The Effects of Policy-Driven Air Quality Improvements on Children's Respiratory Health.

INTRODUCTION: Ambient air pollution causes substantial morbidity and mortality in the United States and worldwide. To reduce this burden of adverse health effects, a broad array of strategies to reduce ambient air pollution has been developed and applied over past decades to achieve substantial reductions in ambient air pollution levels. This has been especially true in California, where the improvement of air quality has been a major focus for more than 50 years. Direct links between regulatory policies, changes in ambient pollutant concentrations, and improvements in public health have not been extensively documented. Data from the Children's Health Study (CHS), a multiyear study of children's respiratory health development, offered a unique opportunity to evaluate the effects of long-term reductions in air pollution on children's health. METHODS: We assessed whether changes in ambient air quality and emissions were reflected in three important indices of children's respiratory health: lung-function growth, lung-function level, and bronchitic symptoms. To make the best use of available data, these analyses were performed across the longest chronological period and largest CHS population available for the respective lung-function or bronchitic symptoms data sets. During field study operations over the course of the CHS, children's health status was documented annually by testing lung-function performance and the completion of standardized questionnaires covering a broad range of respiratory symptoms. Air quality data for the periods of interest were obtained from community monitoring stations, which operated in collaboration with regional air monitoring networks over the 20-year study time frame. Over the 20-year sampling period, common protocols were applied to collect data across the three cohorts of children. Each cohort's data set was assessed to investigate the relationship between temporal changes in lung-function development, prevalence of bronchitic symptoms, and ambient air pollution concentrations during a similar, vulnerable adolescent growth period (age 11 to 15 years). Analyses were performed separately for particulate matter ≤10 µm in aerodynamic diameter (PM10), particulate matter ≤2.5 µm in aerodynamic diameter (PM2.5), ozone (O3), and nitrogen dioxide (NO2). Emissions data and regulatory policies were collected from the staff of state and regional regulatory agencies, modeling estimates, and archived reports. RESULTS: Emissions in the regions of California studied during the 20-year period decreased by 54% for oxides of nitrogen (NOₓ), 65% for reactive organic gases (ROG), 21% for PM2.5, and 15% for PM10. These reductions occurred despite a concurrent 22% increase in population and a 38% increase in motor vehicle miles driven during that time frame. Air quality improved over the same time frame, with reductions in NO2 and PM2.5 in virtually all of the CHS communities. Annual average NO2 decreased by about 53% (from ~41 to 19 ppb) in the highest NO2-reporting community (Upland) and by about 28% (from ~10 to 7 ppb) in one of the lowest NO2-reporting communities (Santa Maria). Reductions in annual average PM2.5 concentrations ranged from 54% (~33 to 15 µg/m³) in the community with the highest concentration (Mira Loma) to 13% (~9 to 8 µg/m³) in a community with one of the lowest concentrations (Santa Maria). Improvements in PM10 and O3 (measured during eight daytime hours, 10 AM to 6 PM) were most evident in the CHS communities that initially had the highest levels of PM and O3. Trends in annual average NO2, PM2.5, and PM10 ambient air concentrations in the communities with higher-pollution levels were generally consistent with observed trends in NOₓ, ROG, PM2.5, and PM10 emissions.Significant improvements in lung-function growth in progressive cohorts were observed as air quality improved over the study period. Improvements in four-year growth of both forced expiratory volume in the first second of exhalation (FEV1) and forced vital capacity (FVC) were associated with declining levels of NO2 (P < 0.0001), PM2.5 (P < 0.01), and PM10 (P < 0.001). These associations persisted after adjustment for important potential confounders. Further, significant improvements in lung-function growth were observed in both boys and girls and among asthmatic and non-asthmatic children. Within-community decreases in O3 exposure were not significantly associated with lung-function growth. The proportion of children with clinically low FEV1 (defined as <80% predicted) at age 15 declined significantly, from 7.9% to 3.6% across the study periods, respectively, as the air quality improved (P < 0.005). We found little evidence to suggest that improvements in lung-function development were attributable to temporal confounding.Reductions in outdoor levels of NO2, O3, PM10, and PM2.5 across the cohort years of participation were associated with significant reductions in the prevalence of bronchitic symptoms regardless of asthma status, but observed improvements were larger in children with asthma. Among asthmatic children, the reductions in prevalence of bronchitic symptoms at age 10 were 21% (P < 0.01) for NO2, 34% (P < 0.01) for O3, 39% (P < 0.01) for PM10, and 32% (P < 0.01) for PM2.5 for reductions of 4.9 ppb, 3.6 ppb, 5.8 µg/m³, and 6.8 µg/m³, respectively. Similar reductions in prevalence of bronchitic symptoms were observed at age 15 among these same asthmatic children. As in the lung-function analyses, we found little evidence that temporal confounding accounted for the observed associations of symptoms reduction with air quality improvement.The large number and breadth of regulatory activities, as well as the prolonged phase-in periods of several policy approaches to reduce emissions, precluded the close temporal linkage of specific policies with specific changes in health status. However, the combination of policies addressing motor vehicle emissions - from on-board diagnostics to emission controls, from low-sulfur fuels to vehicle smog-check recertification, and from re-formulated gasoline to the various strategies contained within the San Pedro Bay Ports Clean Air Plan (especially the Clean Truck Program) - all contributed to an impressive and substantial reduction in emissions. These reductions collectively improved local and regional air quality, and improvements in local and regional air quality were associated with improvements in respiratory health. CONCLUSIONS: This study provides evidence that multiyear improvements in air quality and emissions, primarily driven through a broad array of science-based regulatory policy initiatives, have resulted in improved public health outcomes. Our study demonstrates that improvements in air quality, brought about by science-based regulatory actions, are associated with improved respiratory health in children. These respiratory health metrics include reductions in respiratory symptoms and improvements in lung-function development in a population widely accepted to be at risk and highly vulnerable to the effects of air pollution. Our research findings underscore the importance of sustained air regulatory efforts as an effective means of achieving improved respiratory health in communities and regions affected by airborne pollution.

Exhaled nitric oxide, susceptibility and new-onset asthma in the Children's Health Study.

A substantial body of evidence suggests an aetiological role of inflammation, and oxidative and nitrosative stress in asthma pathogenesis. Exhaled nitric oxide fraction (F(eNO)) may provide a noninvasive marker of oxidative and nitrosative stress, and aspects of airway inflammation. We examined whether children with elevated F(eNO) are at increased risk for new-onset asthma. We prospectively followed 2,206 asthma-free children (age 7-10 yrs) who participated in the Children's Health Study. We measured F(eNO) and followed these children for 3 yrs to ascertain incident asthma cases. Cox proportional hazard models were fitted to examine the association between F(eNO) and new-onset asthma. We found that F(eNO) was associated with increased risk of new-onset asthma. Children in the highest F(eNO) quartile had more than a two-fold increased risk of new-onset asthma compared to those with the lowest quartile (hazard ratio 2.1, 95% CI 1.3-3.5). This effect did not vary with the child's history of respiratory allergic symptoms. However, the effect of elevated F(eNO) on new-onset asthma was most apparent among those without a parental history of asthma. Our results indicate that children with elevated F(eNO) are at increased risk for new-onset asthma, especially if they have no parental history of asthma.

Glutathione-S-transferase (GST) P1, GSTM1, exercise, ozone and asthma incidence in school children.

BACKGROUND: Because asthma has been associated with exercise and ozone exposure, an association likely mediated by oxidative stress, we hypothesised that glutathione-S-transferase (GST)P1, GSTM1, exercise and ozone exposure have interrelated effects on the pathogenesis of asthma. METHODS: Associations of the well characterised null variant of GSTM1 and four single nucleotide polymorphisms (SNPs) that characterised common variation in the GSTP1 locus with new onset asthma in a cohort of 1610 school children were examined. Children's exercise and ozone exposure were classified using participation in team sports and community annual average ozone levels, respectively. RESULTS: A two SNP model involving putatively functional variants (rs6591255, rs1695 (Ile105Va)) best captured the association between GSTP1 and asthma. The risk of asthma was lower for those with the Val allele of Ile105Val (hazard ratio (HR) 0.60, 95% CI 0.4 to 0.8) and higher for the variant allele of rs6591255 (HR 1.40, 95% CI 1.1 to 1.9). The risk of asthma increased with level of exercise among ile(105) homozygotes but not among those with at least one val(105) allele (interaction p value = 0.02). The risk was highest among ile(105) homozygotes who participated in >or=3 sports in the high ozone communities (HR 6.15, 95% CI 2.2 to 7.4). GSTM1 null was independently associated with an increased risk of asthma and showed little variation with air pollution or GSTP1 genotype. These results were consistent in two independent fourth grade cohorts recruited in 1993 and 1996. CONCLUSION: Children who inherit a val(105) variant allele may be protected from the increased risk of asthma associated with exercise, especially in high ozone communities. GSTM1 null genotype was associated with an increased risk of asthma.

Environmental tobacco smoke and absenteeism related to respiratory illness in schoolchildren.

Household environmental tobacco smoke (ETS) exposure accounts for substantial morbidity among young children, but the ETS-associated morbidity burden among school-age children is less well defined. Illness-related school absenteeism is a measure of a broad spectrum of adverse effects of ETS exposure in school-age children. The authors investigated the relations between ETS exposure, asthma status, and illness-related school absenteeism in a cohort of 1,932 fourth-grade schoolchildren from 12 southern California communities during January-June 1996. Incidence rates and adjusted relative risks of illness-related absences were determined by using an active surveillance system. The effects of ETS exposure on absenteeism were assessed by using stratified incidence rates and Poisson regression to adjust for sociodemographic factors. ETS exposure was associated with an increased risk of respiratory-illness-related school absences (relative risk (RR) = 1.27, 95% confidence interval (CI): 1.04, 1.56). Children living in a household with two or more smokers were at increased risk of such absences (RR = 1.75, 95% CI: 1.33, 2.30). Children's asthma status affected their response to ETS. Compared with unexposed children without asthma, children with asthma were at increased risk of respiratory-illness-related school absences when exposed to one (RR = 2.35, 95% CI: 1.49, 3.71) or two or more (RR = 4.45, 95% CI: 2.80, 7.07) household smokers. Children without asthma also had an increased risk if exposed to two or more smokers (RR = 1.44, 95% CI: 1.04, 2.00). Therefore, ETS exposure is associated with increased respiratory-related school absenteeism among children, especially those with asthma.

Respiratory effects of relocating to areas of differing air pollution levels.

We studied 110 children (59 boys and 51 girls, who were 10 yr of age at enrollment and 15 yr of age at follow-up) who had moved from communities participating in a 10-yr prospective study of respiratory health (The Children's Health Study [CHS]) to determine whether changes in air quality caused by relocation were associated with changes in annual lung function growth rates. The subjects were given health questionnaires and underwent spirometry in their homes across six western states, according to a protocol identical to evaluations performed annually on the CHS cohort in school. Changes in annual average exposure to particulate matter with a mean diameter of 10 microm (PM(10)) were associated with differences in annual lung function growth rates for FEV(1), maximal midexpiratory flow, and peak expiratory flow rate. As a group, subjects who had moved to areas of lower PM(10) showed increased growth in lung function and subjects who moved to communities with a higher PM(10) showed decreased growth in lung function. A stronger trend was found for subjects who had migrated at least 3 yr before the follow-up visit than for those who had moved in the previous 1 to 2 yr. We conclude that changes in air pollution exposure during adolescent growth years have a measurable and potentially important effect on lung function growth and performance.

Family history and the risk of early-onset persistent, early-onset transient, and late-onset asthma.

Family history of asthma and allergies strongly influences asthma risk in children, but the association may differ for early-onset persistent, early-onset transient, and late-onset asthma. We analyzed the relation between family history and these types of asthma using cross-sectional data from a school-based study of 5,046 Southern California children. Parental and/or sibling history of asthma and allergy were generally more strongly associated with early-onset persistent asthma compared with early-onset transient or late-onset asthma. For children with two asthmatic parents relative to those with none, the prevalence ratio for early-onset persistent asthma was 12.1 [95% confidence interval (CI) = 7.91-18.7] compared with 7.51 (95% CI = 2.62-21.5) for early-onset transient asthma and 5.38 (95% CI = 3.40-8.50) for late-onset asthma. Maternal smoking in pregnancy was predominantly related to the risk of early-onset persistent asthma in the presence of parental history of allergy and asthma, and the joint effects were more than additive (interaction contrast ratio = 3.10, 95% CI = 1.45-4.75). Our results confirm earlier data that parental history of asthma and allergy is most strongly associated with early-onset persistent asthma and suggest that among genetically predisposed children, an early-life environmental exposure, maternal smoking during pregnancy, favors the development of early-onset asthma that persists into later early childhood.

The effects of ambient air pollution on school absenteeism due to respiratory illnesses.

We investigated the relations between ozone (O3), nitrogen dioxide (NO2), and respirable particles less than 10 microm in diameter (PM10) and school absenteeism in a cohort of 4th-grade school children who resided in 12 southern California communities. An active surveillance system ascertained the numbers and types of absences during the first 6 months of 1996. Pollutants were measured hourly at central-site monitors in each of the 12 communities. To examine acute effects of air pollution on absence rates, we fitted a two-stage time-series model to the absence count data that included distributed lag effects of exposure adjusted for long-term pollutant levels. Short-term change in O3, but not NO2 or PM10, was associated with a substantial increase in school absences from both upper and lower respiratory illness. An increase of 20 ppb of O3 was associated with an increase of 62.9% [95% confidence interval (95% CI) = 18.4-124.1%] for illness-related absence rates, 82.9% (95% CI = 3.9-222.0%) for respiratory illnesses, 45.1% (95% CI = 21.3-73.7%) for upper respiratory illnesses, and 173.9% (95% CI = 91.3-292.3%) for lower respiratory illnesses with wet cough. The short-term effects of a 20-ppb change of O3 on illness-related absenteeism were larger in communities with lower long-term average PM10 [223.5% (95% CI = 90.4-449.7)] compared with communities with high average levels [38.1% (95% CI = 8.5-75.8)]. Increased school absenteeism from O3 exposure in children is an important adverse effect of ambient air pollution worthy of public policy consideration.

Sex-specific effects of asthma on pulmonary function in children.

To evaluate the effects on lung function of asthma, time since diagnosis of asthma, and age at diagnosis of asthma, we examined school children in a cohort of 2,277 fourth- and seventh-graders at least twice during a 4-yr follow-up period. Sex-specific models for each lung function were fitted through mixed-effects models that used regression splines and captured age-dependent trends in the effect of asthma on lung function. In males, a history of asthma was associated with large and statistically significant deficits in maximum midexpiratory flow (MMEF) (-4.89%) and forced expiratory flow at 75% of expired FVC (FEF(75)) (-6.62%), whereas in females these deficits were smaller (-1.93% and -2.45%, respectively) and were not statistically significant. However, larger deficits were seen in both males and females with longer time since diagnosis. In males with more than 6 yr since diagnosis, there were significant deficits in FEV(1) (-3.91%), MMEF (-7.39%), FEF(75) (-8.12%), and peak expiratory flow rate (PEFR) (-4.65%) as compared with children with less than 3 yr since diagnosis. There were fewer females with more than 6 yr since diagnosis, but deficits were similar to those of males for FEV(1) (-2.52%), MMEF (-9.26%), and FEF(75) (-14.28%). Large deficits in flow rates in both large and small airways were observed in males and females for whom asthma was reported to have been diagnosed before age 3 yr. There was little evidence that lung growth in children with asthma "catches up" at older ages. Therefore, because a constant percent deficit in lung function implies an increasingly large absolute deficit in older children with larger lungs, these results are consistent with prior evidence that lung function deficits in children with asthma persist into adulthood. We also suggest that in children, commonly observed differences between sexes in the impact of asthma on lung function may reflect differences in the duration and age of onset of asthma in males and females.

Association between air pollution and lung function growth in southern California children.

Average growth of lung function over a 4-yr period, in three cohorts of southern California children who were in the fourth, seventh, or tenth grade in 1993, was modeled as a function of average exposure to ambient air pollutants. In the fourth-grade cohort, significant deficits in growth of lung function (FEV(1), FVC, maximal midexpiratory flow [MMEF], and FEF(75)) were associated with exposure to particles with aerodynamic diameter less than 10 micrometer (PM(10)), PM(2.5), PM(10)-PM(2.5), NO(2), and inorganic acid vapor (p < 0.05). No significant associations were observed with ozone. The estimated growth rate for children in the most polluted of the communities as compared with the least polluted was predicted to result in a cumulative reduction of 3.4% in FEV(1) and 5.0% in MMEF over the 4-yr study period. The estimated deficits were generally larger for children spending more time outdoors. In the seventh- and tenth-grade cohorts, the estimated pollutant effects were also negative for most lung function measures, but sample sizes were lower in these groups and none achieved statistical significance. The results suggest that significant negative effects on lung function growth in children occur at current ambient concentrations of particles, NO(2), and inorganic acid vapor.

Quality of spirometry test performance in children and adolescents : experience in a large field study.

STUDY OBJECTIVE: To determine the ability of children and adolescents to meet the American Thoracic Society (ATS) goals for spirometry quality that were based on results from adults. DESIGN: Observational. PARTICIPANTS: More than 4,000 public school students, ages 9 to 18 years. MEASUREMENTS: Spirometry was performed annually for 3 years, with the recording of maneuver quality measures of forced expiratory time, end-of-test volume, back-extrapolated volume, and time to peak expiratory flow (PEFT), and the recording of differences between best and second-best FVC, FEV(1), and peak expiratory flow (PEF) values. RESULTS: Regression analyses showed significant influences of participant age, gender, ethnicity, size, clinical status, and previous testing experience, as well as differences among individual test technicians. In general, these influences were small and explained little of the variance in performance. On average, children with a history of asthma or wheeze performed better quality spirometry than did others. Only PEFT improved significantly from year to year. Overall, only 15% of girls' tests and 32% of boys' tests met the PEFT criterion derived from adults in the Lung Health Study. CONCLUSION: Most of the children met adult-based ATS goals for spirometry test performance. Age group-specific criteria are needed to ensure adequately fast PEFT and reproducible PEF values.

Maternal smoking during pregnancy, environmental tobacco smoke exposure and childhood lung function.

BACKGROUND: Exposure to environmental tobacco smoke (ETS) during childhood and in utero exposure to maternal smoking are associated with adverse effects on lung growth and development. METHODS: A study was undertaken of the associations between maternal smoking during pregnancy, exposure to ETS, and pulmonary function in 3357 school children residing in 12 Southern California communities. Current and past exposure to household ETS and exposure to maternal smoking in utero were assessed by a self-administered questionnaire completed by parents of 4th, 7th, and 10th grade students in 1993. Standard linear regression techniques were used to estimate the effects of in utero and ETS exposure on lung function, adjusting for age, sex, race, Hispanic ethnicity, height, weight, asthma, personal smoking, and selected household characteristics. RESULTS: In utero exposure to maternal smoking was associated with reduced peak expiratory flow rate (PEFR) (-3.0%, 95% CI -4.4 to -1.4), mean mid expiratory flow (MMEF) (-4.6%, 95% CI -7.0 to -2.3), and forced expiratory flow (FEF(75)) (-6.2%, 95% CI -9.1 to -3.1), but not forced expiratory volume in one second (FEV(1)). Adjusting for household ETS exposure did not substantially change these estimates. The reductions in flows associated with in utero exposure did not significantly vary with sex, race, grade, income, parental education, or personal smoking. Exposure to two or more current household smokers was associated with reduced MMEF (-4.1%, 95% CI -7.6 to -0. 4) and FEF(75) (-4.4%, 95% CI -9.0 to 0.4). Current or past maternal smoking was associated with reductions in PEFR and MMEF; however, after adjustment for in utero exposure, deficits in MMEF and FEF(75) associated with all measurements of ETS were substantially reduced and were not statistically significant. CONCLUSIONS: In utero exposure to maternal smoking is independently associated with decreased lung function in children of school age, especially for small airway flows.

Air pollution and bronchitic symptoms in Southern California children with asthma.

The association of air pollution with the prevalence of chronic lower respiratory tract symptoms among children with a history of asthma or related symptoms was examined in a cross-sectional study. Parents of a total of 3,676 fourth, seventh, and tenth graders from classrooms in 12 communities in Southern California completed questionnaires that characterized the children's histories of respiratory illness and associated risk factors. The prevalences of bronchitis, chronic phlegm, and chronic cough were investigated among children with a history of asthma, wheeze without diagnosed asthma, and neither wheeze nor asthma. Average ambient annual exposure to ozone, particulate matter (PM(10) and PM(2.5); [less than/equal to] 10 microm and < 2.5 microm in aerodynamic diameter, respectively), acid vapor, and nitrogen dioxide (NO(2)) was estimated from monitoring stations in each community. Positive associations between air pollution and bronchitis and phlegm were observed only among children with asthma. As PM(10) increased across communities, there was a corresponding increase in the risk per interquartile range of bronchitis [odds ratio (OR) 1.4/19 microg/m(3); 95% confidence interval (CI), 1.1-1.8). Increased prevalence of phlegm was significantly associated with increasing exposure to all ambient pollutants except ozone. The strongest association was for NO(2), based on relative risk per interquartile range in the 12 communities (OR 2.7/24 ppb; CI, 1.4-5.3). The results suggest that children with a prior diagnosis of asthma are more likely to develop persistent lower respiratory tract symptoms when exposed to air pollution in Southern California.

Initial field evaluation of the Harvard active ozone sampler for personal ozone monitoring.

Assessing personal exposure to ozone has only been feasible recently with the introduction of passive ozone samplers. These devices are easy to use, but changes in air velocity across their collection surfaces can affect performance. The Harvard active ozone sampler (AS) was developed in response to problems with the passive methods. This active sampler has been tested extensively as a microenvironmental sampler. To test for personal sampling, 40 children attending summer day-camp in Riverside, California wore the active ozone sampler for approximately 2.6 h on July 19 and 21, 1994, when ozone concentrations were about 100 ppb and 140 ppb, respectively. The children spent 94-100% of the sampling period outside, staying within a well-defined area while participating in normal camp activities. Ambient ozone concentrations across this area were monitored by two UV photometric ozone monitors. The active sampler was worn in a small backpack that was also equipped with a passive ozone sampler. Device precision, reported as the percent difference between duplicate pairs of samplers, was +/- 3.7% and +/- 4.2% for the active and passive samplers, respectively. The active sampler measured, on average, 94.5 +/- 8.2% of the ambient ozone while the passive samplers measured, on average, 124.5 +/- 18.8%. The samplers were worn successfully for the entire sampling period by all participating children.

A study of twelve Southern California communities with differing levels and types of air pollution. II. Effects on pulmonary function.

To study the possible chronic respiratory effects of air pollutants, we designed and initiated a 10-yr prospective study of Southern California public schoolchildren living in 12 communities with different levels and profiles of air pollution. The design of the study, exposure assessment methods, and survey methods and results related to respiratory symptoms and conditions are described in the accompanying paper. Pulmonary function tests were completed on 3,293 subjects. We evaluated cross-sectionally the effects of air pollution exposures based on data collected in 1986-1990 by existing monitoring stations and data collected by our study team in 1994. Expected relationships were seen between demographic, physical, and other environmental factors and pulmonary function values. When the data were stratified by sex, an association was seen between pollution levels and lower pulmonary function in female subjects, with the associations being stronger for the 1994 exposure data than the 1986-1990 data. After adjustment, PM10, PM2.5, and NO2 were each significantly associated with lower FVC, FEV1, and maximal midexpiratory flow (MMEF); acid vapor with lower FVC, FEV1, peak expiratory flow rate (PEFR), and MMEF; and O3 with lower PEFR and MMEF. Effects were generally larger in those girls spending more time outdoors. Stepwise regression of adjusted pulmonary function values for girls in the 12 communities showed that NO2 was most strongly associated with lower FVC (r = -0.74, p < 0.01), PM2.5 with FEV1 (r = -0.72, p < 0.01), O3 with PEFR (r = -0.75, p < 0.005), and PM2.5 with MMEF (r = -0.80, p < 0.005). There was a statistically significant association between ozone exposure and decreased FVC and FEV1 in girls with asthma. For boys, significant associations were seen between peak O3 exposures and lower FVC and FEV1, but only in those spending more time outdoors. These findings underline the importance of follow-up of this cohort.

A study of twelve Southern California communities with differing levels and types of air pollution. I. Prevalence of respiratory morbidity.

To study possible chronic respiratory effects of air pollutants, we initiated a 10-yr prospective cohort study of Southern California children, with a study design focused on four pollutants: ozone, particulate matter, acids, and nitrogen dioxide (NO2). Twelve demographically similar communities were selected on the basis of historic monitoring information to represent extremes of exposure to one or more pollutants. In each community, about 150 public school students in grade 4, 75 in grade 7, and 75 in grade 10 were enrolled through their classrooms. Informed consent and written responses to surveys about students' lifetime residential histories, historic and current health status, residential characteristics, and physical activity were obtained with the help of the parents. In the first testing season, 3,676 students returned questionnaires. We confirmed associations previously reported between respiratory morbidity prevalence and the presence of personal, demographic, and residential risk factors. Rates of respiratory illness were higher for males, those living in houses with pets, pests, mildew, and water damage, those whose parents had asthma, and those living in houses with smokers. Wheeze prevalence was positively associated with levels of both acid (odds ratio [OR] = 1.45; 95% confidence interval [CI], 1.14-1.83) and NO2 (OR = 1.54; 95% CI, 1.08-2.19) in boys. We conclude, based on this cross-sectional assessment of questionnaire responses, that current levels of ambient air pollution in Southern California may be associated with effects on schoolchildren's respiratory morbidity as assessed by questionnaire.

Effect of spirometer temperature on FEV1 in a longitudinal epidemiological study.

OBJECTIVES: To assess the magnitude of error in pulmonary function measurements introduced by variation in spirometer temperature under field conditions. In a large scale epidemiological study of school children, the influence was investigated of spirometer temperature on forced expiratory volume in 1 second (FEV1) measured with dry rolling seal volumetric spirometers and conventional body temperature, pressure, and saturation (BTPS) corrections. METHODS: Linear regression analyses were performed on data from 995 test-retest pairs on 851 different children, with 1-110 days between test and retest, and spirometer temperature differences between -13 degrees C and +9 degrees C. RESULTS: After adjusting for effects of growth (test-retest intervals) and circadian variation (changes in times of testing), differences in standard BTPS corrected FEV1 showed significant (p < 0.05) dependence on differences in spirometer temperature between tests (-0.24%/degree C). CONCLUSIONS: When spirometer temperatures vary widely, standard BTPS correction does not fully adjust for gas contraction. To improve accuracy of volume measurements in epidemiological studies, additional correction for variation in spirometer temperature should be considered.

Acute effects of ambient ozone on asthmatic, wheezy, and healthy children.

Southern California children (10 to 12 years old) participated in a two-season study to assess the potential acute respiratory effects of ambient ozone (O3). Asthmatic (n = 49), wheezy (n = 53), and healthy (n = 93) children completed a four-day (Friday through Monday) study protocol, once in spring and again in summer, that included the use of daily activity and symptom diaries, heart rate recording devices, personal O3 samplers, and maximal effort spirometry several times per day. Data from regional monitoring stations were used to establish ambient hourly O3 concentrations. Analyses revealed that the children spent more time outdoors and were more physically active in the spring. Girls spent less time outdoors and were less physically active than boys. Personal O3 samplers correlated poorly with, and generally gave lower readings than, outdoor ambient monitors. Higher personal O3 exposures were associated generally with increased inhaler use, more outdoor time, and more physical activity. Children with asthma spent more time outdoors and were more active in the spring on high-O3 days (measured by personal sampler), and had the most trouble breathing, the most wheezing, and the most inhaler use on these days. Activity pattern data suggested that children with asthma protected themselves by being less physically active outdoors during the summer on high-O3 days. Wheezy children had the most trouble breathing during the summer on low-O3 days (measured by personal sampler). Observed relationships between O3 and pulmonary function were erratic and difficult to reconcile with existing knowledge about the acute respiratory effects of air pollution. We conclude that although asthmatic and wheezy children behave differently from their healthy peers with regard to symptoms and patterns of activity when challenged by ambient ozone, the nature of these changes remains inconsistent and ill-defined.

Temperature standardization of multiple spirometers.

In respiratory health surveys involving multiple spirometers, spirometer differences may introduce important biases. We investigated temperature measurement variability as a cause of spirometer differences. Digital thermometers recorded internal (cylinder) and external (outer casing) temperatures of six similar rolling-seal spirometers during field use and in laboratory tests at controlled room temperatures. Internal and external thermometers substantially agreed in recording spirometer temperature changes, which lagged room temperature changes. Offsets of individual thermometers from overall mean readings were roughly the same in field testing of 3908 students in > 60 schools over 5 months and in subsequent laboratory tests. Thermometers differed by as much as 1.3 degrees C, causing differences as large as 0.8% in vital capacity measurements. We conclude that (1) interior and exterior temperatures of typical rolling-seal spirometers do not differ greatly, although both may differ from surrounding air temperature; and (2) variations between individual digital thermometers may be large enough to bias spirometric data appreciably in large-scale surveys. Variations should be controlled by selection of similar-reading thermometers and/or correction to a uniform standard.

Chamber exposures of children to mixed ozone, sulfur dioxide, and sulfuric acid.

To help assess acute health effects of summer air pollution in the eastern United States, we simulated ambient "acid summer haze" as closely as was practical in a laboratory chamber. We exposed young volunteers who were thought to be sensitive to this pollutant mixture on the basis of previous epidemiologic evidence. Specifically, we exposed 41 subjects aged 9-12 y to mixed ozone (0.10 ppm), sulfur dioxide (0.10 ppm), and 0.6-microm sulfuric acid aerosol (100 +/- 40 microg/m3, mean +/- standard deviation) for 4 h, during which there was intermittent exercise. Fifteen subjects were healthy, and 26 had allergy or mild asthma. The entire group responded nonsignificantly (p > .05) to pollution exposure (relative to clean air), as determined by spirometry, symptoms, and overall discomfort level during exercise. Subjects with allergy/asthma showed a positive association (p = .01) between symptoms and acid dose; in healthy subjects, that association was negative (p = .08). In these chamber-exposure studies, we noted less of an effect than was reported in previous epidemiologic studies of children exposed to ambient "acid summer haze."

Short-term air pollution exposures and responses in Los Angeles area schoolchildren.

We studied 269 school children from three Southern California communities of contrasting air quality in two successive school years, to investigate short-term effects of ambient ozone (O3), nitrogen dioxide (NO2), or particulate matter (PM) on respiratory health. We measured lung function and symptoms twice daily for one week each in fall, winter and spring; and concurrently assessed time-activity patterns and personal exposures. Average daily personal exposures correlated with pollutant concentrations at central sites (r = 0.61 for O3, 0.63 for NO2, 0.48 for PM). Questionnaire-reported outdoor activity increased slightly in communities/seasons with higher pollution. Lung function differences between communities were explainable by age differences. Morning forced vital capacity (FVC) decreased significantly with increase in PM or NO2 measured over the preceding 24 hours. Morning-to-afternoon change of forced expired volume in one second (FEV1) became significantly more negative with increase in PM, NO2, or O3 on the same day. Predicted FVC or FEV1 loss on highest- vs lowest-pollution days was < 2%. Daily symptoms showed no association with current or prior 24-hour pollution, but increased with decreasing temperature. Parents' questionnaire responses suggested excess asthma and allergy in children from one polluted community while children in the other polluted community reported more symptoms, relative to the cleaner community. We conclude that Los Angeles area children may experience slight lung function changes in association with day-to-day air quality changes, reasonably similar to responses seen by others in less polluted areas. Although short-term pollution effects appear small, they should be assessed in longitudinal lung function studies when possible, to allow maximally accurate measurement of longer-term function changes.