Long-term exposure to transportation noise and risk for atrial fibrillation: A Danish nationwide cohort study.

BACKGROUND: Epidemiological studies have linked transportation noise and cardiovascular diseases, however, atrial fibrillation (AF) has received limited attention. We aimed to investigate the association between transportation noise and AF risk. METHODS: Over the period 1990-2017 we estimated road and railway noise (Lden) at the most and least exposed façades for all residential addresses across Denmark. We estimated time-weighted mean noise exposure for 3.6 million individuals age ≥35 years. Of these, 269,756 incident cases of AF were identified with a mean follow-up of 13.0 years. Analyses were conducted using Cox proportional hazards models with adjustment for individual and area-level sociodemographic covariates and long-term residential air pollution. RESULTS: A 10 dB higher 10-year mean road traffic noise at the most and least exposed façades were associated with incidence rate ratios (IRR) and 95% confidence intervals (CI) for AF of 1.006 (1.001-1.011) and 1.013 (1.007-1.019), respectively. After further adjustment for PM2.5, the IRRs (CIs) were 1.000 (0.995-1.005) and 1.007 (1.000-1.013), respectively. For railway noise, the IRRs per 10 dB increase in 10-year mean exposure were 1.017 (1.007-1.026) and 1.035 (1.021-1.050) for the most and least exposed façades, respectively, and were slightly attenuated when adjusted for PM2.5. Aircraft noise between 55 and 60 dB and ≥60 dB were associated with IRRs of 1.055 (0.996-1.116) and 1.036 (0.931-1.154), respectively, when compared to <45 dB. CONCLUSION: Transportation noise seems to be associated with a small increase in AF risk, especially for exposure at the least exposed façade.

Long-term air pollution and road traffic noise exposure and COPD: the Danish Nurse Cohort.

BACKGROUND: While air pollution has been linked to the development of chronic obstructive pulmonary disease (COPD), evidence on the role of environmental noise is just emerging. We examined the associations of long-term exposure to air pollution and road traffic noise with COPD incidence. METHODS: We defined COPD incidence for 24 538 female nurses from the Danish Nurse Cohort (age >44 years) as the first hospital contact between baseline (1993 or 1999) and 2015. We estimated residential annual mean concentrations of particulate matter with an aerodynamic diameter <2.5 µm (PM2.5) since 1990 and nitrogen dioxide (NO2) since 1970 using the Danish Eulerian Hemispheric Model/Urban Background Model/Air Geographic Information System modelling system, and road traffic noise (Lden) since 1970 using the Nord2000 model. Time-varying Cox regression models were applied to assess the associations of air pollution and road traffic noise with COPD incidence. RESULTS: 977 nurses developed COPD during a mean of 18.6 years' follow-up. We observed associations with COPD for all three exposures with HRs and 95% CIs of 1.19 (1.01-1.41) per 6.26 µg·m-3 for PM2.5, 1.13 (1.05-1.20) per 8.19 µg·m-3 for NO2 and 1.15 (1.06-1.25) per 10 dB for Lden. Associations with NO2 and Lden attenuated slightly after mutual adjustment, but were robust to adjustment for PM2.5. Associations with PM2.5 were attenuated to null after adjustment for either NO2 or Lden. No potential interaction effect was observed between air pollutants and noise. CONCLUSION: Long-term exposure to air pollution, especially traffic-related NO2, and to road traffic noise were independently associated with COPD.

Long-term exposure to ambient air pollution and road traffic noise and asthma incidence in adults: The Danish Nurse cohort.

BACKGROUND: Ambient air pollution is likely a risk factor for asthma, and recent evidence suggests the possible relevance of road traffic noise. OBJECTIVES: We examined the associations of long-term exposure to air pollution and road traffic noise with adult-asthma incidence. METHODS: We followed 28,731 female nurses (age > 44 years) from the Danish Nurse Cohort, recruited in 1993 and 1999, for first hospital contact for asthma from 1977 until 2015. We estimated residential annual mean concentrations of particulate matter with diameter < 2.5 µm (PM2.5) since 1990 and nitrogen dioxide (NO2) since 1970 with the Danish DEHM/UBM/AirGIS modeling system, and road traffic noise (Lden) since 1970 with the Nord2000 model. Time-varying Cox regression models were used to associate air pollution and road traffic noise exposure with asthma incidence. RESULTS: During 18.6 years' mean follow-up, 528 out of 23,093 participants had hospital contact for asthma. The hazard ratios (HR) and 95% confidence intervals for asthma incidence associated with 3-year moving average exposures were 1.29 (1.03, 1.61) per 6.3 µg/m3 for PM2.5, 1.16 (1.07, 1.27) per 8.2 µg/m3 for NO2, and 1.12 (1.00, 1.25) per 10 dB for Lden. The HR for NO2 remained unchanged after adjustment for either PM2.5 or Lden, while the HRs for PM2.5 and Lden attenuated to unity after adjustment for NO2. CONCLUSIONS: Long-term exposure to air pollution was associated with adult-asthma incidence independently of road traffic noise, with NO2 most relevant. Road traffic noise was not independently associated with adult-asthma incidence.

Transportation noise and gestational diabetes mellitus: A nationwide cohort study from Denmark.

BACKGROUND: Few studies have investigated whether road traffic noise is associated with gestational diabetes mellitus (GDM), and have yielded inconsistent findings. We aimed to investigate whether maternal exposure to residential transportation noise, before and during pregnancy, was associated with GDM in a nationwide cohort. METHODS: From the Danish population (2004-2017) we identified 629,254 pregnancies using the Danish Medical Birth Register. By linkage with the National Patient Registry, we identified 15,973 pregnancies complicated by GDM. Road traffic and railway noise (Lden) at the most and least exposed façades for all residential addresses from five years before pregnancy until birth were estimated for all. Analyses were conducted using generalized estimating equation models with adjustment for various individual and area-level sociodemographic covariates gathered from Danish registries, as well as green space and air pollution (PM2.5) estimated for all addresses. RESULTS: We found no positive associations between road traffic noise at either façade and GDM. For railway noise, a 10 dB increase in railway noise at the most and least exposed façades during the first trimester was associated with GDM, with an odds ratio (OR) of 1.06 (95% confidence interval (CI): 1.03-1.10) and 1.07 (95% CI: 1.02-1.13), respectively. We found indications of higher odds of GDM among women exposed to both high road traffic and railway noise at the least exposed facade during the first trimester (OR: 1.24; 95% CI: 1.07-1.44). CONCLUSION: In conclusion, this nationwide study suggests that railway noise but not road traffic noise might be associated with GDM.

Long-Term Exposure to Air Pollution and Incidence of Myocardial Infarction: A Danish Nurse Cohort Study.

BACKGROUND: Air pollution exposure has been linked to coronary heart disease, although evidence on PM2.5 and myocardial infarction (MI) incidence is mixed. OBJECTIVES: This prospective cohort study aimed to investigate associations between long-term exposure to air pollution and MI incidence, adjusting for road traffic noise. METHODS: We used data from the nationwide Danish Nurse Cohort on 22,882 female nurses (>44 years of age) who, at recruitment in 1993 or 1999, reported information on cardiovascular disease risk factors. Data on MI incidence was collected from the Danish National Patient Register until the end of 2014. Annual mean concentrations of particulate matter (PM) with a diameter <2.5 µg/m3 (PM2.5), PM10, nitrogen dioxide (NO2), and nitrogen oxides (NOx) at the nurses' residences since 1990 (PM10 and PM2.5) or 1970 (NO2 and NOx) were estimated using the Danish Eulerian Hemispheric Model/Urban Background Model/AirGIS (DEHM/UBM/AirGIS) dispersion model. We used time-varying Cox regression models to examine the association between 1- and 3-y running means of these pollutants, as well as 23-y running means of NO2 and NOx, with both overall and fatal incident MI. Associations were explored in three progressively adjusted models: Model 1, adjusted for age and baseline year; Model 2, with further adjustment for potential confounding by lifestyle and cardiovascular disease risk factors; and Model 3, with further adjustment for road traffic noise, modeled as the annual mean of a weighted 24-h average (Lden). RESULTS: Of the 22,882 women, 641 developed MI during a mean follow-up of 18.6 y, 121 (18.9%) of which were fatal. Reported hazard ratios (HRs) were based on interquartile range increases of 5.3, 5.5, 8.1, and 11.5 µg/m3 for PM2.5, PM10, NO2, and NOx, respectively. In Model 1, we observed a positive association between a 3-y running mean of PM2.5 and an overall incident MI with an HR= 1.20 (95% CI: 1.07, 1.35), which attenuated to HR= 1.06 (95% CI: 0.92, 1.23) in Model 2. In Model 1 for incident fatal MI, we observed a strong association with a 3-y running mean of PM2.5, with an HR= 1.69 (95% CI: 1.33, 2.13), which attenuated to HR= 1.35 (95% CI: 1.01, 1.81) in Model 2. Similar associations were seen for PM10, with 3-y, Model 2 estimates for overall and fatal incident MI of HR= 1.06 (95% CI: 0.91, 1.23) and HR= 1.35 (95% CI: 1.01, 1.81), respectively. No evidence of an association was observed for NO2 or NOx. For all pollutants, associations in Model 2 were robust to further adjustment for road traffic noise in Model 3 and were similar for a 1-y running mean exposure. CONCLUSIONS: We found no association between long-term exposure to PM2.5, PM10, NO2, or NOx and overall MI incidence, but we observed positive associations for PM2.5 and PM10 with fatal MI. We present novel findings that the association between PM and MI incidence is robust to adjustment for road traffic noise. https://doi.org/10.1289/EHP5818.

Long-term residential road traffic noise and mortality in a Danish cohort.

Transportation noise is a growing public health concern worldwide and epidemiological evidence has linked road traffic noise with mortality. However, incongruent effect estimates have been reported between incidence and mortality studies. Therefore, the present study aimed to investigate whether long-term exposure to residential road traffic noise at the most and least exposed façades was associated with all-cause, cardiovascular disease (CVD), ischemic heart disease (IHD), stroke, respiratory, or cancer mortality in a Danish cohort study. In a cohort of 52,758 individuals from Copenhagen and Aarhus, we estimated road traffic noise at the most and least exposed façades, as well as ambient air pollution, at all present and historical residential addresses from 1987 to 2016. Using the Danish cause of death register we identified cause-specific mortality. Analyses were conducted using Cox proportional hazards models. Ten-year time-weighted mean road traffic noise exposure at the most exposed façade was associated with an 8% higher risk for all-cause mortality per interquartile range (IQR; 10.4 dB) higher exposure level (95% CI: 1.05-1.11). Higher risks were also observed for CVD (HR = 1.13, 95% CI: 1.06-1.19) and stroke (HR = 1.11, 95% CI: 0.99-1.25) mortality. Road traffic noise at the least exposed façade (per IQR; 8.4 dB) was associated with CVD (HR = 1.09, 95% CI: 1.03-1.15), IHD (HR = 1.10, 95% CI: 1.01-1.21) and stroke (HR = 1.06, 95% CI: 0.95-1.19) mortality. Results were robust to adjustment for PM2.5 and NO2. In conclusion, this study adds to the body of evidence linking exposure to road traffic noise with higher risk of mortality.

High-resolution assessment of road traffic noise exposure in Denmark.

Recent studies show associations between transportation noise and various diseases. However, selection bias remains an inherent limitation in many cohort studies. In this study, we aimed to model road traffic noise exposure across the entire Danish population and investigate its distribution in relation to area-level socioeconomic indicators and green space. Based on the Nordic prediction method, we estimated road traffic noise for all Danish residential addresses, in total 2,761,739 addresses, for the years 1995, 2000, 2005, 2010, and 2015 at the most and least exposed façades. Area-level sociodemographic variables encompassing education, income, and unemployment were collected and residential green within a 150 m radius buffer at the address level was estimated using high-resolution national land use classification data. Median levels of noise at both the most and least exposed facades across Denmark increased slightly from 1995 to 2015. Correlations between most and least exposed façades varied based on population density and building type, with the highest correlations between the most and least exposed façades found for semidetached homes and lowest for multistory buildings. Increasing median noise levels were observed across increasing levels of higher education, lower income, and higher unemployment. A decreasing trend in median noise levels with increasing levels of green space was observed. In conclusion, we showed that it is feasible to estimate nationwide, address-specific exposure over a long time-period. Furthermore, the low correlations found between most and least exposed façade for multistory buildings, which characterize metropolitan centers, suggests that the most exposed façade estimation used in most previous studies and predicts exposure at the silent façade relatively poorly.

Associations between ambient air pollution and noise from road traffic with blood pressure and insulin resistance in children from Denmark.

BACKGROUND: Road traffic is a major source of air pollution and noise. Both exposures may contribute to increased blood pressure and metabolic disease; however, few studies have examined these relationships in children. OBJECTIVES: We aimed to investigate whether long-term exposures to air pollution and noise from road traffic were associated with increased blood pressure and insulin resistance in children. METHODS: Cardiometabolic outcomes were derived from a follow-up examination of 629 children (10-15 years old) enrolled in the Danish National Birth Cohort. We evaluated associations with prenatal and postnatal residential exposure to nitrogen dioxide (NO2) and noise from road traffic (Lden) using historical addresses and linear regression models. RESULTS: A 10-unit increase in postnatal exposure to NO2 and Lden was associated with a 0.31 (-0.87, 1.48) and 0.18 (-0.61, 0.96) mmHg changes in diastolic blood pressure, respectively. In contrast, both exposures were associated with decreased systolic blood pressure. After adjustment and mutual adjustment for NO2, exposure to Lden was associated with a statistical significant decrease in systolic blood pressure both during prenatal and postnatal life, but the majority of the associations evaluated did not reach statistical significance. Inverse associations were observed for plasma fasting glucose, insulin, and HOMA of insulin resistance for both exposures, exposure windows, before and after adjustment. CONCLUSIONS: The findings do not support evidence of associations between long-term exposures to air pollution and road traffic noise, increased blood pressure, and a metabolic profile characteristic of increased risk for glucose intolerance or type 2 diabetes later in life.

Long-term exposure to residential traffic noise and changes in body weight and waist circumference: A cohort study.

BACKGROUND: Traffic noise can act as a stressor and disturb sleep, and has been associated with cardiovascular disease. Recent studies suggest a possible association to metabolic outcomes and adiposity through biological mechanisms related to physiological stress and sleep disturbance. OBJECTIVES: We aimed to investigate the association between long-term residential traffic noise and changes in adiposity. MATERIALS AND METHODS: The study was based on 39,720 middle-aged Danish men and women from a cohort, with information on weight and waist circumference at two points in time. Residential exposure to traffic noise was calculated for all participants' present and historical addresses using the Nordic prediction method. The associations between traffic noise and changes in adiposity measures after a mean follow-up of 5.3 years were analyzed by linear and logistic regression with adjustments for age, sex, socioeconomic position and lifestyle factors in three models with increasing adjustment. RESULTS: In linear models adjusted for sex, age, socioeconomic position and competing noise sources we found road traffic noise to be significantly associated with small gains in both weight and waist circumference. For example, time-weighted mean exposure 5-years preceding follow-up was associated with a yearly weight gain of 15.4 g (95% confidence interval (CI): 2.14; 28.7) and a yearly increase in waist circumference of 0.22 mm (95% CI: 0.018; 0.43) per 10dB. Similarly, in Poisson regression models we found an 10% increased risk for gaining more than 5 kg body weight during follow-up (95% CI: 1.04; 1.15) per 10 dB higher 5 years exposure preceding follow-up. Exposure to railway noise above 55 dB was associated with weight gain (39.9 g/year (95% CI: 10.2; 69.6)), but not with a significant change in waist circumference. We found baseline BMI (p<0.001) and waist circumference (p=0.001) to be significant effect modifiers for the association between road traffic noise and waist circumference, with gain in waist circumference only among the obese (BMI≥30) participants (1.20 mm/year (95% CI: 0.68; 1.72)) and participants with a large waist circumference (0.83 mm/year (95% CI: 0.42; 1.23)). CONCLUSION: The findings supports previous studies suggesting that traffic noise may be associated with development of adiposity. However, the potential effects are small and suggest an effect mainly among obese participants.

Residential Exposure to Road and Railway Noise and Risk of Prostate Cancer: A Prospective Cohort Study.

BACKGROUND: Few modifiable risk factors for prostate cancer are known. Recently, disruption of the circadian system has been proposed to affect risk, as it entails an inhibited melatonin production, and melatonin has demonstrated beneficial effects on cancer inhibition. This suggests a potential role of traffic noise in prostate cancer. METHODS: Road traffic and railway noise was calculated for all present and historical addresses from 1987-2010 for a cohort of 24,473 middle-aged, Danish men. During follow-up, 1,457 prostate cancer cases were identified. We used Cox Proportional Hazards Models to calculate the association between noise exposure and incident prostate cancer. Incidence Rate Ratios (IRR) were calculated as crude and adjusted for smoking status, education, socioeconomic position, BMI, waist circumference, physical activity, calendar year, and traffic noise from other sources than the one investigated. RESULTS: There was no association between residential road traffic noise and risk of prostate cancer for any of the three exposure windows: 1, 5 or 10-year mean noise exposure before prostate cancer diagnosis. This result persisted when stratifying cases by aggressiveness. For railway noise, there was no association with overall prostate cancer. There was no statistically significant effect modification by age, education, smoking status, waist circumference or railway noise, on the association between road traffic noise and prostate cancer, although there seemed to be a suggestion of an association among never smokers (IRR: 1.16; 95% CI: 1.00-1.36). CONCLUSION: The present study does not support an overall association between either railway or road traffic noise and overall prostate cancer.

Road traffic noise and incident myocardial infarction: a prospective cohort study.

BACKGROUND: Both road traffic noise and ambient air pollution have been associated with risk for ischemic heart disease, but only few inconsistent studies include both exposures. METHODS: In a population-based cohort of 57 053 people aged 50 to 64 years at enrolment in 1993-1997, we identified 1600 cases of first-ever MI between enrolment and 2006. The mean follow-up time was 9.8 years. Exposure to road traffic noise and air pollution from 1988 to 2006 was estimated for all cohort members from residential address history. Associations between exposure to road traffic noise and incident MI were analysed in a Cox regression model with adjustment for air pollution (NO(x)) and other potential confounders: age, sex, education, lifestyle confounders, railway and airport noise. RESULTS: We found that residential exposure to road traffic noise (L(den)) was significantly associated with MI, with an incidence rate ratio IRR of 1.12 per 10 dB for both of the two exposure windows: yearly exposure at the time of diagnosis (95% confidence interval (CI): 1.02-1.22) and 5-years time-weighted mean (95% CI: 1.02-1.23) preceding the diagnosis. Visualizing of the results using restricted cubic splines showed a linear dose-response relationship. CONCLUSIONS: Exposure to long-term residential road traffic noise was associated with a higher risk for MI, in a dose-dependent manner.

Diabetes incidence and long-term exposure to air pollution: a cohort study.

OBJECTIVE: Animal and cross-sectional epidemiological studies suggest a link between air pollution and diabetes, whereas the limited prospective data show mixed results. We studied the association between long-term exposure to traffic-related air pollution and incidence of diabetes. RESEARCH DESIGN AND METHODS: We followed 57,053 participants of the Danish Diet, Cancer, and Health cohort in the Danish National Diabetes Register between baseline (1993-1997) and 27 June 2006. We estimated the mean levels of nitrogen dioxide (NO(2)) at the residential addresses of the cohort participants since 1971 and modeled the association between NO(2) and diabetes incidence with a Cox regression model, separately for two definitions of diabetes: all cases and a more strict definition where unconfirmed cases were excluded. RESULTS: Over a mean follow-up of 9.7 years of 51,818 eligible subjects, there were 4,040 (7.8%) incident diabetes cases in total and 2,877 (5.5%) with confirmed diagnoses. Air pollution was not associated with all diabetes cases (hazard ratio 1.00 [95% CI 0.97-1.04] per interquartile range of 4.9 µg/m(3) mean NO(2) levels since 1971), but a borderline statistically significant association was detected with confirmed cases of diabetes (1.04 [1.00-1.08]). Among confirmed diabetes cases, effects were significantly enhanced in nonsmokers (1.12 [1.05-1.20]) and physically active people (1.10 [1.03-1.16]). CONCLUSIONS: Long-term exposure to traffic-related air pollution may contribute to the development of diabetes, especially in individuals with a healthy lifestyle, nonsmokers, and physically active individuals.

Stroke and long-term exposure to outdoor air pollution from nitrogen dioxide: a cohort study.

BACKGROUND AND PURPOSE: Years of exposure to tobacco smoke substantially increase the risk for stroke. Whether long-term exposure to outdoor air pollution can lead to stroke is not yet established. We examined the association between long-term exposure to traffic-related air pollution and incident and fatal stroke in a prospective cohort study. METHODS: We followed 57,053 participants of the Danish Diet, Cancer and Health cohort in the Hospital Discharge Register for the first-ever hospital admission for stroke (incident stroke) between baseline (1993-1997) and 2006 and defined fatal strokes as death within 30 days of admission. We associated the estimated mean levels of nitrogen dioxide at residential addresses since 1971 to incident and fatal stroke by Cox regression analyses and examined the effects by stroke subtypes: ischemic, hemorrhagic, and nonspecified stroke. RESULTS: Over a mean follow-up of 9.8 years of 52,215 eligible subjects, there were 1984 (3.8%) first-ever (incident) hospital admissions for stroke of whom 142 (7.2%) died within 30 days. We detected borderline significant associations between mean nitrogen dioxide levels at residence since 1971 and incident stroke (hazard ratio, 1.05; 95% CI, 0.99-1.11, per interquartile range increase) and stroke hospitalization followed by death within 30 days (1.22; 1.00-1.50). The associations were strongest for nonspecified and ischemic strokes, whereas no association was detected with hemorrhagic stroke. CONCLUSIONS: Long-term exposure to traffic-related air pollution may contribute to the development of ischemic but not hemorrhagic stroke, especially severe ischemic strokes leading to death within 30 days.

Long-term exposure to air pollution and asthma hospitalisations in older adults: a cohort study.

BACKGROUND: Exposure to air pollution in early life contributes to the burden of childhood asthma, but it is not clear whether long-term exposure to air pollution can lead to asthma onset or progression in adulthood. OBJECTIVES: The authors studied the effect of exposure to traffic-related air pollution over 35 years on the risk for asthma hospitalisation in older people. METHODS: 57 053 participants in the Danish Diet, Cancer and Health cohort, aged 50-65 years at baseline (1993-1997), were followed up for first hospital admission for asthma until 2006, and the annual nitrogen dioxide (NO(2)) levels were estimated as a proxy of the exposure to traffic-related air pollution at the residential addresses of the participants since 1971. The association between NO(2) and hospitalisation for asthma was modelled using Cox regression, for the full cohort and in people with and without previous hospitalisations for asthma, and the effect modification by comorbid conditions was assessed. RESULTS: During 10.2 years' median follow-up, 977 (1.9%) of 53 695 eligible people were admitted to hospital for asthma: 821 were first-ever admissions and 176 were readmissions. NO(2) levels were associated with risk for asthma hospitalisation in the full cohort (HR and 95% CI per IQR, 5.8 µg/m(3): 1.12; 1.04-1.22), and for first-ever admissions (1.10; 1.01-1.20), with the highest risk in people with a history of asthma (1.41; 1.15-2.07) or chronic obstructive pulmonary disease (COPD) (1.30; 1.07-1.52) hospitalisation. CONCLUSIONS: Long-term exposure to traffic-related air pollution increases the risk for asthma hospitalisation in older people. People with previous asthma or COPD hospitalisations are most susceptible.

Air pollution from traffic and cancer incidence: a Danish cohort study.

BACKGROUND: Vehicle engine exhaust includes ultrafine particles with a large surface area and containing absorbed polycyclic aromatic hydrocarbons, transition metals and other substances. Ultrafine particles and soluble chemicals can be transported from the airways to other organs, such as the liver, kidneys, and brain. Our aim was to investigate whether air pollution from traffic is associated with risk for other cancers than lung cancer. METHODS: We followed up 54,304 participants in the Danish Diet Cancer and Health cohort for 20 selected cancers in the Danish Cancer Registry, from enrolment in 1993-1997 until 2006, and traced their residential addresses from 1971 onwards in the Central Population Registry. We used modeled concentration of nitrogen oxides (NO(x)) and amount of traffic at the residence as indicators of traffic-related air pollution and used Cox models to estimate incidence rate ratios (IRRs) after adjustment for potential confounders. RESULTS: NO(x) at the residence was significantly associated with risks for cervical cancer (IRR, 2.45; 95% confidence interval [CI], 1.01;5.93, per 100 µg/m(3) NO(x)) and brain cancer (IRR, 2.28; 95% CI, 1.25;4.19, per 100 µg/m(3) NO(x)). CONCLUSIONS: This hypothesis-generating study indicates that traffic-related air pollution might increase the risks for cervical and brain cancer, which should be tested in future studies.

Chronic obstructive pulmonary disease and long-term exposure to traffic-related air pollution: a cohort study.

RATIONALE: Short-term exposure to air pollution has been associated with exacerbation of chronic obstructive pulmonary disease (COPD), whereas the role of long-term exposures on the development of COPD is not yet fully understood. OBJECTIVES: We assessed the effect of exposure to traffic-related air pollution over 35 years on the incidence of COPD in a prospective cohort study. METHODS: We followed 57,053 participants in the Danish Diet, Cancer, and Health cohort in the Hospital Discharge Register for their first hospital admission for COPD between 1993 and 2006. We estimated the annual mean levels of nitrogen dioxide (NO2) and nitrogen oxides (NO(x)) at all residential addresses of the cohort participants since 1971 to an event or 2006 and used indicators of traffic near the residential address at recruitment. We assessed the association between exposure to air pollution and COPD incidence by Cox regression analyses for the full cohort, and for participants with and without comorbid conditions, including asthma, diabetes, or cardiovascular disease. MEASUREMENTS AND MAIN RESULTS: A first hospital admission for COPD was recorded for 1,786 (3.4%) of 52,799 eligible subjects between recruitment (1993-1997) and 2006. COPD incidence was associated with the 35-year mean NO2 level (hazard ratio, 1.08; 95% confidence interval, 1.02-1.14, per interquartile range of 5.8 µg/m³), with stronger associations in subjects with diabetes (1.29; 1.05-1.50) and asthma (1.19; 1.03-1.38). CONCLUSIONS: Long-term exposure to traffic-related air pollution may contribute to the development of COPD with possibly enhanced susceptibility in people with diabetes and asthma.

Lung and bladder cancer among Danish urban bus drivers and tramway employees: a nested case-control study.

BACKGROUND: The combustion of fossil fuels produces small amounts of mutagenic and carcinogenic compounds. We investigated the association between employment and lung and bladder cancer in Danish bus drivers and tramway employees. METHODS: We carried out a nested case-control study of 153 lung and 84 bladder cancer cases, and 606 controls sampled in a cohort of 18 174 bus drivers or tramway employees employed in Copenhagen during the period 1900-1994. The cases and controls or their next of kin were interviewed about smoking, along with occupational and residential history. An exposure index based on which bus routes the bus drivers had mainly been driving was established. Relative risks (RRs) were estimated by conditional logistic regression. RESULTS: The analysis showed decreasing risk for lung cancer with increasing years of employment as a bus driver (RR = 0.97 for each added year, 95% confidence interval = 0.96-0.99). The air pollution index based on main bus for the bus drivers showed no positive correlation with risk.