Asthma incidence in children growing up close to traffic: a registry-based birth cohort

Air pollution and childhood respiratory consultations in primary care: a systematic review

BACKGROUND

Outdoor air pollution is a known risk factor for respiratory morbidity worldwide. Compared with the adult population, there are fewer studies that analyse the association between short-term exposure to air pollution and respiratory morbidity in children in primary care.

OBJECTIVE

To evaluate whether children in a primary care setting exposed to outdoor air pollutants during short-term intervals are at increased risk of respiratory diagnoses.

METHODS

A search in Medline, the Cochrane Library, Web of Science and Embase databases throughout March 2023. Percentage change or risk ratios with corresponding 95% CI for the association between air pollutants and respiratory diseases were retrieved from individual studies. Risk of bias assessment was conducted with the Newcastle-Ottawa Scale (NOS) for cohort or case-control studies and an adjusted NOS for time series studies.

RESULTS

From 1366 studies, 14 were identified as meeting the inclusion criteria. Most studies had intermediate or high quality. A meta-analysis was not conducted due to heterogeneity in exposure and health outcome. Overall, studies on short-term exposure to air pollutants (carbon monoxide (CO), sulfur dioxide (SO2), nitrogen dioxide (NO2) and particulate matter ≤10 µm (PM10)) were associated with increased childhood respiratory consultations in primary care. In general, exposure to ozone was associated with a reduction in respiratory consultations.

CONCLUSIONS

The evidence suggests CO, SO2, NO2, PM10 and PM2.5 are risk factors for respiratory diseases in children in primary care in the short term. However, given the heterogeneity of the studies, interpretation of these findings must be done with caution.

PROSPERO REGISTRATION NUMBER

CRD42022259279.

Environmental justice and allergic disease: A Work Group Report of the AAAAI Environmental Exposure and Respiratory Health Committee and the Diversity, Equity and Inclusion Committee

Environmental justice is the concept that all people have the right to live in a healthy environment, to be protected against environmental hazards, and to participate in decisions affecting their communities. Communities of color and low-income populations live, work, and play in environments with disproportionate exposure to hazards associated with allergic disease. This unequal distribution of hazards has contributed to health disparities and is largely the result of systemic racism that promotes segregation of neighborhoods, disinvestment in predominantly racial/ethnic minority neighborhoods, and discriminatory housing, employment, and lending practices. The AAAAI Environmental Exposure and Respiratory Health Committee and Diversity, Equity and Inclusion Committee jointly developed this report to improve allergy/immunology specialists' awareness of environmental injustice, its roots in systemic racism, and its impact on health disparities in allergic disease. We present evidence supporting the relationship between exposure to environmental hazards, particularly at the neighborhood level, and the disproportionately high incidence and poor outcomes from allergic diseases in marginalized populations. Achieving environmental justice requires investment in at-risk communities to increase access to safe housing, clean air and water, employment opportunities, education, nutrition, and health care. Through policies that promote environmental justice, we can achieve greater health equity in allergic disease.

Caregiver perceptions of neighbourhood green space quality, heavy traffic conditions, and asthma symptoms: Group-based trajectory modelling and multilevel longitudinal analysis of 9,589 Australian children

BACKGROUND

This study assessed the associations between changes in exposure to green space quality, heavy traffic conditions, and asthma symptoms among children.

METHODS

10-year cohort data of 9589 children, retrieved from the Longitudinal Study of Australian Children, were analysed. Caregiver-reported neighbourhood green space quality, heavy traffic conditions, and asthma symptoms were measured biennially. Group-based trajectory mixture models were used to develop trajectory groups, denoting different patterns of, or changes in, exposure to green space quality, heavy traffic conditions, and asthma symptoms across childhood. Multilevel multinomial logistic regression was used to identify factors associated with trajectory group membership and examine the confounders-adjusted associations between trajectory groups of green space quality, heavy traffic conditions, and asthma symptoms.

RESULTS

Four trajectory groups for each green space quality and heavy traffic conditions, and five trajectory groups for asthma symptoms were developed. Children in less disadvantaged areas were more likely to be in trajectory groups with exposure to quality green space, but less likely to be exposed to heavy neighbourhood traffic. Living in more remote areas was associated with the decreased likelihood to be in groups with exposure to both quality green space and heavy traffic conditions over time. Accumulation of exposure to quality green space across childhood was not found to be protective against asthma symptoms. However, children whose caregiver perceptions of heavy traffic conditions trended from low to moderate levels; or were consistently in high levels across childhood had a higher likelihood to be in trajectory groups with a higher risk of asthma symptoms.

CONCLUSION

Exposure to quality green space was not associated with the reduced risk of asthma symptoms. The accumulation of exposure to heavy traffic conditions increased the likelihood of asthma symptoms among children. Reducing the presence of heavy traffic in neighbourhoods might reduce the risk of childhood asthma.

The first 1000 days of life: traffic-related air pollution and development of wheezing and asthma in childhood. A systematic review of birth cohort studies

BACKGROUND

The first 1000 days of life -including pregnancy and the first 2 years after birth- represent a critical window for health interventions. This systematic review aimed to summarize the evidence on the relationship between traffic-related air pollutants exposure in the first 1000 days of life and the development of wheezing and asthma, with a particular focus on windows of exposure.

METHODS

Medline and Embase were searched from January 2000 to May 2020 to retrieve population-based birth-cohort studies, including registries, providing quantitative information on the association between exposure to traffic-related air pollutants during pregnancy or early life, and the risk of developing wheezing and asthma in childhood. Screening and selection of the articles were completed independently by three reviewers. The quality of studies was assessed using the Newcastle-Ottawa scale.

RESULTS

Out of 9681 records retrieved, 26 studies from 21 cohorts were included. The most common traffic-related air pollutant markers were particulate matter (PM) and nitric oxides (NOx). The variability in terms of pollutants, exposure assessment methods, and exposure levels chosen to present the results did not allow a meta-analysis. Exposure to PM and NOx in pregnancy (10 cohorts) was consistently associated with an increased risk of asthma development, while the association with wheezing development was unclear. The second trimester of pregnancy seemed to be particularly critical for asthma risk. As for exposure during early life (15 cohorts), most studies found a positive association between PM (7/10 studies) and NOx (11/13 studies) and the risk of asthma development, while the risk of wheezing development was controversial. The period of postnatal exposure, however, was less precisely defined and a partial overlap between the period of exposure measurement and that of outcome development was present in a consistent number of studies (14 out of 15) raising doubts on the associations found.

CONCLUSIONS

Traffic-related air pollution during pregnancy is associated with an increased risk of asthma development among children and adolescents. The relationship between exposure in the first two years of life and the development of wheezing and asthma needs to be confirmed in studies with more precise exposure assessment.

Outdoor air pollution from industrial chemicals causing new onset of asthma or COPD: a systematic review protocol

Background

Until today, industrial sources contribute to the multifaceted contamination of environmental air. Exposure to air pollutants has the potential to initiate and promote asthma and chronic obstructive pulmonary disease (COPD). At global scale, both entities cause the majority of about 4 million annual deaths by respiratory disease. However, we identified industrial contamination as a subgroup of air pollution that may be associated with this burden and is underinvestigated in research. Therefore, the aim of this study is to investigate associations between substances industrially released into environmental air and the occurrence of asthma and COPD in the human population. Here we present the protocol for our systematic review of the current evidence.

Methods

The following determinations will be applied during the systematic review process and are specified in the protocol that complies with the PRISMA-P statement. Populations of children and adults, as well as outdoor workers, exposed to industrially released air pollutants are of interest. Eligible studies may include subjects as controls who are non- or less exposed to the investigated air pollutants. The outcomes new-onset asthma and/or COPD investigated with risk ratio, odds ratio, hazard ratio, incidence rate ratio, cumulative incidence, and incidence rate are eligible. We will search the electronic literature databases EMBASE, MEDLINE, and Web of Science for peer-reviewed reports of incidence studies and incidence case-control studies. After systematic sorting of initial records, included studies will be subjected to quality assessment. Data will be synthesized qualitatively and, if appropriate, quantitatively for risk ratio and odds ratio. We will maintain and provide a PRISMA report.

Discussion

Results of this systematic review may indicate alterations of incidence and risk of asthma and/or COPD in populations within industrial exposure radiuses including outdoor workplaces. Specific causal substances and compositions will be identified, but results will depend on the exposure assessment of the eligible studies. Our approach covers effects of industrial contributions to overall air pollution if studies reportedly attribute investigated emissions to industry. Results of this study may raise the question wether the available higher-level evidence sufficiently covers the current scale of industrial exposure scenarios and their potential harm to respiratory health.

Trial registration

This protocol was registered in PROSPERO, registration number CRD42020151573.

Health Impacts from Ambient Particle Exposure in Southern Sweden

A health impact assessment (HIA) is an important tool for making informed decisions regarding the design and evaluation of environmental interventions. In this study, we performed a quantitative HIA for the population of Scania (1,247,993), the southernmost county in Sweden, in 2016. The impact of annual mean concentrations of particulate matter with an aerodynamic diameter <2.5 µm (PM_2.5), modeled at their home residences for the year 2011, on mortality, asthma, dementia, autism spectrum disorders, preeclampsia and low birth weight (LBW) was explored. Concentration–response (C-R) functions were taken from epidemiological studies reporting meta-analyses when available, and otherwise from single epidemiological studies. The average level of PM_2.5 experienced by the study population was 11.88 µg/m³. The PM_2.5 exposure was estimated to cause 9–11% of cases of LBW and 6% of deaths from natural causes. Locally produced PM_2.5 alone contributed to 2–9% of the cases of diseases and disorders investigated. Reducing concentrations to a maximum of 10 µg/m³ would, according to our estimations, reduce mortality by 3% and reduce cases of LBW by 2%. Further analyses of separate emission sources’ distinct effects were also presented. Reduction of air pollution levels in the study area would, as expected, have a substantial effect on both mortality and adverse health outcomes. Reductions should be aimed for by local authorities and on national and even international levels.

The Effects of Air Pollution on the Development of Atopic Disease

Air pollution is defined as the presence of noxious substances in the air at levels that impose a health hazard. Thus, there has been long-standing interest in the possible role of indoor and outdoor air pollutants on the development of respiratory disease. In this regard, asthma has been of particular interest but many studies have also been conducted to explore the relationship between air pollution, allergic rhinitis, and atopic dermatitis. Traffic-related air pollutants or TRAP refers to a broad group of pollutants including elemental carbon, black soot, nitrogen dioxide (NO₂₎, nitric oxide (NO), sulfur dioxide (SO₂₎, particulate matter (PM_2.5 and PM₁₀), carbon monoxide (CO), and carbon dioxide (CO₂). In this review, we aim to examine the current literature regarding the impact of early childhood exposure to TRAP on the development of asthma, allergic rhinitis, and atopic dermatitis. Although there is growing evidence suggesting significant associations, definitive conclusions cannot be made with regard to the effect of TRAP on these diseases. This conundrum may be due to a variety of factors, including different definitions used to define TRAP, case definitions under consideration, a limited number of studies, variation in study designs, and disparities between studies in consideration of confounding factors. Regardless, this review highlights the need for future studies to be conducted, particularly with birth cohorts that explore this relationship further. Such studies may assist in understanding more clearly the pathogenesis of these diseases, as well as other methods by which these diseases could be treated.

Effect of NOx and NO2 Concentration Increase in Ambient Air to Daily Bronchitis and Asthma Exacerbation, Silesian Voivodeship in Poland

There is a discussion in Europe about the dominant role of air pollution for health effects, most researchers claim that the particulate matter is responsible for inflammatory processes in the respiratory system, while others underline the role of nitrogen dioxide. The aim of the study was to assess the risk related to NO_x, NO₂ and PM_2.5 concentration increase and daily outpatient visits or hospitalization due to bronchitis and asthma exacerbation in the entire population of Silesian Voivodeship, Poland. To assess the relationship between daily pollutants concentrations and the number of outpatient visits or hospitalizations due to bronchitis and asthma (available in the regional registry), the multivariable log-linear Poisson regression model was used. Results were presented by relative risk (RR) of health outcomes related to the increase in pollutant concentration by unit (interquartile range). Obtained results confirmed a statistically significant association between outpatient visits and hospitalizations due to bronchitis and asthma exacerbation and daily nitrogen oxides concentrations in Silesian voivodeship, Poland. The strongest relationship was observed in the case of NO₂ and outpatient visits due to bronchitis, e.g., RR = 1.434 (1.308–1.571) for exposure expressed by the 50-day moving average concentration. In the case of hospitalizations, the health effect was lagged a few days in relation to the increase in exposure.

The value of the Skåne Health-care Register: Prospectively collected individual-level data for population-based studies

Aims: This study aimed to examine the population-based Skåne Health-care Register (SHR) regarding feasibility for scientific research and also strengths and weaknesses. Methods: To analyse the feasibility of the SHR, we performed a bibliographic search for peer-reviewed articles based on SHR data from 2000 to 2018. To analyse strengths and weaknesses, we used original SHR data about coverage and validity. Results: We identified 58 articles based on SHR data, covering different study designs and disorders. Most studies focused on musculoskeletal disorders with a cohort design. The majority of all consultations recorded in the SHR have an assigned diagnosis. However, this differs between the levels of care and between types of consultation. For inpatient care, the proportion of consultations with an assigned diagnosis was close to 100% between 1998 and 2017. The proportion of consultations with an assigned diagnosis was lowest within primary care, although the proportion markedly increased in 2004 when the prerequisite for consultation reimbursement was linked to the requirement for an assigned diagnosis. Limitations are that the SHR does not cover health-care provided within nursing homes and equivalent facilities or treatments received by the population of Skåne outside the region. Conclusions: The SHR may be used as a reliable data source for analyses of clinical changes and improvements. Extended use of the SHR in a research context may highlight important shortcomings within the register and thus serve as a way of indirect quality control. To enhance the use of the SHR further, better harmonisation between registers, within and outside of the region and internationally, is of crucial importance.

Effect modifiers of lung function and daily air pollutant variability in a panel of schoolchildren

BACKGROUND

Acute pollutant-related lung function changes among children varies across pollutants and lag periods. We examined whether short-term air pollutant fluctuations were related to daily lung function among a panel of children and whether these effects are modified by airway hyperresponsiveness, location and asthma severity.

METHODS

Students from randomly selected grade 4 classrooms at seven primary schools in Durban, participated, together with asthmatic children from grades 3-6 (n=423). The schools were from high pollutant exposed communities (south) and compared with schools from communities with lower levels of pollution (north), with similar socioeconomic profiles. Interviews, spirometry and methacholine challenge testing were conducted. Bihourly lung function measurements were performed over a 3-week period in four phases. During all schooldays, students blew into their personal digital monitors every 1.5-2 hours. Nitrogen dioxide (NO₂), nitrogen oxide (NO), sulphur dioxide and particulate matter (<10 μm diameter) (PM₁₀) were measured at each school. Generalised estimating equations assessed lag effects, using single-pollutant (single or distributed lags) models.

RESULTS

FEV₁ declines ranged from 13 to 18 mL per unit increase in IQR for NO and 14-23 mL for NO₂. Among the 5-day average models, a 20 mL and 30 mL greater drop in FEV₁ per IQR for NO₂ and NO, respectively, among those with airway hyperresponsiveness compared with those without. Effects were seen among those with normal airways.

CONCLUSIONS

This first panel study in sub-Saharan Africa, showed significant declines in lung function, in response to NO and NO₂ with effects modified by airway hyperresponsiveness or persistent asthma.

Acute respiratory symptoms associated with short term fluctuations in ambient pollutants among schoolchildren in Durban, South Africa

Ambient air pollution has been associated with adverse respiratory outcomes, especially among children with asthma. This study reports on associations between daily ambient air pollutant concentrations and the respiratory symptoms of schoolchildren living in Durban, South Africa. This city is Africa's busiest port and a key hub for imported crude oil and exported refined petroleum and petrochemical products, and it experiences a mixture of air pollutants that reflects emissions from industry, traffic and biomass burning. Children in four communities in the highly industrialized southern portion of the city were compared to children of similar socio-economic profiles living in the north of the city. One school was selected in each community. A total of 423 children were recruited. Symptom logs were completed every 1.5-2 h over 3-week period in each of four seasons. Ambient concentrations of NO₂, NO, SO₂, CO, O_3, PM_2.5 and PM₁₀ were measured throughout the study. Generalized estimating equation (GEE) models were used to estimate odds ratios (ORs) and assess lag effects (1-5 days) using single pollutant (single lags or distributed lags) models. Concentrations of SO₂ and NO_x were markedly higher in the south, while PM₁₀ did not vary. Significant increase in the odds ratios of cough were identified for the various lags analyzed. The OR of symptoms was further increased among those living in the south compared to the north. In conclusion, in this analysis of over 70,000 observations, we provide further evidence that exposure to PM₁₀, SO₂, NO₂ and NO is associated with significantly increased occurrence of respiratory symptoms among children. This was evident for cough, shortness of breath, and chest tightness, across the four pollutants and for different lags of exposure. This is the first study describing these changes in sub-Saharan Africa.

Traffic-Related Air Pollution and Childhood Asthma: Recent Advances and Remaining Gaps in the Exposure Assessment Methods

Background: Current levels of traffic-related air pollution (TRAP) are associated with the development of childhood asthma, although some inconsistencies and heterogeneity remain. An important part of the uncertainty in studies of TRAP-associated asthma originates from uncertainties in the TRAP exposure assessment and assignment methods. In this work, we aim to systematically review the exposure assessment methods used in the epidemiology of TRAP and childhood asthma, highlight recent advances, remaining research gaps and make suggestions for further research. Methods: We systematically reviewed epidemiological studies published up until 8 September 2016 and available in Embase, Ovid MEDLINE (R), and “Transport database”. We included studies which examined the association between children’s exposure to TRAP metrics and their risk of “asthma” incidence or lifetime prevalence, from birth to the age of 18 years old. Results: We found 42 studies which examined the associations between TRAP and subsequent childhood asthma incidence or lifetime prevalence, published since 1999. Land-use regression modelling was the most commonly used method and nitrogen dioxide (NO₂) was the most commonly used pollutant in the exposure assessments. Most studies estimated TRAP exposure at the residential address and only a few considered the participants’ mobility. TRAP exposure was mostly assessed at the birth year and only a few studies considered different and/or multiple exposure time windows. We recommend that further work is needed including e.g., the use of new exposure metrics such as the composition of particulate matter, oxidative potential and ultra-fine particles, improved modelling e.g., by combining different exposure assessment models, including mobility of the participants, and systematically investigating different exposure time windows. Conclusions: Although our previous meta-analysis found statistically significant associations for various TRAP exposures and subsequent childhood asthma, further refinement of the exposure assessment may improve the risk estimates, and shed light on critical exposure time windows, putative agents, underlying mechanisms and drivers of heterogeneity.

Exposure to traffic-related air pollution and risk of development of childhood asthma: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

The question of whether children's exposure to traffic-related air pollution (TRAP) contributes to their development of asthma is unresolved. We conducted a systematic review and performed meta-analyses to analyze the association between TRAP and asthma development in childhood.

DATA SOURCES

We systematically reviewed epidemiological studies published until 8 September 2016 and available in the Embase, Ovid MEDLINE (R), and Transport databases.

STUDY ELIGIBILITY CRITERIA, PARTICIPANTS, AND INTERVENTIONS

We included studies that examined the association between children's exposure to TRAP metrics and their risk of 'asthma' incidence or lifetime prevalence, from birth to age 18years old.

STUDY APPRAISAL AND SYNTHESIS METHODS

We extracted key characteristics of each included study using a predefined data items template and these were tabulated. We used the Critical Appraisal Skills Programme checklists to assess the validity of each included study. Where four or more independent risk estimates were available for a continuous pollutant exposure, we conducted overall and age-specific meta-analyses, and four sensitivity analyses for each summary meta-analytic exposure-outcome association.

RESULTS

Forty-one studies met our eligibility criteria. There was notable variability in asthma definitions, TRAP exposure assessment methods and confounder adjustment. The overall random-effects risk estimates (95% CI) were 1.08 (1.03, 1.14) per 0.5×10^-5m^-1 black carbon (BC), 1.05 (1.02, 1.07) per 4μg/m³ nitrogen dioxide (NO₂), 1.48 (0.89, 2.45) per 30μg/m³ nitrogen oxides (NO_x), 1.03 (1.01, 1.05) per 1μg/m³ Particulate Matter <2.5μm in diameter (PM_2.5), and 1.05 (1.02, 1.08) per 2μg/m³ Particulate Matter <10μm in diameter (PM₁₀). Sensitivity analyses supported these findings. Across the main analysis and age-specific analysis, the least heterogeneity was seen for the BC estimates, some heterogeneity for the PM_2.5 and PM₁₀ estimates and the most heterogeneity for the NO₂ and NO_x estimates.

LIMITATIONS, CONCLUSIONS AND IMPLICATION OF KEY FINDINGS

The overall risk estimates from the meta-analyses showed statistically significant associations for BC, NO₂, PM_2.5, PM₁₀ exposures and risk of asthma development. Our findings support the hypothesis that childhood exposure to TRAP contributes to their development of asthma. Future meta-analyses would benefit from greater standardization of study methods including exposure assessment harmonization, outcome harmonization, confounders' harmonization and the inclusion of all important confounders in individual studies.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO 2014: CRD42014015448.

Association between traffic-related air pollution and asthma in preschool children in a national Japanese nested case-control study

OBJECTIVES

There has been little study on the effect of traffic-related air pollution on the incidence and persistence of asthma in preschool children. We evaluated the association of exposure to traffic-related air pollution with the incidence/persistence of asthma during the first 3 years of life using a population-based study.

METHODS

A baseline survey was conducted in 1½-year-old children (n=63,266). A follow-up survey at 3 years of age (n=43,343) identified new-onset asthma cases (n=853) and persistence of asthma (n=214). In the prevalence/persistence study, the outdoor concentrations of nitrogen oxides (NOx) and elemental carbon (EC) at home during the first 1½ years of life were estimated by a dispersion model. In the nested case-control study, which regarded incidence of asthma as cases, the personal exposure levels were estimated by dispersion model including time-activity pattern.

RESULTS

There was no statistically significant association between the incidence of asthma between age 1½ and 3 years and personal exposure levels to NOx nor EC. However, the persistence of asthmatic symptoms (between 1½ and 3  ears) was significantly associated with outdoor concentrations of NOx. ORs for the persistence of asthmatic symptoms were 6.02 (95% CI 1.51 to 23.92) for the comparison between the upper 5th and lower 25th centiles of NOx.

CONCLUSIONS

While no statistically significant association was observed for the incidence of asthma, the persistence of asthmatic symptoms in preschool children was significantly associated with traffic-related air pollution. This supports its importance as a risk factor in childhood airway disease.

Ever dispense of prescribed allergy medication in children growing up close to traffic: a registry-based birth cohort

Background

Epidemiologic studies have shown conflicting results regarding the role of traffic pollution in the development of allergic disease. This study investigated the relationship between living close to traffic and ever dispense of prescribed oral antihistamines or nasal anti-allergic medication, among young children. The underlying aim was to investigate if children growing up close to traffic pollution are at higher risk of developing allergy in early childhood.

Methods

We investigated a birth cohort in southern Sweden, consisting of N = 26 128 children (0–6 years) with health outcome and exposure data. Of these children, N = 7898, had additional covariate information. Traffic intensity and yearly averages of dispersion-modeled concentrations of NO_X (100 × 100 m grid) at residential addresses, were linked with registry data on dispensed allergy medication (the Swedish Prescribed Drug Register). Individual level covariate information was obtained from questionnaires distributed to parents at Child Health Care-center visits, eight months after birth. Cox proportional hazards regression was used for the statistical analyses.

Results

Living in close proximity to a road with equal to or greater than 8640 cars/day (compared to 0–8639 cars/day), was not associated with higher incidence of ever dispensed oral antihistamine or nasal anti-allergic medication, with or without adjustment for confounders (sex, breastfeeding, parental allergy, parental origin, season, and year of birth). Similar results were found in relation to NO_X.

Conclusions

Traffic-related exposure was not associated with higher incidence of ever dispensed medication against allergy, in children 0–6 years in southern Sweden. These results indicates that traffic-related exposure may not be a risk factor for early onset allergy in children in southern Sweden. However, children with dispense of prescribed allergy medication may be a selected subgroup, and the results for this group may not be generalizable to all children with allergy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-015-2356-3) contains supplementary material, which is available to authorized users.