Expert Panel Report 2: Guidelines for the Diagnosis and Management of Asthma

Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma

1.1. History
Formaldehyde was described in the year 1855 by the Russian scientist Alexander Michailowitsch Butlerow. The technical synthesis by dehydration of methanol was achieved in 1867 by the German chemist August Wilhelm von Hofmann. The versatility that makes it suitable for use in various industrial applications was soon discovered, and the compound was one of the first to be indexed by Chemical Abstracts Service (CAS). In 1944, Walker published the first edition of his classic work Formaldehyde.(1) Between 1900 and 1930, formaldehyde-based resins became important adhesives for wood and wood composites. The first commercial particle board was produced during World War II in Bremen, Germany. Since 1950, particle board has become an attractive alternative to solid wood for the manufacturing of furniture. Particle board and other wood-based panels were subsequently also used for the construction of housing. Adverse health effects from exposure to formaldehyde in prefabricated houses, especially irritation of the eyes and upper airways, were first reported in the mid-1960s. Formaldehyde emissions from particle boards bonded with urea formaldehyde resin were soon identified as the cause of the complaints. As a consequence, a guideline value of 0.1 ppm was proposed in 1977 by the former German Federal Agency of Health to limit human exposure in dwellings. Criteria for the limitation and regulation of formaldehyde emissions from wood-based materials were established in 1981 in Germany and Denmark. The first regulations followed in the United States in 1985 or thereabouts. In Germany and the United States, large-scale test chambers were used for the evaluation of emissions. Although the chamber method is very reliable, it is also time-consuming and expensive. This meant there was a strong demand for simple laboratory test methods.(2)

Formaldehyde in the Indoor Environment

To assess whether school environments can adversely affect academic performance, we review scientific evidence relating indoor pollutants and thermal conditions, in schools or other indoor environments, to human performance or attendance. We critically review evidence for direct associations between these aspects of indoor environmental quality (IEQ) and performance or attendance. Secondarily, we summarize, without critique, evidence on indirect connections potentially linking IEQ to performance or attendance. Regarding direct associations, little strongly designed research was available. Persuasive evidence links higher indoor concentrations of nitrogen dioxide to reduced school attendance, and suggestive evidence links low ventilation rates to reduced performance. Regarding indirect associations, many studies link indoor dampness and microbiologic pollutants (primarily in homes) to asthma exacerbations and respiratory infections, which in turn have been related to reduced performance and attendance. Also, much evidence links poor IEQ (e.g., low ventilation rate, excess moisture, or formaldehyde) with adverse health effects in children and adults and documents dampness problems and inadequate ventilation as common in schools. Overall, evidence suggests that poor IEQ in schools is common and adversely influences the performance and attendance of students, primarily through health effects from indoor pollutants. Evidence is available to justify (1) immediate actions to assess and improve IEQ in schools and (2) focused research to guide IEQ improvements in schools.

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Do indoor pollutants and thermal conditions in schools influence student performance? A critical review of the literature

We reviewed the literature on Indoor Air Quality (IAQ), ventilation, and building-related health problems in schools and identified commonly reported building-related health symptoms involving schools until 1999. We collected existing data on ventilation rates, carbon dioxide (CO2) concentrations and symptom-relevant indoor air contaminants, and evaluated information on causal relationships between pollutant exposures and health symptoms. Reported ventilation and CO2 data strongly indicate that ventilation is inadequate in many classrooms, possibly leading to health symptoms. Adequate ventilation should be a major focus of design or remediation efforts. Total volatile organic compounds, formaldehyde (HCHO) and microbiological contaminants are reported. Low HCHO concentrations were unlikely to cause acute irritant symptoms (<0.05 ppm), but possibly increased risks for allergen sensitivities, chronic irritation, and cancer. Reported microbiological contaminants included allergens in deposited dust, fungi, and bacteria. Levels of specific allergens were sufficient to cause symptoms in allergic occupants. Measurements of airborne bacteria and airborne and surface fungal spores were reported in schoolrooms. Asthma and 'sick building syndrome' symptoms are commonly reported. The few studies investigating causal relationships between health symptoms and exposures to specific pollutants suggest that such symptoms in schools are related to exposures to volatile organic compounds (VOCs), molds and microbial VOCs, and allergens.

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Indoor air quality, ventilation and health symptoms in schools: an analysis of existing information

Background
Children living in a damp house are more likely to suffer from respiratory symptoms and it has been suggested that exposure to fungi is an important contributing factor. However, more knowledge about underlying mechanisms for the association are needed.

Objective
To identify associations between measures of house dampness, levels of airborne fungal spores, housing factors and health outcomes in children.

Methods
Eighty households with 148 children between 7 and 14 years of age were recruited in the Latrobe Valley, Victoria, Australia. Some 36% of participating children were asthmatic. Six sampling visits were made to each house between March 1994 and February 1995 on a 2-monthly cycle. Samples for airborne total and viable fungal spores were collected from bedrooms, living rooms, kitchens and outdoors. A detailed dwelling characterization, using a questionnaire and inspection surveys, was carried out. Skin-prick tests were performed with extracts of common aeroallergens and a respiratory questionnaire was completed for each child.

Results
Large airborne fungal spore concentrations were recorded in association with: musty odour, water intrusion, high indoor humidity, limited ventilation through open windows, few extractor fans and failure to remove indoor mould growth. Visible mould growth or condensation evidence was associated with large concentrationsof Cladosporium spores, but not with large total spore concentrations. Penicillium exposure was a risk factor for asthma, while Aspergillus exposure was a risk factor for atopy. Fungal allergies were more common among children exposed to Cladosporium or Penicillium in winter or to musty odour. Respiratory symptoms were marginally more common with exposure to Cladosporium or total spores in winter.

Conclusion
Indoor exposure to certain fungal genera in winter was a risk factor for asthma, atopy and respiratory symptoms in children. On the other hand, no significant associations were seen between average viable or total spore concentrations and child health. Actual measurements of fungal spores predict health outcomes better than reported dampness.

Indoor airborne fungal spores, house dampness and associations with environmental factors and respiratory health in children

Background: Formaldehyde levels were measured in 80 houses in the Latrobe Valley, Victoria, Australia. An association between exposure to formaldehyde and sensitization to common aeroallergens has been suggested from animal trials, but no epidemiologic studies have tested this hypothesis.



Methods: A total of 148 children 7–14 years of age were included in the study, 53 of whom were asthmatic. Formaldehyde measurements were performed on four occasions between March 1994 and February 1995 with passive samplers. A respiratory questionnaire was completed, and skin prick tests were performed.



Results: The median indoor formaldehyde level was 15.8 μg/m3(12.6 ppb), with a maximum of 139 μg/m3 (111 ppb). There was an association between formaldehyde exposure and atopy, and the adjusted odds ratio was 1.40 (0.98–2.00, 95% CI) with an increase in bedroom formaldehyde levels of 10 μg/m3. Furthermore, more severe allergic sensitization was demonstrated with increasing formaldehyde exposure. On the other hand, there was no significant increase in the adjusted risk of asthma or respiratory symptoms with formaldehyde exposure. However, among children suffering from respiratory symptoms, more frequent symptoms were noted in those exposed to higher formaldehyde levels.



Conclusions: Low-level exposure to indoor formaldehyde may increase the risk of allergic sensitization to common aeroallergens in children.

Increased risk of allergy in children due to formaldehyde exposure in homes

Nitrogen dioxide levels were measured in 80 homes in the Latrobe Valley, Victoria, Australia, using passive samplers. Some 148 children between 7 and 14 yr of age were recruited as study participants, 53 of whom had asthma. Health outcomes for the children were studied using a respiratory questionnaire, skin prick tests, and peak flow measurements. Nitrogen dioxide concentrations were low, with an indoor median of 11.6 μ g/m3 (6.0 ppb), and a maximum of 246 μ g/m3 (128 ppb). Respiratory symptoms were more common in children exposed to a gas stove (odds ratio 2.3 [95% CI 1.0–5.2], adjusted for parental allergy, parental asthma, and sex). Nitrogen dioxide exposure was a marginal risk factor for respiratory symptoms, with a dose–response association present (p = 0.09). Gas stove exposure was a significant risk factor for respiratory symptoms even after adjusting for nitrogen dioxide levels (odds ratio 2.2 [1.0–4.8]), suggesting an additional risk apart from the average nitrogen dioxide exposure associated wi...

Respiratory symptoms in children and indoor exposure to nitrogen dioxide and gas stoves.

Background Eighty households in the Latrobe Valley, Victoria, Australia, were sampled for house-dust-mite allergen (Der p 1). Allergen levels vary greatly between houses within climate regions. The reasons for this are not well understood.



Methods House-dust-mite allergen samples were collected on six occasions between March 1994 and February 1995, All participating households contained at least one child between 7 and 14 years with a total of 148 subjects, 53 of whom were asthmatic. A detailed house survey was performed during every sampling visit, and a dwelling questionnaire was completed. Relative humidity was measured at the time of sample collection.



Results The median bed allergen level was 30 ng/g during the first sampling period. Significantly higher allergen levels were associated with wool bedding and inner-spring mattresses (p < 0.001). As estimated from a multiple linear regression model, up to 70% reduction in bed allergen levels may be achieved by avoiding wool bedding and inner-spring mattresses. Other risk factors for high allergen levels included high indoor relative humidity, presence of substantial visible mould growth, brick cladding, and concrete slab foundation of the house.



Conclusions Avoiding wool bedding and replacing inner-spring mattresses with foam could substantially reduce bed allergen levels.

Indoor environmental factors associated with house-dust-mite allergen (Der p 1) levels in south-eastern Australian houses.

Indoor nitrogen dioxide exposure has been associated with respiratory symptoms in children in many studies, but in Australia, levels and sources of nitrogen dioxide in homes have not been well-characterized. Therefore, as part of a larger indoor environmental study, conducted in the Latrobe Valley, Victoria, nitrogen dioxide was monitored using passive samplers in 80 homes. Samples were collected on five occasions over one year. Mean indoor levels were higher than outdoor levels, and a seasonal variation was evident, with highest levels recorded in winter. The overall median level was 11.6 ug/m3 (6.0 ppb), ranging from <0.7 to 246 ug/m3 (128 ppb). Major indoor nitrogen dioxide sources were: gas stoves, vented gas heaters, and smoking. Some 67% of variation in indoor nitrogen dioxide levels could be explained by presence of major sources, house age, and outdoor levels. Gas stoves were the main contributors.

https://www.tandfonline.com/doi/pdf/10.1080/10473289.1999.10463781

Beverley M Hooper

Papers

Indoor airborne fungal spores, house dampness and associations with environmental factors and respiratory health in children

Increased risk of allergy in children due to formaldehyde exposure in homes

Respiratory symptoms in children and indoor exposure to nitrogen dioxide and gas stoves.

Indoor environmental factors associated with house-dust-mite allergen (Der p 1) levels in south-eastern Australian houses.

Nitrogen dioxide in Australian homes: levels and sources.