Ebba Malmqvist

Gestational Diabetes and Preeclampsia in Association with Air Pollution at Levels below Current Air Quality Guidelines

Background: Several studies have estimated associations between air pollution and birth outcomes, but few have evaluated potential effects on pregnancy complications. Objective: We investigated whether low-level exposure to air pollution is associated with gestational diabetes and preeclampsia. Methods: High-quality registry information on 81,110 singleton pregnancy outcomes in southern Sweden during 1999–2005 was linked to individual-level exposure estimates with high spatial resolution. Modeled exposure to nitrogen oxides (NOx), expressed as mean concentrations per trimester, and proximity to roads of different traffic densities were used as proxy indicators of exposure to combustion-related air pollution. The data were analyzed by logistic regression, with and without adjusting for potential confounders. Results: The prevalence of gestational diabetes increased with each NOx quartile, with an adjusted odds ratio (OR) of 1.69 (95% CI: 1.41, 2.03) for the highest (> 22.7 µg/m3) compared with the lowest quartile (2.5–8.9 µg/m3) of exposure during the second trimester. The adjusted OR for acquiring preeclampsia after exposure during the third trimester was 1.51 (1.32, 1.73) in the highest quartile of NOx compared with the lowest. Both outcomes were associated with high traffic density, but ORs were significant for gestational diabetes only. Conclusion: NOx exposure during pregnancy was associated with gestational diabetes and preeclampsia in an area with air pollution levels below current air quality guidelines.

Maternal Exposure to Air Pollution and Birth Outcomes.

Background The knowledge about air pollution effects on birth weight, prematurity, and small for gestational age (SGA) in low-exposure areas is insufficient. Objectives The aim of this birth cohort study was to investigate whether low-level exposure to air pollution was associated with prematurity and fetal growth and whether there are sex-specific effects. Method We combined high-quality registry information on 81,110 births with individually modeled exposure data at residence for nitrogen oxides (NOx) and proximity to roads with differing traffic density. The data were analyzed by logistic and linear regression with and without potential confounders. Results We observed an increased risk for babies being SGA when we compared highest and lowest NOx quartiles, adjusting for maternal age, smoking, sex, and year of birth. After additional adjustment for maternal country of origin and parity (which were highly intercorrelated), the increase was no longer statistically significant. However, in subgroup analyses when we compared highest and lowest NOx quartiles we still observed an increased risk for SGA for girls [odds ratio (OR) = 1.12; 95% confidence interval (CI), 1.01–1.24); we also observed increased risk among mothers who had not changed residency during pregnancy (OR = 1.09; 95% CI, 1.01–1.18). The confounders with the greatest impact on SGA were parity and country of origin. Concerning prematurity, the prevalence was lower in the three higher NOx exposure quartiles compared with the lowest category. Conclusion For future studies on air pollution effects on birth outcomes, careful control of confounding is crucial.

A national fine spatial scale land-use regression model for ozone.

Uncertainty about health effects of long-term ozone exposure remains. Land use regression (LUR) models have been used successfully for modeling fine scale spatial variation of primary pollutants but very limited for ozone. Our objective was to assess the feasibility of developing a national LUR model for ozone at a fine spatial scale. Ozone concentrations were measured with passive samplers at 90 locations across the Netherlands (19 regional background, 36 urban background, 35 traffic). All sites were measured simultaneously during four 2-weekly campaigns spread over the seasons. LUR models were developed for the summer average as the primary exposure and annual average using predictor variables obtained with Geographic Information Systems. Summer average ozone concentrations varied between 32 and 61 µg/m(3). Ozone concentrations at traffic sites were on average 9 µg/m(3) lower compared to regional background sites. Ozone correlated highly negatively with nitrogen dioxide and moderately with fine particles. A LUR model including small-scale traffic, large-scale address density, urban green and a region indicator explained 71% of the spatial variation in summer average ozone concentrations. Land use regression modeling is a promising method to assess ozone spatial variation, but the high correlation with NO2 limits application in epidemiology.

Fetal growth and air pollution - A study on ultrasound and birth measures

Abstract Air pollution has been suggested to affect fetal growth, but more data is needed to assess the timing of exposure effects by using ultrasound measures. It is also important to study effects in low exposure areas to assess eventual thresholds of effects. The MAPSS (Maternal Air Pollution in Southern Sweden) cohort consists of linked registry data for around 48,000 pregnancies from an ultrasound database, birth registry and exposure data based on residential addresses. Measures of air pollution exposure were obtained through dispersion modelling with input data from an emissions database (NOx) with high resolution (100–500 m grids). Air pollution effects were assessed with linear regressions for the following endpoints; biparietal diameter, femur length, abdominal diameter and estimated fetal weight measured in late pregnancy and birth weight and head circumference measured at birth. We estimated negative effects for NOx; in the adjusted analyses the decrease of abdominal diameter and femur length were −0.10 (−0.17, −0.03) and −0.13 (−0.17, −0.01) mm, respectively, per 10 &mgr;g/m3 increment of NOx. We also estimated an effect of NOx‐exposures on birth weight by reducing birth weight by 9 g per 10 &mgr;g/m3 increment of NOx. We estimated small but statistically significant effects of air pollution on late fetal and birth size and reduced fetal growth late in pregnancy in a geographic area with levels below current WHO air quality guidelines. HighlightsLargest study on ultrasound measures and air pollution to date.Individual data on potential confounders (also SES) and nitrogen oxides.Area with levels below current WHO air quality guidelines.Birth weight was reduced by 9 g per 10 &mgr;g/m3 increment of NOx.Small but statistically significant effects of air pollution on late fetal size.

Maternal exposure to air pollution and type 1 diabetes - Accounting for genetic factors.

BACKGROUND Genetic and non-genetic factors probably act together to initiate and accelerate development of type 1 diabetes [T1D]. One suggested risk factor contributing to development of T1D is air pollution. OBJECTIVE The aim of the study was to investigate whether maternal exposure during pregnancy to air pollution, measured as nitrogen oxides [NOx] and ozone, in a low-dose exposure area was associated with the child developing T1D. METHOD In Scania (Skåne), the most southern county in Sweden, 84,039 infants were born during the period 1999-2005. By the end of April 2013, 324 of those children had been diagnosed with T1D. For each of those T1D children three control children were randomly selected and matched for HLA genotype and birth year. Individually modelled exposure data at residence during pregnancy were assessed for nitrogen oxides [NOx], traffic density and ozone. RESULTS Ozone as well as NOx exposures were associated with T1D. When the highest exposure group was compared to the lowest group an odds ratios of 1.62 (95% confidence interval [CI] 0.99-2.65) was observed for ozone in the second trimester and 1.58 (95% CI 1.06-2.35) for NOx in the third trimester. CONCLUSION This study indicates that living in an area with elevated levels of air pollution during pregnancy may be a risk factor for offspring T1D.

Ebola: Improving the Design of Protective Clothing for Emergency Workers Allows Them to Better Cope with Heat Stress and Help to Contain the Epidemic

It is a complex task to find optimal protective clothing to prevent the spread of Ebola virus disease (Martin-Moreno et al., 2014; Ryschon, 2014). The fear of getting infected is an obstacle for recruiting healthcare workers. In addition, the current design of protective clothing might curtail their working capacity severely in the hot and humid climate of West Africa and, in addition, paradoxically increase the risk of infection. Emergency work in full protective clothing including respiratory mask may lead to extreme heat stress in the hot climates resulting in shortened work time, dehydration, reduced professional judgement, and exhaustion. This increases risk of infection of health stuff (WHO, 2014). In Monrovia, Liberia, daytime maximum temperatures in the end of the year often reach 30–31°C, and the temperatures will be higher January to May, the hot season (Kjellstrom et al., 2014; http://climatechip.org/). In order to manage this heat stress, the workers need breaks (Kjellstrom et al., 2009). This leads to a frequent need to remove the protective gear, which involves an increased risk of infection. The multiple steps to remove the suit can take up to 30min (Kitamura, 2014). The modified Predicted Heat Strain (ISO 7933, 2004) model was used to indicate the expected work times (Fig. 1). The estimation was made based on the following assumptions. Standard man was chosen for the model calculations. Medium heavy activity (300W) was taken as the average work rate. The core temperature limit to cease such emergency work was set to 38.5°C. Three clothing types with different moisture permeability (i m) were selected for comparison: an impermeable outer layer (i m = 0.00), a semipermeable outer layer (i m = 0.07), and a relatively tight but still permeable outer layer (i m = 0.20). The basic clothing insulation in all cases was theoretically taken as 1 clo (0.155 m2K W−1) for comparative purposes. In all air temperature conditions, the other environmental factors were kept constant. Ambient water vapour pressure was set to 3.0 kPa, air velocity/body motion was 1 m s−1, and there was assumed no radiation effect present (work indoors or in shade). 1 Continuous work times for a work rate of 300W at different air temperatures before reaching a core temperature limit at 38.5°C in clothing with different moisture permeability (i m). The chosen work load in impermeable and semipermeable clothing allows 40min or shorter exposure during the hottest periods (Fig. 1) until the core temperature exceeds the suggested safe limit for occupational exposure. Higher core temperature is associated with decreased mental performance and increased misjudgement and mistakes (O’Neal and Bishop, 2010). Maximizing the moisture permeability and minimizing the clothing layers worn beneath the protective gear, provided that it should be resistant to penetration by body fluids, is a simple way of preventing heat stress and increasing the time spent inside the gear. However, dehydration and water intake must also be considered during extended exposures. A heat stress management program including rehydration should be an essential part of the overall health and safety program in any case. A desirable addition would be personal cooling used inside the protective clothing, such as cooling vests with ice or phase change materials (PCMs; Gao, 2014) or filtered ventilated coveralls (Kuklane et al., 2012). This may prolong working time to about 2h and reduce the number of gear changes per day. With 2-h work time in protective gear, the number of required personnel could be halved with possible decrease in contaminated waste. The final choice of the cooling method depends on specific air temperature and humidity. Increasing air temperature and, especially, humidity do reduce the effectiveness of air cooling and increase the benefits of PCM products. The use of PCMs requires freezers or cool areas for solidification after use. Cooling vests with ice are the cheapest and electricity for freezers is required. Power is one of the basic resources to provide healthcare and to cope with epidemics. Otherwise, the other types of PCM, e.g. Glauber’s salt or organic hydrocarbons/wax, with melting/solidifying temperature at about 28°C are available. For workers’ recovery after heat exposure, a room with air temperature below 27°C is recommended. The room or connected facilities could be used for PCM solidification storage. If still unavailable, then the melted PCM can be solidified in a relatively cooler water bath (using underground/well water, etc.), in an underground cave or in a cooler area during night. The higher the melting temperatures are, the less effective cooling is. However, if the temperature gradient is about 6°C or greater, the PCM can still provide a cooling effect. Considering cooling effect in ventilated garments, the provided air flow should be above 100 l min−1. There are filtered fan systems available on the market that manage the flows up to and above 200 l min−1 with the battery power lasting at least 5–8h (recharging takes about 2h). Ventilated systems (positive pressure suits) may allow even drinking water in the suit and that may prolong the work time even more. Table 1 gives a rough cost comparison of the present and a possible future protective clothing system based on 1-day (8-h) shift. It takes into account only the equipment cost. Estimation is based on the work time predictions given in Fig. 1 for the hottest work periods, i.e. 30min for the impermeable set and 2h for the new system that prolongs work period by higher permeability or by use of a cooling device. In both cases, similar final core temperatures are expected to limit the exposure. Also, it is expected that both sets take 30min for dressing, 30min for undressing, and require 30min for recovery between the work periods. As it can be seen the equipment cost of a new, theoretically even a 10 times more expensive solution is almost 3 times higher for a day. Table 1. Comparison of the equipment cost of the present and a possible, 10 times more expensive protective clothing system based on 1-day (8-h) shift. Assumed work time is 30min for present and 2h for the new system. In both cases, expected donning, doffing, ... Simultaneously, there are also other benefits with an actively cooling clothing system. The personnel need to cover one workstation is halved. The personnel have even extra time (about 30min) between the shifts to help with any other tasks or for additional recovery. Due to fewer times of dressing–undressing (16 + 16 times 30min versus 4 + 4 times 30min for present respective new system), there is also less need for assistance and disinfection during these periods. There will be less contaminated waste or fewer amounts of products to be cleaned. The new systems are meant to be reusable (extra costs for decontamination procedures have to be considered) compared to present, supposedly disposable systems, and already 2.5 times reuse will even up the equipment costs at the estimated prices. Infection risks are diminished due to the reduced need for undressing and cleaning procedures. In conclusion, reducing the risk of infection among the front-line healthcare workers and allowing a doubling of their work capacity could be a critical factor to successfully contain the epidemic. Considering that this epidemic is not the last, and with warmer climate both the epidemics are expected becoming more frequent, and conditions to fight them more severe (IPCC, 2013), then the testing and evaluation for selection of the optimal equipment is required long before missions are set out.

Choices Behind Numbers : a Review of the Major Air Pollution Health Impact Assessments in Europe

Purpose of ReviewThe aim of this review is to identify the key contextual and methodological differences in health impact assessments (HIA) of ambient air pollution performed for Europe. We limited our review to multi-country reviews. An additional aim is to quantify some of these differences by applying them in a HIA template in three European cities.Recent FindingsSeveral HIAs of ambient air pollution have been performed for Europe, and their key results have been largely disseminated. Different studies have, however, come up with substantial differences in attributed health effects. It is of importance to review the background contributing to these differences and to quantify their importance for decision makers who will use them.SummaryWe identified several methodological differences that could explain the discrepancy behind the number of attributable deaths or years of life lost. The main differences are due to the exposure-response functions chosen, the ways of assessing air pollution levels, the air pollution scenarios and the study population. In the quantification part, we found that using risk estimates from the European Study of Cohorts for Air Pollution Effects (ESCAPE) instead of the American Cancer Society (ACS) study could nearly double the attributable burden of ambient air pollution.This study provides some insights into the differential results in previously published HIAs on air pollution in Europe. These results are important for stakeholders in order to make informed decisions.

Short-Term Associations between Air Pollution Concentrations and Respiratory Health-Comparing Primary Health Care Visits, Hospital Admissions, and Emergency Department Visits in a Multi-Municipality Study

Acute effects of air pollution on respiratory health have traditionally been investigated with data on inpatient admissions, emergency room visits, and mortality. In this study, we aim to describe the total acute effects of air pollution on health care use for respiratory symptoms (ICD10-J00-J99). This will be done by investigating primary health care (PHC) visits, inpatient admissions, and emergency room visits together in five municipalities in southern Sweden, using a case-crossover design. Between 2005 and 2010, there were 81,019 visits to primary health care, 38,217 emergency room visits, and 25,271 inpatient admissions for respiratory symptoms in the study area. There was a 1.85% increase (95% CI: 0.52 to 3.20) in the number of primary health care visits associated with a 10 µg/m3 increase in nitrogen dioxide (NO2) levels in Malmö, but not in the other municipalities. Air pollution levels were generally not associated with emergency room visits or inpatient admissions, with one exception (in Helsingborg there was a 2.52% increase in emergency room visits for respiratory symptoms associated with a 10 µg/m3 increase in PM10). In conclusion, the results give weak support for short-term effects of air pollution on health care use associated with respiratory health symptoms in the study area.

An efficient sampling strategy for selection of biobank samples using risk scores

Aim: The aim of this study was to suggest a new sample-selection strategy based on risk scores in case-control studies with biobank data. Methods: An ongoing Swedish case-control study on fetal exposure to endocrine disruptors and overweight in early childhood was used as the empirical example. Cases were defined as children with a body mass index (BMI) ⩾18 kg/m2 (n=545) at four years of age, and controls as children with a BMI of ⩽17 kg/m2 (n=4472 available). The risk of being overweight was modelled using logistic regression based on available covariates from the health examination and prior to selecting samples from the biobank. A risk score was estimated for each child and categorised as low (0–5%), medium (6–13%) or high (⩾14%) risk of being overweight. Results: The final risk-score model, with smoking during pregnancy (p=0.001), birth weight (p<0.001), BMI of both parents (p<0.001 for both), type of residence (p=0.04) and economic situation (p=0.12), yielded an area under the receiver operating characteristic curve of 67% (n=3945 with complete data). The case group (n=416) had the following risk-score profile: low (12%), medium (46%) and high risk (43%). Twice as many controls were selected from each risk group, with further matching on sex. Computer simulations showed that the proposed selection strategy with stratification on risk scores yielded consistent improvements in statistical precision. Conclusions: Using risk scores based on available survey or register data as a basis for sample selection may improve possibilities to study heterogeneity of exposure effects in biobank-based studies.

Traffic-Related Air Pollution and Child BMI—A Study of Prenatal Exposure to Nitrogen Oxides and Body Mass Index in Children at the Age of Four Years in Malmö, Sweden

Traffic-related air pollution could be a danger to the health of children. Earlier studies have linked prenatal exposure to an increased risk of a range of diseases and negative health outcomes, including overweight and obesity. Presently, a knowledge gap exists in investigating the risk of overweight and obesity among children exposed to lower levels of air pollution in utero. This study aimed to investigate the relationship between prenatal traffic-related air pollution (nitrogen dioxides (NOx) and traffic density) and childhood overweight and obesity in Malmö, Sweden. A cohort, based on attendance of a four-year check-up examination at Swedish Child Health Care (CHC) centers, and a parent-assessed questionnaire provided data on body-mass index adjusted for four-year-old children (ISO-BMI) as well as socioeconomic and health variables. We estimated exposure by using traffic density and levels of NOx at the maternal geocoded residential level. Analysis of 5815 children was performed using binary logistic regression models. This study showed no associations of increased risk for childhood overweight or obesity through to prenatal exposure to NOx in this low-exposure setting. We further suggest analysis of risks related to exposure levels ranging between the ones presented here and those proposed in previous literature.