Effects of ambient air pollution on symptom severity and medication use in children with asthma

Residential Proximity to Freeways is Associated with Uncontrolled Asthma in Inner-City Hispanic Children and Adolescents

Background. Proximity to heavy traffic has been linked to increased asthma severity. However, it is unknown whether exposure to heavy traffic is associated with the ability to maintain asthma control. Objectives. This study examines whether exposure to heavy traffic is associated with the ability to maintain asthma control in inner-city children. Methods. 756 inner-city asthmatic Hispanic children were followed for one year in a pediatric asthma management program (Breathmobile). At each scheduled visit, asthma specialist tracked patients' asthma severity and managed their asthma based on the NAEPP guidelines. The patients' residential distance from the nearest freeway was calculated based on residential address at study entry. Distance to nearest freeway was used as a surrogate marker for high exposure from traffic-related air pollutants. Results. Patients who lived near a freeway were significantly more likely to have asthma that was not well controlled (P = .03). Patients with intermittent and mild baseline severity have a two-fold increased risk of having asthma that is uncontrolled if they lived <2 miles from a freeway (OR = 2.2, P = .04). Conclusion. In children with asthma, residential proximity to freeways is associated with uncontrolled asthma.

Urinary levoglucosan as a biomarker of wood smoke: results of human exposure studies

Urinary levoglucosan was investigated as a potential biomarker of wood smoke exposure in two different controlled experimental settings. Nine subjects were exposed to smoke from a campfire in a controlled setting, and four were exposed to smoke from an older-model wood stove. All subjects were asked to provide urine samples before and after exposure, and to wear personal particulate matter with a diameter of < or =2.5 microm (PM(2.5)) monitors during exposure. Urinary levoglucosan measurements from both studies showed no consistent response to the smoke exposure. A third experiment was conducted to assess the contribution of dietary factors to urinary levoglucosan levels. Nine subjects were asked to consume caramel and provide urine samples before and after consumption. Urinary levoglucosan levels increased within 2 h of caramel consumption and returned to pre-exposure levels within 24 h. These studies suggest that diet is a major factor in determining urinary levoglucosan levels and that recent dietary history needs to be taken into account for future work involving levoglucosan as a biomarker of wood smoke exposure.

The association between childhood asthma prevalence and monitored air pollutants in metropolitan areas, United States, 2001-2004

BACKGROUND

Air pollution exposure has been linked to adverse respiratory health outcomes among children, primarily in studies of acute exposures that are often in limited geographic areas. We sought to assess the association between chronic outdoor air pollution exposure, as measured by 12-month averages by county, and asthma among children in metropolitan areas across the nation.

METHODS

Eligible children included those aged 3-17 years residing in US metropolitan areas who were sampled in the 2001-2004 National Health Interview Survey (N=34,073). 12-month average air pollutant levels for sulfur dioxide, nitrogen dioxide, ozone and particulate matter were compiled by county for 2000-2004. Eligible children were linked to pollutant levels for the previous 12 months for their county of residence. Adjusted odds ratios of having current asthma or an asthma attack in the past 12 months were estimated in single pollutant logistic regression models.

RESULTS

Children in counties with ozone and, to a less consistent degree, particulate matter levels in the highest quartile were more likely to have current asthma and/or a recent asthma attack than children residing in counties with the lowest pollution levels; the adjusted odds for current asthma for the highest quartile of estimated ozone exposure was 1.56 (95% confidence interval [CI]: 1.15, 2.10) and for recent asthma attack 1.38 (95% CI: 0.99, 1.91). No associations were found with sulfur dioxide or nitrogen dioxide levels.

CONCLUSION

Although the current US standard for ozone is based on short-term exposure, this cross-sectional study suggests that chronic (12-month) exposure to ozone and particles is related to asthma outcomes among children in metropolitan areas throughout the US.

Relationship between visits to emergency departments for asthma and ozone exposure in greater Seattle, Washington

BACKGROUND

Air pollution is known to affect asthma symptoms in controlled and epidemiologic studies.

OBJECTIVE

To determine whether ozone exposure in Seattle is associated with increased use of hospital emergency departments.

METHODS

Hospital data on daily asthma cases for all ages were obtained for 1998 through 2002. Ozone and fine particulate matter (< or = 2.5 microm in diameter) (PM2.5) data were obtained from local air agencies. Poisson regression models were used to assess the association between asthma visits to emergency departments and air pollutants. Maximum daily 1- and 8-hour average ozone concentrations and the daily PM2.5 concentration were used.

RESULTS

We observed associations between both ozone metrics and emergency department visits in children. For the maximum daily 1- and 8-hour average ozone concentrations, the relative risks (RRs) were 1.08 (95% confidence interval [CI], 1.00-1.18) and 1.11 (95% CI, 1.02-1.21), respectively, at 3 days' lag. Weaker but significant associations were also observed for adults. For the maximum daily 1-hour average ozone concentration, the RR was 1.06 (95% CI, 1.01-1.11) at 4 days' lag, and for the maximum daily 8-hour average ozone concentration, the RR was 1.06 (95% CI, 1.01-1.12) at 2 days' lag and 1.08 (95% CI, 1.02-1.14) at 4 days' lag.

CONCLUSION

Ozone exposure exacerbates asthma in people in the Seattle area, especially in children.

Symptoms and medication use in children with asthma and traffic-related sources of fine particle pollution

BACKGROUND

Exposure to ambient fine particles [particulate matter < or = 2.5 microm diameter (PM(2.5))] is a potential factor in the exacerbation of asthma. National air quality particle standards consider total mass, not composition or sources, and may not protect against health impacts related to specific components.

OBJECTIVE

We examined associations between daily exposure to fine particle components and sources, and symptoms and medication use in children with asthma.

METHODS

Children with asthma (n = 149) 4-12 years of age were enrolled in a year-long study. We analyzed particle samples for trace elements (X-ray fluorescence) and elemental carbon (light reflectance). Using factor analysis/source apportionment, we identified particle sources (e.g., motor vehicle emissions) and quantified daily contributions. Symptoms and medication use were recorded on study diaries. Repeated measures logistic regression models examined associations between health outcomes and particle exposures as elemental concentrations and source contributions.

RESULTS

More than half of mean PM(2.5) was attributed to traffic-related sources motor vehicles (42%) and road dust (12%). Increased likelihood of symptoms and inhaler use was largest for 3-day averaged exposures to traffic-related sources or their elemental constituents and ranged from a 10% increased likelihood of wheeze for each 5-microg/m(3) increase in particles from motor vehicles to a 28% increased likelihood of shortness of breath for increases in road dust. Neither the other sources identified nor PM(2.5) alone was associated with increased health outcome risks.

CONCLUSIONS

Linking respiratory health effects to specific particle pollution composition or sources is critical to efforts to protect public health. We associated increased risk of symptoms and inhaler use in children with asthma with exposure to traffic-related fine particles.

Effects of residual oil fly ash (ROFA) in mice with chronic allergic pulmonary inflammation

Exposure to particulate matter (PM) air pollution is associated with increased asthma morbidity. Residual oil flash ash (ROFA) is rich in water-soluble transition metals, which are involved in the pathological effects of PM. The objective of this study was to investigate the effects of intranasal administration of ROFA on pulmonary inflammation, pulmonary responsiveness, and excess mucus production in a mouse model of chronic pulmonary allergic inflammation. BALB/c mice received intraperitoneal injections of ovalbumin (OVA) solution (days 1 and 14). OVA challenges were performed on days 22, 24, 26, and 28. After the challenge, mice were intranasally instilled with ROFA. After forty-eight hours, pulmonary responsiveness was performed. Mice were sacrificed, and lungs were removed for morphometric analysis. OVA-exposed mice presented eosinophilia in the bronchovascular space (p < .001), increased pulmonary responsiveness (p < .001), and epithelial remodeling (p = .003). ROFA instillation increased pulmonary responsiveness (p = .004) and decreased the area of ciliated cells in the airway epithelium (p = .006). The combined ROFA instillation and OVA exposure induced a further increase in values of pulmonary responsiveness (p = .043) and a decrease in the number of ciliated cells in the airway epithelium (p = .017). PM exposure results in pulmonary effects that are more intense in mice with chronic allergic pulmonary inflammation.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Changes in lung function and airway inflammation among asthmatic children residing in a woodsmoke-impacted urban area

Fine particulate matter (PM(2.5)) is associated with respiratory effects, and asthmatic children are especially sensitive. Preliminary evidence suggests that combustion-derived particles play an important role. Our objective was to evaluate effect estimates from different PM(2.5) exposure metrics in relation to airway inflammation and lung function among children residing in woodsmoke-impacted areas of Seattle. Nineteen children (ages 6-13 yr) with asthma were monitored during the heating season. We measured 24-h outdoor and personal concentrations of PM(2.5) and light-absorbing carbon (LAC). Levoglucosan (LG), a marker of woodsmoke, was also measured outdoors. We partitioned PM(2.5) exposure into its ambient-generated (E(ag)) and nonambient (E(na)) components. These exposure metrics were evaluated in relation to daily changes in exhaled nitric oxide (FE(NO)), a marker of airway inflammation, and four lung function measures: midexpiratory flow (MEF), peak expiratory flow (PEF), forced expiratory volume in the first second (FEV(1)), and forced vital capacity (FVC). E(ag), but not E(na), was correlated with combustion markers. Significant associations with respiratory health were seen only among participants not using inhaled corticosteroids. Increases in FE(NO) were associated with personal PM(2.5), personal LAC, and E(ag) but not with ambient PM(2.5) or its combustion markers. In contrast, MEF and PEF decrements were associated with ambient PM(2.5), its combustion markers, and E(ag), but not with personal PM(2.5) or personal LAC. FEV(1) was associated only with ambient LG. Our results suggest that lung function may be especially sensitive to the combustion-generated component of ambient PM(2.5), whereas airway inflammation may be more closely related to some other constituent of the ambient PM(2.5) mixture.

Air quality and pediatric asthma-related emergencies

BACKGROUND

Previous studies suggest a relationship between air pollutants, aeroallergens, and asthma exacerbations.

OBJECTIVE

To simultaneously examine the role of seasonality, air quality, aeroallergens, and climate on asthma-related pediatric emergency department (ED) visits.

METHODS

A retrospective 4-year study of asthma-related ED visits was conducted.

RESULTS

September had the highest number of visits (p < 0.01). There were lower temperatures and precipitation (p < 0.01) and higher tree and weed pollen levels (p = 0.05) on days with more visits (p = 0.05), while grass pollen, mold, ozone, NO2, and PM2.5 levels showed no significant differences.

CONCLUSIONS

Asthma-related visits were associated with aeroallergens and climatic factors and not air-quality factors.

Circulating neutrophil CD14 expression and the inverse association of ambient particulate matter on lung function in asthmatic children

BACKGROUND

Identifying baseline inflammatory biomarkers that predict susceptibility to size-specific particulate matter (PM) independent of gaseous pollutants could help us better identify asthmatic subpopulations at increased risk for the adverse health effects of PM.

OBJECTIVE

To evaluate whether the association between lung function and exposure to ambient levels of PM less than 2.5 microm in diameter (PM2.5) (fine) and 10 to 2.5 microm in diameter (PM(10-2.5)) (coarse) in children with persistent asthma differed across baseline measures of inflammation and innate immune activation.

METHODS

We performed a panel study on a local population of 16 children with persistent asthma and evaluated daily pulmonary function (percentage of predicted peak expiratory flow and forced expiratory volume in 1 second) while concurrently measuring daily PM2.5 and PM(10-2.5) exposure from a central site in Chapel Hill, North Carolina. The children underwent a baseline medical evaluation that included assessment of several immunoinflammatory biomarkers in peripheral blood.

RESULTS

Children without measurable CD14 expression on circulating neutrophils had significantly reduced pulmonary function (forced expiratory volume in 1 second and peak expiratory flow) with each interquartile range (IQR) increase in PM2.5 (IQR = 8.5 microg/m3) and PM(10-2.5) (IQR = 4.1 microg/m3) concentration, unlike children with measurable CD14 expression (P < .001 for interaction).

CONCLUSIONS

Asthmatic children with muted surface expression of CD14 on circulating neutrophils may have a decreased capacity to respond to bacterial components of PM.

The relationship between outdoor air quality and respiratory symptoms in young children

The aim of this study was to investigate the relationship between air pollution and respiratory symptoms in young children. A total of 263 children at high risk of developing asthma or atopy were recruited antenatally and all respiratory symptoms experienced by the children were recorded by their parents for five years. Daily pollutant concentrations and meteorological data (ambient temperature and humidity) were collected from network monitoring sites. Logistic regression models investigating relationships between individual air pollutants and respiratory symptoms showed significant associations between Ozone (O3) (1 h and 8 h) concentrations and raised body temperature (lag 0); Carbon monoxide (CO) (8 h) and wheeze/rattle and runny/blocked nose (lag 5 and additive exposure over 5 days); Nitrogen dioxide (NO2) (24 h) concentrations and cough (lag 0 and additive exposure over 5 days) and PM2.5 and visibility (BSP) (1 h) with cough (lag 0). These associations were observed even though air pollutant concentrations were below national standards throughout the study period.

Ambient air pollution and asthma exacerbations in children: an eight-city analysis

The authors investigated the relation between ambient concentrations of five of the Environmental Protection Agency's criteria pollutants and asthma exacerbations (daily symptoms and use of rescue inhalers) among 990 children in eight North American cities during the 22-month prerandomization phase (November 1993-September 1995) of the Childhood Asthma Management Program. Short-term effects of carbon monoxide, nitrogen dioxide, particulate matter less than 10 mum in aerodynamic diameter (PM10), sulfur dioxide, and warm-season ozone were examined in both one-pollutant and two-pollutant models, using lags of up to 2 days. Lags in carbon monoxide and nitrogen dioxide were positively associated with both measures of asthma exacerbation, and the 3-day moving sum of sulfur dioxide levels was marginally related to asthma symptoms. PM10 and ozone were unrelated to exacerbations. The strongest effects tended to be seen with 2-day lags, where a 1-parts-per-million change in carbon monoxide and a 20-parts-per-billion change in nitrogen dioxide were associated with symptom odds ratios of 1.08 (95% confidence interval (CI): 1.02, 1.15) and 1.09 (95% CI: 1.03, 1.15), respectively, and with rate ratios for rescue inhaler use of 1.06 (95% CI: 1.01, 1.10) and 1.05 (95% CI: 1.01, 1.09), respectively. The authors believe that the observed carbon monoxide and nitrogen dioxide associations can probably be attributed to mobile-source emissions, though more research is required.

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.

Effect of particulate air pollution on lung function in adult and pediatric subjects in a Seattle panel study

STUDY OBJECTIVE

To determine whether increased exposure to particulate matter air pollution (PM), measured with personal, residential, or central site monitoring, was associated with pulmonary function decrements in either adults with COPD or children with asthma.

PARTICIPANTS

We studied 57 adults with or without COPD and 17 children aged 6 to 13 years with physician-diagnosed asthma in Seattle during a 3-year panel study.

STUDY DESIGN AND MEASUREMENTS

Indoor and outdoor PM measurements were made at subjects' homes. The subjects wore personal exposure monitors for 10 consecutive 24-h periods, and PM was also measured at a central outdoor location. We assessed the within-subject effect of particulate exposure on FEV(1) and peak expiratory flow (PEF) in adults, and maximal midexpiratory flow (MMEF), PEF, FEV(1), and symptoms in children.

RESULTS

FEV(1) decrements were associated with 1-day lagged central site PM </= 2.5 microm in diameter (PM(2.5)) in adult subjects with COPD. In children not receiving antiinflammatory medication, same day indoor, outdoor, and central site exposures to PM(2.5) were associated with decrements in MMEF, PEF, and FEV(1). Associations with PM(2.5) and lung function decrements were also observed for 1-day lagged indoor (MMEF, PEF, FEV(1)) and personal (PEF only) exposures. Antiinflammatory medication use in children significantly attenuated the PM effect on airflow rates and volumes.

CONCLUSIONS

This study found consistent decrements in MMEF in children with asthma who were not receiving medications. It is notable that effects were observed even though PM exposures were low for an urban area. These findings suggest the need for future larger studies of PM effects in this susceptible population that repeatedly measure spirometry to include MMEF and potentially more sensitive markers of airway inflammation such as exhaled breath condensate and exhaled nitric oxide.

Nedocromil sodium for chronic asthma in children

BACKGROUND

Currently inhaled corticosteroids are the main stay in the maintenance treatment of chronic asthma in children. Although inhaled corticosteroids play a crucial role in the management of childhood asthma, the long-term side effects of inhaled corticosteroids used in the management of chronic asthma in children are not clearly known.

OBJECTIVES

The objective of this review is to compare the safety and efficacy of inhaled nedocromil sodium with placebo in the treatment of chronic asthma in children.

SEARCH STRATEGY

We searched the Cochrane airway group trials register, Cochrane controlled trials register, Current contents, review articles, reference lists of articles. We also contacted the drug manufacturer and primary authors for additional citations. We also searched abstracts of major respiratory society meetings. The last search was carried out in October 2004

SELECTION CRITERIA

Randomised placebo controlled trials comparing nedocromil sodium to placebo in the treatment of chronic asthma in children (0 to 18 years).

DATA COLLECTION AND ANALYSIS

Both authors independently assessed trial quality and extracted data. Study authors were contacted for additional information.

MAIN RESULTS

Fifteen trials (twelve parallel group studies; three crossover trials recruiting 1422 children (837 males and 585 females)) were included. The studies were generally of good methodological quality. Two large long term studies used nedocromil for six months and four to six years and showed conflicting results in symptom free days. Short term studies (duration between 4 weeks to 12 weeks) showed that nedocromil sodium produced some improvement in a number of efficacy measures compared to placebo including FEV(1), FVC, FEV(1) % predicted, PC20 FEV(1), evening PEF and symptom scores. The parent's assessment of efficacy was in favour of nedocromil (odds ratio (OR) 0.5 (95% CI 0.3 to 0.8). Nedocromil sodium has a good safety profile. The only significant side effect observed was unpleasant taste. There was little evidence for a clinically dose response effect and only a few studies recruited participants with severe asthma.

AUTHORS' CONCLUSIONS

A limited number of small studies have shown that nedocromil is of benefit in improving lung function and some measures of symptoms, but the evidence with regard to the primary outcome of the review was conflicting. Two long-term trials did not show consistent effects on lung function outcomes, whereas several small short-term trials have shown benefit in these outcomes. Differing severities at baseline may explain this difference with milder participants experiencing less benefit, although the discrepancy between study findings may also reflect publication bias. Nedocromil sodium is associated with a very good safety profile with no significant short term or long- term adverse side effects. Although nedocromil may have advantages over inhaled corticosteroids in terms of side effects, there is a need for head to head trials of nedocromil and inhaled corticosteroids to establish whether asthma control is similar, especially in mild asthma. It is not yet clear where nedocromil should sit in relation to other therapies in the treatment of asthma in children.

Low-level subchronic exposure to wood smoke exacerbates inflammatory responses in allergic rats

Epidemiological studies have implicated wood smoke as a risk factor for exacerbating asthma. However, comparisons of findings in animal models with those in humans are currently not possible, because detailed clinically relevant measurements of pulmonary function are not available in animal studies. Brown Norway rats were immunized with ovalbumin and exposed to either filtered air or wood smoke at 1 mg particulate matter/m(3) for 70 days and challenged with allergen during the last 4 days of exposure. Baseline values for dynamic lung compliance were lower while functional residual capacity was increased in rats exposed to wood smoke compared to rats exposed to filtered air. IFN-gamma levels were reduced and IL-4 levels increased in the bronchoalveolar lavage fluid and blood plasma, inflammatory lesions in the lungs were 21% greater, and airway mucous cells/mm basal lamina were non-significantly increased in rats exposed to wood smoke compared to controls. Collectively, these studies suggest that the pulmonary function was affected in rats by exposure to wood smoke and this decline was associated with only minor increases in inflammation of the lung. Therefore, this animal model may be useful to elucidate the mechanisms of the decline in pulmonary function caused by environmental pollutants when asthmatics are exposed to allergen.

Particle Deposition in Children's Lungs: Theory and Experiment

A mathematical model of inhaled aerosol particle deposition for children is presented and validated with data from two published experimental studies. The model accurately predicts deposition fraction (DF) in children as a function of particle size for particles in the size range 1-3 microns for both sedentary and exercise breathing conditions. When the experimental data are grouped according to age, the model is able to predict age-dependent trends in DF at the studied particle sizes under sedentary breathing conditions. The model predicts that when ventilatory conditions are held constant, age-dependent changes in morphology result in decreasing DF with age; however, under realistic conditions these changes may be masked by age-dependent changes in ventilation. Despite the fact that mean DF differs significantly from adult values only in children younger than 9, the model predicted that dose-per-surface area may still be greater in children due to smaller lung sizes.

Glutathione S-transferase P1 gene polymorphism and air pollution as interactive risk factors for childhood asthma

BACKGROUND

Polymorphisms at the glutathione S-transferase (GST) P1 locus were associated with asthma-related phenotypes and bronchial hyper-responsiveness.

OBJECTIVE

This study investigated whether GSTP1 genotypes and outdoor air pollution were interactive risk factors on childhood asthma.

METHODS

Four hundred and thirty-six subjects were recruited for oral mucosa samplings from 2853 fourth- to ninth-grade schoolchildren from three districts with different air pollution levels in southern Taiwan. PCR-based assays were performed by oral mucosa DNA to determine GSTP1 genotypes. We also conducted a nested case-control study comprising 61 asthmatic children and 95 controls confirmed by International Study of Asthma and Allergies in Childhood questionnaire results and methacholine challenge test. Multiple logistic regression was used to adjust for potential confounding factors.

RESULTS

All participants were homozygous at the Ala-114 locus. Although only a marginally significant association existed between the frequency of homozygosity at the Ile-105 locus and asthma when air pollution was not considered, we found a significant gene-environmental interaction between GSTP1-105 alleles and air pollution after adjusting for confounders (P=0.035). Specifically, we found that compared with participants carrying any Val-105 allele in low air pollution, those who are Ile-105 homozygotes in high air pollution district had a significantly increased risk of asthma (adjusted odds ratio (AOR)=5.52, 95% confidence interval (CI)=1.64-21.25). Compared with participants carrying any Val-105 allele, in high air pollution district, children with Ile-105 homozygotes had a significantly increased risk of asthma (AOR=3.79, 95% CI=1.01-17.08), but those who carried two Ile-105 alleles in low or moderate air pollution districts did not show similar tendencies. The risk of asthma also revealed a clear dose-response relationship with outdoor air pollution in children with Ile-105 homozygotes.

CONCLUSION

Our result suggests a gene-environmental interaction between GSTP1-105 genotypes and outdoor air pollution on childhood asthma.

The effects of outdoor air pollution and tobacco smoke on asthma

Outdoor air pollution and environmental tobacco smoke adversely affect health in persons with asthma. Increased levels of ozone, particulate matter, and environmental tobacco smoke have been associated with increased asthma symptoms and health care use and with reduced lung function. These air contaminants have proinflammatory actions that can magnify existing lower airway inflammation in patients with asthma. Exposure to air contaminants can increase the risk of developing asthma in susceptible persons. Outdoor air pollution and environmental tobacco smoke may affect allergen-induced inflammation by initiating TH(2) responses to antigens or by exacerbating such inflammation in persons already sensitized.