Jouni J. K. Jaakkola

Disinfection byproducts and bladder cancer: a pooled analysis.

Background: Exposure to disinfection byproducts in drinking water has been associated with an increased risk of bladder cancer. We pooled the primary data from 6 case-control studies of bladder cancer that used trihalomethanes as a marker of disinfection byproducts. Methods: Two studies were included from the United States and one each from Canada, France, Italy, and Finland. Inclusion criteria were availability of detailed data on trihalomethane exposure and individual water consumption. The analysis included 2806 cases and 5254 controls, all of whom had measures of known exposure for at least 70% of the exposure window of 40 years before the interview. Cumulative exposure to trihalomethanes was estimated by combining individual year-by-year average trihalomethane level and daily tap water consumption. Results: There was an adjusted odds ratio (OR) of 1.24 in men exposed to an average of more than 1 μg/L (ppb) trihalomethanes compared with those who had lower or no exposure (95% confidence interval [CI] = 1.09–1.41). Estimated relative risks increased with increasing exposure, with an OR of 1.44 (1.20–1.73) for exposure higher than 50 μg/L (ppb). Similar results were found with other indices of trihalomethane exposure. Among women, trihalomethane exposure was not associated with bladder cancer risk (0.95; 0.76–1.20). Conclusions: These findings strengthen the hypothesis that the risk of bladder cancer is increased with long-term exposure to disinfection byproducts at levels currently observed in many industrialized countries.

Secular trend in the occurrence of asthma among children and young adults: critical appraisal of repeated cross sectional surveys

Abstract Objectives: To review repeated surveys of the rising prevalence of obstructive lung disease among children and young adults and determine whether systematic biases may explain the observed trends. Design: Review of published reports of repeated cross sectional surveys of asthma and wheezing among children and young adults. The repeated surveys used the same sampling frame, the same definition of outcome variables, and equivalent data collection methods. Setting: Repeated surveys conducted anywhere in the world. Subjects: All repeated surveys whose last set of results were published in 1983 or later. Main outcome measures: Lifetime and current prevalences of asthma and current prevalence of wheezing. The absolute increase (yearly percentage) in the prevalences of asthma and wheezing was calculated and compared between studies. Results: 16 repeated surveys fulfilled the inclusion criteria. 12 reported increases in the current prevalence of asthma (from 0.09% to 0.97% a year) and eight reported increases in the current prevalence of wheezing (from 0.14% to 1.24% a year). Changes in labelling are likely to have occurred for the reporting of asthma, and information biases may have occurred for the reporting of wheezing. Only one study reported an increase in an objective measurement. Conclusions: The evidence for increased prevalences of asthma and wheezing is weak because the measures used are susceptible to systematic errors. Until repeated surveys incorporating more objective data are available no firm conclusions about increases in obstructive lung disease among children and young adults can be drawn. Key messages There is an increase in the reporting of wheezing illness in children The increase may be due to information bias There is a lack of objective measurements in population based samples to support claims for an increase in asthma The changing informational content complicates following the epidemiology of asthma

Maternal Smoking in Pregnancy, Fetal Development, and Childhood Asthma

OBJECTIVES We examined the relationships among maternal smoking in pregnancy, fetal development, and the risk of asthma in childhood. METHODS We conducted a population-based cohort study, where all 58 841 singleton births were followed for 7 years using nationwide registries. RESULTS Maternal smoking increased the risk of asthma (adjusted odds ratio = 1.35; 95% confidence interval = 1.13, 1.62 for high exposure). Low birthweight and preterm delivery increased the risk of asthma at the age of 7, whereas being small for gestational age did not. CONCLUSIONS Maternal smoking in pregnancy increases the risk of asthma during the first 7 years of life, and only a small fraction of the effect seems to be mediated through fetal growth.

Assessment of exposure to environmental tobacco smoke.

We present a theoretical framework for assessment of exposure to environmental tobacco smoke (ETS), and review current methods in order to provide guidelines for different types of studies. Exposure assessment should include both a quantitative dimension and consideration of time-specificity of exposure. The ultimate aim is to measure the concentrations of ETS encountered by an individual for different time periods in various microenvironments. The first step is to identify an indicator of ETS. Personal monitoring of air nicotine and respirable suspended particulates (RSPs) are the most direct assessment methods. Indirect assessment methods include stationary measurements of tobacco smoke constituents in different microenvironments and/or questionnaire-derived information, modelled with time-activity information. Biomarkers, such as nicotine and/or cotinine in body fluids or hair, can be used as surrogate measures of dose, although they are usually affected by individual processes in the body after exposure. The best approach to assess ETS exposure will depend on the aim of the study, the health outcome, and the resources. Personal monitoring of nicotine or RSPs is the best method in studies of short-term health effects with small study samples. Stationary measurements of indoor air nicotine or RSPs are suitable for overall monitoring of ETS in different microenvironments over time. Questionnaires and interviews are suitable when studying health outcomes with a long latency period and rare diseases requiring large study populations. Cotinine in body fluids and nicotine concentration in hair can be used to assess cumulative exposure over days or months, respectively. A combination of different methods is often the best approach.

In utero exposure to cigarette smoking influences lung function at birth

To avoid the possible confounding effects of postnatal exposure to tobacco smoke, we investigated possible effects of uterine tobacco smoke (UTS) exposure upon infant lung function shortly after birth. Infants with no major disease, in one maternity ward in Oslo, Norway, participating in a cohort study established in 1992/1993, were included in the present study (n=803). Exposure information, assessed as maternal active and passive smoking during pregnancy and other personal and environmental factors, was obtained by questionnaire. Tidal flow-volume (TFV) loops (n=802) and compliance (Crs) and resistance (Rrs) of the respiratory system (n=663) were measured at a mean age of 2.7 days. In girls, the TFV ratio (time to reach peak expiratory flow to total expiratory time (tPEF/tE)), and Crs were significantly lower with active as well as passive maternal smoking compared to nonexposure to UTS. Respiratory rate and Rrs were not significantly influenced by UTS exposure. However, in linear regression analysis adjusted for confounding factors (including respiratory rate), tPEF/tE and Crs, but not Rrs, were related to maternal active but not passive daily smoking. One daily cigarette corresponded to a change in tPEF/tE of -0.0021 (95% confidence interval (95% CI) -0.0040 to -0.0002) and a change in Crs of -0.026 mL x cmH2O (95% CI -0.045 to -0.007 mL x cmH2O). The decrease was 0.023 and 0.29, respectively, in infants of an average smoker. Maternal smoking during pregnancy adversely affected tidal flow-volume ratios in healthy newborn babies, as well as the compliance of the respiratory system in girls, independently of the reduced body size also resulting from maternal smoking.

Exposure to pets and atopy-related diseases in the first 4 years of life

Background: It is still unclear how early‐life exposure to pets is related to childrens risk of developing atopy‐related diseases. We estimated associations between early‐life exposure to pets and atopy‐related diseases at 0‐4 years of life in a cohort of Norwegian children.

Interior surface materials in the home and the development of bronchial obstruction in young children in Oslo, Norway.

OBJECTIVES This study assessed the role of polyvinyl chloride (PVC) plastics and textile materials in the home in the development of bronchial obstruction during the first 2 years of life. METHODS The study was a matched pair case-control study based on a cohort of 3754 newborns in Oslo in 1992 and 1993 who were followed up for 2 years. The case group consisted of 251 children with bronchial obstruction; the control group was matched one-to-one for date of birth. RESULTS In conditional logistic regression analysis, the risk of bronchial obstruction was related to the presence of PVC flooring (adjusted odds ratio [OR] = 1.89; 95% confidence interval [CI] = 1.14, 3.14) and textile wall materials (adjusted OR = 1.58; 95% CI = 0.98, 2.54). The reference category was wood or parquet flooring and painted walls and ceiling. Further analysis revealed an exposure-response relationship between the assessed amount of PVC and other plasticizer-containing surface materials and the risk of bronchial obstruction. CONCLUSIONS This study provides new evidence of the role of PVC and textile wall materials in the development of bronchial obstruction in young children.

Day Care Centers and Respiratory Health

Objective. To estimate the effects of the type of day care on respiratory health in preschool children. Methods. A population-based cross-sectional study of Oslo children born in 1992 was conducted at the end of 1996. A self-administered questionnaire inquired about day care arrangements, childrens health, environmental conditions, and family characteristics (n = 3853; response rate, 79%). Results. In logistic regression controlling for confounding, children in day care centers had more often nightly cough (adjusted odds ratio, 1.89; 95% confidence interval, 1.34–2.67), and blocked or runny nose without common cold (1.55; 1.07–1.61) during the past 12 months compared with children in home care. Poisson regression analysis showed an increased risk of the common cold (incidence rate ratio, 1.21; 1.12–1.30) and otitis media (1.48; 1.22–1.80), and the attributable proportion was 17.4% (95% confidence interval, 10.7–23.1) for the common cold and 32.4% (18.0–44.4) for otitis media. Early starting age in the day care center increased the risk of developing recurrent otitis media. Also the lifetime risk of doctor-diagnosed asthma was higher in children who started day care center attendance during the first 2 years of life. Conclusions. Attendance to day care centers increases the risk of upper respiratory symptoms and infections in 3- to 5-year-old children. The starting age seems to be an important determinant of recurrent otitis media as well as asthma. The effect of day care center attendance on asthma is limited to age up to 2 years. This effect is most likely mediated via early respiratory tract infections that are substantially more common in children in day care centers compared with children in home care.

The Role of Exposure to Phthalates from Polyvinyl Chloride Products in the Development of Asthma and Allergies: A Systematic Review and Meta-analysis

Background Phthalates from polyvinyl chloride (PVC) plastics may have adverse effects on airways and immunologic systems, but the evidence has not been reviewed systematically. Objective We reviewed the evidence for the role of exposure to phthalates from PVC products in the development of asthma and allergies. Methods We conducted a Medline database search (1950 through May 2007) for relevant studies on the respiratory and allergic effects of exposure to phthalates from PVC products. Results We based this review on 27 human and 14 laboratory toxicology studies. Two mouse inhalation experiments indicated that mono-2-ethylhexyl phthalate (MEHP) has the ability to modulate the immune response to exposure to a coallergen. The data suggested a no observed effect level of 30 μg MEHP/m3, calculated to be below the estimated level of human exposure in common environments. Case reports and series (n = 9) identified and verified cases of asthma that were very likely caused by fumes emitted from PVC film. Epidemiologic studies in adults (n = 10), mostly small studies in occupational settings, showed associations between heated PVC fumes and asthma and respiratory symptoms; studies in children (n = 5) showed an association between PVC surface materials in the home and the risk of asthma [fixed-effects model: summary odds ratio (OR), 1.55; 95% confidence interval (CI), 1.18–2.05; four studies] and allergies (OR, 1.32; 95% CI, 1.09–1.60; three studies). Conclusions High levels of phthalates from PVC products can modulate the murine immune response to a coallergen. Heated PVC fumes possibly contribute to development of asthma in adults. Epidemiologic studies in children show associations between indicators of phthalate exposure in the home and risk of asthma and allergies. The lack of objective exposure information limits the epidemiologic data.

Home dampness and molds, parental atopy, and asthma in childhood: a six-year population-based cohort study

Previous studies of how parental atopy and exposure to dampness and molds contribute to the risk of asthma have been mainly cross-sectional or prevalent case–control studies, where selection and information bias and temporality constitute problems. We assessed longitudinally the independent and joint effects of parental atopy and exposure to molds in dwellings on the development of asthma in childhood. We conducted a population-based, 6-year prospective cohort study of 1,984 children 1–7 years of age at the baseline in 1991 (follow-up rate, 77%). The study population included 1,916 children without asthma at baseline and complete outcome information. The data collection included a baseline and follow-up survey. The outcome of interest was development of asthma during the study period. The studied determinants were parental allergic diseases and four indicators of exposure at baseline: histories of water damage, presence of moisture and visible molds, and perceived mold odor in the home. A total of 138 (7.2%) children developed asthma during the study period, resulting in an incidence rate of 125 cases per 10,000 person-years [95% confidence interval (CI), 104–146]. In Poisson regression adjusting for confounding, parental atopy [adjusted incidence rate ratio (IRR) 1.52; 95% CI, 1.08–2.13] and the presence of mold odor in the home reported at baseline (adjusted IRR 2.44; 95% CI, 1.07–5.60) were independent determinants of asthma incidence, but no apparent interaction was observed. The results of this cohort study with assessment of exposure before the onset of asthma strengthen the evidence on the independent effects of parental atopy and exposure to molds on the development of asthma.