Effect of classroom air quality on students' concentration: results of a cluster-randomized cross-over experimental study

To assess the effect of indoor air quality as indicated by the median carbon dioxide (CO₂) level in the classroom on the concentration performance (CP) of students, a cross-over cluster-randomized experimental study was conducted in 20 classrooms with mechanical ventilation systems. Test conditions 'worse' (median CO₂ level on average 2115 ppm) and 'better' (median CO₂ level on average 1045 ppm) were established by the regulation of the mechanical ventilation system on two days in one week each in every classroom. Concentration performance was quantified in students of grade three and four by the use of the d2-test and its primary parameter 'CP' and secondary parameters 'total number of characters processed' (TN) and 'total number of errors' (TE). 2366 d2-tests from 417 students could be used in analysis. In hierarchical linear regression accounting for repeated measurements, no significant effect of the experimental condition on CP or TN could be observed. However, TE was increased significantly by 1.65 (95% confidence interval 0.42-2.87) in 'worse' compared to 'better' condition. Thus, low air quality in classrooms as indicated by increased CO₂ levels does not reduce overall short-term CP in students, but appears to increase the error rate.

PRACTICAL IMPLICATIONS

This study could not confirm that low air quality in classrooms as indicated by increased CO₂ levels reduces short-term concentration performance (CP) in students; however, it appears to affect processing accuracy negatively. To ensure a high level of accuracy, good air quality characterized, for example, by low CO₂ concentration should be maintained in classrooms.

Exposure to secondhand tobacco smoke and child behaviour - results from a cross-sectional study among preschool children in Bavaria

AIM

To evaluate the association of postnatal exposure to secondhand tobacco smoke on childhood behavioural problems after taking maternal smoking during pregnancy into account.

METHODS

In a cross-sectional survey of preschool children in Bavaria, exposure to secondhand tobacco smoke in the child's home was assessed via a parent questionnaire. The Strength and Difficulties Questionnaire (SDQ) was applied to assess child's behaviour. The association with secondhand tobacco smoke exposure was assessed for 'probable' outcomes of the problem subscales and of prosocial behaviour.

RESULTS

Among 5494 children (48% female), the SDQ indicated behavioural problems in up to 11%. After adjustment for socioeconomic factors, low birth weight and maternal smoking before and during pregnancy, a dose-response relationship with exposure to secondhand tobacco smoke was observed regarding hyperactivity/inattention (odds ratio compared to 'none' was 1.35 for 'low/medium' and 2.39 for 'high' exposure, 95% confidence intervals 1.02-1.78 and 1.62-3.53, respectively) as well as for conduct problems (OR 1.68 (1.37-2.06) and 1.93 (1.39-2.68)).

CONCLUSION

Secondhand tobacco smoke exposure at home appears to be associated with an increased risk of behavioural problems among preschool children. Prevention of behavioural problems may be a further reason to target secondhand tobacco smoke exposure in children.

[Smoking bans in public places: current epidemiological evidence of cardiovascular health impacts at the population level]

During the past years smoking bans in public places including hospitality venues have been introduced in several countries. Up to now, eight ecological studies on hospital admission rates due to acute myocardial infarction or coronary events after introduction of a smoking ban in the United States, Canada, and Italy have been published. This article reviews these studies and discusses their significance and potential sources of error from an epidemiological point of view. The chronological order of reduction in acute myocardial infarction rates following the smoking ban, the consistency of this association in several countries, and the biological plausibility because of the known acute cardiovascular effects of secondhand smoke suggest a causal association. Thus, if this turns out to be true public smoking bans will be a very effective public health measure.

Perfluorooctane sulphonate (PFOS) and perfluorooctanoic acid (PFOA) in human breast milk: Results of a pilot study

Perfluorinated compounds (PFC) are a large group of chemicals produced for several decades and widely used for many industrial and consumer applications. Because of their global occurrence in different environmental media, their persistence and their potential to bioaccumulate in organisms they are of toxicological and public concern. In the present study, perfluorooctane sulphonate (PFOS) and perfluorooctanoic acid (PFOA) were quantified in 70 breast milk samples. Samples were obtained from Leipzig, Germany (38 archived samples), Munich, Germany (19 fresh samples) and Gyor, Hungary (13 frozen samples). PFOS could be quantified in all 70 samples. The concentration in samples from Germany ranged between 28 and 309 ng/l (median: 119 ng/l). Samples from Hungary showed significantly higher PFOS concentrations (median 330 ng/l, range 96-639 ng/l). In only 11 of 70 samples (16%) PFOA reached the LOQ (200 ng/l); values ranged from 201 to 460 ng/l. If only those samples with PFOA values above the LOQ were considered, we found a significant correlation between the PFOS and PFOA concentrations (r=0.75, p=0.008). Based on the results of the German sample, we estimated an intake of 0.10 microg PFOS/day (using median) or 0.27 PFOS microg/day (using maximum value) via breast milk for an infant of 5 kg bodyweight. Our data suggest that fully breastfed infants are unlikely to exceed the recommended tolerable daily intake of PFC. However, more target-oriented studies are needed to identify the amount and time-trend of PFOS and PFOA in maternal blood during pregnancy, after delivery, as well as in the growing infant and in its diet (e.g., breast milk and formula).

[Air quality in schools - classroom levels of carbon dioxide (CO2), volatile organic compounds (VOC), aldehydes, endotoxins and cat allergen]

Children are assumed to be more vulnerable to health hazards and spend a large part of their time in schools. To assess the exposure situation in this microenvironment, we evaluated the indoor air quality in winter 2004/5 in 92 classrooms, and in 75 classrooms in summer 2005 in south Bavaria, Germany. Indoor air climate parameters (temperature, relative humidity), carbon dioxide (CO2) and various volatile organic compounds, aldehydes and ketones were measured. Additionally, cat allergen (Fel d1) and endotoxin (LAL-test) were analysed in the settled dust of school rooms. Data on room and building characteristics were collected by use of a standardised form. Only data collected during teaching hours were considered in analysis. The median indoor CO2 concentration in the classrooms ranged in the winter and summer period from 598 to 4 172 ppm and 480 to 1 875 ppm, respectively. While during the winter period in 92% of the classrooms the CO2 daily medians went above 1 000 ppm, the percentage of classrooms with increased CO2 concentration fell to 28% in summer. In winter, in 60% of classes the daily median CO2 concentration exceeded 1 500 ppm, while in summer this threshold was reached by only 9%. A high concentration of CO2 was associated with a high number of pupils, a low room surface area and a low room volume. The levels of total volatile organic compounds (TVOC) in classrooms ranged between 110 and 1 000 microg/m3 (median in winter 345 microg/m3, in summer 260 microg/m3). Acetone, formaldehyde and acetaldehyde were measured in concentrations from 14.0 to 911 microg/m3, from 3.1 to 46.1 microg/m3, and from 2.9 to 78 microg/m3, respectively. The other aldehydes were detected in minor amounts only. The median Fel d1 level in winter was 485 ng/g dust (20 to 45 160 ng/g) and in summer it was 417 ng/g (40-7 470 ng/g). We observed no marked differences between the two sampling periods and between smooth floors and rooms with carpeted floors. No differences were found according to room surface area and room volume. The median endotoxin contents in winter and summer were 19.7 EU/mg dust (6.6 to 154 EU/mg) and 32.2 EU/mg (9.6 to 219 EU/mg), respectively. The levels varied significantly between the sampling periods, but were independent of room surface area, room volume and surface floorings. Overall the results of VOC, aldehydes, ketones and endotoxin indicate, in general, a low exposure level in classrooms. The observed concentrations of cat allergens should be considered as a meaningful exposure route and thus could be tackled within preventive programs.

Occurrence of perfluorinated substances in an adult German population in southern Bavaria

OBJECTIVES

Perfluorinated compounds (PFCs) are a large group of chemicals produced for several decades and widely used for many industrial and consumer applications. Because of their global occurrence in different environmental media, their persistence, and their potential to bioaccumulate in organisms they are of toxicological and public concern.

METHODS

In the present study, the internal exposure to perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in 356 human plasma samples collected from an adult population in Germany in 2005 is quantified.

RESULTS

We were able to detect the target analytes in all plasma samples and observed a significant correlation between the PFOS and PFOA concentrations. In female participants, the levels of PFOS and PFOA ranged between 2.5-30.7 (median: 10.9 microg/l) and 1.5-16.2 microg/l (median: 4.8 microg/l), respectively. In males we observed concentrations from 2.1 to 55.0 microg/l (median: 13.7 microg/l) for PFOS and from 0.5 to 19.1 microg/l (median: 5.7 microg/l) for PFOA. A significant correlation between both PFOS and PFOA concentrations and gender was observed. We also found increased levels of the PFCs with increasing age of the participants, but this association reached statistical significance among females only.

CONCLUSIONS

Our data agree well with results of other recent studies in Europe and suggest that the current exposure of the adult German population is lower than the exposure of the US and Canadian population. The sources of human exposure are currently not well understood. Toxicological implications are restricted to animal studies and occupational investigations not adequate for quantitative risk assessment in humans. Overall, more scientific research is necessary to characterize the body burden of PFCs (especially for relevant subsets of the population) and the main sources and routes, which are responsible for human exposure and possible health implications of these compounds.

Long term adherence to dietary recommendations after inpatient rehabilitation: prospective follow up study of patients with coronary heart disease

OBJECTIVE

To evaluate the adherence to nutritional recommendations in inpatient rehabilitation and the long term maintenance of dietary changes among patients with coronary heart disease.

DESIGN

Prospective cohort study.

SETTING

Two rehabilitation clinics in Germany.

PARTICIPANTS

A cohort of 1206 patients undergoing inpatient rehabilitation after an acute manifestation of coronary heart disease.

MAIN OUTCOME MEASURES

Self reported dietary intake before, during, and one and three years after rehabilitation measured with a semiquantitative food frequency questionnaire and summarised to a nutritional index, which was used to categorise patients as having a poor, fair, or good diet.

RESULTS

During rehabilitation the proportion of patients whose dietary intake was categorised as good increased strongly from 30% to 91%. One and three years after rehabilitation a still increased proportion of 49% and 42%, respectively, in the good category was observed. The strong increase in intake of low fat and wholemeal products that was achieved during rehabilitation was followed after rehabilitation discharge by a backslide to the intake observed before rehabilitation admission. The avoidance of unfavourable food items, such as French fries or eggs, was at least partly maintained during the follow up period.

CONCLUSION

During inpatient rehabilitation most patients do have to make major changes in their dietary intake to comply with recommendations. Although some proportion of patients continue to adhere to dietary recommendations in the long run, further research into strategies to improve maintenance of dietary changes is needed to enhance further the long term benefits from cardiac rehabilitation.

[Statistical analysis of community-based studies -- presentation and comparison of possible solutions with reference to statistical meta-analytic methods]

PURPOSE

The statistical analysis of community-based trials and of other cluster-randomised trials, requires specific statistical methods. We show the consequences of the application of these models for study results, using data of the German Cardiovascular Prevention Study (GCP) as an example.

METHODS

Data of 30,285 subjects were analysed, which were collected at the beginning and at the end of the study period. These data had been collected in 7 intervention regions and by national surveys. We grouped data of the national surveys in 7 control clusters to mimick a design typical for cluster-randomised trials. We applied the following statistical models to estimate the effect of the intervention on total cholesterol as well as on systolic blood pressure and the respective confidence intervals: a linear model, a mixed model, and fixed and random effects meta-analyses.

RESULTS

While the estimates and confidence intervals for the intervention effect were similar in mixed model analysis and random effects meta-analysis, results from models incorporating fixed effects only were anti-conservative. The underestimation of variance in models incorporating fixed effects only was especially large in the analysis of systolic blood pressure data, where great heterogeneity between intervention communities was observed. Despite seemingly low intraclass correlation coefficients of 0.0019 for total cholesterol and 0.0166 for systolic blood pressure, respectively, the variance of the intervention effect was increased in the mixed model 2.8fold or 17.1fold, respectively, in comparison to the variance estimated in the linear model. Due to this variance inflation the intervention effect on systolic blood pressure lost statistical significance.

CONCLUSION

Our results emphasise the importance to account for correlations in community-based trials. Besides the mixed model random effects meta-analysis can be applied as an alternative method.