Within city spatiotemporal variation of pollen concentration in the city of Toronto, Canada.

BACKGROUND: The exacerbation of asthma and respiratory allergies has been associated with exposure to aeroallergens such as pollen. Within an urban area, tree cover, level of urbanization, atmospheric conditions, and the number of source plants can influence spatiotemporal variations in outdoor pollen concentrations. OBJECTIVE: We analyze weekly pollen measurements made between March and October 2018 over 17 sites in Toronto, Canada. The main goals are: to estimate the concentration of different types of pollen across the season; estimate the association, if any, between pollen concentration and environmental variables, and provide a spatiotemporal surface of concentration of different types of pollen across the weeks in the studied period. METHODS: We propose an extension of the land-use regression model to account for the temporal variation of pollen levels and the high number of measurements equal to zero. Inference is performed under the Bayesian framework, and uncertainty of predicted values is naturally obtained through the posterior predictive distribution. RESULTS: Tree pollen was positively associated with commercial areas and tree cover, and negatively associated with grass cover. Both grass and weed pollen were positively associated with industrial areas and TC brightness and negatively associated with the northing coordinate. The total pollen was associated with a combination of these environmental factors. Predicted surfaces of pollen concentration are shown at some sampled weeks for all pollen types. SIGNIFICANCE: The predicted surfaces obtained here can help future epidemiological studies to find possible associations between pollen levels and some health outcome like respiratory allergies at different locations within the study area.

Maternal Exposure to Aeroallergens and the Risk of Early Delivery.

BACKGROUND: Daily changes in aeroallergens during pregnancy could trigger early labor, but few investigations have evaluated this issue. This study aimed to investigate the association between exposure to aeroallergens during the week preceding birth and the risk of early delivery among preterm and term pregnancies. METHODS: We identified data on 225,234 singleton births that occurred in six large cities in the province of Ontario, Canada, from 2004 to 2011 (April to October) from a birth registry. We obtained daily counts of pollen grains and fungal spores from fixed-site monitoring stations in each city and assigned them to pregnancy period of each birth. Associations between exposure to aeroallergens in the preceding week and risk of delivery among preterm (<37 gestational weeks), early-term (37-38 weeks), and full-term (≥39 weeks) pregnancies were evaluated with Cox regression models, adjusting for maternal characteristics, meteorologic parameters, and air pollution concentrations, and pooled across the six cities. RESULTS: The risk of delivery increased by 3% per interquartile range width (IQRw = 22.1 grains/m) increase in weed pollen the day before birth among early-term (hazard ratio [HR] = 1.03; 95% confidence interval [CI]: 1.01, 1.05) and full-term pregnancies (HR = 1.03; 95% CI: 1.01, 1.04). Exposure to fungal spores cumulated over 0 to 2 lagged days was associated with increased risk of delivery among full-term pregnancies only (HR = 1.07; 95% CI: 1.01, 1.12). We observed no associations among preterm deliveries. CONCLUSIONS: Increasing concentrations of ambient weed pollen and fungal spores may be associated with earlier delivery among term births.

Airborne Pollen Concentrations and Emergency Room Visits for Myocardial Infarction: A Multicity Case-Crossover Study in Ontario, Canada.

Few studies have examined the acute cardiovascular effects of airborne allergens. We conducted a case-crossover study to evaluate the relationship between airborne allergen concentrations and emergency room visits for myocardial infarction (MI) in Ontario, Canada. In total, 17,960 cases of MI were identified between the months of April and October during the years 2004-2011. Daily mean aeroallergen concentrations (pollen and mold spores) were assigned to case and control periods using central-site monitors in each city along with daily measurements of meteorological data and air pollution (nitrogen dioxide and ozone). Odds ratios and their 95% confidence intervals were estimated using conditional logistic regression models adjusting for time-varying covariates. Risk of MI was 5.5% higher (95% confidence interval (CI): 3.4, 7.6) on days in the highest tertile of total pollen concentrations compared with days in the lowest tertile, and a significant concentration-response trend was observed (P < 0.001). Higher MI risk was limited to same-day pollen concentrations, with the largest risks being observed during May (odds ratio = 1.16, 95% CI: 1.00, 1.35) and June (odds ratio = 1.10, 95% CI: 1.00, 1.22), when tree and grass pollen are most common. Mold spore concentrations were not associated with MI. Our findings suggest that airborne pollen might represent a previously unidentified environmental risk factor for myocardial infarction.