Sources of nitrogen dioxide (NO2) in New Zealand homes: findings from a community randomized controlled trial of heater substitutions

Nitrogen dioxide exposure, health outcomes, and associated demographic disparities due to gas and propane combustion by U.S. stoves

Gas and propane stoves emit nitrogen dioxide (NO2) pollution indoors, but the exposures of different U.S. demographic groups are unknown. We estimate NO2 exposure and health consequences using emissions and concentration measurements from >100 homes, a room-specific indoor air quality model, epidemiological risk parameters, and statistical sampling of housing characteristics and occupant behavior. Gas and propane stoves increase long-term NO2 exposure 4.0 parts per billion volume on average across the United States, 75% of the World Health Organization's exposure guideline. This increased exposure likely causes ~50,000 cases of current pediatric asthma from long-term NO2 exposure alone. Short-term NO2 exposure from typical gas stove use frequently exceeds both World Health Organization and U.S. Environmental Protection Agency benchmarks. People living in residences <800 ft2 in size incur four times more long-term NO2 exposure than people in residences >3000 ft2 in size; American Indian/Alaska Native and Black and Hispanic/Latino households incur 60 and 20% more NO2 exposure, respectively, than the national average.

Crosscutting of the pollutants and building ventilation systems: a literature review

Considering the time spent in enclosed environments, it is essential to study the relationship between pollutants and building ventilation systems to find whether the types and levels of pollutants and greenhouse gasses, which are expected to be exhaled through ventilation systems into the atmosphere, have been adequately evaluated. We propose the hypothesis that the exhaled air from residential buildings contains pollutants that may become another source of contamination affecting urban air quality and potentially contributing to climate drivers. Thus, the main goal of this article is to present a cross-review of the identification of pollutants expected to be exhaled through ventilation systems in residential buildings. This approach has created the concept of "exhalation of buildings" a new concept enclosed within the research project in which this article is included. We analyze the studies related to the most significant pollutants found in buildings and the studies about the relation of buildings' ventilation systems with such pollutants. Our results show that, on the one hand, the increase in the use of mechanical ventilation systems in residential buildings has been demonstrated to enhance the ventilation rate and generally improve the indoor air quality conditions. But no knowledge could be extracted about the corresponding environmental cost of this improvement, as no systematic data were found about the total mass of contaminants exhaled by those ventilation systems. At the same time, no projects were found that showed a quantitative study on exhalation from buildings, contrary to the existence of studies on pollutants in indoor air.

Exposure to Aerosols Emitted from Common Heating Combustion Sources Indoors—The Jordanian Case as an Example for Eastern Mediterranean Conditions

In Jordan, ~61% of total residential energy consumption is consumed by heating spaces using portable kerosene (K) and liquified petroleum gas (LPG) heaters. Here, we evaluated the indoor air quality (IAQ) versus the use of K and LPG heaters inside a test room reflecting the typical conditions of Jordanian dwellings during the winter season. The experimental setup included particle size distribution (diameter 0.01–25 µm) measurements, and we utilized a simple sectional indoor aerosol model (SIAM) to estimate the emission rate and lifetime of the combustion products in the test room. The particle number (PN) concentration during the LPG operation was 6 × 104–5.9 × 105 cm−3, depending on the setting at minimum, medium, or maximum. The K heater operation increased with the PN concentrations to a range of 4 × 105–8 × 105 cm−3. On average, the particle losses were 0.7–1.6 h−1 for micron particles (1–10 µm) and 0.8–0.9 h−1 for ultrafine particles (<0.1 µm). The emission rate from the LPG heater was 1.2 × 1010–2.8 × 1010 particles/s (6.6 × 106–8.0 × 106 particles/J), and that for the K heater was about 4.4 × 1010 particles/s (1.9 × 107 particles/J). The results call for the immediate need to apply interventions to improve the IAQ by turning to cleaner heating processes indoors.

The impact of second-hand smoke on nitrogen oxides concentrations in a small interior

Nitrogen oxides (NO_x), especially nitrogen dioxide (NO₂), are among the most hazardous forms of air pollution. Tobacco smoke is a main indoor source of NO_x, but little information is available about their concentrations in second-hand smoke (SHS), particularly in small indoors. This study presents data of NO_x and its main components nitric oxide (NO) and NO₂ in SHS emitted by ten different cigarette brands measured in a closed test chamber with a volume of 2.88 m³, similar to the volume of vehicle cabins. The results show substantial increases in NO_x concentrations when smoking only one cigarette. The NO₂ mean concentrations ranged between 105 and 293 µg/m³, the NO₂ peak concentrations between 126 and 357 µg/m³. That means the one-hour mean guideline of 200 µg/m³ for NO₂ of the World Health Organization was exceeded up to 47%, respectively 79%. The measured NO₂ values show positive correlations with the values for tar, nicotine, and carbon monoxide stated by the cigarette manufacturers. This study provides NO₂ concentrations in SHS at health hazard levels. These data give rise to the necessity of health authorities' measures to inform about and caution against NO_x exposure by smoking in indoor rooms.

Indoor Exposure to Selected Air Pollutants in the Home Environment: A Systematic Review

(1) Background: There is increasing awareness that the quality of the indoor environment affects our health and well-being. Indoor air quality (IAQ) in particular has an impact on multiple health outcomes, including respiratory and cardiovascular illness, allergic symptoms, cancers, and premature mortality. (2) Methods: We carried out a global systematic literature review on indoor exposure to selected air pollutants associated with adverse health effects, and related household characteristics, seasonal influences and occupancy patterns. We screened records from six bibliographic databases: ABI/INFORM, Environment Abstracts, Pollution Abstracts, PubMed, ProQuest Biological and Health Professional, and Scopus. (3) Results: Information on indoor exposure levels and determinants, emission sources, and associated health effects was extracted from 141 studies from 29 countries. The most-studied pollutants were particulate matter (PM_2.5 and PM₁₀); nitrogen dioxide (NO₂); volatile organic compounds (VOCs) including benzene, toluene, xylenes and formaldehyde; and polycyclic aromatic hydrocarbons (PAHs) including naphthalene. Identified indoor PM_2.5 sources include smoking, cooking, heating, use of incense, candles, and insecticides, while cleaning, housework, presence of pets and movement of people were the main sources of coarse particles. Outdoor air is a major PM_2.5 source in rooms with natural ventilation in roadside households. Major sources of NO₂ indoors are unvented gas heaters and cookers. Predictors of indoor NO₂ are ventilation, season, and outdoor NO₂ levels. VOCs are emitted from a wide range of indoor and outdoor sources, including smoking, solvent use, renovations, and household products. Formaldehyde levels are higher in newer houses and in the presence of new furniture, while PAH levels are higher in smoking households. High indoor particulate matter, NO₂ and VOC levels were typically associated with respiratory symptoms, particularly asthma symptoms in children. (4) Conclusions: Household characteristics and occupant activities play a large role in indoor exposure, particularly cigarette smoking for PM_2.5, gas appliances for NO₂, and household products for VOCs and PAHs. Home location near high-traffic-density roads, redecoration, and small house size contribute to high indoor air pollution. In most studies, air exchange rates are negatively associated with indoor air pollution. These findings can inform interventions aiming to improve IAQ in residential properties in a variety of settings.

The Role of Environmental Controls in Managing Asthma in Lower-Income Urban Communities

Children living in lower-income urban communities are at much greater risk of developing asthma, going to the emergency department for an asthma attack and being hospitalized for asthma than children living in upper- and middle-income communities. For many asthmatic children living in urban communities, especially those with greater morbidity, the allergic pathway is important in the etiology of the disease. The stages of developing allergic disease can be divided into the onset of allergic sensitization, development of allergic disease and subsequent exacerbations, and it is useful to consider the relevance of interventions at each of these stages. Indoor allergens and environmental exposures are a major contributor to allergic disease, particularly among lower socioeconomic status, urban, minority communities. These exposures include allergens, environmental tobacco smoke, combustion by-products, and mold, all of which can play an important role in asthma progression as well as morbidity. These exposures are often not found in isolation and thus these concomitant exposures need to be considered when conducting environmental interventions. There have been numerous studies looking at both primary and tertiary prevention strategies and the impact on allergic sensitization and asthma with varied results. While the outcomes of these studies have been mixed, what has emerged is the need for tertiary interventions to be targeted to the individual and to reduce all relevant exposures to which an asthmatic child is exposed and sensitized. In addition, effective intervention strategies must also consider other social determinants of asthma morbidity impacting low socioeconomic, urban communities.

Evidence base for a housing warrant of fitness

Substandard housing is a major public health issue in New Zealand. Approximately, two-thirds of the housing stock is uninsulated and many homes are inadequately heated, with an average indoor temperature of 14.5°C. Cold, damp, and mouldy housing results in poor health; each year, respiratory hospital admissions are 74% higher during winter, and excess winter mortality is 20% higher than other seasons. The relationship between injury and housing conditions is also well established. Each year, 500,000 New Zealanders suffer falls requiring medical treatment in their homes. As a step towards improving the quality of existing housing, an evidence-based warrant of fitness has been developed. This article outlines the evidence base to each criterion in the warrant of fitness. We conclude that introducing and properly enforcing a housing warrant of fitness will ensure that basic minimum standards are met, which could mitigate the disease burdens and injuries associated with, or caused, by poorer quality housing. In addition, there are potential fiscal and economic advantages of the scheme, including reduced hospitalisations and increased productivity.

Internal living environment and respiratory disease in children: findings from the Growing Up in New Zealand longitudinal child cohort study

BACKGROUND

The incidence of early childhood acute respiratory infections (ARIs) has been associated with aspects of the indoor environment. In recent years, public awareness about some of these environmental issues has increased, including new laws and subsequent changes in occupant behaviours. This New Zealand study investigated current exposures to specific risk factors in the home during the first five years of life and provided updated evidence on the links between the home environment and childhood ARI hospitalisation.

METHODS

Pregnant women (n = 6822) were recruited in 2009 and 2010, and their 6853 children created a child cohort that was representative of New Zealand births from 2007-10. Longitudinal data were collected through face-to-face interviews and linkage to routinely collected national datasets. Incidence rates with Poisson distribution confidence intervals were computed and Cox regression modelling for repeated events was performed.

RESULTS

Living in a rented dwelling (48%), household crowding (22%) or dampness (20%); and, in the child's room, heavy condensation (20%) or mould or mildew on walls or ceilings (13%) were prevalent. In 14% of the households, the mother smoked cigarettes and in 30%, other household members smoked. Electric heaters were commonly used, followed by wood, flued gas and unflued portable gas heaters. The incidence of ARI hospitalisation before age five years was 33/1000 person-years. The risk of ARI hospitalisation was higher for children living in households where there was a gas heater in the child's bedroom: hazard ratio for flued gas heater 1.69 (95% CI: 1.21-2.36); and for unflued gas heater 1.68 (95% CI: 1.12-2.53); and where a gas heater was the sole type of household heating (hazard ratio: 1.64 (95% CI: 1.29-2.09)). The risk was reduced in households that used electric heaters (Hazard ratio: 0.74 (95% CI: 0.61-0.89)) or wood burners (hazard ratio: 0.79 (95% CI: 0.66-0.93)) as a form of household heating. The associations with other risk factors were not significant.

CONCLUSIONS

The risk of early childhood ARI hospitalisation is increased by gas heater usage, specifically in the child's bedroom. Use of non-gas forms of heating may reduce the risk of early childhood ARI hospitalisation.

The Built Environment-A Missing "Cause of the Causes" of Non-Communicable Diseases

The United Nations "25 × 25 Strategy" of decreasing non-communicable diseases (NCDs), including cardiovascular diseases, diabetes, cancer and chronic respiratory diseases, by 25% by 2025 does not appear to take into account all causes of NCDs. Its focus is on a few diseases, which are often linked with life-style factors with "voluntary" "modifiable behavioral risk factors" causes tending towards an over-simplification of the issues. We propose to add some aspects of our built environment related to hazardous building materials, and detailed form of the construction of infrastructure and buildings, which we think are some of the missing causes of NCDs. Some of these could be termed "involuntary causes", as they relate to factors that are beyond the control of the general public.

Impact of kerosene space heaters on indoor air quality

In recent years, the use of kerosene space heaters as additional or principal heat source has been increasing, because these heaters allow a continuous control on the energy cost. These devices are unvented, and all combustion products are released into the room where the heaters are operated. The indoor air quality of seven private homes using wick-type or electronic injection-type kerosene space heaters was investigated. Concentrations of CO, CO2, NOx, formaldehyde and particulate matter (0.02-10 μm) were measured, using time-resolved instruments when available. All heaters tested are significant sources of submicron particles, NOx and CO2. The average NO2 and CO2 concentrations are determined by the duration of use of the kerosene heaters. These results stress the need to regulate the use of unvented combustion appliances to decrease the exposure of people to air contaminants.

Modelling the effects of low indoor temperatures on the lung function of children with asthma

INTRODUCTION

While many epidemiological studies have shown that low outdoor temperatures are associated with increased rates of hospitalisation and mortality (especially for respiratory or cardiovascular disease), very few studies have looked at the association between indoor temperatures and health. Such studies are clearly warranted, as people have greater exposure to the indoor environment than the outdoor environment.

OBJECTIVES

To examine the relationship between various metrics of indoor temperature and lung function in children with asthma. Our specific research questions were: (1) In which room of the home is temperature most strongly associated with lung function? (2) Which exposure metric best describes the relationship between indoor temperature and lung function? (3) Over what lag/time period does indoor air temperature affect lung function most strongly?

METHODS

The Heating Housing and Health Study was a randomised controlled trial that investigated the effect of installing heaters in the homes of children with asthma. This study collected measurements of lung function (daily) and indoor temperature (hourly). Lung function and indoor temperature were measured for 309 children over 12 049 child-days. Statistical models were fitted to identify the best measures and metrics.

RESULTS

The strongest association with lung function was found for the severity of exposure to low bedroom temperatures averaged over the preceding periods of 0-7 to 0-12 days. A 1°C increase in temperature was associated with an average increase of 0.010, 0.008, 10.06, 12.06, in our four measures of lung function (peak expiratory flow rate (PEFR) morning, PEFR evening, forced expiratory volume in 1 s (FEV1) morning and FEV1 evening).

CONCLUSIONS

Indoor temperatures have a small, but significant, association with short-term variations in the lung function of children with asthma.

Indoor air pollution from gas cooking and infant neurodevelopment

BACKGROUND

Gas cooking is a main source of indoor air pollutants, including nitrogen dioxide and particles. Because concerns are emerging for neurodevelopmental effects of air pollutants, we examined the relationship between indoor gas cooking during pregnancy and infant neurodevelopment.

METHODS

Pregnant mothers were recruited between 2004 and 2008 to a prospective birth cohort study (INfancia y Medio Ambiente) in Spain during the first trimester of pregnancy. Third-trimester questionnaires collected information about the use of gas appliances at home. At age 11 to 22 months, children were assessed for mental development using the Bayley Scales of Infant Development. Linear regression models examined the association of gas cooking and standardized mental development scores (n = 1887 mother-child pairs).

RESULTS

Gas cookers were present in 44% of homes. Gas cooking was related to a small decrease in the mental development score compared with use of other cookers (-2.5 points [95% confidence interval = -4.0 to -0.9]) independent of social class, maternal education, and other measured potential confounders. This decrease was strongest in children tested after the age of 14 months (-3.1 points [-5.1 to -1.1]) and when gas cooking was combined with less frequent use of an extractor fan. The negative association with gas cooking was relatively consistent across strata defined by social class, education, and other covariates.

CONCLUSIONS

This study suggests a small adverse effect of indoor air pollution from gas cookers on the mental development of young children.

Modification of the home environment for the reduction of injuries

BACKGROUND

Injury in the home is common, accounting for approximately a third of all injuries. The majority of injuries to children under five and people aged 75 and older occur at home. Multifactorial injury prevention interventions have been shown to reduce injuries in the home. However, few studies have focused specifically on the impact of physical adaptations to the home environment and the effectiveness of such interventions needs to be ascertained.

OBJECTIVES

To determine the effect of modifications to the home environment on the reduction of injuries due to environmental hazards.

SEARCH STRATEGY

We searched The Cochrane Library, MEDLINE, EMBASE and other specialised databases. We also scanned conference proceedings and reference lists. We contacted the first author of all included randomised controlled trials. The searches were last updated to the end of December 2009, and were not restricted by language or publication status.

SELECTION CRITERIA

Randomised controlled trials.

DATA COLLECTION AND ANALYSIS

Two authors screened all abstracts for relevance, outcome and design. Two authors independently assessed methodological quality and extracted data from each eligible study. We performed meta-analysis to combine effect measures, using a random-effects model. We assessed heterogeneity using an I(2) statistic and a Chi(2) test.

MAIN RESULTS

We found 28 published studies and one unpublished study. Only two studies were sufficiently similar to allow pooling of data for statistical analyses. Studies were divided into three groups; children, older people and the general population/mixed age group. None of the studies focusing on children or older people demonstrated a reduction in injuries that were a direct result of environmental modification in the home. One study in older people demonstrated a reduction in falls and one a reduction in falls and injurious falls that may have been due to hazard reduction. One meta-analysis was performed which examined the effects on falls of multifactorial interventions consisting of home hazard assessment and modification, medication review, health and bone assessment and exercise (RR 1.09, 95% CI 0.97 to 1.23).

AUTHORS' CONCLUSIONS

There is insufficient evidence to determine whether interventions focused on modifying environmental home hazards reduce injuries. Further interventions to reduce hazards in the home should be evaluated by adequately designed randomised controlled trials measuring injury outcomes. Recruitment of large study samples to measure effect must be a major consideration for future trials. Researchers should also consider using factorial designs to allow the evaluation of individual components of multifactorial interventions.

Long-term exposure to indoor air pollution and wheezing symptoms in infants

Long-term exposure to air pollution is suspected to cause recurrent wheeze in infants. The few previous studies have had ambiguous results. The objective of this study was to estimate the impact of measured long-term exposure to indoor air pollution on wheezing symptoms in infants. We monitored wheezing symptoms in diaries for a birth cohort of 411 infants. We measured long-term exposure to nitrogen oxides (NO(x)), NO(2), formaldehyde, PM(2.5) and black smoke in the infants' bedrooms and analyzed risk associations during the first 18 months of life by logistic regression with the dichotomous end-point 'any symptom-day' (yes/no) and by standard linear regression with the end-point 'number of symptom-days'. The results showed no systematic association between risk for wheezing symptoms and the levels of these air pollutants with various indoor and outdoor sources. In conclusion, we found no evidence of an association between long-term exposure to indoor air pollution and wheezing symptoms in infants, suggesting that indoor air pollution is not causally related to the underlying disease. Practical Implications Nitrogen oxides, formaldehyde and fine particles were measured in the air in infants' bedrooms. The results showed no evidence of an association between long-term exposure and wheezing symptoms in the COPSAC birth cohort.

Effects of improved home heating on asthma in community dwelling children: randomised controlled trial

OBJECTIVE

To assess whether non-polluting, more effective home heating (heat pump, wood pellet burner, flued gas) has a positive effect on the health of children with asthma.

DESIGN

Randomised controlled trial.

SETTING

Households in five communities in New Zealand.

PARTICIPANTS

409 children aged 6-12 years with doctor diagnosed asthma.

INTERVENTIONS

Installation of a non-polluting, more effective home heater before winter. The control group received a replacement heater at the end of the trial.

MAIN OUTCOME MEASURES

The primary outcome was change in lung function (peak expiratory flow rate and forced expiratory volume in one second, FEV(1)). Secondary outcomes were child reported respiratory tract symptoms and daily use of preventer and reliever drugs. At the end of winter 2005 (baseline) and winter 2006 (follow-up) parents reported their child's general health, use of health services, overall respiratory health, and housing conditions. Nitrogen dioxide levels were measured monthly for four months and temperatures in the living room and child's bedroom were recorded hourly.

RESULTS

Improvements in lung function were not significant (difference in mean FEV(1) 130.7 ml, 95% confidence interval -20.3 to 281.7). Compared with children in the control group, however, children in the intervention group had 1.80 fewer days off school (95% confidence interval 0.11 to 3.13), 0.40 fewer visits to a doctor for asthma (0.11 to 0.62), and 0.25 fewer visits to a pharmacist for asthma (0.09 to 0.32). Children in the intervention group also had fewer reports of poor health (adjusted odds ratio 0.48, 95% confidence interval 0.31 to 0.74), less sleep disturbed by wheezing (0.55, 0.35 to 0.85), less dry cough at night (0.52, 0.32 to 0.83), and reduced scores for lower respiratory tract symptoms (0.77, 0.73 to 0.81) than children in the control group. The intervention was associated with a mean temperature rise in the living room of 1.10 degrees C (95% confidence interval 0.54 degrees C to 1.64 degrees C) and in the child's bedroom of 0.57 degrees C (0.05 degrees C to 1.08 degrees C). Lower levels of nitrogen dioxide were measured in the living rooms of the intervention households than in those of the control households (geometric mean 8.5 microg/m(3) v 15.7 microg/m(3), P<0.001). A similar effect was found in the children's bedrooms (7.3 microg/m(3) v 10.9 microg/m(3), P<0.001).

CONCLUSION

Installing non-polluting, more effective heating in the homes of children with asthma did not significantly improve lung function but did significantly reduce symptoms of asthma, days off school, healthcare utilisation, and visits to a pharmacist.

TRIAL REGISTRATION

Clinical Trials NCT00489762.

Modification of the home environment for the reduction of injuries

BACKGROUND

Injury in the home is extremely common, accounting for around a third of all injuries. The majority of injuries of children under five and people aged 75 and over, occur at home. Multifactorial injury prevention interventions have been shown to reduce injuries in the home. However, few studies have focused specifically on the impact of physical adaptations to the home environment and the effectiveness of such interventions needs to be ascertained.

OBJECTIVES

To review the evidence for the effect on injuries of modification of the home environment with a primary focus on interventions to reduce physical hazards.

SEARCH STRATEGY

We searched The Cochrane Library, MEDLINE, EMBASE, National Research Register and other specialised databases. We also scanned conference proceedings and reference lists. In addition, we contacted experts and trialists in the field. The searches were not restricted by language or publication status. The searches were last updated in December 2004.

SELECTION CRITERIA

Randomised controlled trials.

DATA COLLECTION AND ANALYSIS

All abstracts were screened by two authors for relevance, outcome and design. Two authors independently assessed methodological quality and extracted data from each eligible study.

MAIN RESULTS

We found 18 published and one unpublished trials. Trials were not sufficiently similar to allow pooling of data by statistical analyses, so this review takes a narrative form. Studies were divided into three groups based on the primary population sample; children (five studies), older people (14 studies) and the general population/mixed age group (no studies). None of the studies focusing on children demonstrated a reduction in injuries that might have been due to environmental adaptation in the home; one study reported a reduction in injuries and in hazards but the two could not be linked. Of the 14 included studies in older people, none demonstrated a reduction in injuries due to hazard reduction, although two demonstrated a reduction in falls that could be due to hazard reduction.

AUTHORS' CONCLUSIONS

There is insufficient evidence to determine the effects of interventions to modify environmental home hazards. Further interventions to reduce hazards in the home should be evaluated by adequately designed randomised controlled trials measuring injury outcomes. Recruitment of large study samples to measure effect must be a major consideration for future trials.