Long-Term Exposure to AIR Pollution and COVID-19 Mortality and Morbidity in DENmark: Who Is Most Susceptible? (AIRCODEN)

INTRODUCTION

Early ecological studies have suggested a link between air pollution and Coronavirus Diseases 2019 (COVID-19); however, the evidence from individual-level prospective cohort studies is still sparse. Here, we have examined, in a general population, whether long-term exposure to air pollution is associated with the risk of contracting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and developing severe COVID-19, resulting in hospitalization or death and who is most susceptible. We also examined whether long-term exposure to air pollution is associated with hospitalization or death due to COVID-19 in those who have tested positive for SARS-CoV-2.

METHODS

We included all Danish residents 30 years or older who resided in Denmark on March 1, 2020. and followed them in the National COVID-19 Surveillance System until first positive test (incidence), COVID-19 hospitalization, or death until April 26, 2021. We estimated mean levels of nitrogen dioxide (NO2), particulate matter with an aerodynamic diameter <2.5 μm (PM2.5), black carbon (BC), and ozone (O3) at cohort participants' residence in 2019 by the Danish Eulerian Hemispheric Model/Urban Background Model. We used Cox proportional hazard models to estimate the associations of air pollutants with COVID-19 incidence, hospitalization, and mortality adjusting for age, sex, and socioeconomic status (SES) at the individual and area levels. We examined effect modification by age, sex, SES (education, income, wealth, employment), and comorbidities with cardiovascular disease, respiratory disease, acute lower respiratory infections, diabetes, lung cancer, and dementia. We used logistic regression to examine association of air pollutants with COVID-19-related hospitalization or death among SARS-CoV-2 positive patients, adjusting for age, sex, individual- and area-level SES.

RESULTS

Of 3,721,810 people, 138,742 were infected, 11,270 hospitalized, and 2,557 died from COVID-19 during 14 months of follow-up. We detected strong positive associations with COVID-19 incidence, with hazard ratio (HR) and 95% confidence interval (CI) of 1.10 (CI: 1.05-1.14) per 0.5-μg/m3 increase in PM2.5 and 1.18 (CI: 1.14-1.23) per 3.6-μg/m3 increase in NO2. For COVID-19 hospitalizations and for COVID-19 deaths, corresponding HRs and 95% CIs were 1.09 (CI: 1.01-1.17) and 1.19 (CI: 1.12-1.27), respectively for PM2.5, and 1.23 (CI: 1.04-1.44) and 1.18 (CI: 1.03-1.34), respectively for NO2. We also found strong positive and statistically significant associations with BC and negative associations with O3. Associations were strongest in those aged 65 years old or older, participants with the lowest SES, and patients with chronic cardiovascular, respiratory, metabolic, lung cancer, and neurodegenerative disease. Among 138,742 individuals who have tested positive for SARS-Cov-2, we detected positive association with COVID-19 hospitalizations (N = 11,270) with odds ratio and 95% CI of 1.04 (CI: 1.01- 1.08) per 0.5-μg/m3 increase in PM2.5 and 1.06 (CI: 1.01-1.12) per 3.6-μg/m3 increase in NO2, but no association with PM with an aerodynamic diameter <10 μm (PM10), BC, or O3, and no association between any of the pollutants and COVID-19 mortality (N = 2,557).

CONCLUSIONS

This large nationwide study provides strong new evidence in support of association between long-term exposure to air pollution and COVID-19.

Long-term exposure to traffic-related air pollution and non-accidental mortality: A systematic review and meta-analysis

BACKGROUND

The health effects of traffic-related air pollution (TRAP) continue to be of important public health interest across the globe. Following its 2010 review, the Health Effects Institute appointed a new expert Panel to systematically evaluate the epidemiological evidence regarding the associations between long-term exposure to TRAP and selected health outcomes. This paper describes the main findings of the systematic review on non-accidental mortality.

METHODS

The Panel used a systematic approach to conduct the review. An extensive search was conducted of literature published between 1980 and 2019. A new exposure framework was developed to determine whether a study was sufficiently specific to TRAP, which included studies beyond the near-roadway environment. We performed random-effects meta-analysis when at least three estimates were available of an association between a specific exposure and outcome. We evaluated confidence in the evidence using a modified Office of Health Assessment and Translation (OHAT) approach, supplemented with a broader narrative synthesis.

RESULTS

Thirty-six cohort studies were included. Virtually all studies adjusted for a large number of individual and area-level covariates-including smoking, body mass index, and individual and area-level socioeconomic status-and were judged at a low or moderate risk for bias. Most studies were conducted in North America and Europe, and a few were based in Asia and Australia. The meta-analytic summary estimates for nitrogen dioxide, elemental carbon and fine particulate matter-pollutants with more than 10 studies-were 1.04 (95% CI 1.01, 1.06), 1.02 (1.00, 1.04) and 1.03 (1.01, 1.05) per 10, 1 and 5 µg/m³, respectively. Effect estimates are interpreted as the relative risk of mortality when the exposure differs with the selected increment. The confidence in the evidence for these pollutants was judged as high, because of upgrades for monotonic exposure-response and consistency across populations. The consistent findings across geographical regions, exposure assessment methods and confounder adjustment resulted in a high confidence rating using a narrative approach as well.

CONCLUSIONS

The overall confidence in the evidence for a positive association between long-term exposure to TRAP and non-accidental mortality was high.

Long-term exposure to traffic-related air pollution and stroke: A systematic review and meta-analysis

BACKGROUND

Stroke remains the second cause of death worldwide. The mechanisms underlying the adverse association of exposure to traffic-related air pollution (TRAP) with overall cardiovascular disease may also apply to stroke. Our objective was to systematically evaluate the epidemiological evidence regarding the associations of long-term exposure to TRAP with stroke.

METHODS

PubMed and LUDOK electronic databases were searched systematically for observational epidemiological studies from 1980 through 2019 on long-term exposure to TRAP and stroke with an update in January 2022. TRAP was defined according to a comprehensive protocol based on pollutant and exposure assessment methods or proximity metrics. Study selection, data extraction, risk of bias (RoB) and confidence assessments were conducted according to standardized protocols. We performed meta-analyses using random effects models; sensitivity analyses were assessed by geographic area, RoB, fatality, traffic specificity and new studies.

RESULTS

Nineteen studies were included. The meta-analytic relative risks (and 95% confidence intervals) were: 1.03 (0.98-1.09) per 1 μg/m³ EC, 1.09 (0.96-1.23) per 10 μg/m³ PM₁₀, 1.08 (0.89-1.32) per 5 μg/m³ PM_2.5, 0.98 (0.92; 1.05) per 10 μg/m³ NO₂ and 0.99 (0.94; 1.04) per 20 μg/m³ NO_x with little to moderate heterogeneity based on 6, 5, 4, 7 and 8 studies, respectively. The confidence assessments regarding the quality of the body of evidence and separately regarding the presence of an association of TRAP with stroke considering all available evidence were rated low and moderate, respectively.

CONCLUSION

The available literature provides low to moderate evidence for an association of TRAP with stroke.

Ethnic and socioeconomic inequalities in relation to air pollution exposure in the Netherlands

Background

Air pollution (AP) contributes to a large disease burden and some populations are disproportionately exposed. It is unclear to what extent AP exposure differs across ethnic groups in the Netherlands and how this intersects with socioeconomic position (SEP). First, we identified differences in AP exposures between ethnic groups in the Netherlands. Second, we examined the interrelationships between ethnicity and SEP in relation to AP exposures.

Methods

We assessed AP exposures for residents of the Netherlands in 2019 (N = 17,251,511). Home address AP levels were estimated by dispersion models of the National Institute of Public Health and the Environment (RIVM). We linked exposure estimations of particulate matter &lt;10 or &lt; 2.5 μm (PM10, PM2.5), nitrogen dioxide (NO2), and elemental carbon (EC) to demographic data gathered by Statistics Netherlands. Absolute and relative differences in AP levels across ethnic groups were assessed. We conducted multivariable linear regression analyses and estimated marginal mean exposures to evaluate differences by ethnicity, SEP, age and sex within urban and rural areas. We tested for interactions and stratified accordingly.

Results

For the 40 largest minority ethnic groups (N &gt; 18,314 per group), exposure to all pollutants was higher than for ethnic Dutch, with up to 1.5-fold differences for NO2. After stratification for urbanity and SEP, ethnic exposure inequalities persisted. For ethnic Dutch and some migrant groups, we found the lowest AP exposures in the middle SEP group (i.e. U-shaped trends), while we found linear patterns in other large migrant groups, with higher exposures at lower SEP.

Conclusions

Exposure to PM10, PM2.5, NO2, and EC was consistently higher in minority ethnic groups compared to ethnic Dutch. The association between SEP and AP levels showed different patterns between the majority ethnic Dutch and some of the largest minority ethnic groups. Further research is needed to define the equity and health implications.

Key messages

• Minority ethnic groups in the Netherlands are consistently exposed to higher levels of air pollution (PM10, PM2.5, NO2, and EC) than the ethnic Dutch population.

• Depending on the ethnic group, the association between SEP and air pollution exposure was either linear (i.e. lower exposures at higher SEP) or U-shaped (i.e. lower exposures in the middle SEP group).

Long-term exposure to traffic-related air pollution and selected health outcomes: A systematic review and meta-analysis

The health effects of traffic-related air pollution (TRAP) continue to be of important public health interest. Following its well-cited 2010 critical review, the Health Effects Institute (HEI) appointed a new expert Panel to systematically evaluate the epidemiological evidence regarding the associations between long-term exposure to TRAP and selected adverse health outcomes. Health outcomes were selected based on evidence of causality for general air pollution (broader than TRAP) cited in authoritative reviews, relevance for public health and policy, and resources available. The Panel used a systematic approach to search the literature, select studies for inclusion in the review, assess study quality, summarize results, and reach conclusions about the confidence in the evidence. An extensive search was conducted of literature published between January 1980 and July 2019 on selected health outcomes. A new exposure framework was developed to determine whether a study was sufficiently specific to TRAP. In total, 353 studies were included in the review. Respiratory effects in children (118 studies) and birth outcomes (86 studies) were the most commonly studied outcomes. Fewer studies investigated cardiometabolic effects (57 studies), respiratory effects in adults (50 studies), and mortality (48 studies). The findings from the systematic review, meta-analyses, and evaluation of the quality of the studies and potential biases provided an overall high or moderate-to-high level of confidence in an association between long-term exposure to TRAP and the adverse health outcomes all-cause, circulatory, ischemic heart disease and lung cancer mortality, asthma onsetin chilldren and adults, and acute lower respiratory infections in children. The evidence was considered moderate, low or very low for the other selected outcomes. In light of the large number of people exposed to TRAP - both in and beyond the near-road environment - the Panel concluded that the overall high or moderate-to-high confidence in the evidence for an association between long-term exposure to TRAP and several adverse health outcomes indicates that exposures to TRAP remain an important public health concern and deserve greater attention from the public and from policymakers.

Outlier Detection in Urban Air Quality Sensor Networks

Low-cost urban air quality sensor networks are increasingly used to study the spatio-temporal variability in air pollutant concentrations. Recently installed low-cost urban sensors, however, are more prone to result in erroneous data than conventional monitors, e.g., leading to outliers. Commonly applied outlier detection methods are unsuitable for air pollutant measurements that have large spatial and temporal variations as occur in urban areas. We present a novel outlier detection method based upon a spatio-temporal classification, focusing on hourly NO₂ concentrations. We divide a full year's observations into 16 spatio-temporal classes, reflecting urban background vs. urban traffic stations, weekdays vs. weekends, and four periods per day. For each spatio-temporal class, we detect outliers using the mean and standard deviation of the normal distribution underlying the truncated normal distribution of the NO₂ observations. Applying this method to a low-cost air quality sensor network in the city of Eindhoven, the Netherlands, we found 0.1-0.5% of outliers. Outliers could reflect measurement errors or unusual high air pollution events. Additional evaluation using expert knowledge is needed to decide on treatment of the identified outliers. We conclude that our method is able to detect outliers while maintaining the spatio-temporal variability of air pollutant concentrations in urban areas.

The impact of ambient air pollution on the human blood metabolome

BACKGROUND

Biological perturbations caused by air pollution might be reflected in the compounds present in blood originating from air pollutants and endogenous metabolites influenced by air pollution (defined here as part of the blood metabolome). We aimed to assess the perturbation of the blood metabolome in response to short term exposure to air pollution.

METHODS

We exposed 31 healthy volunteers to ambient air pollution for 5h. We measured exposure to particulate matter, particle number concentrations, absorbance, elemental/organic carbon, trace metals, secondary inorganic components, endotoxin content, gaseous pollutants, and particulate matter oxidative potential. We collected blood from the participants 2h before and 2 and 18h after exposure. We employed untargeted metabolite profiling to monitor 3873 metabolic features in 493 blood samples from these volunteers. We assessed lung function using spirometry and six acute phase proteins in peripheral blood. We assessed the association of the metabolic features with the measured air pollutants and with health markers that we previously observed to be associated with air pollution in this study.

RESULTS

We observed 89 robust associations between air pollutants and metabolic features two hours after exposure and 118 robust associations 18h after exposure. Some of the metabolic features that were associated with air pollutants were also associated with acute health effects, especially changes in forced expiratory volume in 1s. We successfully identified tyrosine, guanosine, and hypoxanthine among the associated features. Bioinformatics approach Mummichog predicted enriched pathway activity in eight pathways, among which tyrosine metabolism.

CONCLUSIONS

This study demonstrates for the first time the application of untargeted metabolite profiling to assess the impact of air pollution on the blood metabolome.

The effect of high indoor temperatures on self-perceived health of elderly persons

INTRODUCTION

Exposure to high ambient temperatures leads to an increase in mortality and morbidity, especially in the elderly. This relationship is usually assessed with outdoor temperature, even though the elderly spend most of their time indoors. Our study investigated the relationship between indoor temperature and heat-related health problems of elderly individuals.

MATERIAL AND METHODS

The study was conducted in the Netherlands between April and August 2012. Temperature and relative humidity were measured continuously in the living rooms and bedrooms of 113 elderly individuals. Respondents were asked to fill out an hourly diary during three weeks with high temperature and one cold reference week, and a questionnaire at the end of these weeks, on health problems that they experienced due to heat.

RESULTS

During the warmest week of the study period (14-20 August), average living room and bedroom temperatures were approximately 5°C higher than during the reference week. More than half of the respondents perceived their indoor climate as too warm during this week. The most reported symptoms were thirst (42.7%), sleep disturbance (40.6%) and excessive sweating (39.6%). There was a significant relationship between both indoor and outdoor temperatures with the number of hours that heat-related health problems were reported per day. For an increase of 1°C of indoor temperature, annoyance due to heat and sleep disturbance increased with 33% and 24% respectively. Outdoor temperature was associated with smaller increases: 13% and 11% for annoyance due to heat and sleep disturbance, respectively. The relationship between outdoor temperature and heat-related health problems disappeared when indoor and outdoor temperatures were included in one model.

CONCLUSIONS

The relationship with heat-related health problems in the elderly is stronger with indoor (living room and bedroom) temperature than with outdoor temperature. This should be taken into account when looking for measures to reduce heat exposure in this vulnerable group.

Particulate matter air pollution components and risk for lung cancer

BACKGROUND

Particulate matter (PM) air pollution is a human lung carcinogen; however, the components responsible have not been identified. We assessed the associations between PM components and lung cancer incidence.

METHODS

We used data from 14 cohort studies in eight European countries. We geocoded baseline addresses and assessed air pollution with land-use regression models for eight elements (Cu, Fe, K, Ni, S, Si, V and Zn) in size fractions of PM2.5 and PM10. We used Cox regression models with adjustment for potential confounders for cohort-specific analyses and random effect models for meta-analysis.

RESULTS

The 245,782 cohort members contributed 3,229,220 person-years at risk. During follow-up (mean, 13.1 years), 1878 incident cases of lung cancer were diagnosed. In the meta-analyses, elevated hazard ratios (HRs) for lung cancer were associated with all elements except V; none was statistically significant. In analyses restricted to participants who did not change residence during follow-up, statistically significant associations were found for PM2.5 Cu (HR, 1.25; 95% CI, 1.01-1.53 per 5 ng/m(3)), PM10 Zn (1.28; 1.02-1.59 per 20 ng/m(3)), PM10 S (1.58; 1.03-2.44 per 200 ng/m(3)), PM10 Ni (1.59; 1.12-2.26 per 2 ng/m(3)) and PM10 K (1.17; 1.02-1.33 per 100 ng/m(3)). In two-pollutant models, associations between PM10 and PM2.5 and lung cancer were largely explained by PM2.5 S.

CONCLUSIONS

This study indicates that the association between PM in air pollution and lung cancer can be attributed to various PM components and sources. PM containing S and Ni might be particularly important.

Quantitative determination of regional contributions to fine and coarse particle mass in urban receptor sites

In this study, we demonstrate that regression analysis of trajectories residence time estimates the contributions of geographical sectors to fine and coarse particle mass in urban receptor sites. We applied the methodology to coarse and fine particles in Amsterdam, Athens, Birmingham and Helsinki. The sectors with the highest contributions on PM2.5 and PM10-2.5 for Amsterdam and Birmingham were Central/Eastern Europe and the Atlantic Ocean/North Sea, respectively. For Athens, the four sectors within 500 km accounted for the largest fraction of PM2.5. The Mediterranean Sea and North Africa added more than half of PM10-2.5 in Athens. For Helsinki, more than 50% of PM2.5 and PM10-2.5 were from sources outside Finland. This approach may be applied to assess the impact of transport on particle mass levels, identify the spatial patterns of particle sources and generate valuable data to design national and transnational efficient emission control strategies.

Lung function and indicators of exposure to indoor and outdoor particulate matter among asthma and COPD patients

OBJECTIVES

Misclassification of exposure related to the use of central sites may be larger for ultrafine particles than for particulate matter < or =2.5 microm and < or =10 microm (PM(2.5) and PM(10)) and may result in underestimation of health effects. This paper describes the relative strength of the association between outdoor and indoor exposure to ultrafine particles, PM(2.5) and PM(10) and lung function.

METHODS

In four European cities (Helsinki, Athens, Amsterdam and Birmingham), lung function (forced vital capacity (FVC), forced expiratory volume in 1 second (FEV(1)) and peak expiratory flow (PEF)) was measured three times a day for 1 week in 135 patients with asthma or chronic obstructive pulmonary disease (COPD), covering study periods of >1 year. Daily concentrations of particle number, PM(2.5) and PM(10) were measured at a central site in each city and both inside and outside the subjects' homes.

RESULTS

Daily average particle number concentrations ranged between 2100 and 66 100 particles/cm(3). We found no association between 24 h average particle number or particle mass concentrations and FVC, FEV(1) and PEF. Substituting home outdoor or home indoor concentrations of particulate air pollution instead of the central site measurements did not change the observed associations. Analyses restricted to asthmatics also showed no associations.

CONCLUSIONS

No consistent associations between lung function and 24 h average particle number or particle mass concentrations were found in panels of patients with mild to moderate COPD or asthma. More detailed exposure assessment did not change the observed associations. The lack of association could be due to the high prevalence of medication use, limited ability to assess lagged effects over several days or absence of an effect.

Bacteria and mould components in house dust and children's allergic sensitisation

It has been suggested that early childhood exposure to microbial agents decreases the risk of allergies in children. The current authors studied the association between microbial agents in house dust and allergic sensitisation in children aged 2-4 yrs. Nested case-control studies were performed within ongoing birth cohort studies in Germany, the Netherlands and Sweden and approximately 180 sensitised and 180 nonsensitised children were selected per country. Levels of bacterial endotoxin, beta(1,3)-glucans and fungal extracellular polysaccharides (EPS) were measured in dust samples from the children's mattresses and the living-room floors. Combined across countries, higher amounts of mattress dust and higher mattress dust loads of endotoxin, beta(1,3)-glucans and EPS were associated with a significantly decreased risk of sensitisation to inhalant allergens. After mutual adjustment, only the protective effect of the amount of mattress dust remained significant (odds ratio (95% confidence interval) 0.57(0.39-0.84)). Higher amounts of mattress dust may decrease the risk of allergic sensitisation to inhalant allergens. The effect might be partly attributable to endotoxin, beta(1,3)-glucans and extracellular polysaccharides, but could also reflect (additional) protective effects of (microbial) agents other than the ones measured. It is not possible to distinguish with certainty which component relates to the effect, since their levels are highly correlated.

Determinants of house dust endotoxin in three European countries - the AIRALLERG study

The comparison of endotoxin levels between study populations and countries is limited as a result of differences in sampling, extraction, and storage procedures. The objective of this study is to assess the levels and determinants of endotoxin in mattress and living room floor dust samples from three European countries, namely, Germany, the Netherlands, and Sweden, using a standardized sampling, storage, and analysis protocol. The mattress and living room floor dust was collected from the homes of 1065 German, Dutch, and Swedish (pre-)school children. All the samples were collected in the cool season and analyzed for endotoxin in a central laboratory. The determinants were assessed by a standardized questionnaire. The endotoxin concentrations in mattress and living room floor dust were found to be the highest in German homes and lowest in the Swedish ones. Differences between the geometric means were small (factor 1.1-1.7). Most of the associations between endotoxin concentrations and potential determinants were not statistically significant and heterogeneous across countries. However, keeping pets and having more than four persons living in the home were consistently associated with up to 1.7-fold higher endotoxin concentrations in mattress and floor dust. Furthermore, having carpets or rugs, and opening the windows frequently was associated with up to 3.4-fold and 1.3-fold higher endotoxin concentrations in living room floor dust, respectively. The proportion of variance explained by the questionnaire variables was generally low. In conclusion, the data on housing characteristics did not accurately predict the endotoxin concentrations in house dust, and could only partly explain the differences between countries.

PRACTICAL IMPLICATIONS

The differences between the endotoxin concentrations in German, Dutch, and Swedish homes are small. House dust endotoxin concentrations are associated with a number of housing factors, such as pet-ownership, floor cover, number of persons living in the home, and ventilation. The variability of the endotoxin levels between homes and countries can only be partly explained by these factors.

Air pollution and development of asthma, allergy and infections in a birth cohort

Few studies have addressed associations between traffic-related air pollution and respiratory disease in young children. The present authors assessed the development of asthmatic/allergic symptoms and respiratory infections during the first 4 yrs of life in a birth cohort study (n = approximately 4,000). Outdoor concentrations of traffic-related air pollutants (nitrogen dioxide PM(2.5), particles with a 50% cut-off aerodynamic diameter of 2.5 mum and soot) were assigned to birthplace home addresses with a land-use regression model. They were linked by logistic regression to questionnaire data on doctor-diagnosed asthma, bronchitis, influenza and eczema and to self-reported wheeze, dry night-time cough, ear/nose/throat infections and skin rash. Total and specific immunoglobulin (Ig)E to common allergens were measured in a subgroup (n = 713). Adjusted odds ratios (95% confidence intervals) per interquartile pollution range were elevated for wheeze (1.2 (1.0-1.4) for soot), doctor-diagnosed asthma (1.3 (1.0-1.7)), ear/nose/throat infections (1.2 (1.0-1.3)) and flu/serious colds (1.2 (1.0-1.4)). No consistent associations were observed for other end-points. Positive associations between air pollution and specific sensitisation to common food allergens (1.6 (1.2-2.2) for soot), but not total IgE, were found in the subgroup with IgE measurements. Traffic-related pollution was associated with respiratory infections and some measures of asthma and allergy during the first 4 yrs of life.

NO2 and children's respiratory symptoms in the PATY study

OBJECTIVES

NO2)is a major urban air pollutant. Previously reported associations between ambient NO2)and children's respiratory health have been inconsistent, and independent effects of correlated pollutants hard to assess. The authors examined effects of NO2 on a spectrum of 11 respiratory symptoms, controlling for PM10 and SO2, using a large pooled dataset.

METHODS

Cross sectional studies were conducted in Russia, Austria, Italy, Switzerland, and the Netherlands, during 1993-99, contributing in total 23 955 children. Study-specific odds ratios for associations with ambient NO2 are estimated using logistic regressions with area-level random effects. Heterogeneity between study-specific results, and mean estimates (allowing for heterogeneity) are calculated.

RESULTS

Long term average NO2 concentrations were unrelated to prevalences of bronchitis or asthma. Associations were found for sensitivity to inhaled allergens and allergy to pets, with mean odds ratios around 1.14 per 10 microg/m3 NO2. SO2 had little confounding effect, but an initial association between NO2 and morning cough was reduced after controlling for PM10. Associations with reported allergy were not reduced by adjustment for the other pollutants. Odds ratios for allergic symptoms tended to be higher for the 9-12 year old children compared with the 6-8 year old children.

CONCLUSIONS

Evidence for associations between NO2 and respiratory symptoms was robust only for inhalation allergies. NO2 most likely is acting as an indicator of traffic related air pollutants, though its direct effect cannot be ruled out. This remains important, as policies to reduce traffic related air pollution will not result in rapid reductions.

Comparison of parental reports of smoking and residential air nicotine concentrations in children

BACKGROUND

Using questionnaires to assess children's residential exposure to environmental tobacco smoke (ETS) may result in misclassification from recall and response bias. Questionnaire data have frequently been validated against urinary cotinine measurements, but rarely against actual measurements of residential air nicotine.

OBJECTIVE

To compare questionnaire reported smoking with air nicotine concentrations in a large population of children and with urinary cotinine levels in a subpopulation; and to assess the potential impact of the symptom status of the children on the agreement between different measures of exposure.

METHODS

The authors assessed residential exposure to ETS in 347 German, 335 Dutch, and 354 Swedish preschool and schoolchildren by questionnaire and air nicotine measurements, and in a subset of 307 German children by urinary cotinine measurements. They then compared the different measures of ETS exposure.

RESULTS

In all countries, air nicotine concentrations increased with increasing questionnaire reported smoking in a dose-response fashion. Specificity and negative predictive values of questionnaire reports for nicotine concentrations were excellent. Sensitivity and positive predictive values were moderate to good. Excluding occasional smokers, the overall percentage of homes misclassified was 6.9%, 6.7%, and 5.1% in Germany, the Netherlands, and Sweden, respectively. Similar results were found for the agreement of urinary cotinine concentrations with questionnaire reports and air nicotine levels. There was no indication of underreporting by parents of symptomatic children.

CONCLUSION

Despite some misclassification, questionnaire reports are an inexpensive and valid estimate of residential ETS exposure among preschool and school children.

Parental education and children's respiratory and allergic symptoms in the Pollution and the Young (PATY) study

Inequalities in health between socio-economic groups are a major public health concern. The current authors studied associations between parental socio-economic status (SES) and children's respiratory and allergic symptoms in 13 diverse countries, including the Russian Federation, North America (Canada and the USA), and countries across Eastern and Western Europe. Data of 57,000 children aged 6-12 yrs, originating from eight cross-sectional studies, were analysed. SES was defined by parental education. Respiratory and allergic symptoms were defined by parental questionnaire reports. Multiple logistic regressions showed that low parental education was associated with a decreased risk of inhalant allergy and itchy rash in school children. Furthermore, low parental education was associated with an increased prevalence of wheeze and nocturnal dry cough. No clear association was found between parental education and prevalence of doctor-diagnosed asthma and bronchitis. Part of the difference between socio-economic groups with regard to their children's symptoms was explained by established risk factors, such as parental allergy, smoking during pregnancy, pet ownership, crowding, mould/moisture in the home, use of gas for cooking, and air pollution (particulate matter with a diameter of <10 microm). However, differences remained after adjusting for these variables. Children's health was associated with parental education. The association could not fully be explained by established risk factors.

Associations between ambient, personal, and indoor exposure to fine particulate matter constituents in Dutch and Finnish panels of cardiovascular patients

AIMS

To assess the relation between ambient, indoor, and personal levels of PM2.5 and its elemental composition for elderly subjects with cardiovascular disease.

METHODS

In the framework of a European Union funded study, panel studies were conducted in Amsterdam, the Netherlands and Helsinki, Finland. Outdoor PM2.5 concentrations were measured at a fixed site. Each subject's indoor and personal PM2.5 exposure was measured biweekly for six months, during the 24 hour period preceding intensive health measurements. The absorbance of PM2.5 filters was measured as a marker for diesel exhaust. The elemental content of more than 50% of the personal and indoor samples and all corresponding outdoor samples was measured using energy dispersive x ray fluorescence.

RESULTS

For Amsterdam and Helsinki respectively, a total of 225 and 238 personal, and 220 and 233 indoor measurements, were analysed from 36 and 46 subjects. For most elements, personal and indoor concentrations were lower than and highly correlated with outdoor concentrations. The highest correlations (median r>0.9) were found for sulfur and particle absorbance, which both represent fine mode particles from outdoor origin. Low correlations were observed for elements that represent the coarser part of the PM2.5 particles (Ca, Cu, Si, Cl).

CONCLUSIONS

The findings of this study provide support for using fixed site measurements as a measure of exposure to particulate matter in time series studies linking the day to day variation in particulate matter to the day to day variation in health endpoints, especially for components of particulate matter that are generally associated with fine particles and have few indoor sources. The high correlation for absorbance of PM2.5 documents that this applies to particulate matter from combustion sources, such as diesel vehicles, as well.

DNA repair polymorphisms and cancer risk in non-smokers in a cohort study

Environmental carcinogens contained in air pollution, such as polycyclic aromatic hydrocarbons, aromatic amines or N-nitroso compounds, predominantly form DNA adducts but can also generate interstrand cross-links and reactive oxygen species. If unrepaired, such lesions increase the risk of somatic mutations and cancer. Our study investigated the relationships between 22 polymorphisms (and their haplotypes) in 16 DNA repair genes belonging to different repair pathways in 1094 controls and 567 cancer cases (bladder cancer, 131; lung cancer, 134; oral-pharyngeal cancer, 41; laryngeal cancer, 47; leukaemia, 179; death from emphysema and chronic obstructive pulmonary disease, 84). The design was a case-control study nested within a prospective investigation. Among the many comparisons, few polymorphisms were associated with the diseases at the univariate analysis: XRCC1-399 Gln/Gln variant homozygotes [odds ratios (OR) = 2.20, 95% confidence intervals (CI) = 1.16-4.17] and XRCC3-241 Met/Met homozygotes (OR = 0.51, 95% CI = 0.27-0.96) and leukaemia. The recessive model in the stepwise multivariate analysis revealed a possible protective effect of XRCC1-399Gln/Gln in lung cancer (OR = 0.22, 95% CI = 0.05-0.98), and confirmed an opposite effect (OR = 2.47, 95% CI = 1.02-6.02) in the leukaemia group. Our results also suggest that the XPD/ERCC1-GAT haplotype may modulate leukaemia (OR = 1.28, 95% CI = 1.02-1.61), bladder cancer (OR = 1.38, 95% CI = 1.06-1.79) and possibly other cancer risks. Further investigations of the combined effects of polymorphisms within these DNA repair genes, smoking and other risk factors may help to clarify the influence of genetic variation in the carcinogenic process.

Exposure to traffic related air pollutants: self reported traffic intensity versus GIS modelled exposure

BACKGROUND

In epidemiological studies of the potential health effects of traffic related air pollution, self reported traffic intensity is a commonly used, but rarely validated, exposure variable.

METHODS

As part of a study on the impact of Traffic Related Air Pollution on Childhood Asthma (TRAPCA), data from 2633 and 673 infants from the Dutch and the German-Munich cohorts, respectively, were available. Parents subjectively assessed traffic intensity at the home address. Objective exposures were estimated by a combination of spatial air pollution measurements and geographic information system (GIS) based modelling using an identical method for both cohorts.

RESULTS

The agreement rates between self reported and GIS modelled exposure--accumulated over the three strata of self assessed traffic intensity--were 55-58% for PM(2.5), filter absorbance (PM(2.5) abs), and nitrogen dioxide in Munich and 39-40% in the Netherlands. Of the self reported low traffic exposed group, 71-73% in Munich and 45-47% in the Netherlands had low modelled exposure to these three air pollutants. Of the self assessed high exposed subgroups in Munich (15% of the total population) and the Netherlands (22% of the total population), only 22-33% and 30-32% respectively had high modelled exposure to the three air pollutants. The subjective assessments tend to overestimate the modelled estimates for PM(2.5) and NO2 in both study areas. When analysis was restricted to the portion of the Dutch cohort living in non-urban areas, the agreement rates were even lower.

CONCLUSIONS

Self reported and modelled assessment of exposure to air pollutants are only weakly associated.

Susceptibility to air pollution in elderly males and females

It is important to know which individuals in the general population have increased susceptibility to air pollution. The aim of this study was to identify susceptible subgroups by studying airways hyperresponsiveness (AHR), high total immunoglobulin (Ig)E and sex. Diary data on lower and upper respiratory symptoms (LRS and URS, respectively), cough, and morning and evening peak expiratory flow (PEF) were collected in 327 elderly patients (50-70 yrs) for a period of 3 months. Acute effects of particulate matter with a diameter <10 microm, black smoke, sulphur dioxide and nitrogen dioxide on symptoms and PEF were estimated using logistic regression. In total, 48 (14.7%) subjects had AHR+/IgE+, 112 (34.3%) had AHR-/IgE+, 42 (12.8%) had AHR+/IgE- and 125 (38.2%) had AHR-/IgE-. In the AHR+/IgE+ group, each 10 microg x m(-3) increase in air pollution was associated with a significant increase in prevalence of URS (odds ratio ranging 1.03-1.19), cough (1.03-1.08) and fall in morning PEF (1.04-1.26). In the AHR+/IgE+ group, males responded predominantly with symptoms and females with a fall in morning PEF. In conclusion, elderly individuals with both airway hyperresponsiveness and high total immunoglobulin E are especially susceptible to air pollution. Identifying susceptible subgroups might enlarge insight into the actual mechanisms by which air pollution evokes specific modes of response.

Sources and elemental composition of ambient PM(2.5) in three European cities

Source apportionment of urban fine particle mass (PM(2.5)) was performed from data collected during 1998-1999 in Amsterdam (The Netherlands), Erfurt (Germany) and Helsinki (Finland), using principal component analysis (PCA) and multiple linear regression. Six source categories of PM(2.5) were identified in Amsterdam. They were traffic-related particles (30% of the average PM(2.5)), secondary particles (34%), crustal material (7%), oil combustion (11%), industrial and incineration processes (9%), and sea salt (2%). The unidentified PM(2.5) fraction was 7% on the average. In Erfurt, four source categories were extracted with some difficulties in interpretation of source profiles. They were combustion emissions related to traffic (32%), secondary PM (32%), crustal material (21%) and industrial processes (8%). In Erfurt, 3% of PM(2.5) remained unidentified. Air pollution data and source apportionment results from the two Central European cities were compared to previously published results from Helsinki, where about 80% of average PM(2.5) was attributed to transboundary air pollution and particles from traffic and other regional combustion sources. Our results indicate that secondary particles and local combustion processes (mainly traffic) were the most important source categories in all cities; their impact on the average PM(2.5) was almost equal in Amsterdam and Erfurt whereas, in Helsinki, secondary particles made up for as much as half of the total average PM(2.5).

Daily variation in fine and ultrafine particulate air pollution and urinary concentrations of lung Clara cell protein CC16

BACKGROUND

Daily variations in ambient particulate air pollution have been associated with respiratory mortality and morbidity.

AIMS

To assess the associations between urinary concentration of lung Clara cell protein CC16, a marker for lung damage, and daily variation in fine and ultrafine particulate air pollution.

METHODS

Spot urinary samples (n = 1249) were collected biweekly for six months in subjects with coronary heart disease in Amsterdam, Netherlands (n = 37), Erfurt, Germany (n = 47), and Helsinki, Finland (n = 47). Ambient particulate air pollution was monitored at a central site in each city.

RESULTS

The mean 24 hour number concentration of ultrafine particles was 17.3x10(3) cm(-3) in Amsterdam, 21.1x10(3) cm(-3) in Erfurt, and 17.0x10(3) cm(-3) in Helsinki. The mean 24 hour PM2.5 concentrations were 20, 23, and 13 microg/m3, respectively. Daily variation in ultrafine particle levels was not associated with CC16. In contrast, CC16 concentration seemed to increase with increasing levels of PM2.5 in Helsinki, especially among subjects with lung disorders. No clear associations were observed in Amsterdam and Erfurt. In Helsinki, the CC16 concentration increased by 20.2% (95% CI 6.9 to 33.5) per 10 microg/m3 increase in PM2.5 concentration (lag 2). The respective pooled effect estimate was 2.1% (95% CI -1.3 to 5.6).

CONCLUSION

The results suggest that exposure to particulate air pollution may lead to increased epithelial barrier permeability in lungs.

Air pollution and mortality in The Netherlands: are the elderly more at risk?

The association between daily mortality and short-term variations in the ambient levels of ozone (O3), black smoke (BS), sulphur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO) and particulate matter was studied in The Netherlands. Daily total and cause-specific mortality counts (cardiovascular, chronic obstructive pulmonary disease (COPD) and pneumonia), air quality, temperature, relative humidity and influenza data were obtained from 1986-1994. The relationship between daily mortality and air pollution was modelled using Poisson regression analysis. All pollution mortality associations were adjusted for potential confounding due to long-term trends, seasonal trends, influenza epidemics, ambient temperature, ambient relative humidity, day of the week and holidays, using generalised additive models. Statistically significant associations were mostly found in the elderly, that is the age categories of 65-74 and > or = 75 yrs for the pollutants PM10 (particles with a 50%, cut-off aerodynamic diameter of 10 microm), BS, SO2, NO2 and CO. This may partly be due to a better precision of relative risk (RR) estimates for the larger numbers of deaths in these age groups. Significant associations for those < 65 yrs were found for O3 (total and COPD mortality), PM10 (pneumonia), NO2 (pneumonia) and CO (pneumonia). RR estimates for deaths between 45-65 yrs tended to be smaller than those in > 65 yrs, with the exception of ozone; for cardiovascular mortality the RR for PM10, O3 and CO were similar in these age groups. In conclusion, larger relative risks for air pollution were mostly found in the elderly except for ozone and for death-cause pneumonia which showed larger relative risk in younger age groups.

Effects of fine and ultrafine particles on cardiorespiratory symptoms in elderly subjects with coronary heart disease: the ULTRA study

The ULTRA Study, a study investigating the association between fine and ultrafine particulate air pollution and cardiorespiratory health, was conducted during the winter of 1998-1999 in Amsterdam, the Netherlands; Erfurt, Germany; and Helsinki, Finland. At each study center, a panel of elderly subjects with coronary heart disease recorded cardiac and respiratory symptoms in a diary. Exposure to ambient air pollution was characterized by measuring daily mass concentrations of particles smaller than 10 micro m (PM(10)) and 2.5 micro m (PM(2.5)), number concentrations of ultrafine particles (NC(0.01-0.1)), and gases. Odds ratios for the relation of symptoms to air pollution, adjusted for time trend, respiratory infections, and meteorologic variables, were mostly homogeneous across the centers. No association was found between air pollution and chest pain. A 10- micro g/m(3) increase in PM(2.5) was positively associated with the incidence of shortness of breath (odds ratio (OR) = 1.12, 95% confidence interval (CI): 1.02, 1.24) and with avoidance of activities (OR = 1.09, 95% CI: 0.97, 1.22). NC(0.01-0.1) was only associated with the prevalence of avoidance of activities (OR = 1.10, 95% CI: 1.01, 1.19). In conclusion, PM(2.5) was associated with some cardiac symptoms in three panels of elderly subjects. PM(2.5 )was more strongly related to cardiorespiratory symptoms than ultrafine particles were.

Estimation of long-term average exposure to outdoor air pollution for a cohort study on mortality

Recent prospective cohort studies have suggested that long-term exposure to low levels of particulate matter (PM) air pollution is associated with increased mortality due to, especially, cardio-pulmonary disease. Exposure to ambient air pollution was estimated mostly as city average concentrations, assuming homogenous exposure within the city. We used an ongoing cohort study - The Netherlands Cohort Study (NLCS) on diet and cancer - to investigate the relationship between traffic-related air pollution and mortality. The baseline data collection took place in 1986. A study was conducted to develop methods for exposure assessment and evaluate the contrast in exposure to air pollution within the cohort. Assessment of long-term exposure to two traffic-related air pollutants, Black Smoke (BS) and Nitrogen Dioxide (NO(2)), consisted of separate estimation of regional background, urban background, and local traffic contributions at the home address. Interpolation of concentration data from a routine monitoring network was used to estimate the regional background concentration. A regression model relating degree of urbanization to air pollution was used to allow for differences between different towns/neighborhoods of cities. Distance to major roads was calculated to characterize local traffic contributions, using a Geographic Information System (GIS). Interpolation resulted in reasonably precise regional background estimation when distant sites were not used and distance squared was used as the weight. Cross-validation showed that prediction errors were about 15% of the range in regional background concentration. Urban and local scales contributed significantly to the contrast within the cohort. Prediction errors for estimating the urban background were about 25% of the range in background concentrations. When the developed model was applied to the study cohort, there was substantial contrast in estimated exposure to BS and NO(2). About 90% of the study population lived 10 years or more at its 1986 home address - supporting the use of the estimated concentration at the 1986 address as a relevant exposure variable.

The association between air pollution and heart failure, arrhythmia, embolism, thrombosis, and other cardiovascular causes of death in a time series study

In a time series study, air pollution was associated with specific cardiovascular causes of death. Deaths due to heart failure (ICD-9 428), arrhythmia (ICD-9 427), cerebrovascular causes (ICD-9 430-436), and thrombocytic causes (ICD-9 415.1, 433-4, 444, 452-3) were more strongly associated with air pollution than cardiovascular deaths (ICD-9 390-448) in general. Excess relative risks were 2.5 to 4 times larger for these categories than for total cardiovascular disease mortality. Heart failure deaths, which made up 10% of all cardiovascular deaths, were found to be responsible for about 30% of the cardiovascular deaths related to particulate matter, SO2, CO, and NO2.

Incidence of influenza-like illness, measured by a general practitioner sentinel system, is associated with day-to-day variations in respiratory health in panel studies

During three consecutive winters beginning in 1992-1993, the association between the incidence of influenza and influenza-like illness (ILI), measured by a general practitioner sentinel system, and respiratory health was investigated in an air pollution panel study. Data from 22 panels of children (7-11 years old) and adults (50-70 years old) in the Netherlands were used. ILI incidence was associated with peak expiratory flow, respiratory symptoms, and bronchodilator use. Peak ILI incidence of 122 cases/10,000 subjects was associated with a decrement in peak expiratory flow of 6% and a 3- to 4.5-fold increase in symptom reporting and bronchodilator use. In panel studies, ILI incidence might be used to adjust for confounding by acute respiratory infections.

Daily mortality and air pollution in The Netherlands

We studied the association of daily mortality with short-term variations in the ambient concentrations of major gaseous pollutants and PM in the Netherlands. The magnitude of the association in the four major urban areas was compared with that in the remainder of the country. Daily cause-specific mortality counts, air quality, temperature, relative humidity, and influenza data were obtained from 1986 to 1994. The relationship between daily mortality and air pollution was modeled using Poisson regression analysis. We adjusted for potential confounding due to long-term and seasonal trends, influenza epidemics, ambient temperature and relative humidity, day of the week, and holidays, using generalized additive models. Influenza episodes were associated with increased mortality up to 3 weeks later. Daily mortality was significantly associated with the concentration of all air pollutants. An increase in the PM10 concentration by 100 micrograms/m3 was associated with a relative risk (RR) of 1.02 for total mortality. The largest RRs were found for pneumonia deaths. Ozone had the most consistent, independent association with mortality. Particulate air pollution (e.g., PM10, black smoke [BS]) was not more consistently associated with mortality than were the gaseous pollutants SO2 and NO2. Aerosol SO4(-2), NO3-, and BS were more consistently associated with total mortality than was PM10. The RRs for all pollutants were substantially larger in the summer months than in the winter months. The RR of total mortality for PM10 was 1.10 for the summer and 1.03 for the winter. There was no consistent difference between RRs in the four major urban areas and the more rural areas.

Personal exposure to fine particulate matter in elderly subjects: relation between personal, indoor, and outdoor concentrations

The time-series correlation between ambient levels, indoor levels, and personal exposure to PM2.5 was assessed in panels of elderly subjects with cardiovascular disease in Amsterdam, the Netherlands, and Helsinki, Finland. Subjects were followed for 6 months with biweekly clinical visits. Each subject's indoor and personal exposure to PM2.5 was measured biweekly, during the 24-hr period preceding the clinical visits. Outdoor PM2.5 concentrations were measured at fixed sites. The absorption coefficients of all PM2.5 filters were measured as a marker for elemental carbon (EC). Regression analyses were conducted for each subject separately, and the distribution of the individual regression and correlation coefficients was investigated. Personal, indoor, and ambient concentrations were highly correlated within subjects over time. Median Pearson's R between personal and outdoor PM2.5 was 0.79 in Amsterdam and 0.76 in Helsinki. For absorption, these values were 0.93 and 0.81 for Amsterdam and Helsinki, respectively. The findings of this study provide further support for using fixed-site measurements as a measure of exposure to PM2.5 in epidemiological time-series studies.

Relation between airborne pollen concentrations and daily cardiovascular and respiratory-disease mortality

In a time-series study in The Netherlands, we found a strong association between the day-to-day variation in pollen concentrations and that of deaths due to cardiovascular disease, chronic obstructive pulmonary disease, and pneumonia.

Acute effects of air pollution on respiratory health of 50-70 yr old adults

The aim of this study was to investigate the association between daily changes in respiratory health and air pollution in 489 adults, aged 50-70 yrs, with and without chronic respiratory symptoms, living in urban and nonurban areas in the Netherlands. Subjects were selected from the general population with a screening questionnaire. During three consecutive winters starting in 1992/1993, peak expiratory flow (PEF) and respiratory symptoms were registered in a daily diary. Daily measurements of particles with a 50% cut-off aerodynamic diameter of 10 microm (PM10), black smoke (BS), sulphate, sulphur dioxide (SO2) and nitrogen dioxide (NO2) were conducted. The difference in PM10, BS and sulphate concentrations between urban and nonurban areas was small, but there was more contrast in the concentrations of SO2 and NO2. In symptomatic subjects from urban areas, PM10, BS, sulphate and SO2 concentrations were associated with the prevalence of large decrements in morning PEF (>20% below the median). BS in particular was also associated with upper respiratory symptoms (URS). The magnitude of the effect estimates was in the order of an 80% increase in PEF decrements and a 20% increase in URS for a 40 microg x m-3 increase of the same day BS concentration. In symptomatic subjects from nonurban areas, no consistent associations between air pollution and health indicators were observed. However, the differences in effect estimates between urban and nonurban symptomatic panels were small and nonsignificant. In nonsymptomatic adults from both areas, no consistent pattern of associations with air pollution was found. In conclusion, air pollution effects were only found in symptomatic adults in the urban areas.

PM10 elemental composition and acute respiratory health effects in European children (PEACE project). Pollution Effects on Asthmatic Children in Europe

The ability of particles with a 50% cut-off aerodynamic diameter of 10 microm (PM10) to cause respiratory health effects possibly depends on their composition. This study evaluated whether the soluble elemental concentrations in PM10 were related to acute respiratory health effects. The Pollution Effects on Asthmatic Children in Europe (PEACE) study is a multicentre study of the acute effects of PM10 and other air pollution components on the respiratory health of children with chronic respiratory symptoms in urban and suburban panels. Children, 1208, divided among 17 panels were followed for > or =2 months. Exposure to air pollution was monitored on a daily basis. Health status was monitored by twice daily peak expiratory flow (PEF) measurements and a symptom diary. Median concentrations of iron ranged 105-1,110 ng x m(-3) in the urban and 32-517 ng x m(-3) in the suburban locations. The daily concentrations of most elements were not associated with daily variation in PEF, prevalence of respiratory symptoms or bronchodilator use. Silicon and iron concentrations tended to be negatively associated with PEF, and positively associated with the prevalence of phlegm. In two pollutant models, PM10 effect-estimates on phlegm prevalence were reduced and lost significance, whereas the effect-estimates of iron or silicon remained essentially unchanged. The effects of silicon and iron could not be separated. In conclusion, this study provides only weak support for the hypothesis that daily fluctuations in soluble elemental concentrations in ambient particulate matter are responsible for acute health effects.

Upper limb tension tests as tools in the diagnosis of nerve and plexus lesions. Anatomical and biomechanical aspects

OBJECTIVE

To analyse the validity of nerve tension tests used in the diagnosis of nerve (root) and plexus lesions of the upper extremity.

DESIGN

In six arms of embalmed human bodies, in situ measurements were performed to assess the effect of nerve tension tests on the median, ulnar and radial nerves and the cords of the brachial plexus.

BACKGROUND

In clinical practice it is useful to have fast, easy and cheap tests for the diagnosis of nerve (root) lesions of the upper extremity, analogous to Lasègue's Straight Leg Raising test.Methods. The Upper Limb Tension Tests for the median, ulnar and radial nerves, as well as the Upper Limb Tension Tests combined with contralateral rotation and lateral bend of the cervical spine (Upper Limb Tension Test+) were used to generate tension to these nerves. Buckle force transducers were used to assess tensile forces in the nerves and in the medial, lateral and posterior cords of the brachial plexus.

RESULTS

Nerve tension introduced in the distal part of the median, ulnar and radial nerves was transmitted upward to the cords of the brachial plexus. Exclusively the median nerve Upper Limb Tension Test and Upper Limb Tension Test+ turned out to be sensitive and specific tension tests. Mechanical tension caused by the Upper Limb Tension Test+ was not significantly higher than that caused by the Upper Limb Tension Tests. The Upper Limb Tension Tests cannot be used to selectively stress cervical nerve roots. The findings justify investigation of exclusively the median nerve Upper Limb Tension Test and Upper Limb Tension Test+ on their clinical validity.

RELEVANCE

Before nerve tension tests for the median, ulnar and radial nerves can be introduced to clinical practice it is necessary to assess their validity quantitatively.

Acute effects of urban air pollution on respiratory health of children with and without chronic respiratory symptoms

OBJECTIVES

To investigate to what extent different components of air pollution are associated with acute respiratory health effects in children with and without chronic respiratory symptoms.

METHODS

During three consecutive winters starting in 1992-3, peak expiratory flow (PEF) and respiratory symptoms were registered daily in panels of children of 7-11 years old with and without symptoms, living in urban areas with high traffic intensity in The Netherlands. Simultaneously, panels of children living in non-urban areas were studied. Daily measurements of particles with aerodynamic diameter < 10 microns (PM10), black smoke (BS), sulphate, SO2, and NO2 were performed in both areas.

RESULTS

The contrast in particle concentrations (PM10, BS, and sulphate) between urban and non-urban areas was small, but there was more contrast in the concentrations of SO2 and NO2. In children with symptoms from both areas, significant associations were found between PM10, BS, and sulphate concentrations and the prevalence of symptoms of the lower respiratory tract (LRS) and decrements in PEF. Particle concentrations were also associated with use of bronchodilators in the urban areas, but not in the non-urban areas. After stratification by use of medication, stronger associations were found in children who used medication than in children who did not use medication. The magnitude of the estimated effects was in the order of a twofold increase in the use of bronchodilators, a 50% increase in LRS, and an 80% increase in decrements in PEF for a 100 micrograms/m3 increase in the 5 day mean PM10 concentration. In children without symptoms, significant associations were found between concentrations of PM10 and BS and decrements in PEF in both areas, but these associations were smaller than those for children with symptoms. No associations with respiratory symptoms were found.

CONCLUSIONS

The results suggest that children with symptoms are more susceptible to the effects of particulate air pollution than children without symptoms, and that use of medication for asthma does not prevent the adverse effects of particulate air pollution in children with symptoms.

Mass concentration and elemental composition of PM10 in classrooms

OBJECTIVES

To investigate the sources of high concentrations of particles of < 10 microns diameter (PM10) in classrooms, observed in a previous study on childhood exposure to PM10, and to study the correlation between classroom and outdoor concentrations of mass and elements of PM10.

METHODS

Measurements of PM10 were conducted in two schools and outdoors in Amsterdam, the Netherlands. Averaging time was 24 hours for the outdoor measurements and both 8 hours (school time) and 24 hours for the classroom measurements. Analysis by x ray fluorescence was used to measure the elemental composition of 55 samples from the 11 days when measurements were conducted simultaneously in both classrooms and outdoors.

RESULTS

For most elements, classroom concentrations were considerably higher than outdoor concentrations, especially during school hours. The highest classroom/outdoor ratios were found for the elements from soils Si, Ca, and Ti. The only measured elements that were not increased were S, Br, Pb, and Cl, which are dominated by non-crustal sources. For S, Br, and Pb, which are generally associated with particles < 1 micron, significant correlations between classroom and outdoor concentrations and between the two classrooms were found. The other elements generally had low correlations.

CONCLUSIONS

The results show that the high PM10 concentrations found in our classrooms are probably due to resuspension of coarse particles or suspension of soil material. Due to these excess coarse particles, the correlation between classroom and outdoor concentrations is lower for elements associated with coarse particles than for elements associated with fine particles. As the general composition of PM10 in classrooms differs from the composition of PM10 in ambient air, the high PM10 mass concentrations in classrooms can probably not be directly compared with ambient air quality guidelines.

Modulation of the acute respiratory effects of winter air pollution by serum and dietary antioxidants: a panel study

This study investigated whether a high dietary intake or serum concentration of antioxidant (pro-) vitamins could attenuate the acute respiratory effects of air pollution in panels of adults (n = 227) aged 50-70 yrs with chronic respiratory symptoms in two winters starting in 1993/1994. Subjects performed daily peak expiratory flow (PEF) measurements in the morning and evening and reported the occurrence of respiratory symptoms in two regions (urban and nonurban) each winter. Logistic regression analysis was used with the prevalences of large PEF decrements as dependent variables and air pollution levels as independent variables. Analyses were performed separately for subjects below and above the median levels of serum beta-carotene and the intake of dietary vitamin C and beta-carotene. Subjects with low levels of serum beta-carotene more often had large PEF decrements when particles <10 microm in diameter or black smoke levels which were higher compared to subjects with high levels of serum beta-carotene. The same results tended to be observed for dietary vitamin C or beta-carotene, but there were less significant air pollution effects in the low dietary antioxidant group. The results suggest that serum beta-carotene and to a lesser extent dietary vitamin C and beta-carotene may attenuate peak expiratory flow decrements due to air pollution in subjects with chronic respiratory symptoms.

Self-reporting versus parental reporting of acute respiratory symptoms of children and their relation to pulmonary function and air pollution

BACKGROUND

Studies of acute effects of outdoor air pollution on acute respiratory symptoms in children generally rely on reports by parents. Little is known about the validity of parental reporting of symptoms of their children. We therefore compared symptoms reported by the parents with self-reported symptoms and measured pulmonary function of 741 7-11-year-old Dutch children. We also analysed the association of symptoms reported by the child or parent and outdoor air pollution.

METHODS

The parents of the children completed a daily diary of symptoms of their children for about 3 months. The children reported presence of acute respiratory symptoms in the preceding week before a pulmonary function test was conducted (6-10 test days).

RESULTS

Children reported between 80% and 220% more acute respiratory symptoms than their parents for them in the same period. The agreement between symptom reports by the parent and the child was low to moderate (Kappa between 0.22 for eye irritation and 0.43 for fever). Presence of cough reported by child or parent was associated with similar small decrements in forced vital capacity (FVC), forced expiratory volume in one second (FEV1.0) and especially peak expiratory flow (PEF) and maximal mid-expiratory flow (FEF25-75). The largest pulmonary function decrements were found when symptoms were reported by both parent and child. Symptoms reported by either child or parent were not associated with air pollution.

CONCLUSIONS

Symptom reports of the children were more prevalent but did not agree well with parental reports. The similar association with pulmonary function suggested that self-reported symptoms were neither superior nor inferior to symptoms reported by the parents.

Effects of ambient air pollution on upper and lower respiratory symptoms and peak expiratory flow in children

BACKGROUND

Previous epidemiological studies have shown acute effects of increased amounts of ambient air pollution on the prevalence of respiratory symptoms in children with respiratory disorders. We investigated whether children with bronchial hyperresponsiveness (BHR) and relatively high serum concentrations of total IgE (>60 kU/L, the median value) are susceptible to air pollution.

METHODS

We collected data from children during three winters (1992-95) in rural and urban areas of the Netherlands. Lower respiratory symptoms (wheeze, attacks of wheezing, shortness of breath), upper respiratory symptoms (sore throat, runny or blocked nose), and peak expiratory flow were recorded daily for 3 months. The acute effects of airborne particulate matter with a diameter of less than 10 microm, black smoke, sulphur dioxide, and nitrogen dioxide were estimated by logistic regression.

FINDINGS

459 (73%) of 632 children had complete data. Of these, 26% had BHR and relatively high (above median) serum total IgE, 36% had no BHR and total IgE of 60 kU/L or less, 15% had BHR and total IgE of 60 kU/L or less, and 23% had a total IgE of more than 60 kU/L but no BHR. In children with BHR and relatively high serum total IgE the prevalence of lower respiratory symptoms increased significantly by between 32% and 139% for each 100 microm/m3 increase in particulate matter, and between 16% and 131% for each 40 microm/m3 increase in black smoke, SO2, or NO2. Decrease in peak expiratory flow of more than 10% in that group was more common with increased airborne particulate matter and black smoke. There were no consistent positive or negative associations between increased air pollution and prevalence of respiratory symptoms or decrease in peak expiratory flow in the other three groups of children.

INTERPRETATION

Children with BHR and relatively high concentrations of serum total IgE are susceptible to air pollution. Although our odds ratios were rather low (range 1.16-2.39) the overall effect of air pollution on public health is likely to be substantial since these odds ratios refer to large numbers of people.

Personal exposure to fine particles in children correlates closely with ambient fine particles

To investigate the validity of ambient fine-particle concentrations as a measure of exposure in epidemiological time-series studies, we established the association between personal and ambient concentrations, within subjects, over time. We conducted repeated measurements of personal and ambient fine-particle concentrations in 13 children who lived in Wageningen, The Netherlands. For each child separately, we related personal exposures to ambient concentrations in a regression analysis. The median Pearson's correlation coefficient was 0.86. Personal fine-particle concentrations were also highly correlated with ambient particulate matter (i.e., < or = 10-microm) concentrations (median Pearson's correlation coefficient = .75). Personal fine-particle concentrations were typically approximately 11 microg/m3 higher than ambient concentrations. We excluded measurements of children who were exposed to environmental tobacco smoke, and the difference was only 5 microg/m3. The findings of high correlations between personal fine-particle concentrations and both ambient fine-particle concentrations and particulate matter (i.e., < or = 10-microm) found in this group of children provide support for investigators to use ambient particulate matter concentrations to measure exposure to fine-particle concentrations in epidemiological time-series studies.

Inhomogeneity in response to air pollution in European children (PEACE project)

OBJECTIVES

The PEACE study is a multicentre panel study of the acute effects of particles with a 50% cut off aerodynamic diameter of 10 microns (PM10), black smoke (BS), sulphur dioxide (SO2), and nitrogen dioxide (NO2) on respiratory health of children with chronic respiratory symptoms. In the complete panels no consistent association between air pollution and respiratory health was found. The study evaluated whether potentially more sensitive subgroups in the panels did show effects of air pollution.

METHODS

To evaluate heterogeneity in response to air pollution, effect estimates of air pollution on peak expiratory flow (PEF) and respiratory symptoms were calculated in subgroups based on presence of chronic respiratory symptoms, use of respiratory medication, atopy, sex, and baseline lung function.

RESULTS

The association between PEF and air pollution was positive in asthmatic children who used respiratory medication whereas the associations tended to be negative in children who did not use respiratory medication selected only on cough. No consistent association was found among asthmatic children who did not use medication. The association between daily prevalence of symptoms and concentrations of air pollution was not different between these subgroups.

CONCLUSION

None of the predefined potentially more sensitive subgroups showed a consistent association between air pollution, PEF, and respiratory symptoms.