Prenatal and early life exposure to air pollution and the risk of severe lower respiratory tract infections during early childhood: the Espoo Cohort Study.

BACKGROUND: There is inconsistent evidence of the effects of exposure to ambient air pollution on the occurrence of lower respiratory tract infections (LRTIs) in early childhood. We assessed the effects of individual-level prenatal and early life exposure to air pollutants on the risk of LRTIs in early life. METHODS: We studied 2568 members of the population-based Espoo Cohort Study born between 1984 and 1990 and living in 1991 in the City of Espoo, Finland. Exposure assessment was based on dispersion modelling and land-use regression for lifetime residential addresses. The outcome was a LRTI based on data from hospital registers. We applied Poisson regression to estimate the incidence rate ratio (IRR) of LTRIs, contrasting incidence rates in the exposure quartiles to the incidence rates in the first quartile. We used weighted quantile sum (WQS) regression to estimate the joint effect of the studied air pollutants. RESULTS: The risk of LRTIs during the first 2 years of life was significantly related to exposure to individual and multiple air pollutants, measured with the Multipollutant Index (MPI), including primarily sulphur dioxide (SO2), particulate matter with a dry diameter of up to 2.5 µm (PM2.5) and nitrogen dioxide (NO2) exposures in the first year of life, with an adjusted IRR of 1.72 per unit increase in MPI (95% CI 1.20 to 2.47). LRTIs were not related to prenatal exposure. CONCLUSIONS: We provide evidence that ambient air pollution exposure during the first year of life increases the risk of LRTIs during the first 2 years of life. SO2, PM2.5 and NO2 were found to contribute the highest weights on health effects.

Residential greenness during pregnancy and early life and development of asthma up to 27 years of age: The Espoo Cohort Study.

Previous studies have suggested that living close to green spaces has protective health effects, but potential effects on asthma are contradictory. We investigated the association between the amount of greenness in the residential area during pregnancy and early life and development of asthma in the first 27 years of life. The study population included all 2568 members of the Espoo Cohort Study, Finland. We calculated individual-level exposure to green space measured as cumulative Normalized Difference Vegetation Index (cumNDVI in unit-months) within 300 m of the participant's residence during pregnancy and the first two years of life in both spring and summer seasons. The onset of asthma was assessed using information from the baseline and follow-up surveys. Exposure to residential greenness in the spring season during pregnancy was associated with an increased risk of asthma up to 6 years of age, with an adjusted hazard ratio (aHR) of 3.72 (95% confidence interval (CI): 1.11, 12.47) per 1 unit increase in cumNDVI. Increased greenness in the summer during pregnancy associated with asthma up to 6 years, with an aHR of 1.41 (95% CI: 0.85, 2.32). The effect was found to be related to increased greenness particularly during the third trimester of pregnancy, with an aHR of 2.37 (95% CI: 1.36, 4.14) per 1 unit increase of cumNDVI. These associations were weaker at the ages of 12 and 27 years. No association was found between NDVI in the first two years of life and the development of asthma. Our findings provide novel evidence that exposure to greenness during pregnancy increases the risk of developing asthma. The adverse effects were strongest for the prenatal greenness in the spring season and in the third trimester of pregnancy. Both the season and trimester of exposure to greenness are critical in the development of asthma.

Effect of cold winters on the risk of new asthma: a case-crossover study in Finland.

BACKGROUND: Cold weather increases respiratory symptoms and provokes exacerbations of asthma, but there are no previous studies on its role in the aetiology of asthma. OBJECTIVE: We tested the hypothesis that a cold winter increases the risk of developing asthma during the following 1 to 2 years. METHODS: We conducted a case-crossover study of 315 newly diagnosed cases of asthma from the population-based Espoo Cohort Study from birth to the age of 27 years. The hazard period constituted 3 winter months preceding the onset of asthma and bidirectional reference periods of 1 year before hazard period and 1 year after onset of asthma. Exposure constituted average ambient temperature during the winter months of December, January and February. The outcome of interest was new doctor-diagnosed asthma. The measure of effect was OR of asthma estimated by conditional logistic regression analysis. RESULTS: The average winter temperature for the study period from winter 1983 to 2010 was -4.4°C (range -10.7 to 0.4). A 1°C decrease in the average winter temperature predicted a 7% increase in the risk of new asthma (OR=1.07, 95% CI 1.02 to 1.13). A cold winter with an average temperature below the climate normal value (-4.5°C; period 1981-2010) increased the risk of new asthma by 41% during the following year (OR: 1.41; 95% CI 1.04 to 1.90). CONCLUSIONS: This case-crossover study provides original evidence that a cold winter with below normal average temperatures increases the risk of developing new asthma during the following 1 to 2 years.

Occupation and occurrence of respiratory infections among adults with newly diagnosed asthma.

BACKGROUND: Work environments are potential areas for spreading respiratory infections. We hypothesized that certain occupations increase susceptibility to respiratory infections among adults with asthma. Our objective was to compare the occurrence of respiratory infections among different occupations in adults with newly diagnosed asthma. METHODS: We analysed a study population of 492 working-age adults with newly diagnosed asthma who were living in the geographically defined Pirkanmaa Area in Southern Finland during a population-based Finnish Environment and Asthma Study (FEAS). The determinant of interest was occupation at the time of diagnosis of asthma. We assessed potential relations between occupation and occurrence of both upper and lower respiratory tract infections during the past 12 months. The measures of effect were incidence rate ratio (IRR) and risk ratio (RR) adjusted for age, gender, and smoking habits. Professionals, clerks, and administrative personnel formed the reference group. RESULTS: The mean number of common colds in the study population was 1.85 (95% CI 1.70, 2.00) infections in the last 12 months. The following occupational groups showed increased risk of common colds: forestry and related workers (aIRR 2.20, 95% CI 1.15-4.23) and construction and mining (aIRR 1.67, 95% CI 1.14-2.44). The risk of lower respiratory tract infections was increased in the following groups: glass, ceramic, and mineral workers (aRR 3.82, 95% CI 2.54-5.74), fur and leather workers (aRR 2.06, 95% CI 1.01-4.20) and metal workers (aRR 1.80, 95% CI 1.04-3.10). CONCLUSIONS: We provide evidence that the occurrence of respiratory infections is related to certain occupations.

Effects of occupational exposures on respiratory health in steel factory workers.

Background: The steel factory work environment contains various chemical exposures that can affect indoor air quality and have impact on respiratory health of the workers. Aims: The objective of this study was to assess potential effects of occupational exposures in steel factory workers in Iran on the respiratory symptoms, occurrence and the lung function levels. Method: This was a cross-sectional study of 133 men working in a steel factory forming the exposed group and 133 male office workers forming the reference group from a steel company in Iran. The participants filled in a questionnaire and underwent spirometry. Work history was used both as dichotomous (exposed/reference) and a quantitative measure of exposure, the latter measured as duration of exposure in the specified work (in years) for the exposed group and zero for the reference group. Results: Multiple linear regression and Poisson regression were used to adjust for confounding. In Poisson regression analyses, an increased prevalence ratio (PR) of all respiratory symptoms was observed in the exposed group. Lung function parameters were significantly reduced in the exposed group (p < 0.001). There was a dose-response relation between duration of occupational exposures and reduction in the predicted value of FEV1/FVC level (0.177, 95% CI -0.198 to -0.156) in all models. Conclusion: The results of these analyses showed that occupational exposures in steel factory work increase the prevalence of respiratory symptoms and reduce lung function. Safety training and workplace conditions were found to need improvement. In addition, use of proper personal protective equipment is recommended.

Subtypes of Adult-Onset Asthma at the Time of Diagnosis: A Latent Class Analysis.

INTRODUCTION: Only a few previous studies have investigated the subtypes of adult-onset asthma. No previous study has assessed whether these subtypes are different between men and women, or whether these subtypes have different risk factors. METHODS: We applied latent class analyses to the Finnish Environment and Asthma Study population, including 520 new cases of adult-onset asthma. We formed subtypes separately between women and men and analyzed the following determinants as potential predictors for these subtypes: age, body mass index, smoking, and parental asthma. RESULTS: Among women, the subtypes identified were: 1. Moderate asthma, 2. Cough-variant asthma, 3. Eosinophilic asthma, 4. Allergic asthma, and 5. Difficult asthma. Among men, the subtypes were: 1. Mild asthma, 2. Moderate asthma, 3. Allergic asthma, and 4. Difficult asthma. Three of the subtypes were similar among women and men: Moderate, Allergic, and Difficult asthma. In addition, women had two distinct subtypes: Cough-variant asthma, and Eosinophilic asthma. These subtypes had different risk factor profiles, e.g., heredity was important for Eosinophilic and Allergic asthma (RR for Both parents having asthma in Eosinophilic 3.55 (1.09 to 11.62)). Furthermore, smoking increased the risk of Moderate asthma among women (RR for former smoking 2.21 (1.19 to 4.11)) and Difficult asthma among men but had little influence on Allergic or Cough-variant asthma. Conclusion: This is an original investigation of the subtypes of adult-onset asthma identified at the time of diagnosis. These subtypes differ between women and men, and these subtypes have different risk factor profiles. These findings have both clinical and public health importance for the etiology, prognosis, and treatment of adult-onset asthma.

Asthma and Respiratory Infections From Birth to Young Adulthood.

We applied data from a population-based prospective study, the Espoo Cohort Study (n = 2,568), to identify the potential susceptibility of persons with asthma to respiratory tract infections (RTIs). Information on the occurrence of asthma and both upper respiratory tract infections (URTIs) and lower respiratory tract infections (LRTIs) was collected with a questionnaire at baseline and at the 6-year and 20-year follow-up studies, and from the Finnish national health registries. We estimated age- and sex-specific incidence rate differences (IRDs) and incidence rate ratios (IRRs) by applying negative binomial regression. Meta-regression was used to summarize the age-specific IRRs from childhood to 27 years of age. Individuals with asthma at any age during the follow-up period had increased risks of both URTIs (adjusted IRD = 72.6 (95% confidence interval (CI): 50.6, 94.7) per 100 person-years; adjusted IRR = 1.27 (95% CI: 1.20, 1.35)) and LRTIs (adjusted IRD = 25.5 (95% CI: 17.9, 33.1); adjusted IRR = 2.87 (95% CI: 2.33, 3.53)) from childhood to young adulthood. In young adulthood, the association between asthma and URTIs was stronger in women than in men, while such an association was not detected for LRTIs. This analysis provides strong evidence that persons with asthma experience more RTIs from preschool age to young adulthood than do those without asthma. Thus, they constitute a susceptible population for RTIs. Women with asthma are at especially high risk.

Residential Exposure to Dampness Is Related to Reduced Level of Asthma Control among Adults.

We assessed potential relations between indicators of indoor dampness and mold exposures at home and the level of asthma control among adults. The present population-based cross-sectional study, the Northern Finnish Asthma Study (NoFAS), included 1995 adult subjects with bronchial asthma who replied to study questionnaires (response rate: 40.4%). The Asthma Control Test (ACT) was used as the measure of asthma control. We calculated the mean difference in ACT score (ACTdifference) and the risk ratio (RR) of poor asthma control (ACT ≤ 19) for the exposure and reference groups and applied Poisson regression to adjust for potential confounding. Exposure to indoor dampness at home was related to a significantly reduced level of asthma control (ACTdifference: -0.83, 95% CI: -1.60 to -0.07), especially among men (ACTdifference: -2.68, 95% CI: -4.00 to -1.37). Water damage (aRR = 1.29, 95% CI: 1.01, 1.65) and indoor dampness, especially among men (aRR = 1.92, 95% CI: 1.15, 3.20), increased the risk of poor asthma control. We provide evidence that exposure to indoor dampness at home reduces asthma control among adults, especially in men. Indoor visible mold and mold odor were not significantly related to asthma control. Advice on how to prevent indoor dampness at home should be an important part of asthma management.

Do hospital workers experience a higher risk of respiratory symptoms and loss of lung function?

BACKGROUND: Hospital work environment contains various biological and chemical exposures that can affect indoor air quality and have impact on respiratory health of the staff. The objective of this study was to investigate potential effects of occupational exposures on the risk of respiratory symptoms and lung function in hospital work, and to evaluate potential interaction between smoking and occupational exposures. METHODS: We conducted a cross-sectional study of 228 staff members in a hospital and 228 employees of an office building as the reference group in Shiraz, Iran. All subjects completed a standardized ATS respiratory questionnaire and performed a spirometry test. RESULTS: In Poisson regression, the adjusted prevalence ratios (aPR) among the hospital staff were elevated for cough (aPR 1.90, 95% CI 1.15, 3.16), phlegm production (aPR 3.21, 95% CI 1.63, 6.32), productive cough (aPR 2.83, 95% CI 1.48, 5.43), wheezing (aPR 3.18, 95% CI 1.04, 9.66), shortness of breath (aPR 1.40, 95% CI 0.93, 2.12), and chest tightness (aPR 1.73, 95% CI 0.73, 4.12). Particularly laboratory personnel experienced increased risks of most symptoms. In linear regression adjusting for confounding, there were no significant differences in lung function between the hospital and office workers. There was an indication of synergism between hospital exposures and current smoking on FEV1/FVC% (interaction term ß = - 5.37, 95% CI - 10.27, - 0.47). CONCLUSIONS: We present significant relations between hospital work, especially in laboratories, and increased risks of respiratory symptoms. Smoking appears to enhance these effects considerably. Our findings suggest that policymakers should implement evidence-based measures to prevent these occupational exposures.

Subtypes of Asthma and Cold Weather-Related Respiratory Symptoms.

(1) Poor asthma control increases the occurrence of cold weather-related symptoms among adult asthmatics. We assessed whether the subtype of asthma, taking into account the severity of the asthma, plays a role in these symptoms. (2) We conducted a population-based cross-sectional study of 1995 adult asthmatics (response rate 40.4%) living in northern Finland using a questionnaire that asked about cold weather-related respiratory symptoms including (1) shortness of breath, (2) prolonged cough, (3) wheezing, (4) phlegm production, and (5) chest pain, as well as questions related to the subtype of asthma. For women, the subtypes identified using latent class analysis were: (1) Controlled, mild asthma, (2) Partly controlled, moderate asthma, (3) Uncontrolled, unknown severity, and (4) Uncontrolled, severe asthma, and for men: (1) Controlled, mild asthma, (2) Uncontrolled, unknown severity, and (3) Partly controlled, severe asthma. (3) According to the subtypes of asthma, more severe and more poorly controlled asthma were related to the increased prevalence of cold weather-related respiratory symptoms when compared with those with mild, controlled asthma. This trend was especially clear for wheezing and chest pain. For example, in men, the adjusted prevalence ratio of wheezing was 1.55 (95% CI 1.09-2.19) in uncontrolled asthma with unknown severity and 1.84 (95% CI 1.26-2.71) in partly controlled severe asthma compared with controlled, mild asthma. (4) Our study provides evidence for the influence of subtypes of asthma on experiencing cold weather-related respiratory symptoms. Both women and men reported more cold weather-related symptoms when their asthma was more severe and uncontrolled compared with those who had mild and well-controlled asthma.

Worldwide prevalence of rhinitis in adults: A review of definitions and temporal evolution.

INTRODUCTION: Although rhinitis is among the most common diseases worldwide, rhinitis prevalence in the general adult population is unclear and definitions differ widely. OBJECTIVE: To summarize the literature on rhinitis prevalence in the general adult population and to assess: (1) the prevalence according to different rhinitis definitions overall and in different regions of the world, and (2) the evolution of rhinitis prevalence over time. METHODS: We conducted an extensive literature review of publications including rhinitis prevalence using Pubmed and Scopus databases up to October 2020. We classified the definitions into three categories: unspecified rhinitis, allergic rhinitis (AR), and nonallergic rhinitis (NAR). RESULTS: Among 5878 articles screened, 184 articles were included, presenting 156 different definitions of rhinitis. Rhinitis prevalence ranged from 1% to 63%. The overall median prevalences of unspecified rhinitis, AR and NAR were 29.4%, 18.1% and 12.0%, and they varied according to the geographical location. Rhinitis prevalence tended to increase over time. CONCLUSIONS: This review highlights the great heterogeneity of the definitions. The majority of studies had focused on AR, while only a few epidemiological data exist on NAR. We found geographical variability in rhinitis prevalence. Most of studies reported an increase of rhinitis prevalence over the last decades.

Different effects of smoking on atopic and non-atopic adult-onset asthma.

BACKGROUND: Both tobacco smoking and atopy increase the risk of adult-onset asthma. We studied if there are differences in the effects of smoking on the risks of atopic and non-atopic adult-onset asthma, and if gender modifies these effects. METHODS: The Finnish Environment and Asthma Study (FEAS) includes 521 incident cases of adult-onset asthma and 932 population-based controls, aged 21 to 63 years, recruited from a geographically defined area of Pirkanmaa, South Finland. Asthma was defined based on symptoms and lung function measurements, atopy by IgE antibodies to common aeroallergens and smoking by the study questionnaire. RESULTS: Altogether 212 cases were atopic, and 251 cases were non-atopic. Regular smoking increased the risk of atopic asthma (adjusted OR 1.24, 95% CI 0.83-1.85), this effect was seen in women (aOR 1.77, 1.06-2.95) but not in men (aOR 0.75, 0.39-1.45). Among regular smokers, the amount smoked was lowest among women with atopic asthma. Recent quitting of smoking was related to increased risk of both atopic (aOR 4.91, 2.26-10.65) and non-atopic (aOR 4.37, 1.87-10.21) asthma. Having quitted smoking over a year ago was related to increased risk of non-atopic asthma (aOR 1.57, 1.08-2.28), mainly in men (aOR 2.03, 1.06-3.88). CONCLUSIONS: In women, rather small amounts of regular smoking increase the risk of atopic asthma. However, for non-atopic asthma, the smoking induced risk continues for longer after quitting, especially in men. In conclusion, the effects of smoking on the risks of atopic and non-atopic asthma differ, and gender modifies these effects.

Occupation and subcategories of asthma: a population-based incident case-control study.

BACKGROUND: We hypothesised that occupational exposures differently affect subtypes of adult-onset asthma. OBJECTIVE: We investigated potential relations between occupation and three subtypes of adult asthma, namely atopic asthma, non-atopic asthma and asthma-COPD overlap syndrome (ACOS). METHODS: This is a population-based case-control study of incident asthma among working-age adults living in Pirkanmaa Hospital District in Southern Finland. The determinant of interest was occupation at the time of diagnosis of asthma or the job that the subject had quit due to respiratory symptoms. Asthma was divided into three mutually exclusive subtypes on the basis of any positive IgE antibody (atopic and non-atopic asthma) and presence of persistent airways obstruction in spirometry (ACOS). We applied unconditional logistic regression analysis to estimate adjusted OR (aOR), taking into account gender, age and smoking. RESULTS: The following occupational groups showed significantly increased risk of atopic asthma: chemical industry workers (aOR 15.76, 95% CI 2.64 to 94.12), bakers and food processors (aOR 4.69, 95% CI 1.18 to 18.69), waiters (aOR 4.67, 95% CI 1.40 to 15.56) and those unemployed (aOR 3.06, 95% CI 1.52 to 6.17). The following occupations showed clearly increased risk of non-atopic asthma: metal workers (aOR 8.37, 95% CI 3.77 to 18.59) and farmers and other agricultural workers (aOR 2.36, 95% CI 1.10 to 5.06). Some occupational groups showed statistically significantly increased OR of ACOS: electrical and electronic production workers (aOR 30.6, 95% CI 6.10 to 153.35), fur and leather workers (aOR 16.41, 95% CI 1.25 to 215.85) and those retired (aOR 5.55, 95% CI 1.63 to 18.97). CONCLUSIONS: Our results show that different occupations are associated with different subtypes of adult-onset asthma.

Airborne pollen concentrations and daily mortality from respiratory and cardiovascular causes.

We conducted a time-series analysis of the relations between daily levels of allergenic pollen and mortality in the Helsinki Metropolitan Area with 153 378 deaths; 9742 from respiratory and 57 402 from cardiovascular causes. Daily (average) pollen counts of alder, birch, mugwort and grass were measured. In quasi-Poisson regression analysis, abundant alder pollen increased the risk of non-accidental deaths with an adjusted cumulative mortality rate ratio (acMRR) of 1.10 (95% CI 1.01-1.19) and of deaths from respiratory-diseases with acMRR of 1.78 (95% CI 1.19-2.65). Abundant mugwort pollen increased cardiovascular mortality (1.41, 1.02-1.95). These findings identify an important global public health problem.

Occurrence of respiratory symptoms and lung function deficits among fruit and vegetable market workers.

OBJECTIVE: The objective of this study was to investigate the potential effects of occupational exposures among fruit and vegetable market workers on the occurrence of respiratory symptoms and on the level of lung function parameters. METHODS: We conducted a cross-sectional study of 140 men working as fruit and vegetable market workers (response rate 100%) and a reference group of 77 male office workers as the reference group (response rate 55%) from Shiraz, Iran. The outcomes of interest included occurrence of respiratory symptoms assessed by a standard respiratory questionnaire and lung function assessed by spirometry. RESULTS: In Poisson regression analyses, the exposed group showed increased prevalence ratio (PR) of wheezing (adjusted PR 5.32, 95% CI 1.40 to 20.26), after controlling for confounding. Cough (PR 3.30, 95% CI 1.16 to 9.40) and wheezing (PR 9.40, 95% CI 2.28 to 38.64) showed increased PRs among vegetable distributors. Forced expiratory volume in 1 s (FEV1) and FEV1/forced vital capacity were significantly decreased among exposed workers after controlling for confounders. The absolute value of FEV1 level was reduced significantly among fruit and vegetable carters (-0.99, 95% CI -1.68 to -0.32) and vegetable (-0.51, 95% CI -0.93 to -0.10) and fruit (-0.51, 95% CI -0.86 to -0.15) distributors in comparison with the reference group in the adjusted full model. CONCLUSIONS: This study provides evidence that fruit and vegetable market workers are at an increased risk of respiratory symptoms and reduced lung function. Workplace conditions and safety training clearly need improvement, and there is a likely role for proper use of personal protective equipment.

Occupational exposures and respiratory symptoms and lung function among hairdressers in Iran: a cross-sectional study.

OBJECTIVE: Exposures at hairdressers' work have been reported to lead to an increased risk of several health outcomes. The present study aimed to investigate the relations between occupational exposures and respiratory symptoms and lung function among hairdressers in Iran. METHODS: We conducted a cross-sectional study to compare potential respiratory effects among 140 women working as hairdressers to such effects among 140 women working as office workers (administrative personnel). Both groups worked in Shiraz, Iran. Respiratory symptoms were assessed by a standard respiratory questionnaire. The questionnaire also inquired about substances used and workspace conditions, including ventilation type. Lung function levels were measured by spirometry. RESULTS: Respiratory symptoms, including cough, wheezing, shortness of breath, and chest tightness were significantly more frequent in hairdressers compared to the reference group (p < 0.05). After controlling for potential confounders, hairdressers had a prevalence ratio (PR) of 2.18 (95% CI 1.26-3.77) for cough, 9.59 (95% CI 1.004-91.73) for wheezing, 2.06 (95% CI 1.25-3.39) for shortness of breath, and 3.31 (95% CI 1.84-5.97) for chest tightness compared to the reference group. Lung function parameters (including VC, FVC, and FEV1) were significantly reduced in hairdressers (p < 0.001). Absence of air conditioning predicted greater reduction in lung function (p < 0.05) in the exposed. Decrease in FVC with normal FEV1/FVC in the exposed group suggested existence of restrictive lung function. CONCLUSIONS: This study provides evidence of increased prevalence of respiratory symptoms and restrictive lung function impairment among hairdressers in Iran.

The effect of sampling height on grass pollen concentrations in different urban environments in the Helsinki Metropolitan Area, Finland.

INTRODUCTION: It is important to study potential differences in pollen concentrations between sampling heights because of diverse outdoor and indoor activity of humans (exposure) at different height levels in urban environments. Previous studies have investigated the effect of height on pollen concentrations based on just one or a few sampling points. We studied the effect of sampling height on grass pollen concentrations in several urban environments with different levels of urbanity. METHODS: This study was conducted in the Helsinki Metropolitan Area, Finland, in 2013 during the pollen season of grasses. Pollen grains were monitored in eight different points in the morning and afternoon. Rotorod-type samplers were attached on sampling poles at the heights of 1.5 meters and 4 meters. RESULTS: Grass pollen concentrations were on average higher at the height of 1.5 meters (Helsinki mean 5.24 grains / m3; Espoo mean 75.71 grains / m3) compared to the height of 4 meters (Helsinki mean 3.84 grains / m3; Espoo mean 37.42 grains / m3) with a difference of 1.40 grains / m3 (95% CI -0.21 to 3.01) in Helsinki, and 38.29 grains / m3 (7.52 to 69.07) in Espoo, although not always statistically significant. This was detected both in the morning and in the afternoon. However, in the most urban sites the levels were lower at 1.5 meters compared to 4 meters, whereas in the least urban sites the concentrations were higher at 1.5 meters. In linear regression models with interaction terms, the modifying effect of urbanity on concentration-height relation was statistically significant in both cities. The effect of urbanity on pollen concentrations at both heights was stronger in less urban Espoo. CONCLUSIONS: The present study provides evidence that height affects the abundance and distribution of grass pollen in urban environments, but this effect depends on the level of urbanity.

Short-term prenatal exposure to ambient air pollution and risk of preterm birth - A population-based cohort study in Finland.

BACKGROUND: Previous studies have provided evidence that prenatal exposure to low-level air pollution increases the risk of preterm birth (PTB), but the findings of the effects of short-term exposure have been inconclusive. Moreover, there is little knowledge on potential synergistic effects of different combinations of air pollutants. OBJECTIVES: To assess independent and joint effects of prenatal exposure to air pollutants during the week prior to the delivery on the risk of PTB. METHODS: The study population included 2568 members of the Espoo Cohort Study, living in the City of Espoo, Finland, born between 1984 and 1990. We assessed individual-level prenatal exposure to ambient air pollutants of interest based on maternal residential addresses, while taking into account their residential mobility. We used both regional-to-city-scale dispersion modelling and land-use regression-based method to estimates the pollutant concentrations. We contrasted the risk of PTB in the highest quartile (Q4) of exposure to the lower exposure quartiles (Q1-Q3) during the specific periods of pregnancy. We applied Poisson regression analysis to estimate the adjusted risk ratios (RRs) with their 95% confidence intervals (CI), adjusting for season of birth, maternal age, sex of the baby, family's socioeconomic status, maternal smoking, and exposure to environmental tobacco smoke during pregnancy, single parenthood, and exposure to other air pollutants (this in multi-pollutant models). RESULTS: The risk of PTB was related to exposures to PM2.5, PM10 and NO2 during the week prior to the delivery with adjusted RRs of 1.67 (95%CI: 1.14, 2.46), 1.60 (95% CI: 1.09, 2.34) and 1.65 (95% CI: 1.14, 2.37), from three-pollutant models respectively. There were no significant joint effects for these different air pollutants (during the week prior to the delivery). CONCLUSION: Our results provide evidence that exposure to fairly low-level air pollution may trigger PTB, but synergistic effects of different pollutants are not likely.