Hind Sbihi

Impact of noise and air pollution on pregnancy outcomes.

Background: Motorized traffic is an important source of both air pollution and community noise. While there is growing evidence for an adverse effect of ambient air pollution on reproductive health, little is known about the association between traffic noise and pregnancy outcomes. Methods: We evaluated the impact of residential noise exposure on small size for gestational age, preterm birth, term birth weight, and low birth weight at term in a population-based cohort study, for which we previously reported associations between air pollution and pregnancy outcomes. We also evaluated potential confounding of air pollution effects by noise and vice versa. Linked administrative health data sets were used to identify 68,238 singleton births (1999–2002) in Vancouver, British Columbia, Canada, with complete covariate data (sex, ethnicity, parity, birth month and year, income, and education) and maternal residential history. We estimated exposure to noise with a deterministic model (CadnaA) and exposure to air pollution using temporally adjusted land-use regression models and inverse distance weighting of stationary monitors for the entire pregnancy. Results: Noise exposure was negatively associated with term birth weight (mean difference = −19 [95% confidence interval = −23 to −15] g per 6 dB(A)). In joint air pollution-noise models, associations between noise and term birth weight remained largely unchanged, whereas associations decreased for all air pollutants. Conclusion: Traffic may affect birth weight through exposure to both air pollution and noise.

Hypertension in noise-exposed sawmill workers: a cohort study

Objective: To investigate the hypothesised association between exposure to high levels of noise and risk of hypertension using quantitative exposure assessment and administrative health data. Methods: This study followed a cohort of 10 872 sawmill workers in British Columbia from 1991 to 1998. Subjects were linked with provincial hospital discharge, outpatient and vital status databases. Cases were males who died, had at least one hospital admission, or who had three doctor visits within 70 days, for hypertension (ICD-9 codes 401–405). We used four exposure metrics: cumulative exposure, and duration of exposure above thresholds of 85 dBA, 90 dBA and 95 dBA. Relative risks were estimated using Poisson regression with the low-exposure group as controls and adjusting for age, ethnicity and calendar period. Results: 828 cases were identified. The results showed a monotonic increase in hypertension incidence with cumulative exposure. The risk in the highest exposed population was 32% higher than baseline. Similar results were found using duration of exposure metrics. The highest relative risk was 1.5 in workers exposed for more than 30 years at 85 dBA. Exposure-response trends were statistically significant. Conclusions: The risk of hypertension was positively associated with noise exposure above 85 dB.

Asthma Trajectories in a Population-based Birth Cohort. Impacts of Air Pollution and Greenness

Rationale: The heterogeneity of asthma phenotypes may explain inconsistencies in observed associations with environmental exposures. Objectives: To identify trajectories of childhood asthma and to characterize the potential impact of residential greenness and air pollution on asthma trajectory subgroups. Methods: Linked administrative databases of medical visits were used to define the occurrence and recurrence of asthma over a 10‐year follow‐up period within a population‐based birth cohort of more than 65,000 children. Group‐based trajectory modeling was used to identify unique asthma trajectories. Weighted multinomial regression was used to assess the relationship between asthma trajectories and risk factors, including environmental exposures. Measurements and Main Results: Group‐based trajectory modeling distinguished four trajectories: one with no asthma representing 88.8% of the cohort, one with transient asthma (5.6% of the cohort), and two trajectories with chronic asthma with early (<1 yr; 1.5%) and late (<3 yr; 4.1%) onset during early childhood. These trajectories differed with respect to socioeconomic markers and modifiable risk factors, including maternal smoking and breastfeeding initiation. After accounting for sex, parity, breastfeeding, term birth weight, household income, maternal education, delivery mode, and smoking, an interquartile increase in nitrogen dioxide exposure increased the risk of membership in the early and late‐onset chronic asthma trajectories, relative to subjects without asthma, by 50% and 20%, respectively (weighted risk ratio, 1.5 and 1.2; 95% confidence interval, 1.2‐1.9 and 1.0‐1.4). Greenness was not associated with any of the asthma trajectories. Conclusions: Traffic‐related air pollution increased the probability of a chronic asthma trajectory.

Greenness and Incident Childhood Asthma: A 10-Year Follow-up in a Population-based Birth Cohort.

Reduced access to greenspace for children has been linked to higher relative prevalence of asthma (1), and increased access to greenspace has been linked to higher physical activity (2), which is itself associated with decreased asthma development. However, in a birth cohort study conducted in New York, asthma at age 7 years and sensitization to tree pollen were significantly increased in those residing on streets with higher tree canopy coverage (3). We report on the effect of early-life exposure to surrounding residential greenness on asthma incidence, using data from a 10-year follow-up of more than 65,000 children in a population-based birth cohort study in British Columbia, Canada. Linked administrative data were used to establish the study cohort comprising all 1999–2002 single births in the metropolitan area of Vancouver, British Columbia, to mothers registered with the provincial universal health insurance program and who resided for their complete pregnancy in the study area (4). Individual covariates obtained through administrative records (5, 6) include the month/year of birth, sex, First Nations status, and maternal parity, age, smoking during pregnancy, and initiation of breastfeeding. Participants were assigned neighborhood-level socioeconomic indicators (household income and maternal education) from Census data, based on their residential census dissemination area (7), a unit representing a target population of 400–700 persons. Using linked physician billing and hospital discharge records (8), children were defined as cases after a validated case definition of asthma (9) of two physician diagnoses in a rolling 12-month period or a minimum of one hospital admission. Cases were sexand age-matched to five randomly chosen controls. Using a nested conditional logistic regression, incident asthma during preschool-age (0–5 yr old) and school-age (6–10 yr old) periods was examined in relation to surrounding greenness based on a satellite-derived normalized difference vegetation index (NDVI). As seasonal values were highly correlated (r. 0.9), average yearly greenness indices during pregnancy were calculated for 100-m areas around residential postal codes (4). This buffer size typically reflects a city block and is at a similar spatial scale as within-city air pollution variation for which exposure estimates were developed and evaluated in the study region. The mean (SD) age at time of incidence was 2.6 (1.4) and 7.0 (1.2) years in the preschool (6,948 cases) and school age (1,711 cases) groups, respectively (see Table E1 in the online supplement). Average greenness levels in metropolitan Vancouver were relatively high (median NDVI = 0.24) and inversely correlated with land use regression models estimates of air pollution (r 20.4; P = 0.07) (4). In adjusted models, we observed during preschool years a decreased risk of asthma per interquartile (0.11) NDVI increase (adjusted odds ratio [aOR] = 0.96; 95% confidence interval [CI], 0.93–0.99). Accounting for contemporaneous co-exposures to air pollutants and road proximity measures enhanced the effect of greenness (Figure 1). No such associations were observed during the school age period (see Figure E1 in the online supplement). Suggestive evidence of effect modification by birth weight was indicated, as surrounding greenness reduced the odds of new asthma onset during preschool years by 44% for children with term birth weight ,2,500 g compared with those weighing >2,500 g at birth. Children born to mothers with low educational attainment were also more likely to benefit from greenness exposure (aOR = 0.92; 95% CI, 0.86–0.97). However, no effect modification by neighborhood-level household income was found (Table 1). The lack of extensive individual level covariate data remains a limitation; however, this may be balanced by the large population-based study design. Although pediatric asthma diagnosis is challenging, especially in very young children, ascertainment bias is unlikely, as 77% of children diagnosed during preschool years remained asthmatic in later childhood. The inverse association between surrounding greenness and development of asthma in preschool-age children may support a hypothesis that biodiversity loss (10), reflected for instance by less interaction with natural spaces, leads to immune dysfunction, inflammation, and asthma. Stress reduction may be another pathway by which greenness influences asthma development. As the protective effect of greenness was enhanced in models including air pollution exposure, despite the absence of a significant interaction term between these covarying exposures, the positive confounding by air pollution may represent a case of variance suppression. Our observations of an association between greenness and incident asthma among preschool children are unlikely to be mediated by increased physical activity, as no association was found between incident asthma and distance to the nearest park (aOR = 0.98; 95% CI, 0.95–1.00). Interaction models confirmed an effect of surrounding greenness that was independent of park proximity. The possible protective effect of surrounding greenness on children weighing less than 2,500 g and for those born in areas of lower socioeconomic status raises the prospect of preventive public health interventions during pregnancy. In one of the largest birth cohort studies to examine within-community NDVI-based contrasts, we found that the The Border Air Quality Study was supported in part by Health Canada via an agreement with the British Columbia Centre for Disease Control. Additional support was provided by the Centre for Health and Environment Research at the University of British Columbia, funded by the Michael Smith Foundation for Health Research. H.S. was funded by the Canadian Institutes of Health Research Banting and Best Doctoral Award.

Perinatal Exposure to Traffic-Related Air Pollution and Atopy at 1 Year of Age in a Multi-Center Canadian Birth Cohort Study.

Background The role of traffic-related air pollution (TRAP) exposure in the development of allergic sensitization in children is unclear, and few birth cohort studies have incorporated spatiotemporal exposure assessment. Objectives We aimed to examine the association between TRAP and atopy in 1-year-old children from an ongoing national birth cohort study in four Canadian cities. Methods We identified 2,477 children of approximately 1 year of age with assessment of atopy for inhalant (Alternaria, Der p, Der f, cat, dog, cockroach) and food-related (milk, eggs, peanuts, soy) allergens. Exposure to nitrogen dioxide (NO2) was estimated from city-specific land use regression models accounting for residential mobility and temporal variability in ambient concentrations. We used mixed models to examine associations between atopy and exposure during pregnancy and the first year of life, including adjustment for covariates (maternal atopy, socioeconomic status, pets, mold, nutrition). We also conducted analyses stratified by time-location patterns, daycare attendance, and modeled home ventilation. Results Following spatiotemporal adjustment, TRAP exposure after birth increased the risk for development of atopy to any allergens [adjusted odds ratio (aOR) per 10 μg/m3 NO2 = 1.16; 95% CI: 1.00, 1.41], but not during pregnancy (aOR = 1.02; 95% CI: 0.86, 1.22). This association was stronger among children not attending daycare (aOR = 1.61; 95% CI: 1.28, 2.01) compared with daycare attendees (aOR = 1.05; 95% CI: 0.81, 1.28). Trends to increased risk were also found for food (aOR = 1.17; 95% CI: 0.95, 1.47) and inhalant allergens (aOR = 1.28; 95% CI: 0.93, 1.76). Conclusion Using refined exposure estimates that incorporated temporal variability and residential mobility, we found that traffic-related air pollution during the first year of life was associated with atopy. Citation Sbihi H, Allen RW, Becker A, Brook JR, Mandhane P, Scott JA, Sears MR, Subbarao P, Takaro TK, Turvey SE, Brauer M. 2015. Perinatal exposure to traffic-related air pollution and atopy at 1 year of age in a multi-center Canadian birth cohort study. Environ Health Perspect 123:902–908; http://dx.doi.org/10.1289/ehp.1408700

Perinatal air pollution exposure and development of asthma from birth to age 10 years

Within-city variation in air pollution has been associated with childhood asthma development, but findings have been inconsistent. We examined whether perinatal air pollution exposure affected asthma onset during “pre-school and “school age” periods in a population-based birth cohort. 65 254 children born between 1999 and 2002 in the greater Vancouver metropolitan region were followed until age 10 years using linked administrative health databases. Asthma cases were sex- and age-matched to five randomly chosen controls. Associations between exposure to air pollutants estimated with different methods (interpolation (inverse-distance weighted (IDW)), land use regression, proximity) and incident asthma during the pre-school (0–5 years) and school age (6–10 years) periods were estimated with conditional logistic regression. 6948 and 1711 cases were identified during the pre-school and school age periods, respectively. Following adjustment for birthweight, gestational period, household income, parity, breastfeeding at discharge, maternal age and education, asthma risk during the pre-school years was increased by traffic pollution (adjusted odds ratio using IDW method per interquartile increase (95% CI): nitric oxide 1.06 (1.01–1.11), nitrogen dioxide 1.09 (1.04–1.13) and carbon monoxide 1.05 (1.01–1.1)). Enhanced impacts were observed amongst low-term-birthweight cases. Associations were independent of surrounding residential greenness. Within-city air pollution variation was associated with new asthma onset during the pre-school years. Air pollution increases the odds of incident asthma from 0 to 5 years, especially in low-term-birthweight children http://ow.ly/WNEln

The Canadian Healthy Infant Longitudinal Development (CHILD) birth cohort study: Assessment of environmental exposures

The Canadian Healthy Infant Longitudinal Development birth cohort was designed to elucidate interactions between environment and genetics underlying development of asthma and allergy. Over 3600 pregnant mothers were recruited from the general population in four provinces with diverse environments. The child is followed to age 5 years, with prospective characterization of diverse exposures during this critical period. Key exposure domains include indoor and outdoor air pollutants, inhalation, ingestion and dermal uptake of chemicals, mold, dampness, biological allergens, pets and pests, housing structure, and living behavior, together with infections, nutrition, psychosocial environment, and medications. Assessments of early life exposures are focused on those linked to inflammatory responses driven by the acquired and innate immune systems. Mothers complete extensive environmental questionnaires including time-activity behavior at recruitment and when the child is 3, 6, 12, 24, 30, 36, 48, and 60 months old. House dust collected during a thorough home assessment at 3–4 months, and biological specimens obtained for multiple exposure-related measurements, are archived for analyses. Geo-locations of homes and daycares and land-use regression for estimating traffic-related air pollution complement time-activity-behavior data to provide comprehensive individual exposure profiles. Several analytical frameworks are proposed to address the many interacting exposure variables and potential issues of co-linearity in this complex data set.

A new exposure metric for traffic-related air pollution? An analysis of determinants of hopanes in settled indoor house dust

BackgroundExposure to traffic-related air pollution (TRAP) can adversely impact health but epidemiologic studies are limited in their abilities to assess long-term exposures and incorporate variability in indoor pollutant infiltration.MethodsIn order to examine settled house dust levels of hopanes, engine lubricating oil byproducts found in vehicle exhaust, as a novel TRAP exposure measure, dust samples were collected from 171 homes in five Canadian cities and analyzed by gas chromatography–mass spectrometry. To evaluate source contributions, the relative abundance of the highest concentration hopane monomer in house dust was compared to that in outdoor air. Geographic variables related to TRAP emissions and outdoor NO2 concentrations from city-specific TRAP land use regression (LUR) models were calculated at each georeferenced residence location and assessed as predictors of variability in dust hopanes.ResultsHopanes relative abundance in house dust and ambient air were significantly correlated (Pearson’s r=0.48, p<0.05), suggesting that dust hopanes likely result from traffic emissions. The proportion of variance in dust hopanes concentrations explained by LUR NO2 was less than 10% in Vancouver, Winnipeg and Toronto while the correlations in Edmonton and Windsor explained 20 to 40% of the variance. Modeling with household factors such as air conditioning and shoe removal along with geographic predictors related to TRAP generally increased the proportion of explained variability (10-80%) in measured indoor hopanes dust levels.ConclusionsHopanes can consistently be detected in house dust and may be a useful tracer of TRAP exposure if determinants of their spatiotemporal variability are well-characterized, and when home-specific factors are considered.

Difficult Family Relationships, Residential Greenspace, and Childhood Asthma

Children with asthma who both have positive family relationships and live in high greenspace areas have the best asthma outcomes. BACKGROUND AND OBJECTIVES: Both the social environment and the physical environment are increasingly recognized as important to childhood diseases such as asthma. This study tested a novel hypothesis: that living in areas high in greenspace may help buffer the effects of difficult family relationships for children with asthma. METHODS: A total of 150 children (ages 9–17), physician-diagnosed with asthma, participated in this study. To assess difficulties in parent-child relationships, parents and children completed measures of harsh/inconsistent parenting and parental hostility. Residential greenspace was calculated by using satellite-derived Normalized Difference Vegetation Index with a buffer of 250 m around the residential address. Outcomes included both clinical and biological measures: asthma control and functional limitations, as well as airway inflammation (fractional concentration of exhaled nitric oxide) and glucocorticoid receptor expression in T-helper cells. RESULTS: After controlling for potential confounding variables, including family income, child demographics, and child medical variables, few main effects were found. However, interactions between residential greenspace and difficult family relationships were found for asthma control (P = .02), asthma functional limitations (P = .04), airway inflammation (P = .007), and the abundance of glucocorticoid receptor in T-helper cells (P = .05). These interactions were all in a direction such that as the quality of parent-child relationships improved, greenspace became more strongly associated with better asthma outcomes. CONCLUSIONS: These findings suggest synergistic effects of positive environments across the physical and social domains. Children with asthma appear to benefit the most when they both live in high greenspace areas and have positive family relationships.