Levels of endotoxin in 390 Swedish homes: determinants and the risk for respiratory symptoms in children.

Endotoxins are microbiological agents which ubiquitously exist in an indoor environment, and are believed to be causal agents for a number of diseases. This study investigated the indoor levels and determinants of endotoxins and their impact on asthma and allergy diseases among Swedish pre-school children. House dust samples from 390 homes of 198 case children with asthma and allergy and 202 healthy control children were collected in the Dampness Building and Health (DBH) study. House dust endotoxin levels in the child's bedroom and living rooms ranged from 479-188,000 EU/g dust and from 138-942,000 EU/g dust, respectively. Pet-keeping and agricultural activities were significantly associated with the higher endotoxin concentration levels in indoor dust. Endotoxins in theindoor environment did not associate to asthma and allergy diseases in the children. However, we found an association between endotoxins and the presence of disease symptoms in the sub-group of families without indoor pets.

Can we trust cross-sectional studies when studying the risk of moisture-related problems indoor for asthma in children?

Most studies studying dampness as a risk factor for asthma are of a cross-sectional design. The aim of this study was to investigate if the association between moisture-related problems indoor and asthma found in cross-sectional questionnaire data can be confirmed in longitudinal analyses. The Dampness in Building and Health (DBH) study started in 2000 in Värmland, Sweden, with a baseline questionnaire to all children aged 1-5 y (n = 14,077) and five years later a follow-up questionnaire was distributed to children aged 6-8 y (n = 7,509). Moisture-related problems that were associated with asthma in cross-sectional analysis decreased or disappeared in the longitudinal analysis. However, the association between reports of moldy odor in the homes at baseline and incident asthma remained and became stronger. Our results suggest that cross-sectional data showing associations between moisture-related problems in homes and asthma in children partly can be explained by reporting bias.

Building characteristics associated with moisture related problems in 8,918 Swedish dwellings.

Moisture problems in buildings have in a number of studies been shown to increase the risk for respiratory symptoms. The study Dampness in Buildings and Health (DBH) was initiated with the aim to identify health relevant exposures related to dampness in buildings. A questionnaire study about home environment with a focus on dampness problems and health was conducted in one county of Sweden (8,918 homes, response rate 79%). Building characteristics that were associated with one or more of the dampness indicators were for single-family houses, older houses, flat-roofed houses built in the 1960s and 1970s, houses with a concrete slab on the ground that were built before 1983. Moreover, tenancy and earlier renovation due to mould or moisture problems was strongly associated with dampness. A perception of dry air was associated with window-pane condensation, e.g. humid indoor air.

Phthalates in indoor dust and their association with building characteristics.

In a recent study of 198 Swedish children with persistent allergic symptoms and 202 controls without such symptoms, we reported associations between the symptoms and the concentrations of n-butyl benzyl phthalate (BBzP) and di(2-ethylhexyl) phthalate (DEHP) in dust taken from the childrens' bedrooms. In the present study we examined associations between the concentrations of different phthalate esters in the dust from these bedrooms and various characteristics of the home. The study focused on BBzP and DEHP because these were the phthalates associated with health complaints. Associations have been examined using parametric and nonparametric tests as well as multiple logistic regression. For both BBzP and DEHP, we found associations between their dust concentrations and the amount of polyvinyl chloride (PVC) used as flooring and wall material in the home. Furthermore, high concentrations of BBzP (above median) were associated with self-reported water leakage in the home, and high concentrations of DEHP were associated with buildings constructed before 1960. Other associations, as well as absence of associations, are reported. Both BBzP and DEHP were found in buildings with neither PVC flooring nor wall covering, consistent with the numerous additional plasticized materials that are anticipated to be present in a typical home. The building characteristics examined in this study cannot serve as complete proxies for these quite varied sources. However, the associations reported here can help identify homes where phthalate concentrations are likely to be elevated and can aid in developing mitigation strategies.

The association between asthma and allergic symptoms in children and phthalates in house dust: a nested case-control study.

Global phthalate ester production has increased from very low levels at the end of World War II to approximately 3.5 million metric tons/year. The aim of the present study was to investigate potential associations between persistent allergic symptoms in children, which have increased markedly in developed countries over the past three decades, and the concentration of phthalates in dust collected from their homes. This investigation is a case-control study nested within a cohort of 10,852 children. From the cohort, we selected 198 cases with persistent allergic symptoms and 202 controls without allergic symptoms. A clinical and a technical team investigated each child and her or his environment. We found higher median concentrations of butyl benzyl phthalate (BBzP) in dust among cases than among controls (0.15 vs. 0.12 mg/g dust). Analyzing the case group by symptoms showed that BBzP was associated with rhinitis (p = 0.001) and eczema (p = 0.001), whereas di(2-ethylhexyl) phthalate (DEHP) was associated with asthma (p = 0.022). Furthermore, dose-response relationships for these associations are supported by trend analyses. This study shows that phthalates, within the range of what is normally found in indoor environments, are associated with allergic symptoms in children. We believe that the different associations of symptoms for the three major phthalates-BBzP, DEHP, and di-n-butyl phthalate-can be explained by a combination of chemical physical properties and toxicologic potential. Given the phthalate exposures of children worldwide, the results from this study of Swedish children have global implications.