Beyond the Runway: Respiratory health effects of ultrafine particles from aviation in children.

Aviation has been shown to cause high particle number concentrations (PNC) in areas surrounding major airports. Particle size distribution and composition differ from motorized traffic. The objective was to study short-term effects of aviation-related UFP on respiratory health in children. In 2017-2018 a study was conducted in a school panel of 7-11 year old children (n = 161) living North and South of Schiphol Airport. Weekly supervised spirometry and exhaled nitric oxide (eNO) measurements were executed. The school panel, and an additional group of asthmatic children (n = 19), performed daily spirometry tests at home and recorded respiratory symptoms. Hourly concentrations of various size fractions of PNC and black carbon (BC) were measured at three school yards. Concentrations of aviation-related particles were estimated at the residential addresses using a dispersion model. Linear and logistic mixed models were used to investigate associations between daily air pollutant concentrations and respiratory health. PNC20, a proxy for aviation-related UFP, was virtually uncorrelated with BC and PNC50-100 (reflecting primarily motorized traffic), supporting the feasibility of separating PNC from aviation and other combustion sources. No consistent associations were found between various pollutants and supervised spirometry and eNO. Major air pollutants were significantly associated with an increase in various respiratory symptoms. Odds Ratios for previous day PNC20 per 3,598pt/cm3 were 1.13 (95%CI 1.02; 1.24) for bronchodilator use and 1.14 (95%CI 1.03; 1.26) for wheeze. Modelled aviation-related UFP at the residential addresses was also positively associated with these symptoms, corroborating the PNC20 findings. PNC20 was not associated with daily lung function, but PNC50-100 and BC were negatively associated with FEV1. PNC of different sizes indicative of aviation and other combustion sources were independently associated with an increase of respiratory symptoms and bronchodilator use in children living near a major airport. No consistent associations between aviation-related UFP with lung function was observed.

Short-term associations between barbecue fumes and respiratory health in young adults.

BACKGROUND: Epidemiological studies have associated biomass combustion with (respiratory) morbidity and mortality, primarily in indoor settings. Barbecuing results in high outdoor air pollution exposures, but the health effects are unknown. OBJECTIVE: The objective was to investigate short-term changes in respiratory health in healthy adults, associated with exposure to barbecue fumes. METHODS: 16 healthy, adult volunteers were exposed to barbecue smoke in outdoor air in rest during 1.5 h, using a repeated-measures design. Major air pollutants were monitored on-site, including particulate matter <2.5 µm (PM2.5), particle number concentrations (PNC) and black- and brown carbon. At the same place and time-of-day, subjects participated in a control session, during which they were not exposed to barbecue smoke. Before and immediately after all sessions lung function was measured. Before, immediately after, 4- and 18 h post-sessions nasal expression levels of interleukin (IL)-8, IL6 and Tumor Necrosis Factor alpha (TNFα) were determined in nasal swabs, using quantitative polymerase chain reaction. Associations between major air pollutants, lung function and inflammatory markers were assessed using mixed linear regression models. RESULTS: High PM2.5 levels and PNCs were observed during barbecue sessions, with averages ranging from 553 to 1062 µg/m3 and 109,000-463,000 pt/cm3, respectively. Average black- and brown carbon levels ranged between 4.1-13.0 and 5.0-16.2 µg/m3. A 1000 µg/m3 increase in PM2.5 was associated with 2.37 (0.97, 4.67) and 2.21 (0.98, 5.00) times higher expression of IL8, immediately- and 18 h after exposure. No associations were found between air pollutants and lung function, or the expression of IL6 or TNFα. DISCUSSION: Short-term exposure to air pollutants emitted from barbecuing was associated with a mild respiratory response in healthy young adults, including prolonged increase in nasal IL8 without a change in lung function and other measured inflammatory markers. The results might indicate prolonged respiratory inflammation, due to short-term exposure to barbecue fumes.

Green space, air pollution, traffic noise and saliva cortisol in children: The PIAMA study.

Green space, air pollution, and traffic noise exposure may be associated with stress levels in children. A flattened diurnal cortisol slope (the decline in cortisol concentrations from awakening to evening) is an indicator of chronic stress. We examined associations of green space, ambient air pollution, and traffic noise with the diurnal cortisol slope in children 12 years of age. METHODS: At age 12 years, 1,027 participants of the Dutch PIAMA birth cohort collected three saliva samples during 1 day. We estimated residential exposure to green space (i.e., the average Normalized Difference Vegetation Index [NDVI] and percentages of green space in circular buffers of 300 m and 3,000 m), air pollution, and traffic noise. Associations of these exposures with the diurnal cortisol slope (in nmol/L per hour) were assessed by multiple linear regression, adjusting for potential confounders. RESULTS: Higher average NDVI and total percentage of green space in a 3,000 m buffer were associated with a larger diurnal decrease in cortisol levels (adjusted difference [95% confidence interval] = -0.11 nmol/L/hr [-0.21, 0.00 nmol/L/hr] per interquartile range increase in the average NDVI; -0.13 nmol/L/hr [-0.26, 0.00 nmol/L/hr] per interquartile range increase in the total percentage of green space). These associations were largely driven by associations with the percentage of agricultural green space and by associations in children living in nonurban areas. We observed no relationships between air pollution or traffic noise and the diurnal cortisol slope. CONCLUSIONS: Residential exposure to green space in a buffer of 3,000 m may be associated with lower stress levels in children 12 years of age.

Acute respiratory effects of livestock-related air pollution in a panel of COPD patients.

Living close to livestock farms has been associated with increased symptoms in patients with chronic obstructive pulmonary disease (COPD). The causes of these effects are still poorly understood. This panel study attempts to assess the acute effects of livestock-related air pollution in patients with COPD living in an area with intensive livestock farming in the Netherlands. Between February 2015 and July 2016, 82 participants took spirometry measurements twice daily (morning and evening) during a 3-month period, resulting in 12,672 FEV1 and PEF records. Participants also kept a diary on respiratory symptoms as well as livestock-related odor annoyance. Daily average ammonia (NH3) (a proxy for livestock-related air pollution) and fine particulate matter (PM10) levels were collected from monitoring stations in the area. Lung function was analyzed as decrements of >10% and >20% from their median as well as absolute values. Self-reported odor annoyance was analyzed as a dichotomous variable. All analyses were done using generalized estimated equations. We adjusted for humidity, temperature, linear trend, and took multiple testing into account. We found an odds ratio of 1.14 95%CI [1.05; 1.25] for decrements >20% in morning FEV1 per interquartile range (12 µg/m3) increase in NH3 concentration (lag 2). Odor annoyance was negatively associated with evening PEF (-4.46 l/min 95%CI [-7.59; -1.33]). Sensitivity analyses showed a stronger effect in participants with worse baseline lung function. No associations with symptoms were found. Our results show acute effects of livestock-related air pollution on lung function in COPD patients living in close proximity to livestock farms.

Considerations in the use of different spirometers in epidemiological studies.

BACKGROUND: Spirometric lung function measurements have been proven to be excellent objective markers of respiratory morbidity. The use of different types of spirometers in epidemiological and clinical studies may present systematically different results affecting interpretation and implication of results. We aimed to explore considerations in the use of different spirometers in epidemiological studies by comparing forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) measurements between the Masterscreen pneumotachograph and EasyOne spirometers. We also provide a correction equation for correcting systematic differences using regression calibration. METHODS: Forty-nine volunteers had lung function measured on two different spirometers in random order with at least three attempts on each spirometer. Data were analysed using correlation plots, Bland and Altman plots and formal paired t-tests. We used regression calibration to provide a correction equation. RESULTS: The mean (SD) FEV1 and FVC was 3.78 (0.63) L and 4.78 (0.63) L for the Masterscreen pneumotachograph and 3.54 (0.60) L and 4.41 (0.83) L for the EasyOne spirometer. The mean FEV1 difference of 0.24 L and mean FVC difference of 0.37 L between the spirometers (corresponding to 6.3 and 8.4% difference, respectively) were statistically significant and consistent between younger (< 30 years) and older volunteers (> 30 years) and between males and females. Regression calibration indicated that an increase of 1 L in the EasyOne measurements corresponded to an average increase of 1.032 L in FEV1 and 1.005 L in FVC in the Masterscreen measurements. CONCLUSION: Use of different types of spirometers may result in significant systematic differences in lung function values. Epidemiological researchers need to be aware of these potential systematic differences and correct for them in analyses using methods such as regression calibration.

Air pollution exposure and lung function until age 16 years: the PIAMA birth cohort study.

Evidence for the effects of air pollution exposure on lung function growth into adolescence is scarce. We investigated associations of air pollution exposure with lung function and lung function growth until age 16.We conducted both longitudinal (n=915) and cross-sectional (n=721) analyses of associations of air pollution exposure with forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) growth from ages eight to 16 and FEV1 and FVC at age 16. We estimated residential concentrations of nitrogen dioxide (NO2), "soot" and particulate matter (PMx, where x is the 50% cut-off aerodynamic diameter in µm) with diameters of <2.5 µm (PM2.5), <10 µm (PM10) and 2.5-10 µm (PMcoarse) during the preschool, primary school and secondary school time windows by land use regression models. Associations with (growth in) FEV1 and FVC were analysed by linear (mixed effects) regression.Higher air pollution exposure was associated with reduced FEV1 growth (e.g. adjusted difference -0.26% (95% CI -0.49 to -0.03%) per interquartile range increase in secondary school PM2.5) and lower FEV1 (adjusted difference -2.36% (95% CI -3.76 to -0.94%)), but was not adversely associated with FVC. Associations with FEV1 were stronger in boys than girls and were not modified by asthma status.Higher air pollution exposure may lead to increased airway obstruction, but not reduced lung volume in adolescence.

Particulate matter composition and respiratory health: the PIAMA Birth Cohort study.

BACKGROUND: Ambient particulate matter (PM) exposure is associated with children's respiratory health. Little is known about the importance of different PM constituents. We investigated the effects of PM constituents on asthma, allergy, and lung function until the age of 11-12 years. METHODS: For 3,702 participants of a prospective birth cohort study, questionnaire-reported asthma and hay fever and measurements of allergic sensitization and lung function were linked with annual average concentrations of copper, iron, potassium, nickel, sulfur, silicon, vanadium, and zinc in particles with diameters of less than 2.5 and 10 µm (PM2.5 and PM10) at birth addresses and current addresses from land-use regression models. Exposure-health relations were analyzed by multiple (repeated measures) logistic and linear regressions. RESULTS: Asthma incidence and prevalence of asthma symptoms and rhinitis were positively associated with zinc in PM10 at the birth address (odds ratio [95% confidence interval] per interquartile range increase in exposure 1.13 [1.02, 1.25], 1.08 [1.00, 1.17], and 1.16 [1.04, 1.30], respectively). Moreover, asthma symptoms were positively associated with copper in PM10 at the current address (1.06 [1.00, 1.12]). Allergic sensitization was positively associated with copper and iron in PM10 at the birth address (relative risk [95% confidence interval] 1.07 [1.01, 1.14] and 1.10 [1.03, 1.18]) and current address. Forced expiratory volume in 1 second was negatively associated with copper and iron in PM2.5 (change [95% confidence interval] -2.1% [-1.1, -0.1%] and -1.0% [-2.0, -0.0%]) and FEF75-50 with copper in PM10 at the current address (-2.3% [-4.3, -0.3%]). CONCLUSION: PM constituents, in particular iron, copper, and zinc, reflecting poorly regulated non-tailpipe road traffic emissions, may increase the risk of asthma and allergy in schoolchildren.

Early exposure to bio-contaminants and asthma up to 10 years of age: results of the HITEA study.

Inverse associations have been found between exposure to bio-contaminants and asthma and allergies. The aim of this study was to prospectively assess whether early exposure to bio-contaminants in dust is associated with asthma and allergy later in childhood among children from (sub)-urban areas. In subsets of three European birth cohorts (PIAMA: n=553; INMA: n=481; and LISAplus: n=395), endotoxin, (1,3,)-ß-d-glucan and extracellular polysaccharide were measured in dust from living rooms shortly after birth. Current asthma at 6 years and 10 years of age and ever asthma up to 10 years of age were assessed by parental questionnaires. Specific IgE levels at 8 years (PIAMA) and 10 years (LISAplus) were available. Adjusted, cohort-specific logistic regression analyses were performed. Higher endotoxin concentrations were positively associated with current asthma at 6 years of age in PIAMA (adjusted OR 1.96, 95% CI 1.07-3.58), but were inversely related with ever asthma up to 10 years of age in INMA (adjusted OR 0.39, 95% CI 0.16-0.94). No associations with asthma were found for LISAplus. No associations were observed with atopic sensitisation in all cohorts. All associations with (1,3)-ß-d-glucan and extracellular polysaccharide were statistically nonsignificant. The suggested immunological mechanisms of early exposure to bio-contaminants with regards to asthma and allergy might be different for children growing up in (sub)-urban environments.

Traffic-related air pollution and noise and children's blood pressure: results from the PIAMA birth cohort study.

AIMS: Elevation of a child's blood pressure may cause possible health risks in later life. There is evidence for adverse effects of exposure to air pollution and noise on blood pressure in adults. Little is known about these associations in children. We investigated the associations of air pollution and noise exposure with blood pressure in 12-year-olds. METHODS: Blood pressure was measured at age 12 years in 1432 participants of the PIAMA birth cohort study. Annual average exposure to traffic-related air pollution [NO2, mass concentrations of particulate matter with diameters of less than 2.5 µm (PM2.5) and less than 10 µm (PM10), and PM2.5 absorbance] at the participants' home and school addresses at the time of blood pressure measurements was estimated by land-use regression models. Air pollution exposure on the days preceding blood pressure measurements was estimated from routine air monitoring data. Long-term noise exposure was assessed by linking addresses to modelled equivalent road traffic noise levels. Associations of exposures with blood pressure were analysed by linear regression. Effects are presented for an interquartile range increase in exposure. RESULTS: Long-term exposure to NO2 and PM2.5 absorbance were associated with increased diastolic blood pressure, in children who lived at the same address since birth [adjusted mean difference (95% confidence interval) [mmHg] 0.83 (0.06 to 1.61) and 0.75 (-0.08 to 1.58), respectively], but not with systolic blood pressure. We found no association of blood pressure with short-term air pollution or noise exposure. CONCLUSIONS: Long-term exposure to traffic-related air pollution may increase diastolic blood pressure in children.

Gas cooking, respiratory and allergic outcomes in the PIAMA birth cohort study.

OBJECTIVES: Evidence for a relationship between gas cooking and childhood respiratory health is inconsistent and few longitudinal studies have been reported. Our aim was to examine the association between gas cooking and the development of respiratory and allergic outcomes longitudinally in a prospective birth cohort study. METHODS: The Prevention and Incidence of Asthma and Mite Allergy birth cohort study followed children from birth (1996/1997) until age 8. Annual questionnaires were used to document respiratory and allergic symptoms. Allergic sensitisation and bronchial hyper-responsiveness (BHR) were measured at age 8 in subpopulations. A total of 3590 children were included in the present analysis. We used generalised estimating equations and discrete-time hazard models to study the overall and age-specific associations between exposure to gas cooking and the risk of developing respiratory illnesses. Sensitivity analyses of intermittent, always, current and early exposure to gas cooking were conducted. RESULTS: Ever gas cooking exposure was associated with nasal symptoms (sneezing, runny/blocked nose without a cold) during the first 8 years of life (OR=1.32, 95% CI 1.09 to 1.59), but not with lower respiratory tract infections, eczema, allergic sensitisation and BHR. Associations with nasal symptoms were similar among children with intermittent, always, current and early exposure. Among girls only, prevalent asthma was associated with ever gas cooking (OR=1.97, 95% CI 1.05 to 3.72). CONCLUSIONS: Overall, our findings provide little evidence for an adverse effect of exposure to gas cooking on the development of asthma and allergies.

Blood pressure in 12-year-old children is associated with fatty acid composition of human milk: the prevention and incidence of asthma and mite allergy birth cohort.

Breastfed individuals have a lower blood pressure than formula-fed individuals. Supplementation with n-3 long-chain polyunsaturated fatty acids in adults is also associated with a lower blood pressure. We studied whether children receiving human milk with a relatively high content of n-3 long-chain polyunsaturated fatty acids have a lower blood pressure at age 12 years, and, if so, whether this association is explained by the n-3 long-chain polyunsaturated fatty acids content in erythrocyte membranes at age 12 years. Within a 12-year follow-up of a population-based birth cohort, we compared blood pressure of 205 never-breastfed children and 109 children who had fatty acid composition of their mothers' breast milk measured during lactation. In addition, 973 children had information on erythrocyte fatty acid composition and blood pressure at age 12 years. Children who received human milk with an n-3 long-chain polyunsaturated fatty acids content above the median (ie, 0.51 weight percentage) had a 4.79-mm Hg lower systolic (95% CI, -7.64 to -1.94) and a 2.47-mm Hg lower diastolic (95% CI, -4.45 to -0.49) blood pressure at age 12 years than never-breastfed children. N-3 long-chain polyunsaturated fatty acids levels in human milk below the median value and current n-3 long-chain polyunsaturated fatty acid status were not associated with blood pressure at age 12 years. Thus, a relatively high content of n-3 long-chain polyunsaturated fatty acids in human milk is associated with a lower blood pressure in children at age 12 years, a finding not explained by current n-3 long-chain polyunsaturated fatty acids status.

Effect of endotoxin and allergens on neonatal lung function and infancy respiratory symptoms and eczema.

BACKGROUND: Exposure to endotoxin and allergens in house dust has been found to be associated with childhood wheeze and asthma. Neonatal lung function is rarely examined in relation to this exposure. OBJECTIVES: To assess the association between exposure to endotoxin, house dust mite and cat allergens and neonatal lung function, and respiratory symptoms and eczema in infancy. METHODS: In the Wheezing Illnesses Study Leidsche Rijn (WHISTLER) birth cohort study, levels of endotoxin, house dust mite allergens, and cat allergen have been measured in dust samples collected in the child's home. Lung function was measured before age 2 months, and respiratory symptoms and eczema were recorded in a daily diary during the first year of life. Associations of lung function (N = 302), respiratory symptoms (N = 361), and eczema (N = 342) with endotoxin and allergen levels have been studied by means of linear and logistic regression, respectively. RESULTS: Mattress dust endotoxin was associated with a significant increase in neonatal respiratory compliance [adjusted mean difference (95% confidence interval) 2.31 (0.33; 4.29) ml/kPa per interquartile range increase in exposure] and a non-significant decrease in neonatal airway resistance [0.32 (-0.77; 0.14) kPa/l/s]. There were no associations between allergen exposure and neonatal lung function and respiratory symptoms. CONCLUSIONS: Environmental exposure to endotoxin may have an important role in the development of lung function.

Early-life determinants of total and HDL cholesterol concentrations in 8-year-old children; the PIAMA birth cohort study.

BACKGROUND: Adult cholesterol concentrations might be influenced by early-life factors, such as breastfeeding and birth weight, referred to as "early programming". How such early factors exert their influence over the life course is still poorly understood. Evidence from studies in children and adolescents is scarce and conflicting. We investigated the influence of 6 different perinatal risk factors on childhood total and HDL cholesterol concentrations and total-to-HDL cholesterol ratio measured at 8 years of age, and additionally we studied the role of the child's current Body Mass Index (BMI). METHODS: Anthropometric measures and blood plasma samples were collected during a medical examination in 751 8-year-old children participating in the prospective Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort study. Linear and logistic regression were performed to estimate associations of total and HDL cholesterol concentrations with breastfeeding, birth weight, infant weight gain, maternal overweight before pregnancy, gestational diabetes and maternal smoking during pregnancy, taking into account the child's current BMI. RESULTS: Linear regressions showed an association between total-to-HDL cholesterol ratio and maternal pre-pregnancy overweight (ß = 0.15, Confidence Interval 95% (CI): 0.02, 0.28), rapid infant weight gain (ß = 0.13, 95%CI: 0.01, 0.26), and maternal smoking during pregnancy (ß = 0.14, 95%CI: 0.00, 0.29). These associations were partly mediated by the child's BMI. CONCLUSION: Total-to-HDL cholesterol ratio in 8-year-old children was positively associated with maternal pre-pregnancy overweight, maternal smoking during pregnancy and rapid infant weight gain.

In-traffic air pollution exposure and CC16, blood coagulation, and inflammation markers in healthy adults.

BACKGROUND: Exposure to traffic-related air pollution is a risk factor for cardiovascular events, probably involving mechanisms of inflammation and coagulation. Little is known about effects of the short exposures encountered while participating in traffic. OBJECTIVES: The objective of the study was to examine effects of exposure of commuters to air pollution on cardiovascular biomarkers. METHODS: Thirty-four healthy adult volunteers commuted for 2 hr by bus, car, or bicycle during the morning rush hour. During the commute, exposure to particle number, particulate matter (PM) ≤ 2.5 µm in aerodynamic diameter (PM2.5), PM ≤ 10 µm in diameter (PM10), and soot was measured. We estimated inhaled doses based on heart rate monitoring. Shortly before exposure and 6 hr after exposure, blood samples were taken and analyzed for CC16 (Clara cell protein 16), blood cell count, coagulation markers, and inflammation markers. Between June 2007 and June 2008, 352 pre- and postexposure blood samples were collected on 47 test days. We used mixed models to analyze the associations between exposure and changes in health parameters. RESULTS: We observed no consistent associations between the air pollution exposures and doses and the various biomarkers that we investigated. CONCLUSIONS: Air pollution exposure during commuting was not consistently associated with acute changes in inflammation markers, blood cell counts, or blood coagulation markers.

Respiratory effects of commuters' exposure to air pollution in traffic.

BACKGROUND: Much time is spent in traffic, especially during rush hours, when air pollution concentrations on roads are relatively high. Controlled exposure studies have shown acute respiratory effects of short, high exposures to air pollution from motor vehicles. Acute health effects of lower real-life exposures in traffic are unclear. METHODS: Exposures of 34 healthy, nonsmoking adult volunteers were repeatedly measured while commuting for 2 hours by bus, car, or bicycle. Particle number (PN), particulate matter (PM2.5 and PM10), and soot exposures were measured. Lung function and airway resistance were measured directly before, directly following, and 6 hours after exposure. Exhaled nitric oxide (NO) was measured directly before and 6 hours after exposure. Inhaled doses were estimated based on monitored heart rates. Mixed models were used to analyze effects of exposure on changes in health parameters after exposure compared with before. RESULTS: PN, PM10, and soot were associated with decreased peak expiratory flow directly following but not 6 hours after exposure. PN doses were associated with decreases in maximum midexpiratory flow and forced expiratory flow (FEV1) 6 hours after exposure, whereas PN and soot exposures were associated with increased maximum midexpiratory flow and FEV1 directly after exposure. PN and soot were associated with increased exhaled NO after car and bus but not bicycle trips. PN was also associated with an increase in airway resistance directly following exposure but not 6 hours later. CONCLUSIONS: We found modest effects of 2-hour in-traffic exposure to air pollutants on peak flow, exhaled NO, and airway resistance.

Commuters' exposure to particulate matter air pollution is affected by mode of transport, fuel type, and route.

BACKGROUND: Commuters are exposed to high concentrations of air pollutants, but little quantitative information is currently available on differences in exposure between different modes of transport, routes, and fuel types. OBJECTIVES: The aim of our study was to assess differences in commuters' exposure to traffic-related air pollution related to transport mode, route, and fuel type. METHODS: We measured particle number counts (PNCs) and concentrations of PM2.5 (particulate matter

Respiratory health effects of ultrafine and fine particle exposure in cyclists.

OBJECTIVES: Monitoring studies have shown that commuters are exposed to high air pollution concentrations, but there is limited evidence of associated health effects. We carried out a study to investigate the acute respiratory health effects of air pollution related to commuting by bicycle. METHODS: Twelve healthy adults cycled a low- and a high-traffic intensity route during morning rush hour in Utrecht, The Netherlands. Exposure to traffic-related air pollution was characterised by measurements of PM(10), soot and particle number. Before, directly after and 6 h after cycling we measured lung function (FEV(1), FVC, PEF), exhaled NO (FE(NO)) and respiratory symptoms. The association between post- minus pre-exposure difference in health effects and exposure during cycling was evaluated with linear regression models. RESULTS: The average particle number concentration was 59% higher, while the average soot concentration was 39% higher on the high-traffic route than on the low-traffic route. There was no difference for PM(10). Contrary to our hypothesis, associations between air pollution during cycling and lung function changes immediately after cycling were mostly positive. Six hours after cycling, associations between air pollution exposure and health were mostly negative for lung function changes and positive for changes in exhaled NO, although non-significant. CONCLUSIONS: We found substantial differences in ultrafine particle number and soot exposure between two urban cycling routes. Exposure to ultrafine particles and soot during cycling was weakly associated with increased exhaled NO, indicative of airway inflammation, and decrements in lung function 6 h after exposure. A limitation of the study was the relatively small sample size.