B. Brunekreef

Validation of a screening questionnaire for atopy with serum IgE tests in a population of pregnant Dutch women

We have started a large birth cohort study in which pregnant women with and without atopy are differentially included. In view of the large number of subjects to be screened (12 000), a simple questionnaire was developed for the assessment of atopy in pregnant women.

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.

Fungal propagules in house dust. I: Comparison of analytic methods and their value as estimators of potential exposure

The presence of viable mold propagules in house dust was investigated by 10 different analytic methods, in order to determine to what extent different results are obtained when different analytic methods are used. Moreover, the value of this measurement as an estimator of the potential exposure to fungi in epidemiologic studies was assessed. Floor and mattress dust was sampled in 60 homes in The Netherlands during autumn 1990. For investigation of the variability in time, sampling was repeated in 20 homes after 6 weeks. Each analytic method is characterized by a unique combination of culture medium, suspension medium, and dilution step. The highest mean number of colony‐forming units (CFU)/g dust was obtained by suspension of at least 100 mg dust in a peptone or sucrose solution in a ratio of 1:50 (w/w), followed by 10‐fold dilution and plating on DG18 agar (geometric mean (GM) approximately 60000 CFU/g dust). The lowest mean number of CFU/g dust was obtained by direct plating of 30 mg dust on V8 agar (GM approximately 5300 CFU/g dust). The mean coefficient of variation of duplicate analyses varied from 11%, for suspension in sucrose and plating on DG18 agar, to 27%, for suspension and dilution in sucrose in combination with V8 agar. The highest mean number of species isolated was obtained by direct plating of 30 mg dust on DG18 agar (mean number of species: 17). Suspension and dilution on DG18 or V8 agars yielded an average of approximately six species. In duplicate analyses, the mean percentage of agreement for the species isolated varied from approximately 35%, for suspension and dilution, to 60%, for direct plating. The reproducibility of the number of CFU/g dust in time was better for mattress dust than for floor dust; however, also for mattress dust, the predictive value of a single measurement was rather low. The variability in time in species isolated was substantial, both for mattress dust and floor dust. We concluded that results of measurements of viable mold propagules in house dust, both quantitatively and qualitatively, depend greatly on the analytic methods used. Furthermore, a single measurement of fungal propagules in settled house dust does not provide a reliable measure of potential exposure to fungi in indoor environments.

Fungal propagules in house dust. II: Relation with residential characteristics and respiratory symptoms

As part of a case‐control study on the relation between home dampness and respiratory symptoms of children, house‐dust samples were collected from bedroom floors and mattresses in 60 homes in The Netherlands. The house‐dust samples were analyzed for the presence of fungal propagules by plating 30 mg of dust directly onto DG18 agar. A checklist and questionnaire were used to obtain information on the home characteristics and occupant behavior that may have an effect on the presence of fungal propagules in house dust. The geometric mean (GM) number of colony‐forming units (CFU)/g dust collected from the floors was 8990. The number of CFU/g dust was significantly higher in dust from carpeted floors than in dust from smooth floors (GM, respectively, 12880 CFU/g dust and 3530 CFU/g dust). The GM number of CFU/g dust collected from mattresses was 6760. Overall, the mean numbers of CFU/g dust collected from floors and mattresses were higher in bedrooms where damp spots mold growth, or both were observed. However, these differences were not statistically significant. The relation between home characteristics and the number of CFU/g dust of the most frequently isolated mold species (n= 17), including Alternaria alternata, Cladosporium cladosporioides, Penicillium brevicompactum, and Scopulariopsis brevicaulis, was also investigated. Only the type of flooring had a significant and consistent effect on the number of CFU/g floor dust of the different mold species. For P. brevicompactum, the number of CFU/g floor dust was significantly higher in bedrooms where damp spots were observed. The number of CFU/g mattress dust of S. brevicaulis was also significantly higher for bedrooms where damp spots were observed. However, in view of the large number of statistical comparisons made, these two significant relationships might have been caused by chance alone. The total numbers of CFU/g mattress and floor dust were not related to the average relative indoor humidity measured over 6 weeks. Furthermore, there was no association between the presence of fungi in house dust and respiratory symptoms. We conclude that there was only a very weak relationship between the home characteristics and occupant behavior, as determined by checklist and questionnaire, and the presence of fungal propagules in floor dust and mattress dust. Only the type of flooring had a substantial and statistically significant effect on the presence of fungal propagules in floor dust. Therefore, the presence of fungal propagules in house dust cannot be predicted reliably by home characteristics.

Short and long term variability of the interrupter technique under field and standardised conditions in 3–6 year old children

Background: The short and long term variability of the interrupter technique was assessed to determine whether interrupter resistance is a stable individual characteristic over time. The effect of field and standardised measurement conditions on the within-subject variability of the interrupter technique was also examined. Methods: The interrupter technique was studied under field and standardised conditions in children aged 3–6 years. Under field conditions, five investigators performed the measurements using two different measurement devices in random sequence. Both short term (20–30 minutes) and long term variability (median 38 days) were assessed in 32 children. Under standardised conditions, a single investigator conducted all measurements using a single device; the repeated measurements were conducted at the same time of day in a familiar quiet classroom. Long term variability (median 11 days) was estimated in 15 children. Within-subject standard deviations were estimated by analysis of variance with adjustment for the effects of different investigators and measurement devices on within-subject variability under field conditions. Results: Under field conditions within-subject standard deviations for short and long term variability were 0.10 kPa/l/s (adjusted 0.10 kPa/l/s) and 0.13 kPa/l/s (adjusted 0.14 kPa/l/s), respectively. Under standardised conditions the within-subject standard deviation for long term variability was 0.10 kPa/l/s. Conclusions: Measurement of interrupter resistance under field conditions only slightly increased the within-subject variability compared with standardised conditions. The results indicate that interrupter resistance is a stable individual characteristic over a period of some weeks.

Der p I concentrations in mattress surface and floor dust collected from infants' bedrooms.

Background Allergen exposure in early childhood is thought to be important for sensitization and subsequent development of asthma. Not much is known, however, about exposure of young children to allergens in the home.

House dust mite allergen (Der p I) and respiratory symptoms in children: a case‐control study

The association between house dust mite allergen in house dust and childhood respiratory symptoms was investigated in a case‐control study of 259 children with reported chronic respiratory symptoms and 257 control children without reported respiratory symptoms. The Der p I concentration in floor dust of the living room and bedroom and in mattress dust was determined using an enzyme immunoassay. Venous blood samples were taken from all children for serum IgE determination against house dust mite (Dermatophagoides pteronyssinus) by radioallergosorbent assay (RAST). A questionnaire was administered to the parents of the children to elicit information about the home, about changes made to the home in the past in relation to respiratory symptoms, and about a number of risk factors for childhood respiratory disease. In 83% of the dwellings of cases and 89% of those of controls, Der p I concentrations higher than 2000 ng/g were found, and in 54% of the dwellings of cases and 57% of those of controls, the concentrations exceeded 10 000 ng/g dust. In a crude analysis, cases were generally exposed to lower Der p I concentrations than controls. Restriction of the analysis to cases sensitized to dust mites, and non‐sensitized controls, taking the type of floor covering into account, showed not significantly higher Der p I concentrations in bedroom floor dust of cases. However, restriction of the analysis to cases sensitizied to dust mites and cases not sensitized to house dust mites — adjusting for allergen avoidance measures taken in the past — revealed a positive association between the Der p I concentrations in bedroom floor dust and mattress dust and sensitization. This finding indicates that allergen avoidance measures modify current exposure to Der p I. This obscures the relationship between the exposure to mite allergens and sensitization, and hampers the estimation of the association between exposure to house dust mite allergens, sensitization and the development of respiratory symptoms.

Repeatability of bronchial hyperresponsiveness to adenosine-5 '-monophosphate (AMP) by a short dosimeter protocol

BACKGROUND To study bronchial responsiveness to adenosine 5′-monophosphate (AMP) in population surveys, repeatability of a rapid dosimetric method with quadrupling doses was evaluated. METHODS Volunteers with symptoms of airway respiratory allergy or asthma were invited for AMP challenges on two occasions. After each dose the fall in forced expiratory volume in one second (FEV1) compared with the post-saline value was determined. The cumulative doses of AMP needed to cause a fall in FEV1 of 20% (PD20), 15% (PD15), and 10% (PD10) were calculated. Agreement was evaluated by means of kappa values. After excluding systematic differences in PD values on two occasions (t test), repeatability of a single estimation of the chosen PD values was calculated and expressed in doubling doses (DD). RESULTS In 28 of 76 subjects a PD20 was estimated on the two visits, in 29 subjects a PD15 was estimated, and in 32 a PD10was obtained. Kappa values for a positive threshold were 0.89 for a cut off level for a 20% fall in FEV1, 0.78 for a 15% fall in FEV1, and 0.76 for a fall in FEV1 of 10%. The PD values did not differ between the two visits and 95% repeatability of a single estimation was ±1.7 DD for PD20, ±2.2 DD for PD15, and ±2.4 DD for PD10. The quadrupling dose method reduced time by 40% in non-hyperresponsive subjects and no adverse effects were observed. CONCLUSION The short dosimeter protocol with quadrupling doses for AMP challenges is a rapid, reproducible tool for estimating bronchial responsiveness in population surveys.

Peak-flow variability in asthmatic children is not related to wall-to-wall carpeting on classroom floors

The hypothesis was tested that wall‐to‐wall carpets on school classroom floors have a negative effect on the respiratory health of asthmatic children. Asthmatic patients (n= 98) were selected from the records of the Sophia Childrens Hospital in Rotterdam. The patients were between 5 and 11 years old. All children had peak‐flow measurements three times a day for a 1‐month period. The parents of the children completed a diary in which respiratory symptoms and medication use were recorded daily for the same period. Dust samples were taken from classroom floors, living‐room and bedroom floors, and mattresses of the children. The dust samples were analyzed for Der p I content, the major allergen of the house‐dust mite Dermatophagoides pteronyssinus. The results of the study showed that there was no significant difference between children visiting schools with or without carpeted classroom floors in peak‐flow variability, acute respiratory symptoms, or medication use. The Der p I content of dust collected from classroom floors was much lower than of dust collected from homes. There was a significant correlation between peak‐flow variability and mattress dust Der p I content in asthmatic children sensitized to dust mites, but not between peak‐flow variability and classroom floor dust Der p I content. We concluded that carpeted classroom floors do not contribute to asthma symptom severity, possibly because of the low levels of Der p I on them.

Particulate matter air pollution components and incidence of cancers of the stomach and the upper aerodigestive tract in the European Study of Cohorts of Air Pollution Effects (ESCAPE)

INTRODUCTION Previous analysis from the large European multicentre ESCAPE study showed an association of ambient particulate matter <2.5 μm (PM2.5) air pollution exposure at residence with the incidence of gastric cancer. It is unclear which components of PM are most relevant for gastric and also upper aerodigestive tract (UADT) cancer and some of them may not be strongly correlated with PM mass. We evaluated the association between long-term exposure to elemental components of PM2.5 and PM10 and gastric and UADT cancer incidence in European adults. METHODS Baseline addresses of individuals were geocoded and exposure was assessed by land-use regression models for copper (Cu), iron (Fe) and zinc (Zn) representing non-tailpipe traffic emissions; sulphur (S) indicating long-range transport; nickel (Ni) and vanadium (V) for mixed oil-burning and industry; silicon (Si) for crustal material and potassium (K) for biomass burning. Cox regression models with adjustment for potential confounders were used for cohort-specific analyses. Combined estimates were determined with random effects meta-analyses. RESULTS Ten cohorts in six countries contributed data on 227,044 individuals with an average follow-up of 14.9 years with 633 incident cases of gastric cancer and 763 of UADT cancer. The combined hazard ratio (HR) for an increase of 200 ng/m3 of PM2.5_S was 1.92 (95%-confidence interval (95%-CI) 1.13;3.27) for gastric cancer, with no indication of heterogeneity between cohorts (I2 = 0%), and 1.63 (95%-CI 0.88;3.01) for PM2.5_Zn (I2 = 70%). For the other elements in PM2.5 and all elements in PM10 including PM10_S, non-significant HRs between 0.78 and 1.21 with mostly wide CIs were seen. No association was found between any of the elements and UADT cancer. The HR for PM2.5_S and gastric cancer was robust to adjustment for additional factors, including diet, and restriction to study participants with stable addresses over follow-up resulted in slightly higher effect estimates with a decrease in precision. In a two-pollutant model, the effect estimate for total PM2.5 decreased whereas that for PM2.5_S was robust. CONCLUSION This large multicentre cohort study shows a robust association between gastric cancer and long-term exposure to PM2.5_S but not PM10_S, suggesting that S in PM2.5 or correlated air pollutants may contribute to the risk of gastric cancer.