested for allergic sensitization (IgE, skin prick test, eosinophilia) and asked about allergic symptoms. Air pollution, temperature, and relative humidity data were available.

RESULTS

Decrements in PEF were observed with previous 24-hr average exposure to air pollution, as well as with 3-10-day average exposure and were associated mainly with PM(10), NO(2), and O(3) in all three categories of allergic sensitization. Even though allergic sensitized children tended to present larger decrements in the PEF measurements they were not statistically different from the non-allergic sensitized. Decrements in FEV1 were observed mainly with previous 24-hr average exposure and 3-day moving average.

CONCLUSIONS

Decrements in PEF associated with air pollution were observed in children independent from their allergic sensitization status. Their daily exposure to air pollution can be responsible for a chronic inflammatory process that might impair their lung growth and later their lung function in adulthood.

Ambient particulate matter and lung function growth in Chinese children

BACKGROUND

Exposure to particulate matter (PM) has been associated with deficits in lung function growth among children in Western countries. However, few studies have explored this association in developing countries, where PM levels are often substantially higher.

METHODS

Children (n = 3273) 6-12 years of age were recruited from 8 schools in 4 Chinese cities. The lung function parameters of forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) were measured using computerized spirometers twice a year for up to 3 years (1993-1996). Dichotomous samplers placed in each schoolyard were used to measure PM2.5 and PM10 (PM with diameter ≤ 2.5 μm and ≤ 10 μm, respectively). Multivariable generalized estimating equations were used to examine the association between the quarterly average PM levels and lung function growth during the period of follow-up.

RESULTS

Annual average PM2.5 and PM10 levels in the 4 cities ranged from 57 to 158 μg/m and 95 to 268 μg/m, respectively. In multivariable models, an increase of 10 μg/m of PM2.5 was associated with decreases of 2.7 mL FEV1 (95% confidence interval = -3.5 to -2.0), 3.5 mL FVC (-4.3 to -2.7), 1.4 mL/year FEV1 growth (-1.8 to -0.9), and 1.5 mL/year FVC growth (-2.0 to -1.0). Similar results were seen with PM10 exposure.

CONCLUSIONS

Exposure to ambient particulate matter was associated with decreased growth in lung function among Chinese children.

Indoor air pollution and lung function growth among children in four Chinese cities

Ambient air pollution has been associated with decreased growth in lung function among children; but little is known about the impact of indoor air pollution. We examined relationships between indoor air pollution metrics and lung function growth, among children (n = 3273) aged 6-13 years living in four Chinese cities. Lung function parameters (FVC and FEV(1) ) were measured twice a year. Questionnaires were used to determine home coal burning and ventilation practices. Generalized estimating equations were used to examine associations. Use of coal as a household fuel was associated with 16.5 ml/year lower (33%, P < 0.001) and 20.5 ml/year lower (39%, P < 0.001) growth in children's FEV(1) and FVC, respectively. FEV(1) growth was 10.2 ml/year higher (20%, P = 0.009), and FVC growth was 17.0 ml/year higher (33%, P < 0.001) among children who lived in houses with the presence of a ventilation device. Among children living in houses where coal was used as a fuel and no ventilation devices were present, adjusted FVC and FEV(1) growth, respectively, were 37% and 61% that of the average growth per year in the full cohort. This suggests that household coal use may cause deficits in lung function growth, while using ventilation devices may be protective of lung development.

PRACTICAL IMPLICATIONS

Nearly 3.4 billion people use solid fuels in homes for cooking and/or heating. We report the following findings from a longitudinal study: (i) household coal use is significantly associated with reduction in children's lung function growth and (ii) the use of household ventilation devices is significantly associated with higher lung function growth, particularly among children living in households where coal is used as a fuel. These findings not only provide evidence that indoor coal use impairs children's lung development but also point to the importance of improving ventilation conditions in reducing harmful effects of indoor air pollution sources.

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.

Disruption of tracheobronchial airway growth following postnatal exposure to ozone and ultrafine particles

This study examined airway structure changes in adult rats after a long recovery period due to sub-chronic juvenile exposure to ozone and ultrafine particles that have a high organic fraction. Neonatal male Sprague-Dawley rats were exposed during lung development to 3 cycles of 0.5 ppm ozone from postnatal day 7 through 25. Two different exposure patterns were used: 5-day exposure per week (Ozone52) or 2-day exposure per week (Ozone25) with or without co-exposure to ultrafine particles (OPFP5252, OPFP5225). Airway architecture was evaluated at 81 days of age, after 56 days of continued development beyond the exposure period in filtered air (FA). By analyzing CT images from lung airway casts, we determined airway diameter, length, branching angle, and rotation angle for most conducting airways. Compared with the FA control group, the Ozone52 group showed significant decreases in airway diameter in generations larger than 10 especially in the right diaphragmatic lobe and in airway length in distal generations, while changes in airway structure due to the Ozone25 exposure were not appreciable. Interaction effects of ozone and ultrafine particle exposures were not significant. These results suggest that airway alterations due to postnatal ozone exposure are not limited to the distal region but occur extensively from the middle to distal conducting airways. Further, alterations due to early ozone exposure do not recover nearly 2 months after exposure has ceased demonstrating a persistent airway structural change following an early life exposure to ozone.

Postnatal growth of tracheobronchial airways of Sprague-Dawley rats

Rats are widely used for the studies of pulmonary toxicology in both juveniles and adults. To facilitate such studies, investigators have developed models of lung architecture based on manual or computerized airway measurements. However, postnatal growth of conducting airways of rat lungs has never been reported. In this paper, we present conducting airway architecture statistics for male Sprague-Dawley rat lungs at ages 15, 28, 40, and 81 days by analyzing CT images from airway silicon casts. Detailed branching characteristics and intersubject variance are presented. This study shows that (i) airway growth in diameter and length is not linear with age, (ii) growth of airway length is faster than that of diameter during the 15-81-day postnatal period, and (iii) asymmetry in airway diameter (ratio of major to minor daughter diameter) increases with age.

Detecting alterations in pulmonary airway development with airway-by-airway comparison

Neonatal and postnatal exposures to air pollutants have adverse effects on lung development resulting in airway structure changes. Usually, generation-averaged analysis of airway geometric parameters is employed to differentiate between pulmonary airway trees. However, this method is limited, especially for monopodial branching trees such as in rat airways, because both quite proximal and less proximal airways that have very different structure and function may be in the same generation. To avoid limitations inherent in generation averaging, we developed a method that compares two trees airway-by-airway using micro CT image data from rat lungs. This computerized technique (1) identifies the geometry and architecture of the conducting airways from CT images, (2) extracts the main tree, (3) associates paired airways from the two different trees, and (4) develops summary statistics on the degree of similarity between populations of animals. By comparing the trees airway-by-airway, we found that the variance in airway length of the group exposed to diffusion flame particles (DFP) is significantly larger than the group raised in filtered air (FA). This method also found that rotation angle of the DFP group is significantly larger than FA, which is not as certain in the generation-based analysis. We suggest that airway-by-airway analysis complements generation-based averaging for detecting airway alterations.

An official American Thoracic Society public policy statement: Novel risk factors and the global burden of chronic obstructive pulmonary disease

RATIONALE

Although cigarette smoking is the most important cause of chronic obstructive pulmonary disease (COPD), a substantial proportion of COPD cases cannot be explained by smoking alone.

OBJECTIVES

To evaluate the risk factors for COPD besides personal cigarette smoking.

METHODS

We constituted an ad hoc subcommittee of the American Thoracic Society Environmental and Occupational Health Assembly. An international group of members was invited, based on their scientific expertise in a specific risk factor for COPD. For each risk factor area, the committee reviewed the literature, summarized the evidence, and developed conclusions about the likelihood of it causing COPD. All conclusions were based on unanimous consensus.

MEASUREMENTS AND MAIN RESULTS

The population-attributable fraction for smoking as a cause of COPD ranged from 9.7 to 97.9%, but was less than 80% in most studies, indicating a substantial burden of disease attributable to nonsmoking risk factors. On the basis of our review, we concluded that specific genetic syndromes and occupational exposures were causally related to the development of COPD. Traffic and other outdoor pollution, secondhand smoke, biomass smoke, and dietary factors are associated with COPD, but sufficient criteria for causation were not met. Chronic asthma and tuberculosis are associated with irreversible loss of lung function, but there remains uncertainty about whether there are important phenotypic differences compared with COPD as it is typically encountered in clinical settings.

CONCLUSIONS

In public health terms, a substantive burden of COPD is attributable to risk factors other than smoking. To prevent COPD-related disability and mortality, efforts must focus on prevention and cessation of exposure to smoking and these other, less well-recognized risk factors.

Small particles disrupt postnatal airway development

Increasing numbers of epidemiologic studies associate air pollution exposure in children with decreased lung function development. The objective of this study was to examine the effects of exposure to combustion-generated fine [230 and 212 nm number mean aerodynamic particle diameter (NMAD)] to ultrafine (73 nm NMAD) particles differing in elemental (EC) and organic (OC) carbon content on postnatal airway development in rats. Neonatal Sprague-Dawley rats were exposed from postnatal day 7 through 25, and lung function and airway architecture were evaluated 81 days of age. In a separate group of rats, cell proliferation was examined after a single particle exposure at 7 days of age. Early life exposure to 73 nm high OC/EC particles altered distal airway architecture and resulted in subtle changes in lung mechanics. Early life exposure to 212 nm high OC/EC particles did not alter lung architecture but did alter lung mechanics in a manner suggestive of central airway changes. In contrast, early life exposure to 230 nm low OC/EC particles did not alter lung architecture or mechanics. A single 6-h exposure to 73 nm high OC/EC particle decreased airway cell proliferation, whereas 212 nm high OC/EC particles increased it and 230 nm low OC/EC particles did not. The early life exposure to ultrafine, high OC/EC particles results in persistent alterations in distal airway architecture that is characterized by an initial decrease in airway cell proliferation.

[Atmospheric air pollution: a risk factor for COPD?]

Tobacco smoking is the leading cause of COPD worldwide but other risk factors have been recognized. Air pollution is one of them, but its exact role in the development of COPD is hard to demonstrate. Its physiological effects on lung function have only been studied since the nineties by long and tedious cohort studies. Difficulties arise from the heterogeneity of air pollution (gas and particles); thus, its respiratory effects have to be examined for every component separately, and in different populations. It is also necessary to analyse the effects of atmospheric pollution in the short and the long term, considering both its physiological, clinical and toxicological effects, from childhood to adulthood. These factors make it difficult to obtain statistically significant results. Nevertheless, most studies seem to point to a role of air pollution in the development of COPD via oxydative stress but further studies are needed to confirm the exact effect of each component of air pollution on the respiratory tract. These studies could lead to improved public health policies and results are awaited that would identify at-risk populations, decide appropriate preventive measures and propose documented thresholds in pollution exposure... thereby limiting the spread of COPD.

Ozone Uptake During Inspiratory Flow in a Model of the Larynx, Trachea and Primary Bronchial Bifurcation

Three-dimensional simulations of the transport and uptake of a reactive gas such as O(3) were compared between an idealized model of the larynx, trachea, and first bifurcation and a second "control" model in which the larynx was replaced by an equivalent, cylindrical, tube segment. The Navier-Stokes equations, Spalart-Allmaras turbulence equation, and convection-diffusion equation were implemented at conditions reflecting inhalation into an adult human lung. Simulation results were used to analyze axial velocity, turbulent viscosity, local fractional uptake, and regional uptake. Axial velocity data revealed a strong laryngeal jet with a reattachment point in the proximal trachea. Turbulent viscosity data indicated that jet turbulence occurred only at high Reynolds numbers and was attenuated by the first bifurcation. Local fractional uptake data affirmed hotspots previously reported at the first carina, and suggested additional hotspots at the glottal constriction and jet reattachment point in the proximal trachea. These laryngeal effects strongly depended on inlet Reynolds number, with maximal effects (approaching 15%) occurring at maximal inlet flow rates. While the increase in the regional uptake caused by the larynx subsided by the end of the model, the effect of the larynx on cumulative uptake persisted further downstream. These results suggest that with prolonged exposure to a reactive gas, entire regions of the larynx and proximal trachea could show signs of tissue injury.

Review Series: What goes around, comes around: childhood influences on later lung health?: Relationship between environmental exposures in children and adult lung disease: The case for outdoor exposures

There is a growing understanding that chronic respiratory diseases in adults have their origins in early life. Adverse environmental exposures occurring in vulnerable periods during lung growth and development in the fetal period and in early childhood that alter lung structure and limit the growth in lung function may have lifelong consequences. Evidence is increasing that exposure to the ambient environment, including air pollutants, persistent toxic substances, water pollutants and respiratory viral infections, can inhibit lung function growth and predispose to chronic non-malignant lung diseases. These exposures generally interact with a genetic predisposition, and gene—environment interactions and epigenetic phenomena are attracting considerable study. An understanding of how ambient exposures impact on normal lung growth and development will aid in understanding of how chronic respiratory diseases of adults develop and may lead to new preventative strategies.

Near-surface ozone levels and trends at rural stations in France over the 1995-2003 period

There is a considerable interest in quantifying near-surface ozone concentrations and associated trends, as they serve to define the impacts on ozone of the anthropogenic precursors reductions and to evaluate the effects of emission control strategies. A statistical test has been used to the ozone air concentrations measured in the French rural monitoring network stations, called MERA, in order to bring out spatio-temporal trends in air quality in France over the 1995-2003 period. The non-parametric Mann-Kendall test has been developed for detecting and estimating monotonic trends in the time series and applied in our study at annual values: mean, 98th percentile and median based on hourly averaged ozone concentrations and applied to daily maxima. In France, when averaged overall 9 stations between 1995 and 2003, a slight increasing trend of the O(3) levels (+0.6 +/- 1.3% year( - 1)) is observed, which is strongly influenced by the concentrations of the high altitude stations. In stations below 1000 m a mean rate of -0.48% year( - 1) from annual average concentrations, of -0.45% year( - 1) for medians and of +0.56% year( - 1) for P.98 over the 1995-2003 period were obtained. In stations above 1,000 m a mean rate of +1.75% year( - 1) from annual averages values, of +4.05% year( - 1) for medians and of +2.55% year( - 1) for P.98 were calculated over the 1997-2003 period. This situation is comparable to the one observed in other countries. In Europe and in France a reduction of precursor emissions is observed whereas a slight increasing trend of the O(3) levels is observed over the 1995-2003 period. One reason is the non-linearity of chemical ozone production with respect to precursor emissions. Possible explanations are an increase in near-surface ozone values caused by a reduced ozone titration by reduced NO( x ), the meteorological parameters change, an increase in bio-geogenic compound concentrations, the intercontinental transport from North America and Asia and the influence of stratospheric-tropospheric exchanges. These possible explanations must be interpreted carefully as on the short time scales considered.

Effect of air pollution on lung function in schoolchildren in Rio de Janeiro, Brazil

OBJECTIVE

To assess the association between daily exposure to air pollution and lung function in school children.

METHODS

Panel study with a random sample of 118 students (between 6 and 15 years of age), enrolled in a public school of the city of Rio de Janeiro, state of Rio de Janeiro, and living within 2 km of the study site. Data on students' characteristics were obtained with a questionnaire, including the International Study of Asthma and Allergies in Childhood - ISAAC. Daily peak expiratory flow measurements were taken to measure lung function. Daily data on PM10, SO2, O3, NO2 and CO levels, temperature and humidity were provided by a portable monitor. Repeated measurements of lung function were associated with pollutant levels with a multilevel model adjusted for time trend, temperature, air humidity, exposure to smoking at home, presence of asthma, height, sex, weight and age of children.

RESULTS

Mean peak expiratory flow was 243.5 l/m (sd=58.9). The lowest mean peak expiratory flow was 124 l/m, and the highest, 450 l/m. For the 10 microg/m(3) increase in PM10, there was a 0.34 l/min decrease in mean peak flow on the third day. For the 10 microg/m(3) increase in NO2, there was a decrease between 0.23 l/min and 0.28 l/min in mean peak flow after exposure. CO and SO2 effects on students' peak flow were not statistically significant. O3 showed a protective result: an increase in 10 microg/m(3) of O3 would be associated, after a day of exposure, with a 0.2 l/min increase in mean lung function.

CONCLUSIONS

Even within acceptable levels most of the time, air pollution, especially PM10 and NO2, was associated with a decrease in lung function in children living in the city of Rio de Janeiro.

Long-term effects of ambient air pollution on lung function: a review

Lung function is an important measure of respiratory health and a predictor of cardiorespiratory morbidity and mortality. Over the past 2 decades, more than 50 publications have investigated long-term effects of ambient air pollution on lung function with most finding adverse effects. Several studies have also suggested effects from traffic-related air pollution. There is strong support for air pollution effects on the development of lung function in children and adolescents. It remains unclear whether subjects with slower development of lung function compensate by prolonging the growth phase, or whether they end their development at a lower plateau, thus entering the decline phase with a reduced lung function. In adults, the evidence for long-term air pollution effects is mostly based on cross-sectional comparisons. One recent longitudinal study observed that decreasing pollution attenuated the decline of lung function in adults. Earlier inconclusive cohort studies were based on limited data. There is great diversity in study designs, markers of air pollution, approaches to the measurement of exposure, and choices in lung function measures. These limit the comparability of studies and impede quantitative summaries. New studies should use individual-level exposure assessment to clarify the role of traffic and to preclude potential community-level confounding. Further research is needed on the relevance of specific pollution sources, particularly with regard to susceptible populations and relevant exposure periods throughout life.

Breath acidification in adolescent runners exposed to atmospheric pollution: a prospective, repeated measures observational study

BACKGROUND

Vigorous outdoors exercise during an episode of air pollution might cause airway inflammation. The purpose of this study was to examine the effects of vigorous outdoor exercise during peak smog season on breath pH, a biomarker of airway inflammation, in adolescent athletes.

METHODS

We measured breath pH both pre- and post-exercise on ten days during peak smog season in 16 high school athletes engaged in daily long-distance running in a downwind suburb of Atlanta. The association of post-exercise breath pH with ambient ozone and particulate matter concentrations was tested with linear regression.

RESULTS

We collected 144 pre-exercise and 146 post-exercise breath samples from 16 runners (mean age 14.9 years, 56% male). Median pre-exercise breath pH was 7.58 (interquartile range: 6.90 to 7.86) and did not change significantly after exercise. We observed no significant association between ambient ozone or particulate matter and post-exercise breath pH. However both pre- and post-exercise breath pH were strikingly low in these athletes when compared to a control sample of 14 relatively sedentary healthy adults and to published values of breath pH in healthy subjects.

CONCLUSION

Although we did not observe an acute effect of air pollution exposure during exercise on breath pH, breath pH was surprisingly low in this sample of otherwise healthy long-distance runners. We speculate that repetitive vigorous exercise may induce airway acidification.

Is there an association between lifetime cumulative exposure and acute pulmonary responses to ozone?

OBJECTIVE

To investigate the potential effects of lifetime cumulative ozone (O3) exposure on acute pulmonary responses to O3.

METHODS

Fifteen healthy subjects from a larger cohort of young adults were exposed to 200 ppb O3 for 4 hours followed by bronchoscopy and bronchoalveolar lavage 18 hours later. Lung function, symptom questionnaires, and blood samples were obtained before and after each exposure. Subjects' lifetime cumulative O3 exposures were estimated from residential histories and air-quality monitoring data.

RESULTS

Acute exposure to O3 caused decrements in forced expiratory volume in 1 second (FEV1), maximal mid-expiratory flow rate (FEF25-75), and forced expiratory flow rate at 75% of forced vital capacity (FEF75), and an increase in plasma clara cell protein (CC16) level. Changes in CC16 and lower respiratory symptoms, but not in lung function, were positively correlated with lifetime cumulative O3 exposure.

CONCLUSION

Higher lifetime cumulative O3 exposure was associated with airway injury and respiratory symptom responses, but not with airway inflammatory or lung function responses, to acute O3 exposure.

Health effects of ambient air pollution in children

Children seem to be most vulnerable to the harmful effects of ambient air pollutants because their defence mechanisms are still evolving and because they inhale a higher volume of air per body weight than adults. Air pollutants can also harm the foetus if the mother is exposed to high levels of air pollution during pregnancy. An increase in respiratory neonatal mortality has been associated with ambient levels of air pollutants. Exposure to fine particles has been shown to increase allergen sensitisation, increase the risk of worsening asthma and decrease lung function. Lung growth, as measured by lung function, seems to be adversely affected in children exposed to various oxidant air pollutants. Oxidative stress is the main underlying mechanism responsible for the harmful effects of air pollutants and preliminary studies have indicated that antioxidant supplementation can offer some protection.

Lung function growth in children with long-term exposure to air pollutants in Mexico City

RATIONALE

Although short-term exposure to air pollution has been associated with acute, reversible lung function decrements, the impact of long-term exposure has not been well established.

OBJECTIVES

To evaluate the association between long-term exposure to ozone (O(3)), particulate matter less than 10 mum in diameter (PM(10)), and nitrogen dioxide (NO(2)) and lung function growth in Mexico City schoolchildren.

METHODS

A dynamic cohort of 3,170 children aged 8 years at baseline was followed from April 23, 1996, through May 19, 1999. The children attended 39 randomly selected elementary schools located near 10 air quality monitoring stations and were visited every 6 months. Statistical analyses were performed using general linear mixed models.

MEASUREMENTS AND MAIN RESULTS

After adjusting for acute exposure and other potential confounding factors, deficits in FVC and FEV(1) growth over the 3-year follow-up period were significantly associated with exposure to O(3), PM(10), and NO(2). In multipollutant models, an interquartile range (IQR) increase in mean O(3) concentration (IQR, 11.3 ppb) was associated with an annual deficit in FEV(1) of 12 ml in girls and 4 ml in boys, an IQR range (IQR, 36.4 microg/m(3)) increase in PM(10) with an annual deficit in FEV(1) of 11 ml in girls and 15 ml in boys, and an IQR range (IQR, 12.0 ppb) increase in NO(2) with an annual deficit in FEV(1) of 30 ml in girls and 25 ml in boys.

CONCLUSIONS

We conclude that long-term exposure to O(3), PM(10), and NO(2) is associated with a deficit in FVC and FEV(1) growth among schoolchildren living in Mexico City.

Asthma/allergic airways disease: does postnatal exposure to environmental toxicants promote airway pathobiology?

The recent, dramatic increase in the incidence of childhood asthma suggests a role for environmental contaminants in the promotion of interactions between allergens and the respiratory system of young children. To establish whether exposure to an environmental stressor, ozone (O3), and an allergen, house dust mite (HDMA), during early childhood promotes remodeling of the epithelial-mesenchymal trophic unit (EMTU) of the tracheobronchial airway wall by altering postnatal development, infant rhesus monkeys were exposed to cyclic episodes of filtered air (FA), HDMA, O3, or HDMA plus O3. The following alterations in the EMTU were found after exposure to HDMA, O3, or HDMA plus O3: (1) reduced airway number; (2) hyperplasia of bronchial epithelium; (3) increased mucous cells; (4) shifts in distal airway smooth muscle bundle orientation and abundance to favor hyperreactivity; (5) interrupted postnatal basement membrane zone differentiation; (6) modified epithelial nerve fiber distribution; and (7) reorganization of the airway vascular and immune system.

CONCLUSIONS

cyclic challenge of infants to toxic stress during postnatal lung development modifies the EMTU. This exacerbates the allergen response to favor development of intermittent airway obstruction associated with wheeze. And, exposure of infants during early postnatal lung development initiates compromises in airway growth and development that persist or worsen as growth continues, even with cessation of exposure.

Effect of exposure to traffic on lung development from 10 to 18 years of age: a cohort study

BACKGROUND

Whether local exposure to major roadways adversely affects lung-function growth during the period of rapid lung development that takes place between 10 and 18 years of age is unknown. This study investigated the association between residential exposure to traffic and 8-year lung-function growth.

METHODS

In this prospective study, 3677 children (mean age 10 years [SD 0.44]) participated from 12 southern California communities that represent a wide range in regional air quality. Children were followed up for 8 years, with yearly lung-function measurements recorded. For each child, we identified several indicators of residential exposure to traffic from large roads. Regression analysis was used to establish whether 8-year growth in lung function was associated with local traffic exposure, and whether local traffic effects were independent of regional air quality.

FINDINGS

Children who lived within 500 m of a freeway (motorway) had substantial deficits in 8-year growth of forced expiratory volume in 1 s (FEV(1), -81 mL, p=0.01 [95% CI -143 to -18]) and maximum midexpiratory flow rate (MMEF, -127 mL/s, p=0.03 [-243 to -11), compared with children who lived at least 1500 m from a freeway. Joint models showed that both local exposure to freeways and regional air pollution had detrimental, and independent, effects on lung-function growth. Pronounced deficits in attained lung function at age 18 years were recorded for those living within 500 m of a freeway, with mean percent-predicted 97.0% for FEV1 (p=0.013, relative to >1500 m [95% CI 94.6-99.4]) and 93.4% for MMEF (p=0.006 [95% CI 89.1-97.7]).

INTERPRETATION

Local exposure to traffic on a freeway has adverse effects on children's lung development, which are independent of regional air quality, and which could result in important deficits in attained lung function in later life.

Adverse health effects of outdoor air pollutants

Much research on the health effects of outdoor air pollution has been published in the last decade. The goal of this review is to concisely summarize a wide range of the recent research on health effects of many types of outdoor air pollution. A review of the health effects of major outdoor air pollutants including particulates, carbon monoxide, sulfur and nitrogen oxides, acid gases, metals, volatile organics, solvents, pesticides, radiation and bioaerosols is presented. Numerous studies have linked atmospheric pollutants to many types of health problems of many body systems including the respiratory, cardiovascular, immunological, hematological, neurological and reproductive/ developmental systems. Some studies have found increases in respiratory and cardiovascular problems at outdoor pollutant levels well below standards set by such agencies as the US EPA and WHO. Air pollution is associated with large increases in medical expenses, morbidity and is estimated to cause about 800,000 annual premature deaths worldwide [Cohen, A.J., Ross Alexander, H., Ostro, B., Pandey, K.D., Kryzanowski, M., Kunzail, N., et al., 2005. The global burden of disease due to outdoor air pollution. J Toxicol Environ Health A. 68: 1-7.]. Further research on the health effects of air pollution and air pollutant abatement methods should be very helpful to physicians, public health officials, industrialists, politicians and the general public.

Cyclic exposure to ozone alters distal airway development in infant rhesus monkeys

Inner city children exposed to high levels of ozone suffer from an increased prevalence of respiratory diseases. Lung development in children is a long-term process, and there is a significant period of time during development when children growing up in urban areas are exposed to oxidant air pollution. This study was designed to test whether repeating cycles of injury and repair caused by episodes of ozone exposure lead to chronic airway disease and decreased lung function by altering normal lung maturation. We evaluated postnatal lung morphogenesis and function of infant monkeys after 5 mo of episodic exposure of 0.5 parts per million ozone beginning at 1 mo of age. Nonhuman primates were chosen because their airway structure and postnatal lung development is similar to those of humans. Airway morphology and structure were evaluated at the end of the 5-mo exposure period. Compared with control infants, ozone-exposed animals had four fewer nonalveolarized airway generations, hyperplastic bronchiolar epithelium, and altered smooth muscle bundle orientation in terminal and respiratory bronchioles. These results suggest that episodic exposure to environmental ozone compromises postnatal morphogenesis of tracheobronchial airways.

Relationship between radical generation by urban ambient particulate matter and pulmonary function of school children

The mechanisms by which particulate matter (PM) produces adverse effects on the respiratory system, such as pulmonary dysfunction in children, are largely unknown. However, oxidative stress is thought to play an important role. Various chemical compounds in ambient particulate matter, including transition metals and aromatic organic compounds, may contribute to adverse effects through intrinsic generation of reactive oxygen species (ROS). It was hypothesized that ROS generation by PM, as determined through electron spin resonance (ESR) spectroscopy, may be negatively associated with pulmonary function in school children. PM(2.5), PM(10), and total suspended particulates (TSP) were sampled at the playgrounds of six elementary schools in the city of Maastricht, the Netherlands. All children (8-13 yr) from the six schools were asked to undergo spirometry. Multivariate linear regression models were constructed to evaluate associations between oxygen radical formation by PM and lung function. The radical-generating capacity per microgram PM correlated negatively to forced expiratory volume in 1 s (FEV(1)) and forced expiratory flow at 50% (FEF(50%)) of forced vital capacity (FVC). The data indicate that chemical features that contribute to intrinsic generation of ROS may be relevant for PM risk assessment.

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.

The effect of air pollution on lung development from 10 to 18 years of age

BACKGROUND

Whether exposure to air pollution adversely affects the growth of lung function during the period of rapid lung development that occurs between the ages of 10 and 18 years is unknown.

METHODS

In this prospective study, we recruited 1759 children (average age, 10 years) from schools in 12 southern California communities and measured lung function annually for eight years. The rate of attrition was approximately 10 percent per year. The communities represented a wide range of ambient exposures to ozone, acid vapor, nitrogen dioxide, and particulate matter. Linear regression was used to examine the relationship of air pollution to the forced expiratory volume in one second (FEV(1)) and other spirometric measures.

RESULTS

Over the eight-year period, deficits in the growth of FEV(1) were associated with exposure to nitrogen dioxide (P=0.005), acid vapor (P=0.004), particulate matter with an aerodynamic diameter of less than 2.5 microm (PM(2.5)) (P=0.04), and elemental carbon (P=0.007), even after adjustment for several potential confounders and effect modifiers. Associations were also observed for other spirometric measures. Exposure to pollutants was associated with clinically and statistically significant deficits in the FEV(1) attained at the age of 18 years. For example, the estimated proportion of 18-year-old subjects with a low FEV(1) (defined as a ratio of observed to expected FEV(1) of less than 80 percent) was 4.9 times as great at the highest level of exposure to PM(2.5) as at the lowest level of exposure (7.9 percent vs. 1.6 percent, P=0.002).

CONCLUSIONS

The results of this study indicate that current levels of air pollution have chronic, adverse effects on lung development in children from the age of 10 to 18 years, leading to clinically significant deficits in attained FEV(1) as children reach adulthood.

All I need is the air that I breath: outdoor air quality and asthma

In recent years, developing insight into the pathophysiology of asthma and advances in asthma management have been substantial. Despite these advancements, asthma remains a significant health problem in the paediatric population. In the USA, the prevalence of asthma in children under 18 years of age is estimated at 7% [US Environmental Health Protection Agency. Publication # EPA-100-r-018. Washington, DC, 2000]. Prevalence rates in various subpopulations, particularly African and Hispanic Americans, are much higher. Certain inner-city census tracts have estimated prevalence rates of 20 to 25% [ Crain EF Weiss KP, Stein REK. Pediatric 1994; 94: 356-362]. Many of these subpopulations experience alarmingly disparate and apparently increasing morbidity and mortality associated with asthma. Similar trends in prevalence and morbidity have been observed in urban populations outside the USA as well [Sears MR. Lancet 1997; 350: 1015-1020]. There is considerable controversy as to the scientific basis for these observed trends. While the identification of a single factor or even a closely related group of factors appears unlikely, there is considerable speculation about the role of environmental factors, particularly outdoor air quality. In the USA, the National Ambient Air Quality Standards (NAAQs) offer specific standards for air quality. These standards are applied to certain criteria pollutants, including ozone, particulate matter (both PM(10) and PM(2.5)), sulfur dioxide, nitrogen dioxide, lead and carbon monoxide [ Committee on Environmental Health, AAP. In: Handbook of Pediatric Environmental Health. Elk Grove Village, IL, 1999; 181-191]. The NAAQs were recently revised for both ozone and particulate matter based on data that suggested health risks existed at levels below those set forth in the previous standards. Monitoring data reveals that urban populations are more likely to be exposed to elevated levels of these pollutants [Dickey JH. Disease Monitor 2000; 46(9): 566-589]. Children are uniquely predisposed to the potential harmful effects of these pollutants. This predisposition is related to unique physiologic, anatomic and behavioural characteristics of the infant, child and adolescent. There is compelling evidence that an interplay of genetic predisposition and environmental exposure to a number of chemical and infectious agents may be operative in both the inception and persistence of the clinical asthma phenotype. The relative role of the criteria air pollutants in this interplay is the subject of considerable study. The potential value of intervention by regulatory agencies or by behavioural modification among individuals or communities should be explored. At the very least, the current data offers implications for situational strategies of asthma management based on local monitoring data.

Breathless in Los Angeles: the exhausting search for clean air

Population growth and the proliferation of roadways in Southern California have facilitated a glut of mobile air pollution sources (cars and trucks), resulting in substantial atmospheric pollution. Despite successful efforts over the past 40 years to reduce pollution, an alarming set of health effects attributable to air pollution have been described in Southern California. The Children's Health Study indicates that reduced lung function growth, increased school absences, asthma exacerbation, and new-onset asthma are occurring at current levels of air pollution, with sizable economic consequences. We describe these findings and urge a more aggressive effort to reduce air pollution exposures to protect our children's health. Lessons from this "case study" have national implications.

Repeated episodes of ozone inhalation amplifies the effects of allergen sensitization and inhalation on airway immune and structural development in Rhesus monkeys

Twenty-four infant rhesus monkeys (30 days old) were exposed to 11 episodes of filtered air (FA), house dust mite allergen aerosol (HDMA), ozone (O3), or HDMA + O3 (5 days each followed by 9 days of FA). Ozone was delivered for 8 h/day at 0.5 ppm. Twelve of the monkeys were sensitized to house dust mite allergen (Dermatophagoides farinae) at ages 14 and 28 days by subcutaneous inoculation (SQ) of HDMA in alum and intraperitoneal injection of heat-killed Bordetella pertussis cells. Sensitized monkeys were exposed to HDMA aerosol for 2 h/day on days 3-5 of either FA (n = 6) or O3 (n = 6) exposure. Nonsensitized monkeys were exposed to either FA (n = 6) or O3 (n = 6). During the exposure regimen, parameters of allergy (i.e., serum IgE, histamine, and eosinophilia), airways resistance, reactivity, and structural remodeling were evaluated. Eleven repeated 5-day cycles of inhaling 0.5 ppm ozone over a 6-month period had only mild effects on the airways of nonsensitized infant rhesus monkeys. Similarly, the repeated inhalation of HDMA by HDMA-sensitized infant monkeys resulted in only mild airway effects, with the exception of a marked increase in proximal airway and terminal bronchiole content of eosinophils. In contrast, the combined cyclic inhalation of ozone and HDMA by HDMA sensitized infants monkeys resulted in a marked increase in serum IgE, serum histamine, and airways eosinophilia. Furthermore, combined cyclic inhalation of ozone and HDMA resulted in even greater alterations in airway structure and content that were associated with a significant elevation in baseline airways resistance and reactivity. These results suggest that ozone can amplify the allergic and structural remodeling effects of HDMA sensitization and inhalation.